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Diverticular Disease of the Colon

Tonia M. Young-Fadok, MD, MS
Associate Professor of Surgery
Mayo Medical School
Division of Colon and Rectal Surgery
Mayo Clinic
Rochester, MN

Terminology

A diverticulum (plural diverticula) is a saccular protrusion of mucosa through the colonic wall. The presence of diverticula is indicated by diverticulosis, which usually denotes the absence of symptoms. Inflammation of diverticula is diverticulitis. Diverticular disease includes all manifestations of diverticula, i.e. their existence, inflammation or bleeding. Diverticulitis may be simple or complicated. Complicated diverticulitis refers to abscess, fistula, obstruction, bleeding and perforation. Simple diverticulitis is inflammation in the absence of these complications.

Pathology and Pathophysiology

A colonic diverticulum is a false or pulsion diverticulum, as it does not contain all layers of the wall. Mucosa herniates through the muscle layer, covered only by serosa. Diverticula develop in four "rows" at the points of the colonic circumference where the vasa recta penetrate the circular muscle layer.(1) It was previously believed that obstruction of the ostia of the diverticula, e.g. by fecoliths or seeds, led to increased intradiverticular pressure and perforation; this hypothesis is now thought to be rare.(2) Increased intraluminal pressure and/or local trauma of inspissated food particles may erode the wall of the diverticulum. Inflammation and necrosis result in perforation.

Clinical Presentation, Diagnosis and Imaging

Clinical Presentation
Diverticulosis may exist in the absence of symptoms. It is often an incidental finding on a test performed for other indications. Some patients with diverticulosis complain of cramping, bloating, flatulence and irregular defecation. These symptoms may also be present with irritable bowel syndrome. Fortunately, the treatment for both is simple: increased dietary fiber.

Diverticulitis results from micro- or macroscopic perforation of a diverticulum. If inflammation is mild, a small perforation is walled off by pericolic fat or is contained within the mesentery. This may result in a localized abscess, or in a fistula. Poor containment results in peritonitis.

Left lower quadrant pain occurs in 70% of patients,(3) and is frequently present for several days prior to presentation, differentiating from other causes of acute abdominal pain. Up to one half have had one or more previous episodes of similar pain. Other symptoms include nausea and vomiting in 20-62%, constipation in 50%, diarrhea in 25-35% and urinary symptoms (dysuria, urgency, frequency) in 10-15%.(3)

On examination left lower quadrant tenderness is characteristic.(4) The tenderness may extend across the suprapubic region and into the right lower quadrant if the sigmoid is redundant. Generalized tenderness suggests free perforation and peritonitis. A tender mass on abdominal or rectal examination is present in 20%.(5) Low grade fever and mild leukocytosis are common, but the diagnosis is not excluded by normal temperature and white blood count, which are seen in up to 45% of patients.(6) Sterile pyuria indicates adjacent inflammation in the sigmoid. Colonic or mixed bacteria on urine culture suggest a colovesical fistula.

Diagnosis and Imaging
The diagnosis of acute diverticulitis can frequently be made on the history and examination alone. It has been recommended that when the clinical picture is clear additional tests are not necessary to make a diagnosis.(7) A clinical diagnosis, however, may be incorrect in up to one third of patients.(8) Also, should there be additional attacks, a patient may be refused a justifiable operation if the prior attacks were unconfirmed. Thus in the patient who has symptoms sufficient to merit hospitalization, we prefer to obtain CT confirmation.

Abdominal and chest radiographs exclude free air and causes of abdominal pain, such as obstruction, rather than making the diagnosis of diverticulitis. Contrast enema, ultrasound (US) and computed tomography (CT) scan have a role in diagnosing diverticulitis. CT scan is the preferred method, as it is diagnostic and therapeutic, and evaluates extramural inflammation. Features of diverticulitis on CT include: increased soft tissue density in pericolic fat in 98%; colonic diverticula in 84%; bowel wall thickening in 70%; and soft tissue masses representing phlegmon, or pericolic fluid collections representing abscesses in 35%.(9,10) CT-guided drainage of abscesses may avoid emergent operation, and allow a single-stage procedure.

High-resolution compression ultrasonography may reveal a thickened colonic wall, or cystic masses with echogenic densities suggestive of abscess.(11) In 85% of patients an abnormal colonic segment, thicker than 4mm over a segment of 5cm or longer, is found at the point of maximal tenderness.(12) The colon has a target-like appearance in cross-section. Sensitivies range from 85-98% and specificities from 80-98%.(12) The technique is operator dependent and hampered by the presence of abdominal distension.

