Per-Olof Nyström
Think about acute diverticulitis as a left-sided acute appendicitis which is, however, usually treated without an operation.
Diverticula of the colon are not “true” diverticula but herniations of the mucosa through a weak spot of the muscular bowel wall. They can occur in all parts of the colon but are most abundant in the sigmoid colon. The mucosa bulges out through the points of entry for the blood vessels, which transgress the bowel wall on each side, where the mesentery joins the bowel. It is thought that the pressure inside the sigmoid colon, which can be very high, causes expulsion of the mucosa. The smooth muscle of the affected sigmoid colon, unlike that of the rest of the colon and rectum, is often hypertrophied. This thickening is always located at the summit of the sigmoid loop and rarely extends for more than 15 cm. The diverticula mainly appear within this thickened segment of the sigmoid but are not restricted to it. The thickening may reach the rectosigmoid junction but never extends into the rectum proper (15 cm from anal verge). However, it is common to find diverticula extend- ing into the descending colon. Be aware that diverticulosis – the mere presence of sigmoid diverticula – is extremely prevalent in persons consuming a Western-type diet, while acute diverticulitis, inflammation of the diverticula-bearing segment of the colon, is relatively much rarer.
Surgical Pathology
A wide spectrum of pathological conditions is covered by the term “acute diverticulitis” – each correlating with a specific clinical scenario, which in turn necessitates selective management.
At operation for acute diverticulitis the sigmoid usually feels like a thick fusi- form tumor, with only a few diverticula. There are also cases of minor thickening with many diverticula, one of which has perforated and is the cause of the acute inflammation.Such observations make one think about the basic pathology of acute diverticulitis.B.C.Morson,the famous pathologist at St Mark’s,London,highlighted
* A comment by the Editors is found at the end of the chapter.
the hypertrophy of the bowel wall as the primary pathology and we are inclined to accept this, with the addition that the mesenteric fat tissue also plays a role. It is this fat that creeps up the bowel wall, becomes inflamed, produces the phlegmon or abscess, and heals with fibrosis. In our experience, many cases of acute diverticulitis might better be termed acute sigmoiditis – recognizing that it is an acute inflam- mation of the thickened bowel wall and mesentery. When it is a diverticulum that has been eroded by a fecalith, one finds a localized inflammation, which identifies the site of the perforation.In cases of free fecal peritonitis a perforated diverticulum is the cause although more often it has been walled off by the mesentery or epiploic appendices to produce a peri-colic abscess. Sometimes, the perforation occurs entirely within the mesentery,forming a mesenteric phlegmon or abscess.The latter may secondarily perforate into the free peritoneal cavity but usually this variety only gives rise to minor abdominal and systemic signs but can occasionally produce septicemia in a patient who is unable to contain and isolate the perforation.
There is a strong tendency for diverticulitis and sigmoiditis to adhere locally and fistulize. The formation of fistulas has an obscure mechanism as most patients with such a fistula present as non-emergency cases and often do not even give a history of previous attacks of acute diverticulitis. Most often the fistulas are into the bladder. The patient seeks attention for pneumaturia or persistent urinary tract infection. Fistulas can also communicate with the fallopian tubes, the uterus, small bowel or the skin. It is usually thought that the fistula is the sequel of an abscess but commonly there is no sign of an associated abscess; if there had been one it must have been silent or drained spontaneously via the fistulous tract.
Clinical Features, Diagnosis and Approach
It is clinically pragmatic to think about acute diverticulitis or sigmoiditis as a “left-sided acute appendicitis”. Unlike appendicitis, however, most episodes of acute diverticulitis are successfully managed without an operation. [As most episodes of acute appendicitis might be. See
>Chap. 28 – The Editors].
Practically, we find it convenient to think about the clinical scenarios of acute diverticulitis in order of increasing severity:
Simple-phlegmonous diverticulitis and COMPLICATED FORMS:
Peri-colic abscess
Free perforation with purulent peritonitis
Free perforation with fecal peritonitis
Phlegmonous Diverticulitis
Most patients admitted to the hospital with acute diverticulitis harbor a phleg- mon; they are still capable of mounting an anti-inflammatory response that quench- es the inflammation. Such patients are in good condition but suffer from acute pain and tenderness in the left lower quadrant and above the symphysis pubis. A mass may be felt on abdominal or rectal examination. There are signs of systemic in- flammation with fever,increased CRP (C-reactive protein) and leukocytosis with left shift.For this stage the diagnosis is clinical.The patient is treated conservatively and usually responds.
