VALUE OF MRI ENTEROCOLONOGRAPHY AND FAECAL CALPROTECTIN FOR DIAGNOSIS OF CROHN'S DISEASE

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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY

Vestina Strakšytė

VALUE OF MRI

ENTEROCOLONOGRAPHY AND

FAECAL CALPROTECTIN FOR

DIAGNOSIS OF CROHN'S DISEASE

Doctoral Dissertation Medical and Health Sciences,

Medicine (M 001)

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The dissertation has been prepared at the Department of Radiology of Lithuanian University of Health Sciences from 2011 to 2020.

The dissertation is defended extramurally.

Scientific Consultant:

Prof. Dr. Gediminas Kiudelis (Lithuanian University of Health Sciences,

Medical and Health Sciences, Medicine – M 001).

The dissertation is defended at the Medical Research Council of the Lithuanian University of Health Sciences:

Chairperson

Assoc. Prof. Dr. Vaidotas Gurskis (Lithuanian University of Health Sciences, Medical and Health Sciences, Medicine – M 001).

Members:

Prof. Dr. Rymantė Gleiznienė (Lithuanian University of Health Sciences, Medical and Health Sciences, Medicine – M 001);

Prof. Dr. Kristina Žvinienė (Lithuanian University of Health Sciences, Medical and Health Sciences, Medicine – M 001);

Prof. Dr. Nomeda Rima Valevičienė (Vilnius University, Medical and Health Sciences, Medicine – M 001);

Dr. Povilas Ignatavičius (Zurich University, Medical and Health Scien-ces, Medicine – M 001).

Dissertation will be defended at the open session of the Medical Research Council of Lithuanian University of Health Sciences on the 26th of January, 2021 at 11 a.m. in A-203 of the Centre for the Advanced Pharmaceutical and Health Technologies of Lithuanian University of Health Sciences.

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LIETUVOS SVEIKATOS MOKSLŲ UNIVERSITETAS MEDICINOS AKADEMIJA

Vestina Strakšytė

MRT ENTEROKOLONOGRAFIJOS IR

IŠMATŲ KALPROTEKTINO REIKŠMĖ

DIAGNOZUOJANT KRONO LIGĄ

Daktaro disertacija Medicinos ir sveikatos mokslai,

medicina (M 001)

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Disertacija rengta 2011–2020 metais Lietuvos sveikatos mokslų universiteto Medicinos akademijos Radiologijos klinikoje.

Disertacija ginama eksternu.

Mokslinis konsultantas

prof. dr. Gediminas Kiudelis (Lietuvos sveikatos mokslų universitetas, medicinos ir sveikatos mokslai, medicina – M 001).

Disertacija ginama Lietuvos sveikatos mokslų universiteto medicinos mokslo krypties taryboje:

Pirmininkas

doc. dr. Vaidotas Gurskis (Lietuvos sveikatos mokslų universitetas, medicinos ir sveikatos mokslai, medicina – M 001).

Nariai:

prof. dr. Rymantė Gleiznienė (Lietuvos sveikatos mokslų universitetas, medicinos ir sveikatos mokslai, medicina – M 001);

prof. dr. Kristina Žvinienė (Lietuvos sveikatos mokslų universitetas, medicinos ir sveikatos mokslai, medicina – M 001);

prof. dr. Nomeda Rima Valevičienė (Vilniaus universitetas, medicinos ir sveikatos mokslai, medicina – M 001);

dr. Povilas Ignatavičius (Ciuricho universitetas, medicinos ir sveikatos mokslai, medicina – M 001).

Disertacija bus ginama viešame Lietuvos sveikatos mokslų universiteto medicinos mokslo krypties tarybos posėdyje 2021 m. sausio 26 d. 11 val. Lietuvos sveikatos mokslų universiteto Naujausių farmacijos ir sveikatos technologijų centro A-203 auditorijoje.

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ABBREVIATIONS

ADC  apparent diffusion coefficient AIS  acute inflammatory score

AGA  American Gastroenterological Association anti-TNF  antibodies directed against tumor necrosis factor BW  pixel bandwidth

BW  bowel wall BMI  Body Mass Index CD  Crohn's disease

CDAI  Crohn's Disease Activity Index

CDEIS  Crohn's Disease Endoscopic Index of Severity CRP  C reactive protein

DWI  diffusion-weighted imaging

eAIS  endoscopic biopsy acute inflammatory score FC  faecal calprotectin

FISP  fast imaging with steady precession FOV  field of view

fs  fat-suppressed GI gastrointestinal

HASTE  Half Fourier acquisition single-shot turbo spin-echo HBI  Harvey-Bradshaw Index

IBD  inflammatory bowel disease

IBDQ  inflammatory bowel disease questionnaire IBS  Irritable bowel syndrome

IVC  intravenous contrast IV  intravenous

LI  Lemann index

MaRIA  Magnetic Resonance Index of Activity

mMaRIA  modified Magnetic Resonance Index of Activity MR  magnetic resonance

MRI  magnetic resonance imaging

MR-EC  magnetic resonance enterocolonography PACS  picture archiving and communication system PEG  polyethyleneglycol

RCE  relative contrast enhancement ROI  region of interest

T1W  T1 weighted T2W  T2 weighted TE  echo time TR  repetition time

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INTRODUCTION

Crohn's disease (CD) is one of the subtypes of idiopathic inflammatory bowel disease. It is characterized by chronic transmural intestinal inflam-mation [1, 2] of the gastrointestinal tract anywhere from the mouth to the anus, with a tendency for the small intestine [3] and an inflammatory response associated with lymphoid aggregates and granulomas [4].

CD affects more than 2.5 million individuals in the Western world and has an increasing incidence in the developing world [4].

It is most prevalent in young adults and remains incurable. Patients usually require lifelong medication and multiple surgeries [5].

CD is usually inflammatory when first recognized but progresses over time to stricturing or penetrating disease at 3.8–7.5% per year [6].

The symptoms of active CDs, such as abdominal pain and diarrhea, have a poor correlation to disease severity and behavior (inflammatory, penetrating, or stricturing) [7]. Additionally, the disease is heterogeneous, comprising multiple complex phenotypes that vary depending on the age of onset, disease location, and behavior [8].

Ileocolonoscopy and upper endoscopy are considered the gold standard to evaluate mucosal inflammation [6]. Endoscopy has the advantage of getting the tissue sample and investigating the microscopic disease activity [9]. Nevertheless, they only cover proximal small bowel or terminal ileum and do not provide information on the possible extra-luminal complications (fistulas, abscesses), requiring other evaluation modalities [10–13]. More-over, endoscopy evaluates only the superficial mucosa, while deeper layers of the bowel wall are not assessed [10].

Thus, cross-sectional imaging is a significant adjunct to endoscopic evaluation, to allow a complete and sensitive staging of the small bowel and perineum with the unique advantage to assess mural and extramural disease [14, 15]. Magnetic resonance imaging (MRI) plays a key role in confirming the diagnosis, identifying and managing complications, evaluate disease severity, and determining response to medical therapy [3, 6, 11, 16].

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Also, faecal calprotectin (FC) is a useful biomarker for CD diagnosis of relapse or mucosal healing [18]. Also, FC is a well-established, useful tool to identify patients most likely to require conventional colonoscopy for suspected CD [19].

