Diverticular disease of the colon
The term diverticulum indicates an abnormal pouch opening from a hollow organ such as the colon. Literally, diverticulum means a wayside house of ill-repute. Diverticular disease is a problem associated with a Western lifestyle. The incidence increases with age and is more common in females. It is infrequent before the age of 40 years but increases thereafter so that at least half the population aged 80 years has diverticula present in the colon.
Diverticular disease of the colon comprises acquired mucosal herniations protruding through the circular muscle at sites weakened by entry blood vessels. The incidence appears to be related to the amount of intake of fibre in the diet. The over-refined and fibre-deficient diet of Western countries produces small, hard stools. As the faecal stream is more viscous by the time it reaches the sigmoid colon, hypersegmentation of the colon occurs to generate higher pressures to propel these stools. Diverticular disease is thus the result of increased intraluminal pressure within the colon.
Diverticula break through the circular muscle in four main sites, each relating to penetrating vasa recta (xref linkend="ch25-fig1" xrefstyle="select:title"/>). Characteristically, the diverticula are of the pulsion type and occur in two rows between the mesenteric and antimesenteric taeniae. Diverticula project into the appendices epiploicae and may not be apparent on external examination of the colon. In about 40% of cases, diverticula occur between the antimesenteric taeniae.
The sigmoid colon affected by diverticular disease appears shortened and thickened. The muscular abnormality is the most important and consistent feature. There is gross thickening of both the longitudinal and circular muscles of the colon, and progressive elastosis of the taeniae coli. This muscular abnormality often precedes the development of diverticulosis and occurs predominantly in the sigmoid colon. The muscle of the sigmoid colon and rectosigmoid is different from that of the more proximal colon, in that it is thicker and more prone to spasm. The colonic mucosa is pleated, with a saccular appearance. Narrowing of the lumen is due to muscular hypertrophy, redundant mucosal folds and pericolic fibrosis.
In classic situations, diverticula with associated muscular hypertrophy occur predominantly on the left side of the colon and are characterised by inflammation and perforative complications. There appears to be another kind of diverticular disease that is present throughout the entire colon without associated muscle abnormality. This latter group tends to occur in younger patients and may be due to a connective tissue abnormality that allows development of diverticula. Bleeding as a complication is more common in this atypical group. Rightsided diverticulitis with right-sided abdominal pain occurs almost exclusively in the Asian population but whether this is due to genetic or dietary factors remains undetermined.
Microscopically, diverticula have two coats, an inner mucosal and an outer serosal layer. An artery, vein or attenuated muscle may be present close to the neck of the diverticulum. Antimesenteric diverticula do not herniate fully through the circular muscle coat and have a thinned layer of circular muscle in their wall.
Most patients remain asymptomatic. The presence of diverticula is often referred to as diverticulosis. Of those with symptomatic diverticular disease, about 30% will develop troublesome complications that require an operation in their management. The disease tends to pursue a more aggressive course in the young. The likelihood of complications is unrelated to the number of diverticula present. Common complications are listed in Common complications of diverticular disease
Symptomatic diverticular disease
Common symptoms of symptomatic diverticular disease include left iliac fossa pain, which may be an ache or colicky in nature. Associated symptoms of flatulence, altered bowel habit (usually constipation) and nausea may occur. On examination, the sigmoid colon is often palpable, and on rectal examination the thickened sigmoid colon may be palpated in the pelvis. Rigid sigmoidoscopy will often be limited to the rectosigmoid junction, as the thickened muscular changes in the bowel wall will make advancement beyond that level difficult. Saint's triad, which refers to the association of diverticular disease, cholelithiasis and hiatus hernia (Saint's triad), has also been stressed. Differential diagnoses are listed in Differential diagnosis of symptomatic diverticular diseaseB
AIR-CONTRAST BARIUM ENEMA
Typical changes include colonic spasm, segmental ‘zigzag’ deformity of the sigmoid colon and multiple diverticula that rarely extend distal to the upper rectum. In chronic cases, the bowel lumen may become stenotic. In severe cases, radiological examination is often unsatisfactory. Cleansing of the bowel in preparation for air-contrast barium enema is often incomplete. Residual faecal debris may produce filling defects in the colon that cause concern about possible tumours. The presence of diverticula in an area of colonic narrowing favours the diagnosis of diverticular disease but in no way rules out the presence of a concomitant carcinoma (Double-contrast barium enema showing extensive diverticular disease, which is most severe in the sigmoid colon.).