Conservative Treatment of Acute Diverticulitis
Traditionally patients with “mild” phlegmonous diverticulitis are admitted to the hospital; they are kept nil-per-mouth and on intravenous fluids.Wide spectrum antibiotics are given and continued until local and systemic inflammatory mani- festation subsides. The colon, however, contains feces and will contain feces even after a few days of starvation. So what is the rationale of the “traditional” regimen?
We contend that in the absence of an associated intestinal ileus you may feed your patient or at least provide him with oral fluids instead of the intravenous. The same is also true concerning antibiotics: a perfectly adequate “coverage”of anaerobic and aerobic colonic bacteria can be achieved using oral agents such as metronidazole and ciprofloxacin.So if intravenous therapy is not necessary – why admit the patient at all? And in fact mild acute diverticulitis can be managed with oral antibiotics on an outpatient basis.
Complicated Diverticulitis
In the minority of diverticulitis patients local and systemic signs of inflam- mation will persist or increase over the next couple of days. This is when you should start considering the presence of complicated forms of diverticulitis. Now it is time to order an abdominal CT (
>Chap. 5) to better define the pathological anatomy.
P. Ambrosetti in Geneva has devised criteria to grade acute diverticulitis on CT in a clinically meaningful way
1:
Simple attack: bowel wall thickness of more than 5 mm with signs of inflam- mation of the pericolic fat
Severe attack: In addition, abscess, extra-luminal gas or leakage of contrast
1
Ambrosetti P, Grossholz M, Becker C, Terrier F, Morel P (1997) Computed tomography
in acute left colonic diverticulitis. Br J Surg 84:532–534.
About half of the patients found on CT to have a “severe attack” required an operation during the current admission or subsequent to it. Significantly, however, half of such patients did not require an operation, suggesting that CT findings are to be used together with the clinical picture in tailoring the proper management.
Should you order a routine CT in all patients suspected of suffering from acute diverticulitis? This is surely unnecessary “overkill”as most patients respond to con- servative treatment. In addition, in many instances of clinically mild diverticulitis the CT is negative.
Approach to Complicated Diverticulitis
A small number of patients present from the start with diffuse peritonitis,with or without free intra-peritoneal gas on abdominal X-ray (
>Chaps. 3, 4 and 5). Here of course a CT scan may be a waste of time, which would be better used in the inten- sive care unit for preoperative preparation (
>Chap. 6). The final diagnosis will then be established at the operation. The same applies for patients who show signs of spreading peritonitis and increasing systemic inflammation accompanied by tachycardia, tachypnea, hypovolemia with oliguria, hypoxia or acidosis.
CT manifestations of a “severe attack” (e.g., extraluminal gas, leakage of contrast or abscess) in a patient who failed to resolve after a few days of antibiotics are not necessarily an immediate indication for an operation.Instead,in the absence of spreading abdominal signs, or systemic deterioration, even small (<5 cm) peri- colic abscesses usually resolve without an operation (probably spontaneously drain- ing back into the bowel). In such cases we would therefore advise the continuation of conservative treatment.
Larger pericolic abscesses (>5 cm) should be drained; this is best done percu- taneously under CT guidance. After successful drainage a “semi-elective” resection of the sigmoid is usually recommended. We do not know, however, whether this is absolutely necessary since an unknown percentage of such patients would probably never develop another attack of acute diverticulitis.
The Operation for Acute Diverticulitis
When you are “forced” to operate for acute diverticulitis the procedure of
choice is sigmoidectomy.It is usually best to open the abdomen with a lower midline
incision, which should extend above the umbilicus to allow access to the descend-
ing colon, and be extended further to reach the left flexure should it be necessary
to mobilize it. The inflamed sigmoid has frequently folded itself into the pelvis –
adherent to the left pelvic brim, and may rest against the bladder or uterus.At times
it will descend further into the pelvis between the rectum and bladder in the man, and behind the uterus and upper vagina in the woman, depending upon how deep the fossa is. The differential diagnosis of a perforated cancer easily comes to mind.
