12.1 Rectal Atresia
12.1.1 Introduction
Rectal atresia is a rare type of anorectal malformation (ARM) constituting 1–2% of the ARM (Table 12.1).
However, an incidence of 14% was reported from the southern part of India at one stage [1]. The anomaly is no longer as common, even in that region. The male:female ratio is 7:3 [1]. In fact, because of its rar- ity, many pediatric surgeons have not had the chance to see and manage such cases. Rectal atresia is charac- terized by the presence of the proximal rectum, which ends at or above the pubococcygeal (PC) line, and a well-formed distal anus that is in its normal location and has a normal appearance, which is about 1–3 cm in depth. The two pouches may be connected to each other by a fibrous strand that may be hugged by the puborectalis sling. Unlike other ARM, the anal canal and lower rectum are well surrounded by the sphinc- ter complexes and hence the outcome after surgery is good.
Contents
12.1 Rectal Atresia . . . 223 12.1.1 Introduction . . . 223 12.1.2 Classification . . . 223 12.1.3 Embryogenesis . . . 224 12.1.4 Clinical Features . . . 224 12.1.5 Investigations . . . 224 12.1.6 Treatment . . . 224 12.2 Rectal Ectasia . . . 225 12.2.1 Classification . . . 225 12.2.2 Embryogenesis of Primary
Rectal Ectasia . . . 225 12.2.3 Pathophysiology . . . 226 12.2.4 Clinical Features . . . 226 12.2.5 Investigations . . . 227 12.2.6 Treatment . . . 228
12.2.6.1 Medical Management . . . 228 12.2.6.2 Surgical Treatment . . . 228 12.2.7 Summary . . . 229
References . . . 229
Table 12.1 Incidence of rectal atresia associated with anorec- tal malformations at the All India Institute of Medical Sciences, New Delhi (N = 820, 1995–2004)
Gender N
Male 6
Female 14
Total 20 (2.4%)
12.1.2 Classification
Rectal atresia has been classified as type IV using the Ladd-Gross classification, and as a separate high or intermediate variety using the International clas- sification of ARM and under the group of rarities by the Wingspread classification. Depending upon the distance between the proximal rectum and dis- tal anorectum, four grades have been described [1]:
grade 1 – rectal atresia with a short gap between each (most common), grade 2 – rectal atresia with a long gap, grade 3 – membranous septal type, and grade 4 – rectal stenosis. Grade 2 rectal atresias have not been found in clinical practice, even in areas with a very high incidence of this anomaly. Moreover, a few cases of double rectal atresia (multiple) have been reported recently [2–5]. There is neither a mesentery to the rectum nor a fistula described with this anomaly. In
12 Rectal Atresia and Rectal Ectasia
Devendra K. Gupta and Shilpa Sharma
Fig. 12.1 Revised classification of rectal atresia. Type I: rectal stenosis (rare); type II: rectal atresia with a septal defect; type III: rectal atresia with a fibrous cord between the two atretic ends (common); type IV: rectal atresia with a gap; type V: mul- tiple rectal atresia with stenosis (A), and multiple atresia (B;
only four cases reported)
view of this, the authors propose the modified clas- sification shown in Fig. 12.1, which incorporates all the various types seen.
12.1.3 Embryogenesis
The exact embryogenic process underlying this anom- aly is not known, but the following theories have been postulated.
1. Embryological theory: rectal atresia develops due to a vascular accident that occurs at a window in time between 13 and 14 weeks of gestation.
2. Genetic theory: there is high incidence of these anomalies among consanguinous marriages, es- pecially in South India. This supports the genetic association of the condition.
3. Infective theory: this theory was supported by Magnus [6] and she believed that intrauterine infection causing thrombosis of the vessels could lead to acquired atresia of the already formed rec- tum
Due to the pattern of geographic distribution noted with this anomaly, a racial or genetic defect may be much more important as the possible etio- logical factor.