COLONOSCOPY OR FLEXIBLE SIGMOIDOSCOPY
Colonoscopy or flexible sigmoidoscopy is most useful in differentiating diverticular disease from carcinoma (Colonoscopic views of sigmoid diverticular disease.). However, the area of colonic narrowing must be traversed and fully evaluated. The presence of colonic bleeding strongly suggests the presence of other concomitant lesions such as a carcinoma or polyp. Diverticula are often better appreciated on contrast enema than on flexible endoscopy.
DIET AND BULK-FORMING AGENTS
A high-fibre diet and ingestion of bran (20 to 30 g/day) are effective in producing a significant increase in stool weight, a decrease in transit time and a lower intraluminal pressure in the colon. Coarse bran is more effective than fine bran. Because a high-fibre diet is often unpalatable, the addition of bulk-forming agents such as psyllium derivatives is helpful. While the use of bran and bulking agents are helpful in controlling the symptoms of pain, there is no evidence that once the diverticula are formed dietary management will prevent the complications of diverticular disease.
Non-constipating analgesics should be used. Morphine should be avoided because it increases intracolonic pressure.
Antibiotics are not indicated in the absence of septic complications.
Anticholinergics are often prescribed because some symptomatic patients have hypermotility of the sigmoid colon. Their value, however, has never been proven.
Indications for operative treatment
Determining factors include the patient's age, general health, and the severity and frequency of the symptoms. Indications for surgery include:
- chronic symptoms despite the use of a high-fibre diet and bulk-forming agents
- recurrent acute diverticulitis
- persistent tender mass
- inability to distinguish colonic lesion from carcinoma (Table 30, “Features differentiating diverticular disease from carcinoma”).
|Pain||Colic or dull||Colic|
|Fever and leucocytosis||Common||Uncommon|
|Affected bowel||Longer segment, gradual transition, mucosa preserved||Shorter, abrupt, mucosa destroyed|
Elective operations for symptomatic diverticular disease are more commonly recommended in younger patients (<55 years), in those who are immunosuppressed (e.g. after renal transplantation) because of the morbidity of complications, and in patients with significant radiological abnormalities such as extravasation of contrast or a sigmoid stricture.
The timing of elective operation should ideally be about 8 weeks after the most recent attack of diverticulitis. Only the segment of colon affected by the inflammatory reaction to the diverticula needs to be removed. In general, this includes the entire sigmoid colon and the rectosigmoid junction. The distal margin of resection must extend below the level of muscular thickening and is usually in the upper rectum. The proximal extent of transection should include all induration palpable at the junction of the mesocolon with the colon itself and is usually in the descending colon. It is not usually necessary to resect the entire diverticula-bearing proximal colon. A primary colorectal anastomosis is generally utilised. In most cases, a laparoscopic approach is possible, rather than the conventional big incision.
Approximately 20% of patients with known diverticulosis will develop one or more bouts of diverticulitis. Among patients who require hospitalisation, 20% require an emergency operation. The primary pathogenesis is presumably related to obstruction at the neck of the diverticulum, giving rise to an inflammatory reaction in the pericolic tissues. In severe cases, an inflammatory phlegmon will form. Resolution may result in fibrosis. Progression of sepsis can result in perforation, which is often contained locally in the form of an abscess. Pericolic abscesses are usually walled off and, with repeated episodes, the colon may become ensheathed in fibrous tissue and adherent to surrounding structures. Less commonly, free perforation from the diverticulum or the pericolic abscess may ensue, resulting in pelvic or generalised peritonitis. Fistulisation to adjacent organs such as bladder, small bowel or vagina may occur.