Grading the activity of CD nowadays is essential [20]. In order to objectively evaluate the clinical symptoms of a disease, the course, severity, extent, and to monitor expensive treatment [21]. There are a lot of indices and scores invented for disease activity and severity evaluation. The most well-known quality of life assessment – inflammatory bowel disease questionnaire (IBDQ) [22], Endoscopic Disease Severity Assessment- Crohn's Disease Endoscopic Index of Severity (CDEIS) [23], and Magnetic Resonance Index of Activity (MaRIA) [24].

The new quantitative tool for assessing bowel damage in CD is the Crohn's Disease Digestive Damage Score – the Lemann index (LI) has recently been developed. [25, 26]. It combines clinical, surgical, endoscopic, and imaging findings from all digestive tract segments into one composite score [27].

Current treatments include traditional anti-inflammatory agents, immu-nomodulators, biological agents with antibodies directed against tumor necrosis factor (anti-TNF), antibiotics, and surgery [4, 28]. The treatment goal has changed from symptomatic to complete mucosal healing and requires periodic imaging examinations to monitor the treatment response [6, 10, 29–31].

The aim of the study

The aim of the study was to evaluate the role of MR-EC and faecal calprotectin in the diagnosis and assessment of Crohn's disease.

The objectives of the study

1. To assess the prognostic values of MR-EC in the diagnosis of CD. 2. To compare MR-EC imaging parameters of patients with proven

Crohn's disease with controls (patients without organic gastro-intestinal lesions).

3. To evaluate the correlations of different Crohn's disease MR-EC activity indices with CDEIS, clinical activity indices, and IBDQ. 4. To determine the value of apparent diffusion coefficient (ADC) and

DWI for assessment CD inflammatory activity.

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The novelty of the study

CD remains a clinical challenge due to nonspecific symptoms and a weak correlation between symptoms and disease activity [32].

In the past two decades, there have been advances in modalities for imaging the bowel and technologies, providing increased imaging demand for patients with CD. Improvements in the temporal and spatial resolution of MRI and the development of enteric agents to distend the bowel have led to routine visualization of the small and large bowel lumen, wall, and perienteric tissues using MR-EC [33–36]. Currently, MR-EC is considered the gold standard to identify and define small bowel CD [14].

The development of modern biologic and immunomodulatory therapies has increased the need for bowel imaging. The demand to detect, to stage, and classify inflammatory, penetrating, and stricturing disease, determine treatment strategies, assess response to therapy, reduce complications, and reproducibly and accurately track inflammation that is beyond the reach of the endoscope [37]. In up to 50% of patients with active small bowel disease, inflammation may skip the terminal ileum or be intramural and not detected by ileocolonoscopy [38].

The MR-EC methodology was initiated in 2013 at the Department of Radiology, Lithuanian University of Health Sciences Kauno klinikos. This clinical study is the first in Lithuania to evaluate CD extension and activity, so it has considerable scientific and practical value in optimizing the use of MRI in CD diagnostics.

We performed the first perspective MR-EC study in Lithuania, which includes CD in a multidisciplinary approach. We evaluated clinical CD activity indices: CDAI and Harvey Bradshaw, also IBDQ – the quality of life. Laboratory test whole blood count, CRP, faecal calprotectin. Endoscopy with biopsy and MR-EC investigation with index calculation was performed.

Also, we adapted the MR-EC protocol in clinical practice. Until now, routine testing of CD patients in the MR-EC study has not been accepted.

Also, in the present study, we performed a quality of life analysis using IBDQ.

Up to date, we have not found any study looking for the correlation of Crohn's Disease Digestive Damage Score – LI and patients' quality of life measured by IBDQ.

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1. LITERATURE REVIEW

1.1. Epidemiology, Etiology, and Pathogenesis

CD is more common in industrialized than in non-industrialized count-ries [39]. In the 21st century, inflammatory bowel disease (IBD) became a global disease with accelerating incidence in the newly industrialized count-ries of Africa, Asia [40–42]. In Europe alone, more than three million people are affected by IBD [43]. The highest incidence rates are in Scandinavia, the United Kingdom [39]. However, the classic geographical distribution of the disease is changing. Low incident regions such as Eastern Europe have recently reported rising incidence rates that mean their CD occurrence is comparable to Western Europe [39]. Increased awareness of the disease has improved access to healthcare and diagnostic procedures, or real changes in lifestyle and environmental factors due to the socio-economic transition from "developing" to "developed" in many Eastern European countries [44].

Etiology is complex, and the most widely accepted hypothesis purports CD as an immune-mediated condition in genetically susceptible individuals. The disease's onset is triggered by environmental factors that disturb the mucosal barrier, the healthy balance of the gut microbiota, and starts abnor-mally stimulating gut immune responses [45]. These factors: genetics, gut immune response, and the microbiota are influenced by the individual's environmental exposures or triggers to engage different mechanisms giving rise to CD (Fig. 1.1.1) [4].

Another theory, other autoimmune and allergic diseases in modern society, is the "hygiene hypothesis". The hypothesis proposes that these diseases are caused by abnormal development and response of the immune system due to the reduced exposure to microorganisms, such as the microbes in the gut [5].

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Fig. 1.1.1. Crohn's disease: multi-layer communication in pathogenesis

and clinical evaluation (with permission of Faculty Opinions) [4]

1.2. Clinical classification of Crohn's disease

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Table 1.2.1. Vienna and Montreal classification for Crohn's disease

(Permission License Number 4860270033677) [48]

Vienna Montreal

Age at diagnosis

A1 below 40 years old A2 above 40 years old

A1 below 16 years old

A2 between 17 and 40 years old A3 above 40 years old

Location L1 ileal L2 colonic L3 ileocolonic L4 upper L1 ileal L2 colonic L3 ileocolonic

L4 isolated upper disease* Behavior B1 non-stricturing, non-penetrating

B2 stricturing B3 penetrating

B1 non-stricturing, non-penetrating B2 stricturing

B3 penetrating

*L4 is a modifier that can be added to L1–L3 when a concomitant upper gastrointestinal disease is present.

1.3. Clinical manifestation of Crohn's disease

The most common presenting symptom of CD is chronic diarrhea [49]. More acute presentations may occur, and severe terminal ileal CD may be mistaken for acute appendicitis, unexplained anemia [45]. Abdominal pain and weight loss are seen in about 80% and 60% of patients before diagnosis, respectively [50]. Blood and/or mucus in the stool may be in up to 40–50% of patients with Crohn's colitis [19]. Patients may present with extraintestinal manifestations of CD before the gastrointestinal symptoms become prominent [50]. Extraintestinal manifestations are most common when CD affects the colon. Perianal fistulas are present in 4–10% of patients at the time of diagnosis [19].

1.4. Clinical activity scores 1.4.1. Crohn's disease activity index (CDAI)

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Although the CDAI index has mostly been used in clinical trials. It has some limitations: high scores for subjective sign "general well being" and intensity of "abdominal pain", misleading results in fistulating and stenosing disease [54]. It is also limited for patients with ileocolic resection and stoma.