Contrast enema is safe in the acute setting if single contrast technique is used. In the presence of free air, barium is absolutely contraindicated,(13) but water soluble contrast is safe and may indicate the site of perforation. Even in the absence of peritoneal signs, most prefer to use water soluble contrast in any patient with suspected diverticulitis. With the availability of CT scan, contrast enemas are infrequently used, but have a role if the diagnosis is unclear on CT.

Endoscopic evaluation (rigid proctoscopy or flexible sigmoidoscopy) is relatively contraindicated in acute diverticulitis. Air insufflation may convert a sealed perforation to a free leak. Occasionally, limited sigmoidoscopy is necessary to rule out e.g. inflammatory bowel disease, and in experienced hands, a gentle examination with minimal air insufflation is considered safe.(14)

Medical Therapy and Indications for Operation

Simple diverticulitis, in 75% of cases, is not associated with complications and most patients respond to medical therapy. Most patients with complicated diverticulitis (perforation, obstruction, abscess or fistula, in 25% of patients in the first episode) will require operation, but some may be converted from an emergent to an elective procedure.

Medical Therapy
In the absence of systemic symptoms and signs, patients with mild abdominal tenderness may be treated on an outpatient basis. This includes a low residue diet and an oral antibiotic (e.g. metronidazole and/or ciprofloxacin). Hospitalization is recommended for increasing abdominal tenderness, fever, or inability to tolerate oral intake. It is also recommended for those who may mask reliable symptoms and signs, such as immunosuppressed patients and diabetics.

Hospitalization is indicated for those with significant pain or localized peritonitis in the absence of free perforation. Initial therapy is conservative, with the aim to avoid surgery, or convert an urgent situation to an elective one. Therapy includes bowel rest (a nasogastric tube is only required if there is an obstructive picture with an incompetent ileocecal valve and small bowel distension), and intravenous fluids. Intravenous broad-spectrum antibiotics should cover anaerobic and Gram-negative flora. Recommended regimens, based on consensus rather than randomized trials, include antianaerobic coverage with metronidazole or clindamycin, and Gram- negative coverage with an aminoglycoside (e.g. gentamicin), monobactam (e.g. aztreonam), or third generation cephalosporin (e.g. ceftazidime, ceftriaxone).(15) Single agent coverage with second generation cephalosporins (e.g. cefotetan) or B-lactamase inhibitor combinations (e.g. ampicillin-sublactam, ticarcillin-clavulanate) are also reasonable.(16) Intravenous analgesia is important for patient comfort, but should be titrated so as not to preclude accurate assessment of abdominal signs. Abscesses found on CT should be drained.

The three possible outcomes are improvement, failure to improve and deterioration. Improvement should be apparent within 48 hours, with decreased tenderness, fever and leucocytosis. Persistent signs suggest an incorrect diagnosis or an unresolving phlegmon or abscess, and CT scan may identify those who have developed an abscess and may respond to percutaneous drainage. Those who improve are discharged on a low-residue diet. Six weeks later they are evaluated with colonoscopy, or with flexible sigmoidoscopy plus barium enema.

Indications for Operation

Emergent
Evidence of diffuse peritonitis mandates resuscitation, broad spectrum antibiotics and emergent exploration. Extensive diagnostic testing is rarely necessary. Examples of antibiotic regimens are: ampicillin + gentamicin + metronidazole; or imipenem/cilastin; or piperacillin-tazobactam.

Certain patients who initially fulfil criteria for conservative management will require emergent or semi-emergent surgical intervention. If a patient's condition deteriorates, (increasing pain, more localized peritonitis or diffuse tenderness, increasing white count) a search should be made for a reversible condition, i.e. CT scan to rule out drainable abscess. Operation is necessary if there is no reversible condition, if an abscess cannot be drained, or if drainage does not result in improvement. Failure to improve is also an indication for operation.

Elective
Elective surgical intervention is recommended for: patients who have had one episode of complicated diverticulitis (abscess, obstruction or fistula); and those who have had two confirmed episodes of acute diverticulitis severe enough to require hopitalization. Elective resection is usually performed 6-8 weeks after the acute episode to allow inflammation to subside.

