Complications of diverticular disease
Fistula
Fistula is the presenting complication in 10% to 15% of patients who require surgery for diverticular disease. There is often no history of acute diverticulitis. Patients may present with symptoms related primarily to the organ involved with the di-verticular fistula, which is the bladder in most cases. Diverticular disease is the most common cause of colovesical fistula, followed by colon cancer and Crohn disease. Colovesical fistulas are much less common in women than in men, presumably because the uterus is interposed between the sigmoid colon and the bladder. Patients with colovesical fistulas usually present with recurrent polymicrobial bladder infections, pneumaturia, or both. Fistulas may also connect with other parts of the colon, the small bowel, the uterus, or the vagina. Colocutaneous fistulas are unusual and generally occur after surgery for diverticulitis.
Colovesical fistulas are difficult to visualize. CT scanning may be the most useful single study. Even though fistulas are rarely directly visualized, CT is very sensitive for detection of air in the bladder, which is virtually diagnostic of an enterovesical fistula in the absence of prior bladder catheterization. CT demonstrates the presence of diverticula, and thickening of the bladder wall adjacent to an area of diverticulitis supports the di-agnosis.52 Colovesical fistulas are often not identified by a barium enema study, although secondary changes of diverticulitis are usually apparent. Cystoscopy often reveals focal mucosal inflammation in the area of a fistula, even though the opening is not apparent. Fistulas may be visualized by contrast cystogra-phy.53 Colonoscopy should be done at some point to exclude cancer or inflammatory bowel disease, but it rarely reveals the fistula. CT, barium enema, cystoscopy, and colonoscopy are complementary studies for the evaluation of a suspected colovesical fistula.52 Patients with a diverticular fistula should have elective surgical resection of the involved segment of colon once the acute inflammatory process has been controlled. In the case of colovesical fistulas, the adherent colon can usually be dissected off the bladder and the involved bladder oversewn, rather than resected.54
Obstruction and Stricture
Acute obstruction during an episode of diverticulitis is often self-limited. It may be caused by a large phlegmon or abscess. Secondary ileus may mimic obstruction. Chronic stricture is an uncommon presentation of diverticular disease. It usually occurs after repeated episodes of diverticulitis. A diverticular stricture may be difficult to distinguish from a malignant stricture, particularly by CT or a barium enema study. Colonoscopy with biopsies is the best means of making this distinction, although visualization may be limited even with colonoscopy.
Segmental Colitis Associated with Diverticular Disease
In about 1% of cases, chronic diverticular disease is associated with patchy mucosal hemorrhage, congestion, and granularity in the sigmoid colon. On microscopic examination, a lymphocyt-ic infiltrate, lymphoglandular complexes, mucin depletion, mild cryptitis, crypt distortion, Paneth cell metaplasia, and ulceration can be seen. These changes may mimic Crohn colitis, ulcerative colitis, or ischemic colitis. However, in segmental colitis associated with diverticular disease (SCAD), the changes are limited to areas of diverticulosis.55,56
Risk of Colon Cancer in Diverticular Disease
Some studies have shown an increased risk of sigmoid colon cancer in patients with a history of diverticulitis, but other studies have not confirmed this finding.57-59 In addition to the difficulty in distinguishing a diverticular stricture from a malignant stricture, perforated colon cancer can mimic acute diverticulitis accompanied by a phlegmon or abscess. Thus, it seems prudent to recommend elective colonoscopy to patients with diverticular disease.
Diverticular bleeding
Diverticular bleeding is less frequent than diverticulitis as a complication of diverticulosis. It is difficult to arrive at a firm estimate of what proportion of major lower gastrointestinal bleeding is caused by colonic diverticula. Estimates have ranged from 15% to 56%.60-62 In many cases, the source is presumed to be di-verticular when no other cause is found.
Diverticular bleeding is usually sudden and painless. Typically, moderate to large amounts of bright-red blood, clots, or maroon stool are passed. Bleeding stops spontaneously in 70% to 80% of cases; bleeding eventually recurs in 25% to 35% of cas-es.63,64 Lower gastrointestinal bleeding (occult bleeding in particular) should not be attributed to diverticulosis unless other causes have been excluded. The most common causes of lower gastrointestinal bleeding in adults are diverticulosis, inflammatory bowel disease, neoplasm, angioectasias, benign anorectal disease, and upper gastrointestinal sources.