Acute diverticulitis is associated with a constant and protracted pain in the left iliac fossa, with systemic symptoms and fever, leucocytosis and sometimes an abdominal mass. Alteration of bowel habit, with constipation or diarrhoea, may occur. If the inflammatory process involves the bladder, urinary symptoms may be present. In more severe cases, abdominal distension is also present, either secondary to ileus or to partial colonic obstruction. Rectal examination may reveal tenderness in the pelvis and a mass or pelvic collection may be felt. Use of rigid sigmoidoscopy is usually limited because of pain. Differential diagnoses are listed in Causes of small bowel obstruction.
Plain abdominal X-ray is rarely helpful because there are no specific features.
Computed tomography (CT) scanning provides good definition of the extraluminal extent of the disease and is particularly helpful in diagnosing complications such as abscesses and colovesical fistula. Percutaneous drainage of localised collection of pus can also be performed under CT guidance.
Ultrasound can provide information similar to a CT scan and can facilitate percutaneous drainage of a localised abscess. However, with the extent of gaseous dilatation of the bowel during acute diverticulitis, images from sonography may be limited.
Flexible sigmoidoscopy adds little useful information and risks perforating an acutely inflamed bowel. It may have a role if ischaemic colitis, Crohn's colitis or carcinoma is strongly suspected.
Air-contrast barium enema is generally contraindicated during the acute episode because instillation of the contrast may disrupt a well-contained sepsis. Contrast examination and flexible endoscopy are best deferred for 3 weeks after an acute episode has settled.
Patients can be managed with broad-spectrum antibiotics (ciprofloxacin and metronidazole; augmentin) for 7 days, as outpatients. Clear liquids by mouth should be taken for 2–3 days, followed by bland solid food as symptoms subside.
Patients need to be hospitalised for bowel rest with nil by mouth. Intravenous fluid replacement is provided. A nasogastric tube is used if there is evidence of significant ileus or bowel obstruction. In severe cases, intravenous antibiotics (e.g. cefotaxime and metronidazole) that cover Gram-negative organisms and anaerobes are prescribed. Pethidine is usually effective in providing analgesia. Morphine should be avoided because it increases intraluminal pressure.
The patient's symptoms should begin to subside within 48 hours. If resolution continues, further investigation with colonoscopy or contrast enema is performed 3 weeks later. If medical therapy should fail, further investigation with a CT scan may be necessary. Approximately one-fifth of patients with severe diverticulitis will require operation during the first hospital admission.
For patients with an initial uncomplicated attack of diverticulitis who have responded to medical therapy, 70% will have no recurrence. It is not clear whether the complication rate increases with subsequent attacks.
Indications for operative management include generalised peritonitis and failure of non-operative therapy after 3–5 days. The decision to intervene depends on the severity and extent of peritonism and systemic disturbance.
PERCUTANEOUS DRAINAGE OF DIVERTICULAR ABSCESSES
With a confined pericolic or pelvic abscess, CT- or ultrasound-guided percutaneous drainage is helpful (Computed tomography scan showing a localised abscess in the left pelvic region due to complicated diverticulitis.). The optimal timing for subsequent elective resection is probably after a period of 6 weeks.
The drainage catheter is kept patent by regular irrigation with normal saline and kept in place until drainage ceases and the abscess cavity is completely collapsed. Sinography is performed once or twice a week to assess shrinkage of the abscess cavity and closure of the fistula.
Hartmann's procedure (Hartmann's procedure.) has the advantage of removing the septic focus (i.e. phlegmonous or perforated sigmoid colon) and avoids an anastomosis in the presence of gross sepsis and faecal contamination. However, a second-stage operation is necessary after 4–6 months to re-establish intestinal continuity and entails a further laparotomy, bowel mobilisation and further resection, and colorectal anastomosis with all its attendant risks.
Hartmann's procedure has evolved as the treatment of choice for patients with purulent or faecal peritonitis. It is no longer the treatment of first choice in patients with an abscess, which should be treated primarily by percutaneous drainage.