1.4.2. The Harvey Bradshaw index (HBI)

The HBI is a modified and simplified version of the CDAI. HBI uses a single day's reading for diary entries and excludes three variables: body weight, hematocrit, and drugs for diarrhea [55]. Scores range from 0 to 20, with higher scores corresponding to worse disease. The CDAI can be predicted reasonably well from the HBI [55, 56]. All the clinical indices can only give an indirect assessment of disease activity. Furthermore, they are rather complicated and time-consuming to collate. The application of indices is limited to clinical trials [57].

1.4.3. IBDQ – inflammatory bowel disease questionnaire

The IBDQ examines aspects of the patient's life: bowel and systemic symptoms, emotional and social functions [22].

Global assessments of patient well-being are subjective and influenced by disease-specific, inflammatory, psychological, and sociological factors [58]. A simplified, more reproducible and validated score combining items from the CDAI and IBDQ could serve in clinical practice and clinical trials [59].

1.5. Crohn disease diagnostic gold standard

A single reference standard for the diagnosis of CD does not exist. CD's determination is based on a combination of clinical, biochemical, stool, endoscopic, cross-sectional imaging, and histological investigations [37].

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is safer, and ileocolonoscopy should be postponed until the clinical condition improves [65]. Ileocolonoscopy is superior for diagnosing CD of the terminal ileum [66–68] compared with radiology techniques, including MRI and CT, especially for mild lesions [19].

In 2018, ECCO-ESGAR jointly issued a guideline for Diagnostic Assessment in IBD where initial diagnosis, monitoring of known IBD, detection of complications are discussed [37].

One of the ECCO-ESGAR statement states, "For suspected IBD, ileocolonoscopy with biopsies from inflamed and uninflamed segments are required to establish the diagnosis [EL1]" [37].

A study by Samuel et al. evaluated CD patients with CT enterography and ileocolonoscopy. From the group of patients with normal ileoscopy, 53.7% of these patients had active small-bowel CD. The ileocolonoscopic examination can thus miss CD of the terminal ileum, as the disease can skip the distal ileum or be confined to the intramural portion of the bowel wall and mesentery [69].

Various endoscopic scoring systems for assessing disease severity and activity have developed over time, notably the Crohn's disease endoscopic index of severity (CDEIS).

CDEIS scoring system was developed in 1989 by a French group of GETID (Groupe d'Etude Therapeutique des Affections Inflammatoires Digestive) [23] and based upon the presence or absence of four types of the lesion (superficial ulcers, deep ulcers, ulcerated stenosis, and non-ulcerated stenosis). The score can range from 0 to 30. Over time CDEIS was established as the gold standard for endoscopic evaluation of activity [23].

1.6. Markers of Crohn's disease activity 1.6.1. C reactive protein (CRP)

CRP is a useful laboratory surrogate of gut inflammation. However, low CRP levels were reported in clinically active CD patients with ileal disease distribution and a low body mass index [3].

CRP – is one of the essential acute phase proteins produced exclusively in hepatocytes in response to stimuli, including infections, inflammation, stress, tissue necrosis, trauma, and childbirth [70]. IL-6 and TNF influence its production, and it has a half-life of 19 hours with a baseline concentration of 0.8 mg/L [71, 72].

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improve-ment in inflammation [73]. Its levels are not directly affected by the admi-nistration of anti-inflammatory or immunosuppressive drugs [73].

CRP correlates reasonably well with CDAI [7, 74]. A rise in CRP is commonly seen with moderate to severe clinical activity in CD, and there is a reasonable correlation with other biomarkers (thrombocytosis, anemia, and hypoalbuminemia) and endoscopic findings. However, the association between CRP and radiological and histologic disease activity markers is less potent [75].

1.6.2. Faecal calprotectin

Calprotectin is a 36 kDa calcium-zinc binding protein, consisting of a heterodimer of the S100 proteins A8 and A9 [76]. It is expressed abundantly in the cytoplasm of neutrophils, monocytes, and macrophages [77]. When the intestine is inflamed, calprotectin is secreted into the faeces from these types of cells. FC's amount correlates with the degree of neutrophil infiltration in the gut [76, 78]. FC is a useful and convenient test to distinguish CD from irritable bowel syndrome (IBS) and assess intestinal inflammatory activity in patients with CD [79, 80]. FC levels have been reported to correlate with endoscopic activity of CD [77, 80].

Surprisingly, patients may display elevated FC levels, even when endo-scopic disease activity is absent [81]. This elevation could be due to disease activity proximal to the terminal ileum in CD patients or other pathology in the upper gastrointestinal tract such as peptic ulcers or nonsteroidal entero-pathy [82].

Alternatively, these elevated calprotectin levels could also be explained by low-grade inflammation only detectable upon histological evaluation. Kiesslich et al. and Moum et al. have shown that histological inflammation can be more extensive and severe than can be appreciated endoscopically [54, 83]. Earlier studies have shown that elevated calprotectin levels can predict relapse during follow-up in clinical remission patients with a pooled sensitivity of 78% and a specificity of 73% [81, 84].

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1.7. Magnetic resonance enterocolonography diagnostic features of Crohn's disease

Many MR-EC parameters are associated with inflammation and damage, but reported sensitivities and specificities vary widely. Studies have been performed with different MR-EC protocols and using different thresholds for a positive. Also, different reference standards have been used, with different limits. This heterogeneity caused difficulties in choosing the essential MR-EC parameters in clinical practice [6].

1.7.1. The general principle of magnetic resonance enterocolonography

There is evidence of optimal patient preparation before MR-EC and recommendations concerning no solid food and mainly fluid-based diet [86].

Cronin et al. confirmed that superior bowel distension was achieved in the prone position [87]. There is no reliable evidence that helps to improve diagnostic accuracy. Some patients may have difficulty lying prone. Either supine or prone positioning is considered acceptable [86].

There was no consensus that field strength, either 1.5T or 3T, was optimal for enteric MRI [88, 89].

There is some evidence that MR-EC can achieve high diagnostic accuracy without using a spasmolytic [90]. However, other data show significantly superior distension with the use of these agents [91]. The use of spasmolytic before MR-EC is, therefore, recommended.

1.7.2. Enteric contrasts

The accuracy of MR-EC is improved by the administration of oral contrast in comparison to unprepared MR-EC [92, 93]. Many oral contrast agents are described in the literature, but no substantial evidence from patient studies supports one particular oral contrast agent over another [94, 95–98]. Therefore, many contrasts are recommended, usually with hyperosmolar properties and ingested over 46–60 min before the exami-nation [86].

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Contrast agents:

Negative contrast media – appears low signal intensity on both T1W and T2W images. Provide better visualization of bowel wall edema and mucosal enhancement and help to discriminate between intraluminal and extraluminal fluid (abscess) [100, 101]. The negative contrast agents have a less pleasant taste compared to others and are more expensive.

Positive contrast media – is high signal intensity on both T1W and T2W and is helpfully delineating the bowel wall [100]. In general, positive agents are rarely used in clinical practice.

Biphasic contrast media – is high signal intensity on T2W and low signal on T1W images [102]. The biphasic contrast agents group is the largest (including osmotic agents such as mannitol and non-osmotic such as polyethylene glycol (PEG)). It is the most used type of enteric contrast. The "dark lumen" on T1W images is essential for evaluating the bowel mucosa and detecting mural enhancement after intravenous contrast (IVC) administration. The most commonly used oral contrast agents are mannitol and PEG.