Practice guidelines for the evaluation and management of lower gastrointestinal bleeding have been published.
Emergent Management and Evaluation
The first priority in lower gastrointestinal bleeding is volume restoration with intravenous fluids and blood. During resuscitation, a directed history is taken and a physical examination is performed; the physical examination includes anoscopy and proctoscopy to exclude an anorectal source. A nasogastric aspirate should be obtained, because about 10% to 15% of apparent major lower gastrointestinal bleeding is, in actuality, from an upper gastrointestinal source.61 Lack of blood in the nasogastric aspirate, however, is not conclusive proof of a lower gastrointestinal source. Bleeding from an upper gastrointestinal source may have stopped, and the stomach may have evacuated residual blood. Blood from a duodenal source may not reflux into the stomach. Some clinicians perform an upper gastrointestinal en-doscopy before colonoscopy even if the nasogastric aspirate is negative for blood, particularly for apparent major lower gastrointestinal bleeding.
Colonoscopy Many clinicians consider colonoscopy to be the most useful initial study for the evaluation of patients presenting with major lower gastrointestinal bleeding of unknown cause.66 Lower gastrointestinal bleeding is usually intermittent and often stops before hospital admission or shortly thereafter. Adequate colonic purging followed by colonoscopy is almost always possible even in spite of moderate active lower gastrointestinal bleeding.61,66 The most important contribution of colo-noscopy is to establish a presumptive diagnosis of diverticular bleeding by excluding other causes and to determine the distribution of diverticula, which is important if colonic resection becomes necessary. Some authors recommend urgent colonoscopy and report a high success rate in localizing and treating divertic-ula responsible for bleeding.66 In another report, however, there was no correlation between the timing of colonoscopy and success in localizing the bleeding diverticulum over an interval of 7 to 29 hours.67 If active bleeding or an adherent clot is found at the time of colonoscopy, endoscopic therapy can be performed with epinephrine injection, cautery, hemostatic clips, or banding.
Labeled blood cell scintigraphy Technetium-99m ("mTc)-labeled red blood cell scintigraphy is another tool for the evaluation of acute lower gastrointestinal bleeding. After injection with 99mTc, imaging is done continuously for 60 to 120 minutes. Dynamic scans are viewed in a computer-generated cinematic format. Continuous scanning improves the probability of detecting intermittent bleeding.70 The radioactive label remains active for over 24 hours; thus, if the scan is not positive initially, scanning can be repeated at any time during the first day if there are indications of recurrent bleeding. A scan is considered positive if there is a focus of increased activity that changes in location and intensity over time [see Figure 2]. 99mTc-labeled red blood cell scanning is the most sensitive study for detection of acute gastrointestinal bleeding. It can theoretically detect bleeding rates as low as 0.5 ml/min. Localization of bleeding to the small bowel, right colon, or left colon is generally possible, but reports of the accuracy of 99mTc-labeled red blood cell scanning have been in-consistent.70-72 False positive readings may occur with vascular neoplasms, inflammatory conditions, vascular grafts, varices, splenosis, and bladder or penile activity.
99mTc scanning does not elucidate the cause of bleeding; rather, it demonstrates active bleeding and the approximate location of its source. Colonoscopy is still necessary to determine the presence of diverticula and exclude other potential colonic sources. Once diverticula have been established as the probable cause of bleeding, scanning has a role in detecting recurrent bleeding. A positive 99mTc scan also provides prognostic information; patients with positive scans are much more likely to have positive arteriograms and are more likely to require surgery than those with negative scans.72
Treatment
Visceral angiography and vasopressin infusion Visceral angiography may be useful in persistent moderate to severe lower gastrointestinal bleeding, particularly when the site has not been discovered by colonoscopy and upper gastrointestinal endoscopy or when colonoscopy is not feasible. Angiography can provide precise localization of bleeding in patients who have a positive bleeding scan. If active bleeding is detected and localized, it may then be treated with intra-arterial vasopressin infusion. Rebleeding occurs in 25% of patients when the vasopressin infusion is stopped. Even temporary control may provide time to stabilize the patient and prepare for elective surgery.64,71
Figure 2 (a) Technetium-99m red cell scanning shows increased tracer activity in the area of the hepatic flexure (arrow). (b) Later, tracer activity has progressed to the transverse colon (broad arrow), as well as the splenic flexure and descending colon (small arrow), confirming that the right colon is the source of the bleeding.