A clue is to remember that the inflammation is always at the summit of the sigmoid loop. The rectum and the rectosigmoid junction anterior to the promontory are always unaffected. It is usually possible to reach the anterior rectum from the right side of the pelvis to identify the folding of the sigmoid. Try not to use sharp dissec- tion in this inflammatory and adherent situation; using finger dissection is your best bet; gentle finger-pinching of the planes will separate the inflamed sigmoid from its attachments to the surrounding viscera.
This is not a cancer operation and your aim is simply to remove the sigmoid colon, which is the source of the problem. Staying near the bowel wall helps you to stay out of danger, away from the left ureter and ovarian and spermatic vessels, which may be part of the inflammatory mass. It is best to start dividing the mesen- tery away from the inflammatory process below and above the sigmoid.After divid- ing and clamping (or using a linear stapler) the sigmoid at both ends, the rest of the sigmoid mesentery is dealt with. It is prudent to suture-ligate vessels within the thick-edematous mesentery rather then use simple ligatures that may slip. Using a vascular cartridge in a linear stapler to control the mesentery is another, albeit more expensive, alternative. Remove any residual blood, pus or intestinal contents
(
>Chap. 12) and consider the next step. [The present author believes that the
inflamed mesentery of the sigmoid should be removed as well.]
To Anastomose or Not?
Should the two bowel ends be joined together or is a Hartmann procedure
with an end sigmoid colostomy to be preferred? An anastomosis is justified in the
majority of patients but there are a number of factors to consider.Localized perito-
nitis or an abscess is certainly not a contraindication to an anastomosis. General-
ized peritonitis is also not a contraindication in itself but the surgeon needs to give
it special consideration. Whether purulent or feculent the generalized peritonitis
signifies a greater insult to the patient as reflected by the corresponding APACHE II
score and the higher risk of dying (
>Chap. 6). Operative trauma adds to the post-
operative SIRS (systemic inflammatory response syndrome) and MODS (multi-
organ dysfunction syndrome) (
>Chap. 48). Most patients with generalized perito-
nitis due to perforated diverticulitis have an immunological defect that prevents
localization of the process. Typically, they suffer from chronic obstructive lung
disease or chronic arthritis with anti-inflammatory drugs or steroid dependence for
years. Occasionally they have received chemotherapy or are just recovering from
major surgery such as a coronary bypass. On the other hand it seems that patients
without such immunologic defects are capable of containing the inflammation and rarely have free peritonitis. Patients with free peritonitis will certainly not tolerate an anastomotic failure and it is therefore all the better if there is no need to worry about the integrity of an anastomosis during the postoperative course. Therefore, in such patients we choose a Hartmann’s procedure-sigmoidectomy, end-colostomy and closure of the rectal stump.
It is our impression that surgeons pay little attention to the consequences of the operative trauma added to the acute inflammation. We find surgeons blaming the unfavorable course of some of these patients on the diverticulitis and peritonitis, believing that residual infection is the problem.They should instead think about the operative trauma and postoperative SIRS. Consider this. If a sick patient is thrown out of the window (inadvertently of course) and the surgeon then blames the sub- sequent course on the original illness, we would all say it is a misconception of the situation. The height the patient falls is the operative trauma. The longer the opera- tion takes, the more dissection that is necessary and the more bleeding it causes, the greater the operative trauma. This metaphor encapsulates the modern concept of damage control (
>Chaps. 12 and 35) and surgeons need to have a firm understand- ing of when enough is enough.
Fecology
Reasonable amounts of feces in the colon are not a contraindication for an anastomosis.You can evacuate most of the fecal material from the left colon by milk- ing it into a dish.Occasionally,however,the colon may contain large amounts of fecal material because the sigmoiditis has caused a relative obstruction in the days preceding the acute attack. Massive fecal loading is a factor against an anastomosis.
To overcome this it has been proposed that on-table antegrade bowel irrigation (through the cecum or appendiceal stump) be added to clean the colon before the anastomosis.Unless such irrigation is common practice in your hospital,with all the equipment available, the irrigation will take at least half an hour and often much more to accomplish. The subsequent anastomosis will add another 20–30 minutes to the operation.If this is the case a stoma is quicker and gives better damage control.
In summary: consider an anastomosis in patients who are in reasonable health and without diffuse peritonitis. There should be no technical problems in making the anastomosis if the bowel ends are healthy and without tension. [How to do it?
Consult
>Chap. 13].
A Few Controversies
Some surgeons believe that the inflamed mesentery should be anatomically resected together with the sigmoid, claiming that it usually provides for a better source control and anastomosis, when there is no intervening mesentery left.