RESECTION AND PRIMARY COLORECTAL ANASTOMOSIS
Resection and primary colorectal anastomosis has the advantage that the diseased segment is resected and the anastomosis is established. In most cases of severe acute diverticulitis a proximal diverting colostomy or ileostomy is used. Subsequent closure of the diverting stoma is easier than the second-stage reversal of Hartmann's procedure. However, it involves extensive dissection in the presence of intraperitoneal sepsis with the attendant risk of spreading the infective process. The diverting stoma is generally closed after 2–3 months. A limited gastrografin enema is performed prior to closure of the stoma to ensure healing and patency of the colorectal anastomosis.
With on-table large bowel irrigation, resection and primary colorectal anastomosis may be performed without a protecting proximal stoma. On-table colonic washout is performed to wash out the faecal residue in the otherwise unprepared colon. This manoeuvre is cumbersome and may contaminate the operative field. This surgical option should be considered only in highly selected situations where the sepsis is confined with minimal bowel distension and oedema.
TRANSVERSE COLOSTOMY AND DRAINAGE
This outdated three-stage procedure involves an initial diverting transverse loop colostomy and tube drainage of the septic area, a subsequent sigmoid resection and, finally, closure of the colostomy. The combined morbidity and mortality of the three stages of operations are high and the procedure is associated with long periods of hospitalisation.
Fistulas develop from localised perforations to which an adjacent viscus becomes adherent. Eventually the abscess or faeces drains through that viscus.
Most patients are male; presumably the uterus acts as a protective shield between the bladder and colon in females.Commonsymptoms are those of cystitis. There is usually a history of recurrent urinary tract infections that fail to respond to appropriate antibiotic therapy. Faecaluria is diagnostic. Pneumaturia that occurs at the end of voiding is strongly suggestive but gas-forming organisms in the bladder can simulate the condition. Bowel symptoms may be absent.
Flexible sigmoidoscopy will rule out inflammatory bowel disease and may identify the fistula and the presence of diverticula. Barium enema will show the diverticular disease but demonstrates the fistulous communication in only about 50% of cases. Cystoscopy may reveal cystitis and the fistulous opening. Cystograms may demonstrate the fistula in 30% of cases. A CT scan may be most useful because it defines the extent and degree of pericolic inflammation and may detect air in the bladder that is associated with a colovesical fistula.
Treatment involves separation of the sigmoid colon from the bladder, and sigmoid resection followed by a primary colorectal anastomosis. The opening in the bladder is often not obvious. If an opening in the bladder is seen, it is repaired. The omentum is interposed between the colorectal anastomosis and the bladder.
Other rarer forms of fistulas present with discharge of purulent fluid, flatus or faeces on the abdominal wall (colocutaneous fistula), via the vagina (colovaginal fistula) or with diarrhoea (coloenteric fistula).
Bleeding diverticular disease
Massive diverticular bleeding probably arises from injury to the vasa recta. The characteristic presentation is that of an otherwise well individual who suddenly passes a large amount of maroon-coloured stool. Bleeding stops spontaneously in about 70% of cases. Physical examination is usually unrevealing. Proctoscopy and rigid sigmoidoscopy are performed to exclude bleeding haemorrhoids. In addition, a neoplasm and inflammatory bowel disease of the rectum can be excluded.
Management of massive rectal bleeding is discussed in Chapter 61. Considerable difficulty exists in identifying the source and cause of the colonic bleeding. In patients with a minor degree of persistent rectal bleeding, the bleeding should not be attributed too readily to the diverticular disease. In many patients, there is a coexistent carcinoma or polyp of the colon. If diverticular disease is identified confidently as the source of recurrent colonic bleeding, segmental resection is recommended.
There is an association between Crohn's colitis and diverticulitis in elderly patients. Involvement of the diverticula by Crohn's disease may result in an increased incidence of diverticulitis. The clinical, radiological and endoscopic differentiation between the two entities is often difficult. The diagnosis is often made only after microscopic examination of the resected specimen. Presence of Crohn's disease should be suspected when there is anorectal disease or perirectal fistulas.
Immunosuppressed patients may not give a classic picture of diverticulitis but may present with complications in an unexpected fashion and with few signs. Sepsis is the major cause of the high morbidity and mortality in this group in whom the diagnosis is often delayed.
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