Special Cases
In certain circumstances surgical resection is offered after only one attack. These include immunocompromised patients, young patients, and those with connective tissue disorders. The immunocompromised patient is predisposed to infection, has delayed wound healing and an increased incidence of complicated diverticulitis.(17) Additionally, such patients often mask typical symptoms and signs of acute inflammatory processes of the abdomen. Patients with connective tissue disorders are often immunocompromised secondary to corticosteroids, but they appear to have an additional risk of complicated diverticulitis related to the underlying disorder.(18)

Young patients are traditionally offered surgical intervention after a single episode, based on two premises. The first is that young patients manifest a more virulent form of the disease, thus are more likely to have complications and require operation for the first episode. The second premise is young patients who respond to medical management are more likely to suffer recurrent episodes. Consistent findings are male dominance in younger patients, with the ratio ranging from 2:1 - 4:1.(3,6,19,20) and comorbid conditions are unusual with the exception of obesity, present in 84-96%.(3,19) The percentage who undergo resection, however, varies widely as does the rate of preoperative misdiagnosis. One way to make sense of conflicting data is to consider the overall operative rate, including both the first admission and subsequently.(21) This overall rate is more consistent, and is in the range of 50%. Thus some series suggest a high operative rate at first presentation,(3,20,22) and others show a lower rate at first admission of 15-25%, but with a poor outcome in up to 29%(6) of patients at first admission or subsequent operation in 32% of patients.(23) The data are relatively consistent when examined in this fashion, but again discrepancies arise when different authors have different interpretations. Some state that after medical therapy, a risk of subsequent operation of 32-41% in patients followed for 5-9 years does not justify elective resection.(23) Others disagree, and recommend elective operation on the basis of the same data.(24) Our approach is to advise younger patients, whose first episode has responded to medical therapy, of risks and benefits of operation versus observation. This issue thus rests on the patient's own evaluation of risks and lifestyle concerns.

Conduct of Operation

Laparotomy: Emergent and Semi-Emergent Setting
An emergent situation exists in the presence of free perforation with either purulent or fecal peritonitis (Hinchey stages III and IV)(25) and an acute abdomen. Also in this category is sepsis from an undrainable abscess, and unrelieved large bowel obstruction. Bowel preparation is not indicated, and attention is focused on rapid resuscitation, correction of fluid and electrolyte abnormalities, and broad-spectrum antibiotics. The patient is informed of the need for stoma and is marked in the right and left lower quadrants.

The basic tenets are: control of sepsis, resection of diseased tissue, and restoration of intestinal continuity, with or without a protective stoma. There are four basic surgical options: (1) outdated 3-stage colostomy and drainage only, (2) 2-stage colostomy and resection (Hartmann procedure), (3) primary resection, anastomosis and diversion, and (4) primary resection with anastomosis.

Three-Stage Procedure: Transverse Colostomy and Drainage: Option (1), the 3-stage procedure, is rarely indicated, and in most settings is to be condemned.(26,27) Greater morbidity has been reported in patients treated with colostomy and drainage alone, and there is also a higher mortality rate for the 3-stage procedure, of 26% vs. 7% in those undergoing resection.(26) Only on rare occasions are the inflammatory changes so extensive as to preclude mobilization and resection because of concerns regarding the ureter and iliac vessels. The procedure may have merit as a temporizing procedure before the patient is transferred to a tertiary center.

Two-Stage Procedure versus Primary Anastomosis: The patient is placed in synchronous lithotomy position to permit access to the perineum. An adequate incision is made. A dense inflammatory reaction around the sigmoid often precludes initiation of dissection in this area. It is helpful to begin dissection more peripherally, both proximally along the lateral peritoneal reflection of the descending colon and distally in the rectum. This allows a "proximal-to-distal" resection, in which the colon is divided proximal to the phlegmon with a linear stapler, and the colon is dissected proximal-to-distal rather than the usual lateral-to-medial dissection.(14) Ureteral stents are often helpful in identifying the course of the ureters. Once the diseased segment has been mobilized, a decision is made to perform either an anastomosis or colostomy.

Two-Stage: Hartmann Procedure: Contraindications to primary anastomosis include both intraoperative findings and patient comorbidities. A primary anastomosis should not be performed in the presence of malnutrition, severe anemia, feculent peritonitis, immuno- suppression, and uncertain viability of the bowel. In these cases a Hartmann procedure should be performed. The rectal stump may be stapled or sutured, with drains left in the pelvis and a rectal tube to prevent disruption of the rectal stump. Use of long, non-absorbable monofilament sutures to mark the top of the rectal stump assists in identification when returning to close the colostomy.

Two-Stage: Resection, Primary Anastomosis and Proximal Stoma: The Hartmann procedure removes the source of sepsis, but reversal of the colostomy is often difficult because of adhesions and difficulty identifying the rectal stump. Up to one third of patients are left with a permanent stoma.(28) Relative contraindications to an unprotected anastomosis include presence of a chronic abscess cavity and mild systemic illness, in which case the patient may be better served by creation of a primary anastomosis that is protected by a proximal diverting colostomy or ileostomy. Our practice is for a loop ileostomy (in the absence of significant fecal loading of the colon) as it is easy to close, and is less bulky and easier to manage than a loop colostomy.