Critical issues related to the use of oral contrast are the volume of contrast and administration time. There is high interpersonal variability in transit times, even higher than the variability between healthy subjects and patients with CD [103]. The patient takes 1 L in the first 30 min and then 250 ml every 15 min. Immediately before imaging, the patient drinks about 500 ml of water [103].

Table 1.7.2.1. Enteric contrast agents for MR imaging (Permission License

Number 4860271176009)[103]

Contrast agents Limitations

Positive Gadolinium chelates Costs

Manganese Low availability

Food (milk, juice) Storage, expiration Negative Superparamagnetic particles Low availability

Ferrous oral suspension Cost, taste, poor distention

Biphasic Water Rapidly absorbed, poor distention

Polyethylene glycol Rapid transit, diarrhea

Mannitol The osmotic effect, third space Methylcellulose Availability

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1.7.3. Spasmolytics

The wide variability of spasmolytics is described in the literature [103]. Most authors use N-Butyl Scopolamine or glucagon intravenous (IV) or intramuscularly immediately before the procedure, as suggested by some authors [94, 104–107].

Both N-Butyl Scopolamine and glucagon are acceptable agents with different properties regarding the effect's duration, although they are most effective when given intravenously [108]. N-Butyl Scopolamine is recom-mended as the first-line spasmolytic, with glucagon as the second line [109].

The spasmolytics usually are administered before motioning sensitive sequences and either a single or a split dose [86]. Post-gadolinium T1W images' use increases diagnostic accuracy [110, 111] and utility of bowel wall enhancement in validated disease activity scores [24, 86, 112].

1.7.4. Imaging classification of Crohn's disease

CD is classified into several subgroups, and patients may exhibit cha-racteristics of more than one disease subtype [107, 113]. The subtypes are the active inflammatory subtype (non-stricturing, non-penetrating), penetrating, stricturing, and reparative-regenerative subtype. This classification is useful for determining whether a patient can receive medical or surgical treatment [103–113].

1.7.4.1. Active inflammatory disease subtype

Early CD manifestations include edema and aphthous ulcers easily detected by endoscopy, and MRI is less useful [113, 114]. The initial muco-sal inflammation can progressively develop into deep ulcers, transmural inflammation, and granuloma formation with further wall thickening, hyperemia, submucosal edema, and mesenteric fat hypertrophy [103]. Minimal active inflammatory signs are characterized as aphthous or superficial ulcers on endoscopic images [113].

Endoscopic and barium examinations are superior in detecting these superficial mucosal abnormalities [115], which may not identify on MR imaging even with optimal luminal distension [107, 114]. Mucosal hyperemia is an area of intense enhancement after contrast agent administration. The early signal intensity after contrast administration correlates well with the CDAI [106], as well as a stratified pattern of contrast enhancement with active inflammation [103].

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proliferation around the affected loop. Regional lymphadenopathy was seen in patients with inflammatory changes [116].

The signs of severe inflammatory activity include deep mucosal ulcera-tions and a "cobblestone" appearance of the bowel mucosa, very charac-teristic of CD.

Deep transmural ulcers were readily detected on True FISP, HASTE, and T1W fat-suppressed (fs) images after IV contrast administration. These deep transmural ulcers progress to fistula formation [103].

1.7.4.2. Penetrating subtype

This subtype is described by severe inflammation that progresses to transmural ulceration with fistula formation or intestinal perforation. Before fistulization, large penetrating ulcers may occur. Differentiation between deep transmural ulcerations and well-established fistulas is critical as fissures may respond to more aggressive immunomodulatory treatments (TNF inhibitors) [103].

Fistula formation has been reported in up to one-third of patients with CD [117]. MR-EC's sensitivity for detecting fistulizing/penetrating disease ranges from 83.3–84.4%, with a specificity of 100% [118].

Active fistulas show marked contrast, and chronic fistulas are considered low signal serpiginous tracts with no enhancement after contrast injection. Sagittal sequences help delineate fluid-filled tracts that extend from the small bowel to the anterior abdominal wall [102]. Desmoplastic reaction incited by transmural inflammation in the mesentery can occur in band-like areas of fibrosis, often bridging surrounding small bowel loops in a stellate configuration, also referred to as the "star-sign". These fibrous bands often show delayed progressive enhancement and are indirect evidence of enteroenteric fistula [102].

Fistulous may develop between bowel loops or between loops and skin or other adjacent organs [103].

Extramural complications such as abscesses, inflammatory masses, or adjacent organ involvement are easily seen at MR-EC [103].

1.7.4.3. Stenosing subtype

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Chronic fibrotic stenoses are typically hypointense on T1W and T2W, unlike inflammatory stenoses with transmural edema are hyperintense on T2W fs [103].

Pseudosacculation ("omega" sign) is caused by asymmetric fibrosis involving the mesenteric margin of the loop resulting in pseudosaccule formation [103].

Functionally significant stenosis than prestenotic dilatation of bowel lumen proximal to the stenosis measured >3 cm in diameter [16].

Functionally not significant stenosis than bowel lumen narrowing >10% compared with normal adjacent bowel in the absence of dilatation [16].

One of the significant disadvantages of MR-EC is the low specificity and sensitivity in the detection of strictures. Although symptomatic strictures may be detected, incipient or partial strictures are often missed on MR-EC because the enterocolonographic technique may not provide adequate distension of the bowel to highlight partial strictures [102].

1.7.4.4. Reparative-regenerative subtype

Mucosal atrophy and regenerative polyps characterize this phase. Mucosal atrophy with focal areas of sparing seen as pseudopolyps that demonstrate no significant enhancement or edema.

Regenerative pseudo-polyps should not be confused with the deep ulcerations that develop in the advanced inflammatory disease ("cobblestone" sign) [103].

1.7.5. Magnetic resonance enterocolonography signs of Crohn's disease activity, severity, and complications

The assessment of active CD with MRI may determine the management of the patient. The findings associated with CD on MRI are divided into mural and extramural. Mural findings include thickening and enhancement of the bowel wall, patterns of enhancement, hyperintensity on T2W, ulcerations. Extramural findings are fibrofatty proliferation, "comb sign", lymph nodes.

1.7.5.1. Bowel wall assessment 1.7.5.1.1. Bowel wall thickening

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activity with a sensitivity and specificity (88% and 75%) [121]. Also, a significant reduction in mural thickening was in response to the treatment [122, 123]. Florie et al. stated that wall thickness correlated well with clinical activity grade (r=0.47, P=0.003) and Van Hees activity index (r=0.41, P=0.007) [109]. Nonetheless, Punwani et al. reported a precise correlation between mural thickness on MRI and surgical specimens [103].

Typically, abnormal wall thickening in the acute inflammatory phase of CD measures >5 mm in thickness. Fat-suppressed balanced steady-state free precession imaging is best for evaluating wall thickness [102].

1.7.5.1.2. Enhancement of the bowel wall

Mural enhancement in active inflammation is significantly higher than in normal segments and is highly specific for detecting segmental involve-ment [121]. Studies comparing seginvolve-ments with active inflammation before and after treatment showed that the signal intensity decreases significantly after medical treatment [122, 123].

