DIVERTICULAR DISEASE

DIVERTICULAR DISEASE
A diverticulum is an abnormal sac or pouch protruding from the wall of a hollow organ, which is, for the purposes of this discussion, the colon.
A true diverticulum is composed of all layers of the intestinal wall, whereas a false diverticulum, or pseudodiverticulum, lacks a portion of the normal bowel wall.
The diverticula that commonly occur in the human colon are protrusions of mucosa through the muscular layers of the intestine.
Because these mucosal herniations are devoid of the normal muscular layers, they are pseudodiverticula.

Diverticulosis or diverticular disease are terms used to indicate the presence of colonic diverticula. Diverticulosis is a common condition of Western society and seems to be an unfortunate product of the Industrial Revolution.
It is interesting that there seem to be no specimens of colonic diverticulosis in anatomic or medical museums in Europe that were archived before the Industrial Revolution.
The process of roller-milling wheat flour was introduced in Europe approximately a quarter of a century earlier than the appearance of diverticulosis, which was initially observed in the first decade of the 20th century.
It has been postulated that the decreased consumption of unprocessed cereals along with the increased consumption of sugar and meat by the general population are factors largely responsible for the appearance of diverticulosis.
Over the past 75 years the amount of fiber consumed by individuals in North America and Western Europe has decreased while the prevalence of diverticulosis has increased significantly.
The formation of diverticula is also related to aging.
Diverticula are rare in individuals younger than the age of 30 years,
but at least two thirds of Americans will have developed colonic diverticula by the age of 80.

Further evidence that a diet low in fiber and high in carbohydrates and meat contributes to the incidence of diverticulosis is the observation that diverticulosis is rare in sub-Saharan African blacks, who consume a high-fiber diet; however, blacks in Johannesburg who consume a low-fiber diet have the same incidence of diverticulosis as South African whites.

Pathogenesis
Diverticula are actually herniations of mucosa through the colon at sites of penetration of the muscular wall by arterioles.
These sites are on the mesenteric side of the antimesenteric teniae.
In some cases the arteriole penetrating the wall can be displaced over the dome of the diverticulum.
This close relationship between the artery and diverticulum is responsible for the massive hemorrhage that occasionally can complicate diverticulosis.
Vessel rupture is thought to be the result of ‘pressure erosion’. Associated diverticulitis or inflammation is usually absent.
It is interesting that when urgent angiography is carried out, most bleeding sites are at the hepatic flexure. The reason for this is not clear, but it has happened in every series.

There is often a striking hypertrophy of the muscular layers of the colonic wall associated with diverticulosis.
This thickening of the colonic wall, most commonly affecting the sigmoid colon, may precede the appearance of diverticula.
Diverticula most commonly affect the sigmoid colon and are confined to the sigmoid in about half of patients with diverticulosis.
Diverticula are invariably associated with thickening of the colonic smooth muscle.
This muscular thickening, termed myochosis, is believed to predate the appearance of diverticula.
The term ‘pre-diverticular state' has been used to describe myochosis without recognizable diverticula.

The next most common area involved is the descending colon (about 40% of affected individuals), and the entire colon will have diverticula in 5% to 10% of patients with diverticulosis.
Even in patients with diverticula involving the entire colon, the muscular thickening characteristic of the disease is usually confined to the sigmoid.

The sigmoid colon, the most common site of diverticula formation,
is also the segment of colon with the smallest luminal diameter.
If the colonic lumen contains a large volume of fiber, the contractile pressure required to propel the feces forward is low.
In such circumstances the colonic pressure in the sigmoid is only slightly above atmospheric pressure.
However, with the decreased amount of fiber typically provided by today’s typical dietary regimens, there is decreased colonic luminal content, requiring generation of increased colonic pressures to propel the feces forward.
Colonic pressures as high as 90 mm Hg can be generated by contraction of the narrow sigmoid colon.
These high intraluminal pressures are thought to be responsible for the herniations of mucosa through the anatomically weak points in the colonic wall.
Several studies have shown progressive changes in elastin and collagen in the colon with increasing age.
Abnormalities in elastin content have been reported in diverticular disease.
Reported associations with Marfan syndrome, Ehlers–Danlos syndrome, and polycystic renal disease support the concept of a connective tissue abnormality predisposing to the formation of diverticula.
Diverticulitis
Diverticulitis is the result of a perforation of a colonic diverticulum. The term is somewhat of a misnomer because the disease is actually an extraluminal pericolic infection caused by the extravasation of feces through the perforated diverticulum. Peridiverticulitis would actually be the term to more appropriately describe the infectious process. Recognition that the infection is actually caused by a perforation of the colon, an event that is often controlled by the body’s natural defenses, provides a basis for understanding the signs and symptoms of the disease as well as the rationale for determining appropriate diagnostic tests and treatment. The sigmoid colon is the segment of large bowel with the highest incidence of diverticula, and it is by far the most frequent site for involvement with diverticulitis.
· Patients with diverticulitis usually complain of left lower quadrant abdominal pain that may radiate to the suprapubic area, left groin, or back.
· Alteration in bowel habit is a very common complaint, and fever, chills, and urinary urgency are common.
· Acute diverticulitis affects the sigmoid or descending colon in at least 85 per cent of cases.
· The clinical features resemble ‘left-sided appendicitis'.
o Pain starts in the lower abdomen, tending to localize in the left iliac fossa.
· If the inflamed segment of colon is adjacent to the bladder, urinary symptoms occur.
o If the inflamed sigmoid is ‘flopped' over to the right side, the clinical presentation is difficult to distinguish from appendicitis.
· This is an infectious, inflammatory process, and rectal bleeding is not usually associated with an attack of diverticulitis.
· The physical findings are dependent on the site of perforation, the amount of contamination, and the presence or absence of secondary infection of adjacent organs.
· The most common physical finding is tenderness of the left lower abdomen.
· There may be voluntary guarding of the left abdominal musculature, and a tender mass in the left lower abdomen is suggestive of a phlegmon or abscess.
· Abdominal wall distention may be detected if there is associated ileus or small bowel obstruction secondary to the inflammatory process.
· A rectal or vaginal examination may reveal a tender fluctuant mass typical of a pelvic abscess.