12.1.4 Clinical Features
Rectal atresia presents in the newborn period with a history of nonpassage of meconium in spite of having an anal opening. The presentation is usually late as
the normal anus is present. Newborns present usually 3–5 days after birth with abdominal distension. Bil- ious vomiting may be associated in cases with delayed presentation. The condition may mimic and needs to be differentiated from long-segment Hirschsprung’s disease, intestinal atresia, colonic atresia, and meco- nium ileus. A forceful anal/rectal catheterization may easily perforate the bowel resulting in peritonitis and septicemia.
Physical examination reveals marked abdomi- nal distension with a normal-appearing anus and perineum. The diagnosis becomes evident when a rectal a thermometer, finger, or a red rubber catheter is passed and stops at about 1.5–3 cm depth from the anal verge. Associated anomalies, although rare, may be sacral, cardiac, or renal anomalies [7,8].
12.1.5 Investigations
A preoperative invertogram or prone crosstable view shows the rectal gas shadow stopping abruptly at or above the pubococcygeal (PC) line in spite having an anal opening. After the colostomy, a combination contrast procedure involving contrast medium in- stilled into the distal stoma and Hegar’s dilator (or the contrast medium) in the anus, not only confirms the diagnosis but also depicts the distance between the two ends (Fig. 12.2), which helps to plan the surgi- cal approach. A barium enema is usually performed to establish the diagnosis of microcolon; however, as a very high incidence of bowel perforation has been reported in cases with rectal atresia, the utmost care is needed to avoid injury to the bowel.
A computed tomography scan of the pelvis with contrast medium in the stoma and anus also helps to obtain anatomical details. Magnetic resonance imag- ing provides an excellent indication of the relation- ship between the two pouches and of sphincter com- plex integrity. Finally, a sigmoidoscopic examination of the distal colostomy stoma may be helpful to rule out proximal webs or obstructions.
12.1.6 Treatment
The initial treatment is sigmoid colostomy with sero- muscular biopsy to rule out Hirschsprung’s disease with no other additional manipulation. The next step would be to confirm the diagnosis and the gap between the two pouches. Many definitive surgical methods are described reflecting the nonstandard- ized options and difficulty faced in managing this
Fig. 12.2 Combined study with contrast from the colostomy and the anus, depicting the gap between two pouches
condition [8,9]. Most techniques are of historical sig- nificance [10–12] and are no longer adopted since the popularization of the posterior sagittal anorectoplasty (PSARP) approach.
The authors prefer and suggest the following ap- proach to manage babies with rectal atresia. A sig- moid colostomy in the newborn period is mandatory, except in cases with rectal stenosis, if they are able to decompress effectively. Rectal stenosis can be man- aged with anal dilatations in a gradual manner until the desired lumen is achieved. For a rectal septum or a membrane, the septum can be made to project at the verge, with a Hegar’s dilator passed from the sig- moid colostomy. The septum is held with stay sutures and divided under vision, and the edges can be su- tured. Postoperative dilatation is maintained to avoid stricture formation. For rectal atresia, an end-to-end anastomosis with PSARP gives satisfactory results.
The PSARP approach can also be used for patients presenting with multiple (type V) atresia. Only in rare instances, an additional abdominal approach may be needed for a pull-through procedure.
Fluoroscopic string placement followed by pro- gressive dilatation with Tucker’s dilators [13], abdom- inoperineal pull-through similar to Swenson’s opera- tion, and abdominoperineal endorectal pull-through after stripping the mucous membrane of the distal pouch have been described in the literature, but are not popular. Transanal end-to-end rectorectal anas- tomosis using an indigenously designed instrument, was described by Upadhyaya with a successful out- come [14,15]. Recently, a case has been described in- volving the antenatal repair of the defect diagnosed in conjunction with sacrococcygeal teratoma [16]. Post- operative dilatation is very important and should be continued for at least 3 months to achieve a normal lumen and function. The postoperative outcome is good as the anal sphincter complex is normally de- veloped and is usually not damaged by the surgical approach. The colostomy should be closed early so as to allow the feces to dilate the new passage.
12.2 Rectal Ectasia
Rectal ectasia is not uncommon in the field of pe- diatric coloproctology, either de novo or associated with ARM [17]. Rectal ectasia is defined as a state of massive dilatation of the rectum and sigmoid colon.