Single-Stage Procedure with On-Table Lavage: In the emergent setting, bowel preparation is not possible, and a large fecal load precludes a primary anastomosis. Consideration may be given to intraoperative lavage if it permits primary resection and anastomosis. In addition to mobilization of the affected sigmoid colon, mobilization of the splenic and sometimes the hepatic flexure may help.(14) Bowel proximal to the sigmoid is occluded with tape, and immediately above this, the lumen is cannulated with large bore corrugated plastic tubing (ventilator tubing). The end of the tube is passed off the field. The cecum or appendix base is cannulated with a Foley catheter through which warm saline is infused until the efflux is clear.(29)

Laparotomy: Elective Setting
Elective resection is performed 6-8 weeks after the most recent episode. This allows the inflammatory process to subside. A longer waiting period may increase the risk of another attack, but there is no clear data for this commonly held belief. One's usual bowel preparation is used, e.g. either 2-4 liters of polyethylene glycol solution (at 5pm) or two 45ml bottles of sodium phosphate (at 5pm and 10pm), in addition to 2 gm each of metronidazole and neomycin at 7pm and 11pm. The patient is placed in synchronous position. Ureteral catheters are used selectively in patients who had significant prior phlegmon, prior abscess drainage, and persistent discomfort in the left lower quadrant suggestive of continued inflammation.

In quiescent disease, the standard lateral-to-medial approach is possible. In the presence of continued inflammation and obliteration of the normal plane, the method of commencing peripherally in normal planes and "moving in" on the difficult area is successful. The proximal resection margin should be in bowel that feels soft and pliable, usually the distal descending colon. This area does not have to be free of diverticula, but must be free of bowel wall thickening. The distal resection margin must be in the proximal rectum. Below this diverticula rarely if ever occur.(30) The splenic flexure should be mobilized if necessary to achieve a tension-free anastomosis, but is not necessary in all cases. Dissection of the upper presacral space and mobilization of the proximal rectum may also assist with creation of the anastomosis.

Laparoscopy
Laparoscopic techniques have a role in several facets of diverticular disease, including diagnosis, diversion, resection, and restoration of colonic continuity.(31) Free perforation and fecal or purulent peritonitis are contraindications to the laparoscopic approach, because of limitations on complete exploration and clearance of contaminated material. Single institution(32,33) and multicenter studies(34) have demonstrated benefits in terms of reduced ileus and hospital stay.

The severe inflammation that may accompany diverticulitis is frequently challenging even in open procedures. Resolution of inflammation allows for a successful laparoscopic approach in most cases.(31) The presence of a fistula reduces the chances of completing the procedure laparoscopically, as does prior use of a drain, but is not an absolute contraindication to this approach. Even in open cases, the bladder side of a colovesical fistula frequently requires nothing more than pinching off the fibrous fistula track and leaving the bladder decompressed with catheter drainage, and the same principles apply to the laparoscopic approach. Ureteral stents may be helpful, as the firm tubular structure of the stent in the retroperitoneum can usually be detected with the laparoscopic instruments. It is helpful to approach the mass in the sigmoid from both cephalad and caudad directions having identified normal tissue planes away from the phlegmon. A low threshold for conversion to laparotomy should be maintained to avoid injury. The same extent of resection should be accomplished laparoscopically, i.e. proximal resection of the sigmoid back to soft, pliable tissue, and distal resection to a point where the tenia have coalesced, requiring resection to a point below the sacral promontory and intracorporeal anastomosis.

Outcomes and Long-Term Follow-Up

The need for operation with the first attack of diverticulitis is 20-29%; most have complicated diverticulitis.6 The mortality rate is 1.3-5%.(35) Almost all patients with simple diverticulitis are initially treated conservatively. Approximately 85% respond and 15% will require operation.35 Following successful conservative therapy for a first attack, 30-40% of patients will remain asymptomatic, 30-40% will have episodic abdominal cramps without confirmed diverticulitis, and one third will have a second attack.(5) Long-term follow up shows a readmission rate for diverticulitis of 2% per patient year in patients treated successfully with conservative therapy.(35) Thus elective resection is not necessary for all patients who respond to medical therapy. There is an increased risk of complications, however, after a second attack, as the rate of complicated diverticulitis approaches 60% and the mortality rate is doubled.(5) Only 10% subsequently remain asymptomatic. These values form the basis for recommending elective resection after two confirmed attacks.

Those who are treated operatively are generally considered cured. Progression of diverticulosis in the remaining colon occurs in only 15%(36) and there is a need for further operation in only 2-11%.(30,36) Perforated diverticulitis has a mortality rate of 6% for purulent peritonitis and 35% for fecal peritonitis.(26)

References

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