Sigmoid diverticulitis should be distinguished from cancer of the rectosigmoid, although it is seldom necessary to establish the distinction on an emergency basis.
However, the surgical approach to diverticulitis is significantly different than that required for a perforated sigmoid cancer, and if urgent operation is indicated an effort should be taken to exclude the diagnosis of cancer.
A limited sigmoidoscopic examination may at times be helpful in such circumstances.
However, air should not be insufflated through the endoscope because of distention of the colon and the possibility that increased colonic pressure could force more bacteria through the perforation into the peritoneal cavity.
The sigmoidoscope can seldom be advanced beyond 12 cm in a patient with diverticulitis, and the examination is usually only useful to exclude a cancer of the rectum as a cause of the symptoms .
The diagnosis of diverticulitis can often be presumed with a fair degree of reliability by a careful history and physical examination, and it is reasonable to begin treatment with antibiotics on this evidence alone. However, if the diagnosis is in doubt, four diagnostic tests can be considered: computed tomography (CT) of the abdomen, magnetic resonance imaging (MRI), abdominal ultrasound, and water-soluble contrast enema. The CT and MRI provide essentially the same information and advantages. There has been more experience with CT, and this is considered by most surgeons to be the preferred test to confirm the suspected diagnosis of diverticulitis. It reliably reveals the location of the infection, the extent of the inflammatory process, the presence and location of an abscess, and the sympathetic involvement of other organs, with secondary complications such as ureteral obstruction or a fistula to the bladder. In addition, an abscess detected by CT may often be drained by a percutaneous approach with the aid of CT guidance.
Ultrasound of the abdomen offers many of the advantages of CT, including the possibility of percutaneous drainage of an abscess with ultrasound guidance. The selection between CT, MRI, and ultrasound examinations varies considerably among institutions, but all have been shown to be useful in establishing the diagnosis of diverticulitis, especially when an abscess has complicated the disease. The use of a contrast enema in the evaluation of a patient suspected of having diverticulitis has diminished considerably because of the advantages offered by the noninvasive tests described earlier. An enema carries the risk of increasing the colonic pressure and causing further extravasation of feces through the perforated diverticulum. Some studies have shown an advantage of the contrast enema in distinguishing acute diverticulitis from perforated cancer, but many surgeons feel the risk associated with a contrast enema outweighs the potential gain. If a contrast enema is used, the contrast agent should be water soluble. Water-soluble contrast enemas do not carry the risk of barium-fecal peritonitis, but there is still a considerable risk of extravasation of contrast material from the colon that may aggravate the infection and spread the extent of the peritonitis.
Recently, contrast CT has become the investigation of choice in the acute assessment of patients with suspected acute diverticulitis.
Localized thickening of the colonic wall (over 4 mm) in association with diverticula and inflammation of adjacent pericolic fat and mesentery support the diagnosis (Fig. 6).
CT has the advantage over water-soluble contrast enema of more accurately assessing complications such as abscess
Diverticulitis obviously presents in a variety of ways with a broad spectrum of severity, from a single episode of mild self-limited disease to repeated pisodes that respond to antibiotics to fulminant complicated disease characterized by life-threatening sepsis. Hinchey and colleagues[43] have described practical classification system that provides some organization of the broad clinical spectrum of the disease:
Stage I: Pericolic or mesenteric abscess
Stage II: Walled-off pelvic abscess
Stage III: Generalized purulent peritonitis
Stage IV: Generalized fecal peritonitis
Appropriate treatment obviously must be individualized based on the severity of the disease.
Uncomplicated Diverticulitis
Uncomplicated diverticulitis (disease not associated with free intraperitoneal perforation, fistula formation, or obstruction) can often be treated with antibiotics on an outpatient basis. If the patient has significant pain characteristic of localized peritonitis, hospitalization and intravenous antibiotics are indicated. The use of morphine should be avoided because of the increased intracolonic pressure associated with that drug; meperidine has been reported to decrease intraluminal pressure and is a more appropriate analgesic. Patients with uncomplicated diverticulitis usually respond promptly to antibiotic treatment, with marked improvement in symptoms within 48 hours. After the symptoms have subsided for at least 3 weeks, investigative studies should be conducted to establish the presence of diverticula and to exclude cancer, which can mimic diverticulitis. The preferred test is a colonoscopic examination, which can directly visualize the colonic lumen even in the presence of numerous diverticula. A barium enema can demonstrate the extent of the diverticular disease, but a sigmoid cancer may be hidden by the numerous contrast-filled diverticula of the sigmoid colon, a fact that considerably diminishes the value of the contrast enema in the evaluation of the patient with diverticulosis. A first attack of uncomplicated diverticulitis that responds to antibiotic therapy is generally treated nonoperatively, with the introduction of a high-fiber diet. The chances of a second attack of diverticulitis are relatively low, less than 25%. The management of patients younger than 45 years of age affected by an attack of uncomplicated diverticulitis is somewhat controversial. Many surgeons have recommended an elective sigmoidectomy after recovery in young patients because the natural history of diverticulitis in the young is not well understood and there may be a high risk of recurrence of the disease over the expected long life span. However, Vignati and coworkers studied 40 patients younger than 50 years of age who were hospitalized with diverticulitis and followed for up to 9 years.[44] Two thirds of these patients did not equire surgery during the follow-up period. These results are similar to the expectations for patients older than the age of 50, and the authors concluded that younger patients should be treated in the same manner as patients whose first attack of diverticulitis occurs after the age of 50. If a patient suffers recurrent attacks of iverticulitis, surgical treatment should be considered. The chance of a third episode after a second bout of iverticulitis is greater than 50%, and the risk increases with each subsequent attack. Each uncomplicated attack of diverticulitis is treated with antibiotics to allow resolution of the acute infection. After the inflammation has resolved, usually 4 to 6 weeks after the episode, elective resection of the involved colon should be done. Diverticulitis in the immunocompromised host represents a special challenge for the surgeon. We believe that elective sigmoidectomy after a single attack of diverticulitis should be considered in such patients because of their diminished ability to combat an infectious insult. There is some suggestion that medical therapy is less effective in these patients, resulting in an increased incidence of emergent surgery. Unfortunately, mortality rates after surgery are higher when compared with patients whose immune system is not compromised.
A growing trend in elective surgery for diverticular disease has been the utilization of a laparoscopic approach. Most studies reveal a hospital length of stay 2 to 3 days shorter for patients undergoing sigmoidectomy by a laparoscopic approach when compared with patients receiving a standard midline incision. A hand-assisted laparoscopic procedure has been advocated by some surgeons, who believe this technique facilitates the division of fused tissue planes and the blunt disruption of fistula tracts.
Complicated Diverticulitis
Abscess
· As discussed earlier, an abscess complicating diverticulitis is usually confined to the pelvis.
· Usually patients with pelvic abscesses caused by diverticulitis have significant pain, fever, and leukocytosis.
· The abdominal, pelvic, or rectal examinations may detect a tender, fluctuant mass, and CT, MRI, or ultrasound will confirm the diagnosis and location of the abscess.
· Unless the abscess is quite small (less than 2 cm in diameter) it should be drained, and the preferred method of drainage is by a percutaneous route guided by CT or ultrasound.
· Occasionally, a pelvic abscess can be drained into the rectum through a transanal approach.
· These methods of drainage are highly preferable to a transabdominal approach by laparotomy, which risks spreading the contents of the abscess throughout the peritoneal cavity.
· Adequate drainage of the abscess, accompanied by administration of intravenous antibiotics, usually results in a rapid clinical improvement.
· Although a fistula may result from the sigmoid colon to the insertion site of the percutaneous catheter that provided drainage, this can be easily handled at the time of elective surgery when the intense intra-abdominal infection has subsided.