It may be primary (presenting at the time of birth) or secondary (developing later as a result of distal ob- struction or inadequate evacuation) [18].
Many confusing terminologies have been used in
the past to describe this entity. These include; bal- loon-like rectum, colonic inertia, megarectum, termi- nal fecal reservoir syndrome, pseudo-Hirschsprung’s disease and rectal inertia [19,20]. Congenital pouch colon, which was initially considered by some as a part of this entity, has now been universally accepted as a separate anomaly and is thus excluded from this chapter.
12.2.1 Classification
Rectal ectasia can be broadly classified into two types:
primary and secondary rectal ectasia. Primary rectal ectasia is congenital in origin, and is attributable to a mid-anal sphincter defect or a deficiency of the rectal musculature. This excludes cases of congenital pouch colon, which were previously included in this cat- egory. However, 2–5% of cases of ARM present with a congenital rectal ectasia that has a normal blood sup- ply, unlike that in congenital pouch colon. There is no known cause for primary rectal ectasia; however, if the patient is symptomatic and investigated further, the rectosigmoid region is found to be very capacious.
Secondary rectal ectasia, which develops after birth and is usually associated with distal obstruction sec- ondary to fecal impaction or surgery at the anorec- tum. Dilatation of the rectum will depend upon the degree and the duration of the obstruction.
Acquired ectasia develops after birth if the rectum or anus is partially obstructed or if the colon distal to a colostomy is cleansed inadequately, resulting in a bolus of desiccated meconium or a hard fecaloma.
The presence of a fecaloma in the rectum may initiate a vicious cycle and worsen the dilatation further.
12.2.2 Embryogenesis of Primary Rectal Ectasia
Many theories have been proposed to explain the de- velopment of primary rectal ectasia.
1. The cloaca is normally divided by the urorec- tal septum into urinary and rectal passages. The cloaca in babies with ARM may be initially more voluminous than normal before partition, with consequent oversized passage or passages after partition [18].
2. The rectum is normally modeled into two ampul-
lae, one in the midrectum and one in the region
of the future anal canal. The former becomes
the ampulla of the mature rectum and the latter
moulds into the anal canal. Primary rectal ectasia
that occurs in association with ARM may be an example of developmental overgrowth of the up- per or lower primitive ampullae or both [18].
3. The tail gut is an extension of the undivided clo- aca into the temporary tail of the human embryo.
It is initially quite voluminous, but becomes atro- phic and disappears before partition of the cloaca is complete. Incorporation and persistence of part of the tail gut into the rectum may result in ano- rectal ectasia [18].
4. It may be a variant of segmental dilatation of the intestine, which is a well-known cause of obstruc- tion [18].
5. Primary hypomotility of the distal rectum has also been proposed [21].
6. Weakness of the posterior rectal wall or a defect in the external anal sphincter has been suggested.
The authors have found a primary deficiency of the musculature of the posterior rectal wall and the external anal sphincter, resulting in rectal in- ertia followed by rectal ectasia. This is well appre- ciated on surgical dissection during the PSARP procedure. Approximation of the defect improves the clinical symptoms.
In 1984, Upadhyaya suggested a similar cause of mid-anal sphincteric defect as the possible cause of constipation in anterior perineal anus [22]. It may also be possible that not much attention has been given to this entity so far and many more cases may be diag- nosed in future. This possible cause also explains the clinically and radiologically evident posterior rectal shelf in a few cases of primary rectal ectasia.
12.2.3 Pathophysiology
It has been shown that the primary pathology in the causation of primary rectal ectasia is due to a defi- ciency in the smooth muscle causing weakening and dilatation of the rectal wall [17]. Secondary rectal ec- tasia develops due to the response to the obstructed rectum. The elasticity of the rectal wall permits the normal rectum to expand to approximately double the caliber, but it returns to its normal size. In the newborn, ectasia beyond this diameter is predictive of a primary developmental ectasia, which is made even more apparent when overdistended by gas and meconium content.