Florie et al. reported that the bowel wall's enhancement showed a significant correlation with the clinical grade (r=0.29, P=0.045), CDAI (r=0.31, P=0.033). The enhancement based on the dynamic series correlated significantly with the CDAI (r=0.38, P=0.016) [109]. Koh et al. results analyzing the ratio of the signal intensity of abnormal to normal bowel were higher in patients with active disease (P<0.05) and had a sensitivity and specificity (68% and 94%) [121]. Del Vescovo et al. have confirmed that the layered enhancement has a high sensitivity of 100%, specificity of 87% in detecting active inflammation [124]. There is evidence suggesting that bowel wall enhancement is the parameter that correlates with the degree of inflammation [103].

1.7.5.1.3. Patterns of enhancement

Normal enhancement of adjacent small bowel loops should be used as a reference when assessing abnormal mural enhancement [102].

Several mural enhancement patterns are described:

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– Mucosal enhancement may be the only sign of early active inflam-mation [103].

– Homogeneous mural enhancement is typical for the chronic or inactive disease [103]. The diffuse transmural enhancement pattern reflects the transmural nature of the CD [102].

– The absence of mucosal enhancement and weak, homogeneous enhancement in the rest layers is an indicator of inactive disease. [103].

Punwani et al. stated statistically significant differences between the different enhancement patterns and the histologic indexes of acute inflam-mation [126]. Segments with layered enhancement have a significant inflammatory component in the histologic analysis, while those with homogeneous enhancement lack acute inflammatory component [126].

1.7.5.1.4. Bowel wall hyperintensity on T2W images

In segments with wall thickening, edema is best evaluated by comparing the bowel wall between fat-suppressed and non-fat-suppressed T2W images. Both mural edema and fat will appear hyperintense on non-fat-suppressed T2W images. Whereas mural edema alone will persist as a hyperintense wall signal on fat-suppressed sequences, indicating active inflammation. Mural fat will lose signal on T2W fs images, suggesting chronic disease.

Several studies have shown the significant correlation between signal hyperintensity on T2W images of the affected loops and the presence of active inflammation [110, 126, 127], as well as significant differences between healthy individuals and patients with response to treatment [103].

1.7.5.1.5. Bowel wall ulceration

The deep and superficial ulcers are characteristic of active inflammation. When there is adequate luminal distention, we can observe aphthous ulcers on MR-EC. The aphthous ulcers are seen as a central focal area of high T2W signal surrounded by a mound of T2W intermediate signal [106]. Usually, they are not visualized on MRI [107, 114]. In this case, conventional endoscopy, capsule endoscopy, and barium imaging are superior to MRI for aphthous ulcers detection [115].

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Gourtsoyiannis et al. categorized the bowel wall thickness, lymph node enhancement, and intestinal ulcers as having the strongest correlation with active CD [129]. These findings were confirmed by Sinha et al. in a sizeable validated study of surgically excised bowel segments compared with MR-EC [102].

1.7.5.2. Extramural findings

1.7.5.2.1. The fibrofatty proliferation

The fibrofatty proliferation may appear in both active and inactive CD. The fat signal will be hypointense on T2W fs images due to a higher fibrous content in the inactive disease. In active CD, there is an increase in signal [130].

1.7.5.2.2. Mesenteric vascularity "comb" sign

Increased vascular engorgement can persist for a long time in patients with inactive or quiescent disease due to chronic mesenteric fibrosis [103, 116].

The comb sign has a high sensitivity to active disease detection but low specificity without statistical significance [117]. It has been suggested that increased vascular spills can persist for a long time in patients with inactive or transient disease due to chronic mesenteric fibrosis [93, 111].

1.7.5.2.3. Lymph nodes enhancement

Mesenteric lymph nodes moderate or intense contrast enhancement is highly suggestive of active CD. However, modest lymph node enhancement can also be seen in 50% of inactive disease [116]. Meanwhile, the regional lymph nodes' size shows a weak correlation with the degree of inflammatory activity [103, 131].

1.7.6. DWI for CD activity evaluation 1.7.6.1. Technical aspects of DWI

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the 180° refocusing pulse [134]. This approach quantifies the restriction of the motion of water molecules. The more free water molecules can move, the more signal attenuation there will be on DWI compared with the T2W sequence [135]. The b-value (also known as the diffusion coefficient; expressed in s/mm²) is proportional to these three factors and quantifies diffusion sensitivity. On DWI, applying small (e.g., 50–100 s/mm²) b-values water molecules with a large degree of motion will show signal attenuation. The slow-moving water molecules need higher (e.g., 500–1000 s/mm²) b-values [136].

Table 1.7.6.1.1. General features of conventional and diffusion-weighted MRI

sequences (Permission License Number 4860300020553) [136]

Principle High signal intensity Low signal intensity Conventional T1W spin-echo sequence Measuring spin-lattice relaxation with a short repetition and echo time

Fat and paramagnetic substances* Water content Conventional T2W spin-echo sequence Measuring spin-spin relaxation with a long repetition and echo time

Water content Fat

Diffusion-weighted sequence Measuring Brownian motion of water molecules

Water molecules with a small degree of motion or diffusion distance† and high cellular environment and integrity (e.g., cytotoxic edema, fibrosis, abscesses, and tumor)

Water molecules with a large degree of motion or diffusion distance† and low cellular environment and integrity (e.g., vascular tissue and necrosis)

*Dynamic contrast-enhanced imaging is based on a T1W spin-echo sequence with the administration of gadolinium contrast injection. †Higher b-values are needed to detect small degrees of motion or diffusion distances compared with large degrees of motion or diffusion distances.

1.7.6.2. DWI assessment

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automated process done by all commercially available MR scanners. Calculation of ADCs requires the application of at least two b-values, with the ADC map's accuracy increasing with the number of b-values [136].

Oto et al. were the first to evaluate DWI and ADC's role in detecting bowel inflammation and demonstrating increased signal and lower ADC values in inflamed segments [137]. This observation was confirmed by other studies [138], and the use of DWI in CD continues to develop [46, 132, 139]. Because of the increased use of DWI in the radiological assessment of disease activity, Kim et al. recently proposed a modifying MR-EC index, which replaces ulcers with DWI grade [140]. The similar correlation was obtained for CDEIS (r=0.737 and r=0.742, P=0.387, respectively) and did not differ in the ability to diagnose active (r=0.909 and r=0.903, P=0.571) or severe (r=0.907 and r=0.892, P=0.443) inflammation.

1.7.7. Crohn's disease activity indices 1.7.7.1. Lemann index

The Lemann index (LI) differs from other indices by assessing structural damage rather than the extent of disease activity and mucosal inflammation [25, 27]. The LI is a gut damage score. GI tract is divided into four parts for calculation the score: upper tract (esophagus, stomach, duodenum), small bowel (each segment is 20 cm), colon (cecum, ascending/transverse/descending, and sigmoid colon, rectum) and anus. All the sections are evaluated according to three parameters: surgical intervention, stricturing lesions, and penetrating lesions, which are being assessed by either endoscopy, colonoscopy, CT, or MRI and are graded between 0–3. LI significantly increased with disease durations of years <2 years, ≥2 years, <10 years, and ≥10 years corresponding to LI values of 6.3, 14.3, and 19.0, respectively (P<0.001).