Elective surgery should be offered after the patient has completely recovered from the infection, usually about 6 weeks following the drainage of the abscess.
· At that time it is usually feasible to excise the diseased sigmoid colon and fashion an anastomosis between the descending colon and rectum, thus avoiding a colostomy.
· It is essential to remove all of the colon that is abnormally thickened and to incorporate rectum that is not inflamed or thickened into the distal component of the anastomosis.
· A major cause of recurrent diverticulitis after sigmoidectomy is failure to completely remove the entire abnormally thickened bowel that is associated with this disease.
· If the distal sigmoid colon is not resected, the rate of recurrent diverticulitis is unnecessarily elevated.
· Benn and colleagues found the rate of recurrent diverticulitis to be 12% if the distal sigmoid was not resected, compared with 6% if the anastomosis was to the top of the rectum.[45]
· It is seldom necessary to mobilize the rectum farther than 2 cm below the sacral promontory to obtain normal bowel for a satisfactory anastomosis.
· Although diverticula may be present throughout the colon, it is not necessary to excise the entire colon in such circumstances; only the colon that is thickened and brittle (usually the entire sigmoid) need be resected.

A fistula between the sigmoid colon and the skin (which may result from percutaneous drainage of an abscess), bladder, vagina, or small bowel is a relatively frequent complication of diverticulitis.
· Such a fistula commonly forms when an abscess is either drained or involves an adjacent organ or the skin.
· The source of the infection (the perforated diverticulum) continues to supply the fistula, and cure will not be achieved until the source is eradicated by excising the diseased sigmoid colon.

Diverticulitis is a more common cause of a fistula between the colon and bladder than is Crohn’s disease or cancer.
· Sigmoid vesical fistulas are more common in men than women, because the uterus prevents the sigmoid from adhering to the bladder in women.
· Women with sigmoid fistulas have usually had a prior hysterectomy.
· Symptoms of a sigmoid-vesical fistula include pneumaturia (with the passage of air from the urethra classically noted at the end of micturition), fecaluria, and recurring urinary tract infections.
· The fistula may cause significant urosepsis in men, with prostatic hypertrophy causing a relative obstruction of the distal urinary tract.
· The most reliable test to confirm the suspicion of a fistula between the intestine and the bladder is CT, which may demonstrate air in the bladder.
· A barium enema will fail to reveal a fistula half of the time, and an intravenous pyelogram is even less accurate.
· Cystoscopy usually reveals cystitis and bullous edema at the site of the fistula, but the test is helpful to exclude cancer (colon or bladder) as the cause of the fistula.
· Initial treatment of any fistula caused by diverticulitis is to control the infection and reduce the associated inflammation.