Although the sigmoiditis affects the apex of the sigmoid colon the mesentery is often shortened by the inflammation. The distal transection of the bowel should always be at the rectosigmoid junction because leaving a part of the distal sigmoid is the cause of recurrent diverticulitis. For these several reasons some think that it is often better to resect the sigmoid in much the same way as one does a resection for cancer.
Should the left flexure always be mobilized? No. This is indicated only in the minority of patients in whom the proximal colon fails to reach the rectum for a good anastomosis without tension, or in patients in whom the blood flow in the marginal artery is uncertain. Diverticula of the descending colon are common but we do not hesitate to anastomose diverticula-containing descending colon to the rectum.
Recurrent diverticulitis proximal to the sigmoid is extremely rare.
What should you do with phlegmonous diverticulitis, which is accidentally discovered during operation with no frank perforation or suppuration present?
Probably do nothing at all; just close-up and treat with antibiotics. Most such patients will never return.
Newer Concepts
There are reports of successful laparoscopic management with peritoneal lavage of perforated diverticulitis and generalized peritonitis, without resection of the involved bowel. All patients recovered uneventfully and were well during 12–24 months of follow-up. The concept that emerges is that the disease process can be reversed without a bowel resection,which can be postponed or not be performed at all. Larger experience is necessary to validate such an approach.
After the Attack
Most patients with acute diverticulitis respond to conservative therapy; it is
estimated that around one-fourth will experience a recurrence. Somewhat confus-
ingly this is variably interpreted as either confirming the need for elective surgery
or indicating that the majority of patients do not require an operation. A second
attack is probably an indication for an elective sigmoidectomy – this being parti-
cularly true in the younger patient.
Looking at the “whole picture” it appears that we operate too early in acute diverticulitis, perform too many CTs, carry out too many percutaneous drainage procedures, remove too many colons, raise too many colostomies, re-operate elec- tively on too many patients, and perform too few randomized controlled trials in order to know what is right and what is wrong.
Editorial Comment – Other Forms
Though sigmoid diverticulitis is so common in our daily practice other forms of diverticulitis should be kept in mind.
With the horrendous amount of junk food consumed by “western societies”
we see a growing number of younger patients with colonic pandiverticulosis extending from the rectosigmoid junction to the ileocecal valve. Not a few of these present with acute diverticulitis in the right or transverse colon, which may mimic acute cholecystitis or acute appendicitis. The key to diagnosis here is an abdominal CT scan finding a localized colonic phlegmon. This avoids unnecessary laparotomy and the temptation to proceed with colonic resection when the vast majority would respond to conservative treatment with antibiotics.
“Solitary” cecal diverticulitis. This is a different entity: young, mostly male, patients with one or two diverticula in the cecum – in the absence of diverticula distally. Once or twice a year you will see a patient presenting with what you think to be “classical” acute appendicitis but at operation you’ll find a cecal inflammatory mass or phlegmon of variable size. Free perforation and localized peritonitis are uncommon.On CT scan a good radiologist should be able to distinguish cecal diver- ticulitis from acute appendicitis; if this is the case, you can treat conservatively as these patients would respond to antibiotics – exactly like those with sigmoid diver- ticulitis. And, of course, recurrent cecal diverticulitis has been reported in con- servatively treated patients. Most patients, however, come to operation, either because CT is not done or its findings are mistaken as acute appendicitis. What to do at operation depends on the size of the process, ranging from diverticulectomy (place a liner stapler across the base of the diverticulum – including healthy cecal wall – and fire) to partial cecotomy (again, fire a stapler across and be careful not to narrow the ileo-cecal junction). Surgeons who are not aware of this condition or cannot recognize it are often carried away and perform right hemi-colectomy. But now you know that this is unnecessary. Surgeons who discover the process at laparoscopic appendectomy usually do not know what they see (one has to palpate it) and have to convert.
For the sake of “completeness”let us mention here that acute diverticulitis very
rarely affects patients with jeunal diverticulosis. These patients present with
systemic signs of inflammation as well as with local peritoneal signs in the center of
the abdomen. The key to diagnosis and to a trial of non operative management and treatment with antibiotics (usually successful) is a CT scan – showing an inflam- matory mass affecting a segment of the jejunum and its mesentery. If forced to operate, all you have to do is a segmental small bowel resection and anastomosis.
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