1.7.7.2. MaRIA and mMaRIA

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WSI pre-gadolinium)/(WSI pre-gadolinium)] × 100 × [standard deviation (SD) noise pre-gadolinium/SD noise postgadolinium]. SD noise pre and postgadolinium is measured outside of the body before and after gadolinium injection, respectively.

The following formula calculates the segmental MaRIA score: 1.5 × wall thickness (mm) + 0.02 × RCE + 5 × edema + 10 × ulceration. The MaRIA score had a high (r=0.81, P<0.001) correlation with the CDEIS of the correspondent segment. A global MaRIA score is a sum of six bowel seg-ments. The significant correlation with CDEIS (r=0.78, P<0.001), HBI (r=0.56, P<0.001) and CRP (r=0.53, P<0.001) was assessed. Rimola and colleagues established cutoff points for disease severities [24].

Scardapane et al. obtained the same calculation as MaRIA, excluding the data related to RCE (0.02 × RCE), and modified the formula: 1.5 × wall thickness (mm) + 5 × edema + 10 × ulceration [142]. The index was called mMaRIA.

Recently Ordas et al. developed a simplified version of MaRIA (sMaRIA); instead of RCE, new item fat stranding was added [143, 144].

1.7.7.3. Clermont index

Buisson et al. developed the first index, which combines DWI and ADC measurements in the ileum using the MaRIA score as a reference standard [145]. The Clermont index was proposed by findings showing lower ADC values in acutely inflamed bowel tissue than in normal tissue [145]. ADC values and combined conventional MR-EC parameters derived by the MaRIA index (bowel wall thickness, edema, and ulceration) are used to calculate the score [146]. The calculation is performed by using the following formula:

−1.321 × ADC (mm2_{/s) + 1.646 × wall thickening +} + 8.306 × ulcers + 5.613 × edema + 5.039 [145].

Validation showed a high correlation of the Clermont index with the MaRIA score at the ileum and remission prediction after biological therapy [147–149]. The Clermont index also correlated with ileal CDEIS (r=0.63,

P<0.05) and ileal SES-CD (r=0.58, P<0.05) [150]. A score greater than 18.9

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assessment of DWI. Li X-H et al. [152] confirmed an increased accuracy of ADC values for the differentiation of inactive-mild CD and moderate-severe CD compared with conventional MRI parameters [153]. A study by Pendsé and colleagues [154] supported the use of qualitative grading of DWI signal to define the burden in CD, and quantitative ADC measurements had a poor discriminatory ability for segmental disease activity [136].

The Clermont score is highly correlated with the MaRIA (rho=0.99) in ileal CD. A Clermont score >8.4 was predictive of active ileal disease, which was defined as MaRIA ≥7, and a score ≥ of 12.5 was predictive of severe ileal disease (MaRIA ≥ 11).

Table 1.7.7.3.1. Magnetic resonance enterocolonography parameters used

for indices calculation (with permission) [155]

Score

MR-EC parameters Validated parts

of the GI tract Enhan cemen t Wall t hicknes s

Ulcers ADC Mur

al T2 W si gnal St en os is Ab scess

Fistula Jejunum Ile

um Co lon MaRIA      Clermont      Lemann index         

GI – gastrointestinal, MaRIA – Magnetic Resonance Index of Activity.

1.8. Crohn disease management

To effectively treat CD, the anatomic distribution, disease activity is essential factors to be considered [156].

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Treatment goals for CD that were initially based on symptom control using corticosteroids have been modified since immunomodulators' introduction (azathioprine, 6-mercaptopurine, and methotrexate), anti-TNF therapies (infliximab, adalimumab, and certolizumab pegol). The target of novel therapies integrin-adhesion molecule interaction-mediated leukocyte trafficking (vedolizumab) and interleukin-12/23 mediated T-cell activation (ustekinumab) was introduced into clinical practice [157–158]. The American Gastroenterological Association (AGA) and European Crohn's and Colitis Organisation (ECCO) suggests early recognition of disease severity and inflammatory burden to classify patients at moderate-to-high risk of disease progression [159]. The known risk factors: diagnosis at age less than 30 years (expected post-diagnosis life expectancy greater than 30– 40 years); extensive anatomic involvement; perianal and/or severe rectal disease; deep ulcers in the colon; prior surgical resection; and stricturing/penetrating disease phenotypes [160- 161]. In the moderate- to the high-risk patient, the AGA guidelines on medical therapy in CD suggest the use of a top-down approach with anti-TNF in combination with a thiopurine is the preferred treatment strategy, in the absence of contraindications [162].

A subgroup of individuals rapidly progresses to complicated disease behaviors (stricturing or penetrating disease, or both). These patients are in the high-risk group. Risk factors for CD progression include young age at the time of diagnosis, ileal disease location, serological response to specific microbial antigens, initial extensive bowel involvement, perianal/severe rectal disease, and presence of a penetrating or stenosis disease phenotype at diag-nosis [156].

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2. METHODS

2.1. Ethics

We performed a single-center study in the Radiology and Gastroente-rology Department at the Hospital of Lithuanian University of Health Sciences Kauno klinikos during 2013–2018.

The Kaunas Regional Ethics Committee approved the study for Biomedical Research No. BE-2-48 (21st of December, 2012). All patients have signed an informed consent form before inclusion.

2.2. Patient selection criteria 2.2.1. Inclusion criteria

1. Patients with suspected or established CD. 2. Patients 18 years and older.

3. No pacemakers, metal devices, prostheses, or foreign bodies in the patient's body.

4. The patients with no evidence of renal insufficiency (serum creati-nine lower than 130 mg/L).

5. Patient in whom complete MR-EC has been performed.

2.2.2. Exclusion criteria

1. Patients with a high BMI>30. 2. Patients with stomas.

3. Patients with perianal CD only. 4. Patients with ulcerative colitis.

5. Other pathology found on MR-EC: tumors, diverticulitis, adhesions.

6. Incomplete MR-EC investigation or with severe artifacts.

2.3. Study design

Our study included consecutive patients with suspected or already diagnosed CD who were referred for MR-EC.

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proce-dure. Endoscopy and histology were performed within 14 days before the MR-EC examination. The stool samples were collected for FC analysis (from 2014 years). The study flow chart is presented in Fig. 2.3.1.

Fig. 2.3.1. Flow chart of the study

Gastroenterologists had evaluated the patients who fulfilled Copenhagen Diagnostic Criteria for diagnosing CD (at least two of the criteria present) [44] and made the final diagnosis:

1. History of abdominal pain, weight loss, and/or diarrhea for more than three months.

2. Characteristic endoscopic findings of ulceration (aphthous lesions, snail track ulceration) or cobblestoning or radiological features of stricture or cobblestoning.

3. Histopathology consistent with Crohn's disease (epitheloid granulo-ma of Langerhans type or transmural discontinuous focal or patchy inflammation).

4. Fistula and/or abscess concerning affected bowel segments.

One hundred patients fulfilled the Copenhagen Diagnostic Criteria for CD (at least two of the criteria).

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2.3.1. Questionnaire survey data

All patients filled questionnaire forms: inflammatory bowel disease questionnaire (IBDQ), Crohn's Disease Activity Index (CDAI), Harvey-Bradshaw Index (HBI).