A fistula arising from the colon is rarely a cause for emergency surgery; in fact, the patient’s condition is often improved when the drainage of an abscess results in the formation of a fistula.
· Antibiotics should be administered to reduce the adjacent cellulitis, and diagnostic steps should be taken to confirm the cause of the fistula before a definitive operation is undertaken.
· A colonoscopy should be done to examine the sigmoid mucosa and exclude colon cancer (or Crohn’s disease) as the cause of the fistula.
· Every effort should be made to rule out cancer, because the operation for a sigmoid-vesical fistula secondary to sigmoid cancer requires enbloc excision of the involved organs, a more extensive operation than is required to interrupt the nonmalignant fistula and excise the diseased (but benign) sigmoid colon.

Fistulas caused by diverticulitis can usually be treated by a one-stage operation, taking down the fistula and excising the sigmoid colon, then fashioning an anastomosis between the descending colon and the rectum.
· The secondary organs involved (usually the bladder) will heal once the source of the infection, the sigmoid colon, is removed.
· The bladder defect is usually so small that no closure is necessary, and healing will occur if the bladder is drained with a Foley catheter or suprapubic cystostomy for 7 days after the operation.
· Larger bladder openings may require suture closure with absorbable (chromic) sutures combined with drainage.
· If there is significant inflammation in the abdomen and pelvis, despite a “cooling off” period, the use of ureteral stents placed preoperatively can facilitate identification of the ureters and minimize inadvertent ureteral injury.
· A technique of early identification of the ureter and proximal to distal dissection of the sigmoid colon facilitates the resection when a phlegmon caused by diverticulitis obliterates the normal anatomy.

Colovaginal
This usually presents with an obvious faeculent vaginal discharge.
It occurs more commonly in women who have had a hysterectomy.
The fistula is usually demonstrated by barium enema, although occasionally a contrast study per vagina is diagnostic.
Fistulation into the uterus or fallopian tubes is rare.
Enterocolic
A fistula into the small bowel usually presents with diarrhoea due to large-volume small-bowel contents passing directly into the colon.
The degree of symptoms will depend on the level of small bowel (and colon) affected.
The diagnosis is made by contrast radiology, either a small-bowel or a barium enema.

Colocutaneous
This usually starts as a subcutaneous abscess, which once drained (either surgically or spontaneously) drains faecal material (Fig. 11).
Alternatively, a colocutaneous fistula may develop spontaneously at the site of a previous surgical scar or drain site.

Colonic stricture
Repeated episodes of mild diverticulitis may result in progressive fibrosis and narrowing of the affected segment.
This may present gradually with a change in bowel habit, crampy abdominal pain, and distension.
Alternating constipation and diarrhoea is characteristic of a sigmoid stricture.
The major differential diagnosis is of colonic malignancy.
A stricture is usually identified by barium enema or colonoscopy.
Radiologically, a diverticular stricture has a tapered appearance, without the shouldered ends suggestive of malignancy.
Colonoscopically, diverticular strictures appear as a narrowed segment without obvious mucosal irregularity.
Malignancy is difficult to rule out entirely.
Multiple biopsies and brushings for cytology are helpful.

Alternatively a diverticular stricture may present as an emergency with complete large-bowel obstruction.
A water-soluble contrast enema is important to confirm complete mechanical obstruction and rule out pseudo-obstruction.
Differentiation between diverticular and malignant large-bowel obstruction may, however, be difficult before resection.

Retroperitoneal perforation
Occasionally, sepsis from acute diverticulitis spreads posteriorly into the retroperitoneal tissues.
The patient may have features of diverticulitis plus back or loin pain.
Retroperitoneal sepsis may spread inferiorly, for example along the psoas muscle, presenting as an inflamed area or abscess in the groin.
Sometimes the retroperitoneal features may overshadow the abdominal signs and symptoms.
Tenderness, redness or swelling in these areas, in the context of a patient with possible diverticulitis, should alert the clinician to the possibility of retroperitoneal sepsis.
Pain on hyperextension of the hip suggests inflammation in the region of the psoas muscle.
Radiologically, gas may be seen in the soft tissues of the retroperitoneum on plain abdominal radiographs.
The diagnosis is usually confirmed by CT.