In the case of obstructive anorectal conditions, the rectal caliber soon reverts to normal dimensions after the relief of obstruction by surgery. If the rectal am- pulla is developmentally ectatic, the dilatation may
persist and lead postoperatively to fecal accumula- tion, further enlargement, troublesome constipation, and soiling.
With high rectal anomalies, the terminal bowel is frequently focally ectatic, and in many patients the ectasia is primary or developmental. In others, hy- pertrophy and dilatation may occur as reactions to propulsive activity against an obstruction or upon a retained meconium bolus in the terminus of the bowel after a defunctioning colostomy [23]. Primary and secondary rectal ectasia can be differentiated histologically by examining rectal specimens: hyper- trophy and hyperplasia of smooth muscle cells is evi- dent in acquired cases, and are normal or smaller in newborns with a primary or developmental anomaly.
Dysplastic nitrergic neurons in the rectum of a patient with rectal ectasia have also been demonstrated [24].
Bowel activity after anorectal reconstruction for high lesions is compatible with near-normal continence in many children. Even when the sphincter muscles are adequate for high-grade continence, the ectatic ter- minal reservoir may overload and overflow, requiring long-term treatment.
12.2.4 Clinical Features
The most common symptom is refractory constipa- tion, either primarily or persistent after successful re- constructive surgery for a known ARM. Rectal ectasia predisposes to ampullary overloading and constipa- tion. Patients usually present after 6 months of age, the most common period being around 1–3 years.
Paradoxical diarrhea occurs when peristalsis re- lentlessly pushes the column of feces against the pu- borectalis sling and levator diaphragm. These mus- cles fatigue, relax, and temporarily lose the important sphincter functions that control the entrance to the rectoanal canal. Soft feces are then massaged by peri- stalsis over the fecal masses to escape constantly from the anus (known as a “hold-back dyschesia cycle”
or “pseudoincontinence”), in spite of good surgery [21,23].
The clinical significance of the anomaly is two fold. First, following PSARP, the ectatic rectum may become a passive reservoir for feces, which accumu- lates and impacts; second, the large bulk of the walls of the intact wide rectum may impair the reconstruc- tion of the sphincter muscles at the time of the PSARP, thus lessening the ultimate degree of continence.
Paradoxical diarrhea and incontinence resulting from
anatomically defective sphincters may be differenti-
ated by rectal examination. Digital palpation of the
strongly contracting sphincters of the anal canal or satisfactory pressure profiles in the anal canal indi- cates that the leakage is more likely to be paradoxical.
The proximal ectatic bowel remains large and dilated even after a defunctioning colostomy.
In a study including adults who were diagnosed with rectal ectasia, it was noticed that all of the pa- tients were symptomatic since childhood, with the most common symptom being soiling and impaction [25].
On per rectal examination, ballooning of the pos- terior rectal shelf may be found, in which the finger in the rectum can be brought very close to the perineum with very little intervening tissue. Typically, the child presents with chronic constipation, straining at stool, and only able to pass small amounts of hard fecal mat- ter by rubbing the bottom against the floor/toilet seat.
12.2.5 Investigations
Anorectal ectasia may be established by digital ex- amination or barium enema studies, but it is unlikely that a distinction can be made between primary and secondary rectal ectasia unless there is a history of previous surgery, clinically evident anal stenosis, or a stricture. Contrast studies may delineate the di- lated rectum with or without a posterior rectal shelf (Fig. 12.3). Manometry will show normal rectoanal inhibitory reflex, unlike patients with Hirschsprung’s disease. Persisting ectasia in infancy can be demon- strated by distal cologram when associated with ARM (Fig. 12.4).
Differential diagnoses include habitual constipa- tion, ultrashort segment Hirschsprung’s disease, and pouch colon syndrome. Rectal punch or suction bi-
Fig. 12.3 A Contrast study delineating the posterior rectal shelf. B Persistence of the shelf on a defecogram
Fig. 12.4 Distal colostogram sug- gestive of rectal ectasia. This patient had an anorectal malformation with a long fistula opening in the bulbar urethra
opsy should be performed to rule out Hirschsprung’s disease in suspected cases. Congenital pouch colon needs to be differentiated from rectal ectasia on x-ray or cologram, which would show a large communica- tion with the bladder or the vestibule.