2.3.1.1. Inflammatory bowel disease questionnaire

IBDQ is a validated, disease-specific quality of life assessment instru-ment (Annex 3) [164]. This questionnaire includes four main problems that reflect the quality of life: bowel and systemic symptoms, emotional and social functions [164]. IBDQ questionnaire consists of 32 questions. In our study, patients were interviewed, and IBDQ results were calculated according to the survey's instructions. The response for each item was graded on a 7-point Likert scale, ranging from 1 (reflects "worst" condition) to 7 (reflects the "best" condition). The total IBDQ score varies between 32 and 224, and the higher score reflects a better quality of life [165].

2.3.1.2. Crohn's disease activity index

CDAI calculation is basedon symptoms: including the number of liquid stools, abdominal pain, general well-being, extraintestinal complications, usage of antidiarrhoeal drugs, abdominal mass, hematocrit, and body weight (Annex 1) [51]. The measured score varies from 0 to 600, and the higher score corresponds to more severe disease. Values below 150 suggest quiescent disease (remission), and values above 450 are associated with very severe disease [51]. Severe disease is thought to be above 300. However, some researchers have arbitrarily labeled CDAI scores of 150– 219 as mildly active disease and scores of 220–450 as a moderately active disease [52].

2.3.1.3. Harvey-Bradshaw Index

The HBI is a more simple index than CDAI. The index considers five clinical parameters only: general well-being, abdominal pain, number of daily liquid stools, abdominal mass, complications [166]. For each parameter, a specific score is assigned (Annex 2).

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2.3.2. Blood tests

Routine blood tests were performed. Normal values were established according to laboratory standards.

2.3.3. Faecal calprotectin

Patients have provided a stool sample within a week after the MR-EC examination, which was used for FC measurement.

FC was analyzed by a sandwich enzyme-linked immunosorbent assay (Calprotectin ELISA; Bühlmann Laboratories AG, Basel, Switzerland) (Fig.2.3.3.1) using a monoclonal capture antibody specific for calprotectin, according to the manufacturer's instructions.

The calprotectin's measurement range was between 0 and 300 µg/g, and samples were diluted to obtain calprotectin levels above the upper limit. Levels 0<50 µg/g were considered normal, >200 µg/g active process with inflammation.

Fig. 2.3.3.1. Quantum Blue® – Calprotectin reader

2.3.4. Endoscopy with histology

An experienced gastroenterologist performed the endoscopy to evaluate lesions in the colon and terminal ileum blinded to MR-EC results. To assess the severity and activity of endoscopic inflammation, CDEIS was calculated. Conventional colonoscopy was performed using standard equipment (Olympus, Tokyo, Japan). Suspicious inflammatory segments were recorded, and biopsy samples were collected. Also, the biopsy sample was collected from healthy-looking bowel segments.

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Table 2.3.4.1. Histopathology grading for endoscopic acute inflammation

score (eAIS)

Histological variable Grade

Erosion or ulceration 0=No, 1=Yes

Polymorphs in the lamina propria 0=No, 1=Yes

Cryptitis 0=No, 1=Yes

Crypt abscess formation 0=No, 1=Yes

Inflammatory exudates 0=No, 1=Yes

Granulomas 0=No, 1=Yes

2.3.5. Magnetic resonance enterocolonography protocol

The applied MR-EC protocol included bowel cleaning and pre-examination fasting overnight.

On the examination day, about the one-hour before the examination, each patient has received an orally 2.5% 1500–2000 mL solution of mannitol. Before starting the MR-EC examination and injection of contrast media, 20 mg/mL N-Butyl Scopolamine (Buscopan, Boehringer, Ingelheim, Germany) was injected intravenously, inhibiting bowel peristalsis. The imaging protocol consisted of the following sequences Table 2.3.5.1.

Table 2.3.5.1. Imaging sequences at 1.5T

Plane Slice thickness

(mm) FOV TR/TE (ms) Flip angle True-FISP Coronal 4 400 4.18/2.09 70 T2-HASTE Axial 5 360 1200/124 150

T2-HASTE fat saturation Axial 5 360 1200/124 150

T2-HASTE Coronal 5 440 1200/124 150

T1VIBE Coronal 1.8 400 2.93/1.36 10

T1VIBE Axial 3 420 4.49/2.16 10

DWI Axial 6 380 1500/74 –

True-FISP – Fast imaging with steady precession, HASTE – Half Fourier acquisition single-shot turbo spin-echo, VIBE – Volumetric interpolated breath-hold examination, DWI – diffusion-weighted imaging.

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All MR-EC scans were performed on 1.5 Tesla MRI unit (Siemens Healthcare GmbH, Erlangen, Germany) using the manufacturer's phased-array body coils in the prone position Table 2.3.5.2.

Table 2.3.5.2. The protocol of MR enterocolonography with gadolinium

injection for the detection and evaluation of suspected Crohn's disease

 Patient fasted overnight

 Oral administration of 1500–2000 mL of 2.5% of mannitol solution (60 min before MRI)

 Patient placed in the prone position in an MR scanner  Buscopan injection

 Axial and coronal T2W, T1W images

 Axial DWI (b values=50, 400 and 800 s/mm2)  Buscopan injection

 Axial and coronal T1W images with contrast media  Patient placed in the supine position in an MR scanner  Coronal T2W images

2.3.5.1. MR image interpretation

MR-EC images were evaluated on the picture archiving and communi-cation system (PACS, Syngo.via, Siemens Healthineers) workstation.

The bowel was divided into nine segments: jejunum, proximal ileum, terminal ileum, caecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum [169].

The jejunum is considered a segment I, assumed in the abdomen's left upper quadrant, bowel with a typical feathery fold pattern. The proximal and middle ileum represented segment II, located in the left lower quadrant. The terminal ileum – represented segment III as the 10 cm of ileum immediately proximal to the ileocaecal valve [112].

2.3.5.2. Evaluation of MR-EC parameters

The small bowel and colon each segment was evaluated for: 1. Mural wall thickness (≥3 mm estimated as a thickening).

2. Mural edema, T2W fs mural signal intensity was scored 0 (definitely normal), 1 (dark grey), 2 (light grey), or 3 (grey-white). 3. Mural contrast enhancement at 70 seconds after contrast admission

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4. Contrast enhancement pattern was also graded (normal, stratified pattern and homogeneous),

5. Inflammated segment length measured via electronic calipers, 6. Ulcers, phlegmon, fistulae or abscesses, lymph nodes ≥1 cm (short

axis diameter), comb sign also were evaluated.

7. Stenosis defined as luminal narrowing of more than 80% compared with unaffected adjacent bowel segments, and the diameter and length of stricturing parts were measured using electronic calipers. 8. On DWI, using a b value of 800 sec/mm2, the mural SI was graded.

We used 4-point scale: 0 (normal), 1 (probably normal), 2 (probably abnormal), 3 (abnormal).

9. ADC maps used for quantitative analysis of DWI data. Two regions of interest (ROI) were placed manually on the ADC map on the wall of the most abnormal bowel wall area and the other normal looking intestine wall segments without including the bowel content. The average ADC of these measurements for each patient was calculated.