Generalized Peritonitis
Generalized peritonitis caused by diverticulitis can be caused in two ways:
(1) a diverticulum may perforate into the peritoneal cavity and the perforation is not sealed by the body’s normal defenses or
(2) an abscess that is initially localized expands and suddenly bursts into the unprotected peritoneal cavity.
· In the former instance the peritoneal cavity is contaminated with feces;
· in the latter, contamination is from pus containing enteric bacteria.
In either situation, the result is an overwhelming infection that requires immediate operative intervention.
· Fortunately, both of these circumstances are relatively rare.
· Patients with generalized peritonitis caused by a perforated diverticulum exhibit diffuse abdominal tenderness, with voluntary and involuntary guarding over the entire abdomen.
· Abdominal radiographs or CT scans may reveal intraperitoneal free air, but the absence of extraintestinal air does not exclude the diagnosis.
· Signs of generalized sepsis include an elevated white blood cell count, fever, tachycardia, and hypotension.
· Immediate celiotomy is mandatory to identify and excise the segment of colon containing the perforation.
· Under such circumstances it is not safe to restore intestinal continuity because of the high likelihood that an intestinal anastomosis will not heal when fashioned in such a hostile infectious environment.
· The proper operation in this situation is to resect the diseased sigmoid colon, construct a colostomy using noninflamed descending colon, and suture the divided end of the rectum closed.
· This procedure is called Hartmann’s operation, after Henri Hartmann, the French surgeon who described this technique in 1921.
· Hartmann’s operation, although initially described for the treatment of cancer, is the most common technique for emergency operations required for control of infection secondary to diverticulitis.
· Eliminating the source of infection by excising the perforated sigmoid colon, establishing diversion of the feces with a colostomy, and controlling the peritoneal infection by irrigating the peritoneal cavity and administering intravenous antibiotics, along with appropriate generalized and nutritional support, should result in resolution of the infection.
· When the patient has recovered completely from the illness, usually after a period of at least 10 weeks, taking down the colostomy and fashioning an anastomosis between the descending colon and the rectum will restore intestinal continuity.
Treatment
Diverticulosis
Patients with diverticulosis are advised to take to a high-fibre diet,
although evidence from randomized, controlled trials that this reduces the risk of diverticulitis is lacking.
Several uncontrolled studies and one small, randomized, controlled trial by Brodribb suggest that a high-fibre diet reduces symptoms in patients with symptomatic diverticular disease.
One recent, multicentre, randomized, controlled trial has suggested significant benefit from the poorly absorbed antibiotic rifaximin in symptomatic diverticular disease, although further studies are needed to substantiate this.

A recent prospective study of over 47 000 American men aged 40 to 75–years, without known colonic disease, suggested that increased physical activity (in addition to a high-fibre diet) protects against the development of symptomatic diverticular disease.

Anticholinergic drugs, such as propantheline bromide (15 mg three times a day), and spasmolytic agents, such as mebeverine hydrochloride (135 mg three times a day), are commonly prescribed for symptomatic diverticulosis, although their efficacy is unproved.

Acute, uncomplicated diverticulitis
Acute diverticulitis should be treated by bowel rest and antibiotics.
Outpatient treatment with clear fluids and antibiotics orally is appropriate for patients with mild disease.
Patients with more severe disease or significant comorbidity require inpatient treatment with intravenous fluids and antibiotics.
Antibiotics with adequate Gram-negative and anaerobic cover are required.
Cefuroxime (750 mg three times a day) and metronidazole (500 mg three times a day) is a frequently used combination.

Early confirmation of the diagnosis by CT (as discussed above) is helpful in the management of these patients.
The vast majority with uncomplicated acute diverticulitis will settle with conservative treatment.
Once the acute episode has settled, usually 4 to 6 weeks later, it is important to visualize the colon by colonoscopy or barium enema to rule out a coexisting neoplasm.
Subsequent treatment is with a high-fibre diet, which may reduce the risk of further acute episodes.
Surgery is required occasionally when the acute episode fails to respond to conservative treatment and should be considered after recurrent episodes of acute diverticulitis (see below).

Acute diverticulitis with localized abscess (Hinchey 1 and 2)
All patients should be treated with intravenous fluids, appropriate antibiotics, and general supportive medical care in the first instance.
Small abscesses may respond to such treatment alone.
All other abscesses require drainage.
In general it is preferable to drain abscesses percutaneously, under radiological guidance (Fig. 12), followed by elective resection, rather than undertake urgent surgery.
Approximately 70 to 90 per cent of diverticular abscesses that are amenable to CT-guided, percutaneous drainage are successfully treated in this way.
Acute surgical intervention is indicated if the patient does not respond to conservative therapy and percutaneous drainage, or if the abscess is inaccessible or too multiloculated to be adequately drained percutaneously.

Once the acute episode has subsided the colon should be visualized by colonoscopy or barium enema.
Elective surgery should be considered after resolution of an acute episode of complicated diverticulitis.

Diverticulitis associated with generalized peritonitis (Hinchey stage 3 and 4)
Patients with generalized peritonitis require immediate resuscitation followed by prompt surgery.
Surgical options are discussed below.

Diverticulitis associated with fistulas
Patients with diverticular-associated fistulas should be thoroughly investigated to determine the site and complexity of the fistula and to rule out other fistula-causing diseases such as malignancy or Crohn's.
Most patients may be operated on in an elective setting, after medical optimization and full bowel preparation.
The general principle is to resect the diverticular segment of bowel and to repair the defect in the contiguous structure.
A primary anastomosis is usually appropriate.

Diverticular stricture
Complete large-bowel obstruction due to a diverticular stricture requires rapid resuscitation followed by prompt surgery.
The standard surgical options are discussed below. Recently, experience with expandable metal stents to relieve acute large-bowel obstruction has been reported.
This technique may obviate the need for emergency surgery and allow planned surgery to be undertaken when the patient is in a more favourable condition.
A diverticular stricture presenting less acutely can usually be operated on in a planned fashion after thorough investigation and full bowel preparation.