12.2.6 Treatment
12.2.6.1 Medical Management
The initial treatment is medical and depends upon the consistency of the stool, as judged by digital exami- nation. Fecoliths may need digital disimpaction and saline washouts with a large rectal tube and funnel, whereas semisolid or soft impactions can be liquefied by enemas and catheter irrigation or suppositories.
Evacuation of hard feces may entail daily washouts for several days, followed by less rigorous measures on a diminishing scale (i.e., bowel washouts, irrigations, or enemas three times per week for 3 weeks, twice per week for 2 weeks, and then once per week for sev- eral weeks depending on the response). Bulk-form- ing agents (fruits, fresh vegetables, husks) are added to the diet on a daily basis. Routine consumption of constipating agents (e.g., soft drinks, chocolates) is to be avoided. The child is trained to attend to the toi- let every day at a fixed time and spend enough time there until he is successful in evacuating the bowel by using his abdominal muscles. Medication in adequate amounts is needed to maintain a suitable stool con- sistency. While the rectal ectasia persists, relapses are prone to occur, necessitating vigilance on the part of parents and physicians, and repeating the local bowel toilet regimen. A minimum trial with medical man- agement of 6 months duration should be given under
continuous supervision before resorting to surgical options.
12.2.6.2 Surgical Treatment
The use of surgery depends on the primary pathology and is considered only if the medical management fails. The main principle of surgery is to excise or pli- cate the redundant bowel to prevent postoperative incontinence or constipation. Resection or tailoring of the ectatic segment should be an integral part of the primary reconstructive procedure if rectal ecta- sia is recognized perioperatively in association with anomalies like ARM or anal stenosis.
In selected cases with a prominent posterior shelf (suggesting the selective dilation of the posterior rec- tal wall), a rectal wall plication procedure would be therapeutic. Similarly, a midsphincteric defect, if de- tected on surgical dissection, can be repaired in lay- ers. Several investigators have described varying tech- niques for dealing with rectal ectasia:
1. Anterior resection [26]. This is a major procedure that would be indicated only for patients with a hugely dilated rectum, and is not amenable to evacuation and medical management. In this technique, excision of the dilated bowel is per- formed to leave a normal-sized bowel, which is anastomosed to the distal rectum at the peritoneal reflection (Fig. 12.5).
2. Endorectal pull-through [27]. Resection of the ab- normal bowel by an endorectal pull-through pro- cedure has been reported to give good to excellent results [20].
3. Swenson’s pull-through.
Fig. 12.5 Perioperative photograph showing the ectatic rectosigmoid segment filled due to fecal impaction (A), and with prominent but ineffective peristalsis (B)
4. Tailoring and tapering of the dilated segment of rectum via the PSARP route is also a preferred method with desirable results [28].
5. Duhamel’s pull-through has also been tried in few cases with good postoperative results [27].
6. Resection of the terminal bowel down to the den- tate line when associated with low ARM [19].
7. Plication of the dilated segment through the PSARP route. The author prefers this method as it is associated with lower morbidity, preserves the sphincter complex, leaves the pelvic nerve plexus undisturbed, strengthens the deficient rectal mus- cle, and has been found to produce good postop- erative results (Fig. 12.6).
12.2.7 Summary
Rectal ectasia is focal dilatation of the rectum due to either a primary muscle defect or a secondary re- sponse to an obstructive anorectal condition. Ectasia should be suspected in all patients with chronic con- stipation in association with ARM. Postoperative anal stricture after an otherwise good surgical repair of ARM may also result in rectal ectasia.
Barium studies of the posterior shelf require care- ful evaluation for midsphincteric and rectal wall de- fects. An effective medical therapy would be helpful in the majority of cases; however, surgery may be needed if the ectasia is too severe or present for too long, where the symptoms are not likely to improve with conservative medical management.
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