2.3.5.3. Crohn's disease classification 2.3.5.3.1. Active inflammation

 Bowel wall edema increased the signal of the BW compared with normal BW evaluated on T2W sequences.

 Inflammatory stenosis associated with a segment of thick-walled bowel, high signal intensity on T2W images (Fig. 2.3.5.3.1.1).

Fig. 2.3.5.3.1.1. T2W HASTE (A), T2W HASTE (B) with fat suppression

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 Increased intensity of the segmental mural hyperenhancement compared with normal bowel wall appearance after intravenous contrast administration.

 Mural stratification visualization of two/ three layers within the BW ("target" or "double halo") appearance (Fig. 2.3.5.3.1.2).

Fig. 2.3.5.3.1.2. T1W with contrast media mural stratification

with hyperenhancement and superficial ulceration (arrow)

 "Comb sign" increased vascularity of the vasa recta supplying the small bowel or colon perpendicularly to the gut (Fig. 2.3.5.3.1.3).

Fig. 2.3.5.3.1.3. The coronal postcontrast T1W image shows

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 Lymphoid node enlargement of more than 5 mm measured in the shortest diameter.

Fig. 2.3.5.3.1.4. The coronal postcontrast T1W image shows

the "comb sign" (arrow)

 Deep transmural ulceration/fistulation – thin linear structures/protrusions with high signal intensity on T2W images surrounded by a zone of a lower signal intensity exceeding the mucosal layer and/or penetrating the thickened BW (Fig. 2.3.5.3.1.5, 2.3.5.3.1.6).

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Fig. 2.3.5.3.1.6. T2W HASTE images show abscess (long white arrows),

a fistula between intestine and abscess (grey arrow), thickened bowel walls (short white arrows)

2.3.5.3.2. Chronic inflammation

 Reparative changes: regenerative polyps, luminal narrowing, hete-rogeneous mild to moderate wall enhancement, fibrofatty prolife-ration, lymphadenopathy, low to moderate T2W signal intensity (Fig. 2.3.5.3.2.1).

Fig. 2.3.5.3.2.1. TRUFI coronal image is showing

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 Pseudodiverticula (Fig. 2.3.5.3.2.2) asymmetrical bowel fibrosis and shortening due to ulceration of the mesenteric side of the bowel.

Fig. 2.3.5.3.2.2. T2W HASTE with fat suppression long-standing

CD pseudodiverticula (omega sign) (arrow)

 Fibrotic stenosis – fixed narrowing, low to moderate T2W signal intensity, minor nonhomogeneous contrast enhancement without any edema/ surrounding mesenteric inflammation (Fig. 2.3.5.3.2.3).

Fig. 2.3.5.3.2.3. T2W HASTE with fat suppression significant stenosis

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2.3.5.4. Crohn's disease activity grading 2.3.5.4.1. Bowel damage assessment

Lemann index (LI) is an innovative tool based on imaging measuring an appropriate individual's cumulative digestive tract damage at the moment [170].

LI calculation also includes the esophagus, stomach, duodenum [171]. The whole digestive tract per segment is analyzed from mouth to anus. Each portion is graded for stricturing and penetrating lesions according to severity. Also, a history of organ resection is included [170].

Before starting the LI analysis, the gastrointestinal tract was divided into segments: small bowel 20 segments, colon/rectum six segments, anus one segment. We calculated bowel segments according to LI calculation instructtions. We used a Microsoft Excel (Microsoft Corporation, Redmond, WA, USA) – based calculator provided by the LI score creator group (Annex 4). LI was assessed basing on the following three visible features: stricturing lesions, penetrating lesions, and the history of surgery. For each element, grading from 0 (none) to 3 was performed [16] and 10 for each resected segment. LI ranging between 0 – was considered as "no bowel damage", and 140, – as "the most massive bowel damage" [27].

2.3.5.4.2. Crohn's disease activity evaluation

MaRIA is the first developed MRI index for grading disease activity and severity [172]. The reference standard for the MaRIA index was CDEIS [155].

MaRIA was calculated according to the formula by Rimola et al. [24]. MaRIA Global (MaRIA-G) was calculated as the sum of all segments of each patient. MaRIA (segment) = 1.5 × wall thickness (mm) + 0.02 × RCE + 5 × edema + 10 × ulceration. RCE is calculated according to the following formula: RCE = [(wall signal intensity (WSI) postgadolinium – WSI pre-gadolinium)/(WSI pre-gadolinium)] × 100 × (SD noise pre-gadolinium /SD noise postgadolinium) [24].

mMaRIA calculated according to the formula mMaRIA (segment) = 1.5 × wall thickness (mm) + 5 × edema + 10 × ulceration [142]. mMaRIA Global (mMaRIA-G) was calculated as the sum of all segments of each patient.

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2.4. Statistical analysis

Data analysis was performed using the program package SPSS 20.0 (Statistical Package for Social Sciences, SPSS Inc., USA) and Windows Excel (Microsoft Corporation, Redmond, WA, USA) programs.

Shapiro-Wilk test was used to check data normality. Having determined that we have no reason to reject the nil hypothesis of the normal distribution of the data analyzed, we continued to use standard methods for analyzing averages and dispersions of the normal distribution data. Otherwise, we used the non-parametric statistics criterion. For descriptive statistics, frequencies, means, medians, and standard deviations were calculated.

We compared the Student t criterion or the non-parametric Mann-Whitney U test between the two quantitative parameters. Comparing the quantitative parameters of more than two groups, we used a parametric analysis of dispersion ANOVA and non-parametric analysis of Kruskal-Wallis.

The Spearman rho was used to calculate the correlation. Correlation coefficients were interpreted accordingly: correlation was considered very weak if 0.0 < |R| < 0.2; weak, if 0.2 < |R| < 0.4; moderate, if 0.4 < |R| < 0.7; strong, if 0.7 < |R| < 0.9; and very strong, if 0.9 < |R| < 1.0 [173].

The chi-square (χ2) criterion was used to analyze qualitative data. Areas under the receiver operating characteristic (ROC) curve were calculated and points for the best specificity and sensitivity were established, positive predictive value (PPV), negative predictive value (NPV), and accuracy estimated. The susceptibility and specificity of the investigated features are computed according to the following formulas: Sensitivity = ca a +, Specificity = db d +, where: a – the number of positive cases; b – number of false-positive cases; c – the number of false-negative cases; d – the actual number of negative cases. P-values less than 0.05 were considered to be statistically significant.

The required minimum number of patients to get statistically reliable conclusions was calculated using the formula:

2 2 ) 1 (    z  n

VALUE OF MRI ENTEROCOLONOGRAPHY AND FAECAL CALPROTECTIN FOR DIAGNOSIS OF CROHN'S DISEASE

Vestina Strakšytė

VALUE OF MRI

ENTEROCOLONOGRAPHY AND

FAECAL CALPROTECTIN FOR

DIAGNOSIS OF CROHN'S DISEASE

Vestina Strakšytė

MRT ENTEROKOLONOGRAFIJOS IR

IŠMATŲ KALPROTEKTINO REIKŠMĖ

DIAGNOZUOJANT KRONO LIGĄ

CONTENTS

ABBREVIATIONS

INTRODUCTION

1. LITERATURE REVIEW

2. METHODS