Surgery for diverticular disease
The indications to operate as an emergency, urgently, or soon for complications of diverticular disease are fairly clear.
Elective surgery after resolution of acute complications is more controversial.
Clearly this must take account of
the patient's biological age and
comorbidity,
the number and severity of attacks of diverticulitis,
their speed of response to medical treatment, and
the magnitude of symptoms between attacks.
There is some evidence that recurrent attacks of acute diverticulitis become increasingly less likely to respond to medical therapy.
A prospective audit of 120 patients treated for complicated diverticular disease in the United Kingdom demonstrated that 70 (58 per cent) were asymptomatic at 5 year follow-up and 50 (42 per cent) were symptomatic; 39 developed serious complications, of whom 10 died as a result.
The investigators advocated elective surgical resection for patients who have survived an acute episode of complicated diverticular disease managed conservatively, provided that they are fit for elective surgery.
Similarly, the American Society of Colon and Rectum Surgeon's (ASCRS) guidelines (1995) are that elective resection is indicated after two proven episodes of acute, uncomplicated diverticulitis or after one episode of complicated acute diverticulitis.

Preoperative preparation
Patients should be prepared for surgery as thoroughly as the clinical situation permits.
Patients with generalized peritonitis require correction of dehydration and major electrolyte abnormalities, such as hypokalaemia, as rapidly as safely possible.
Cardiac arrhythmias causing circulatory compromise, such as fast atrial fibrillation, should be corrected.
All patients should be given broad-spectrum antibiotics and prophylaxis for deep venous thrombosis preoperatively.

In less acute circumstances, patients should undergo full bowel preparation. They should be seen by a stomatherapist and optimal stoma sites marked preoperatively.

Operative treatment
Operative treatment of diverticular disease may be difficult; sepsis, scarring, foreshortening, thickening and narrowing of the bowel, associated abscesses, obstruction, and fistulas present challenges that require both technical expertise and mature judgement.
Patients should be positioned in the modified Lloyd-Davies position.
A midline incision is the most conventional, although some surgeons prefer a left paramedian incision or a curved oblique incision in the left iliac fossa.
Laparoscopic and laparoscopically assisted resections are becoming increasingly popular, although learning such procedures is difficult and to date there are no data from randomized trials that there is any benefit compared to laparotomy.

There is a wide spectrum of surgical procedures to choose from when operating for diverticular disease. A major skill of the surgeon is to select the correct procedure for the individual patient.
Most elective operations for diverticular disease involve resection and primary anastomosis (one-stage approach).
The operation of sigmoid myotomy, popularized by Reilly in the 1970s, is no longer performed.

The choice is more difficult in an emergency or urgent situation.
The three-stage approach was once favoured for diverticulitis associated with generalized peritonitis.
However, this approach has fallen into disrepute:
the septic focus is not removed;
multiple operations in elderly patients result in high cumulative mortality, morbidity, and
total hospital stay, and
many patients fail to complete all three stages.
A major review of the operative management of acute, complicated diverticular disease by Krukowski and Matheson emphasized the need to resect the diseased segment of colon.
However, their conclusions were largely based on retrospective studies, which may be prone to consistent biases.
One small, randomized trial by Kronborg favoured transverse colostomy and suture of the colonic perforation over acute resection without a primary anastomosis for purulent peritonitis.
Despite this, most surgeons (and the ASCRS guidelines) favour resection of the diseased segment of colon at the initial operation.
The most frequent surgical decision is whether or not to do a primary anastomosis or whether to exteriorize the proximal colon and close off the distal rectal stump (Hartmann's procedure).
Opinions differ in this matter:
proponents of the Hartmann's approach argue about the safety of avoiding an anastomosis in the presence of sepsis;
opponents emphasize the difficulty of reversing a Hartmann's procedure and point out that up to one-third of patients never have their colostomy reversed.
No randomized trials have addressed this question.

The ASCRS Standards Task Force (1995) favours a Hartmann's procedure for diverticulitis with free perforation (Hinchey stage 3 and 4).
Acute surgery for diverticulitis associated with a localized abscess is more debatable.
If contamination is minimal and adequate bowel preparation can be achieved, resection and primary anastomosis, with or without a defunctioning stoma, is appropriate.
Otherwise a Hartmann's procedure should be performed.
If a defunctioning stoma is utilized,
the evidence favours loop ileostomy over a transverse colostomy.

When operating for acute large-bowel obstruction, the Hartmann's procedure is often appropriate.
A one-stage approach with on-table lavage and primary anastomosis is favoured by some surgeons, particularly in the United Kingdom, although there are no trials comparing these techniques.
In the very frail or unstable patient, a preliminary transverse colostomy (three-stage approach) may be appropriate.
If the ileocaecal valve is competent and the caecum critically distended, a subtotal colectomy with ileosigmoid or ileorectal anastomosis may be undertaken.
Although this usually permits a primary anastomosis with no defunctioning stoma, the increased bowel frequency afterwards may be troublesome, especially in the elderly individual.

The spleen and left ureter are at particular risk during resections for diverticular disease.
Accidental splenic injury and subsequent splenectomy increase the risk of venous thromboembolic complications and permanently impair immunity.
The left ureter may be adherent to the sigmoid mesentery or bound in dense scar tissue in the region of the pelvic brim, sometimes with partial ureteric obstruction.
Preoperative placement of a left ureteric stent may help to identify the ureter in an area of inflammation or dense scarring.
Ureteric injury can be avoided by dissecting the mesentery of the descending colon from Gerota's fascia, identifying the ureter near the pelvic brim, then dissecting downward through the difficult area, keeping the ureter in a posterior position and always in view.

The length of colon resected depends upon the extent of the muscular abnormalities in the gut wall as well as the extent of the inflammatory changes.
· Resection for sigmoid diverticular disease should extend distally to the upper rectum.
· Anastomoses may be hand-sewn or stapled, depending on the surgeons' preference.
· Comparative trials show no significant difference.

Postoperative care
Patients should receive standard postoperative care.
Where there is established infection, antibiotics should be continued for 5–days; otherwise, prophylactic antibiotics only should be given perioperatively.
Thromboprophylaxis should be continued in all patients until they are fully mobile.

Postoperative complications are not uncommon, particularly when surgery is undertaken acutely in elderly patients.
Reported mortality rates from faecal and purulent peritonitis are 48 per cent and 27 per cent, respectively.
General complications include respiratory infection, cardiac events, thromboembolic disease, urinary-tract infection or retention, renal impairment, and strokes.

Specific complications include
· haemorrhage,
· intra-abdominal abscesses,
· ileus,
· mall-bowel obstruction,
· wound infection, and
· stoma-related problems.
Ureteric or splenic damage is rare.
The most feared postoperative problem is sepsis: this may be due to continuation of pre-existing infection or may occur because of an anastomotic leak postoperatively.
Several studies have shown that the mortality rate from complicated diverticulitis is proportional to the degree of peritonitis at operation.
Patients with generalized peritonitis are at high risk of developing multisystem failure, which requires support under intensive care.
Problems related to anastomotic leakage typically present 5 to 7–days postoperatively.
The clinical features vary from obvious peritonitis to non-specific malaise or confusion.

It is important to have a high index of suspicion for septic complications following surgery for complicated diverticulitis.
CT scanning, or contrast enema if a recent anastomosis has been fashioned, are the principal investigations.
Early reoperation with peritoneal lavage, stoma formation, and drainage is usually required.
In cases of extremely severe intra-abdominal contamination, leaving the abdomen completely open as a laparostomy is an option.


Special conditions

Diverticular disease in young patients
Diverticulosis occurs in about 6 to 9 per cent of the population under 40 years of age.
Approximately 11 to 30 per cent of proven cases of acute diverticulitis occur in the same age group.
Some reports suggest an association with obesity in the young.
Acute diverticulitis tends to be misdiagnosed in the young, particularly as appendicitis or pelvic inflammatory disease in women.
Many retrospective reviews suggest that acute diverticulitis in the young is a more aggressive disorder than in older patients.
Eusebio and Eisenberg reported that two-thirds of 181 patients presenting with diverticular disease under 40–years ultimately required surgery.
However, this may be a false impression, given that acute diverticulitis in the young (particularly milder episodes) tends not to be diagnosed accurately and younger patients are less likely to require hospital admission for comorbidity.
The management principles are similar to those for older patients, except that many surgeons would recommend elective resection after one episode of proven, uncomplicated diverticulitis in the young.

Diverticular disease in the immunocompromised
Immunocompromised patients are encountered increasingly in modern hospital practice.
Common causes include congenital or acquired immune disorders, uraemia, haematological malignancies, and immunosuppressant drug therapy, especially steroids.
The mortality of diverticulitis in immunocompromised patients is much greater than in immunocompetent patients.
Review of 90 immunocompromised patients with acute diverticulitis (from eight published series) demonstrated a surgical mortality of 40 per cent.
Reasons for this include delayed diagnosis due to masked clinical features, higher rates of free perforation due to impaired ability to localize sepsis, impaired immune function, and coexistent medical problems.
Management therefore requires a higher index of suspicion of complications than usual.
A lower threshold for investigation, particularly CT and repeat CT, is required.
Surgery in the acute phase should not involve an anastomosis.
First-line antibiotic therapy should be the same as in immunocompetent patients, although fungal or cytomegalovirus infection should be considered if the clinical state is not improving.

Patients with polycystic kidney disease have a very high frequency of diverticulosis, 33 per cent of whom develop diverticulitis at some stage. There may be a case for elective resection for diverticulosis in this defined group.

Diverticulitis after previous resection
Recurrent diverticulitis following previous resection is fortunately rare.
The most important cause is retention of some distal sigmoid colon after a sigmoid colectomy.
Recurrent diverticulitis is reported in 12.5 per cent of patients following sigmoid colectomy when the distal sigmoid is retained, compared to 6.7 per cent when the anastomosis is to the upper rectum.

In cases of assumed recurrent diverticulitis after previous resection, it is important to confirm both the original and current diagnoses.
The original pathology specimen should be reviewed, particularly to rule out Crohn's disease.
The current diagnosis should be confirmed by CT in the acute phase and subsequently by colonoscopy once the acute phase has subsided.
Elective re-resection should be considered after a complicated episode or repeated, uncomplicated attacks.
Repeat surgery may be technically difficulty and ureteric stenting is recommended.

Right-sided and caecal diverticulitis
Caecal and ascending diverticula account for the majority of diverticula in Oriental populations.
Right-sided diverticula tend to occur at a younger age than left-sided disease.
Interestingly, although migration of Oriental populations to a ‘Western' environment is associated with an increase in prevalence of diverticular disease, the disease is still predominantly right-sided.
This suggests that both genetic and environmental factors influence the development of diverticular disease.

Right-sided diverticula tend to be multiple and false, although a solitary true diverticulum is a well-recognized entity.
Caecal diverticulitis presents with clinical features similar to acute appendicitis, the diagnosis usually being made intraoperatively.
A locally inflamed, easily identifiable caecal diverticulum is best treated by diverticulectomy, drainage, and antibiotics.
The more common operative finding is of an inflammatory mass in the caecum that is difficult to distinguish from a locally perforated neoplasm.
A right hemicolectomy is the usual treatment.
Generalized peritonitis due to a perforated, right-sided diverticulum is usually treated by a right hemicolectomy, with or without a primary anastomosis, depending on the clinical situation.

Giant diverticulum
Giant diverticula of the colon are extremely rare, but sizes of up to 30 to 40 cm have been reported.
They present chronically with bloating and vague discomfort or acutely as a result of perforation, torsion, or infarction.
Plain abdominal radiography shows a solitary, gas-filled, cyst-like structure.
Confirmation of the diagnosis requires barium enema or CT.
Treatment is resection, either as a one-stage (elective presentation) or two-stage (acute presentation) procedure.

Diverticular haemorrhage
It has been estimated that significant bleeding occurs in about 5 per cent of patients with diverticulosis at some stage in their life.
Bleeding is characteristically of sudden onset, painless, and severe but may be intermittent or minimal.
The main differential diagnoses are angiodysplasia, ischaemic colitis, and neoplasia.

Patients presenting with lower gastrointestinal bleeding should be rapidly assessed and resuscitated as appropriate.
A history shouldbe taken, concentrating on the colour and volume of blood loss, other gastrointestinal symptoms, medical comorbidity, and drug therapy.
Examination should focus on general condition, features of hypovolaemia, coexisting medical conditions, and clues on the source of bleeding.
All patients should have blood sent for routine biochemistry and haematology, including a clotting screen and cross-matching.
Reliable venous access should be established and appropriate monitoring commenced.
All patients should undergo rectal examination, proctoscopy, and rigid sigmoidoscopy to rule out major anorectal pathology responsible for the bleeding.
It should be remembered that approx. 10 to 15 per cent of apparently lower gastrointestinal bleeding is in fact from an upper gastrointestinal (or small bowel) source.
A raised urea:creatinine ratio is suggestive of upper rather than lower gastrointestinal bleeding.
A nasogastric tube draining bile-stained fluid is a popular but not entirely reliable method of excluding an upper gastrointestinal source.
If any doubt exists an upper gastrointestinal endoscopy is mandatory.

Patients with lower gastrointestinal bleeding will tend to fall into one of three categories:
those who clearly continue to bleed;
those who stop,
and those who slow down but continue to trickle or bleed intermittently.

Continued active bleeding
These patients clearly require active resuscitation and simultaneous investigation.
Mesenteric angiography may identify bleeding at rates of 0.5 ml/min or greater.
The pathognomonic finding of diverticular haemorrhage is pooling of contrast in the diverticulum.
The main disadvantage of this technique is its invasiveness and that the patient must be actively bleeding at the time of the study.
Review of 972 published cases of mesenteric angiography for lower gastrointestinal bleeding showed that a bleeding site was identified in 56 per cent of cases.
Angiographic localization allows a limited colonic resection to be undertaken with a very low risk of rebleeding.
Angiography may also allows access for therapeutic measures such as the infusion of vasoconstrictive agents (e.g. vasopressin) or for selective embolization of the bleeding vessel.
Therapeutic angiography may have a role in stabilizing patients before surgery or in avoiding the need for surgery altogether in selected patients.
Although the immediate response rate with vasopressin is good, the risk of rebleeding is high.
Selective embolization of the bleeding vessel has been reported, although the
poor collateral vasculature of the colon means that ischaemic complications may occur.
Recent reports of superselec-tive embolization suggest lower risks of bleeding and fewer complications.
In most hospitals however, whenever angiography identifies a bleeding site, surgical resection is felt to be appropriate.
If angiography is negative but major bleeding continues, surgical intervention is required; intraoperative colonoscopy after on-table lavage is recommended.

Patients who bleed slowly or intermittently
Patients who continue to bleed intermittently or who trickle at a slow rate such that angiography is negative are difficult to manage well.
Colonoscopy after full bowel preparation is probably the most useful investigation.
Scintigraphy using technetium-labelled red blood cells has been reported to identify bleeding at rates as low as 0.05 to 0.1 ml/min, although the overall results from published series are less encouraging.
The key to this group of patients is to investigate very thoroughly and repeat investigations if necessary.
Colonoscopy, angiography, scintigraphy, upper gastrointestinal endoscopy, small-bowel enema, and abdominal CT are the mainstays of such investigation.
If all of these are negative but bleeding persists, laparotomy with panendoscopy is necessary.

Patients who stop bleeding
Patients who present with a lower gastrointestinal bleed who settle rapidly should be investigated electively by colonoscopy, looking principally for diverticula, neoplasia, or angiodysplasia.
Approximately 25 per cent of patients who have a diverticular bleed managed conservatively will have another bleed.
If recurrent bleeding occurs, resection should be considered, although it is critical to confirm accurately the site of bleeding before laparotomy.
Although most diverticula are left-sided, right-sided diverticula account for about 50 per cent of bleeding diverticuloses.

Surgery for diverticular haemorrhage
The majority of patients with diverticular haemorrhage do not require surgical intervention.
Patients who require four or more units of blood during the first 24 h of treatment have a 50 per cent chance of needing operative intervention.
Preoperative localization of the bleeding point permits a limited rather than extensive colonic resection.
Many studies have demonstrated a dramatically reduced mortality and morbidity from such an approach.
If the bleeding site cannot be identified preoperatively or operatively, transillumination of the bowel and colonoscopy are recommended to find the source.
If no precise bleeding point can be identified and rectal, upper-, and small-bowel causes are excluded, a subtotal colectomy is indicated.