Arterial embolization Arterial embolization of the bleeding artery has been reported, but it is associated with a substantial risk of intestinal infarction, particularly if followed by vaso-pressin infusion.71 Bowel or myocardial ischemia, as well as other complications inherent to contrast arteriography, may complicate both vasopressin infusion and embolization.
Surgery About 20% of patients hospitalized for diverticular bleeding require surgery during that hospitalization.63 Patients who initially require four units or more of blood have a 50% risk of continued bleeding, as compared with a 2% risk of continued bleeding for patients who require two or more units of blood. Persistent instability despite aggressive resuscitation demands surgical intervention.
Elective surgery for recurrent bleeding The risk of recurrent diverticular bleeding after the first episode is about 10% after 2 years and 25% after 4 years.60 The risk is higher after a second episode. Elective surgery is usually recommended after two or more episodes of bleeding. If diverticula are limited to the left side of the colon, left hemicolectomy is appropriate. The decision regarding the extent of resection is more difficult when divertic-ula are distributed throughout the colon. If all previous episodes of diverticular bleeding have been localized to either the right or the left side by scintigraphy or angiography, some clinicians would advocate a corresponding hemicolectomy. The risk of recurrent bleeding from diverticula in the remaining colon is not known. Other clinicians would recommend a subtotal colecto-my. Occasionally, persistent or recurrent severe lower gastrointestinal bleeding cannot be localized. Blind segmental resection is associated with an unacceptable recurrence rate, and subtotal colectomy is the favored procedure.
Anatomy and pathogenesis
The adult topic is a tubular structure that is 4 to 25 cm long and arises from the medial posterior wall of the cecum several centimeters below the ileocecal valve. Its location in the peritoneal cavity varies. Atypical locations, such as the pelvis, retro-cecal area, and right upper quadrant, lead to atypical clinical presentations [see Atypical Presentations, below].
Foreign bodies, tumor (e.g., carcinoid or cecal adenocarcinoma), barium, and adhesions may also cause obstruction. Obstruction leads to bacterial overgrowth. Mucus accumulates in the lumen proximal to the obstruction, and intraluminal pressure increases. Impairment of lymphatic and venous drainage leads to mucosal ul-ceration, bacterial invasion, transmural inflammation, and ischemia. During the first 24 hours after obstruction, most patients have only inflammation. The incidence of necrosis and perforation increases markedly after that. Patients who present with a history of symptoms for 48 hours should be strongly suspected of having perforation and abscess. Free perforation causes generalized peritonitis.
Diagnosis
Clinical Presentation
It has the qualities of midgut visceral pain and is referred to the periumbilical or epigastric areas. It may be cramping or aching in nature, but it is often difficult for patients to describe. Within 12 to 24 hours, inflammation becomes transmural, involving the adjacent parietal peritoneum. Pain then becomes somatic in quality: sharper and more localized. At this time, patients may note exacerbation of pain by coughing, sneezing, or movement.
Anorexia is present in 80% to 90% of patients. Vomiting, when it occurs, does not occur initially but follows the onset of pain. Prominent vomiting is unusual and suggests the possibility of another diagnosis, such as gastroenteritis or small bowel obstruction. Fever is usually low grade. High fever or rigors suggest perforation.
Tenderness in the right lower quadrant can be elicited in more than 90% of patients. Proximity of the inflammatory process to the retroperitoneal muscles produces the psoas and obturator signs. The psoas sign is present when pain occurs as the patient raises the right leg against resistance or, alternatively, when the physician passively extends the right hip with the patient lying on the left side. The obturator sign is present when pain occurs upon internal rotation of the hip. Local hyperesthe-sia of the skin in the right lower quadrant may be noted. Voluntary guarding progresses to involuntary muscle rigidity as the inflammatory process worsens. Diffuse abdominal tenderness and rigidity suggest perforation. An abdominal mass suggests phlegmon or abscess formation.
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Table 3 Differential Diagnosis of Appendicitis |
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Crohn disease |
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Gynecologic conditions: ovarian torsion (especially during pregnancy), ovarian vein thrombosis, endometriosis |
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Perforated right-sided colon cancer |
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Cecal diverticulitis |
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Foreign-body perforation of right colon |
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Meckel diverticulitis |
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Omental torsion |
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Epiploic appendagitis |
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Infections (particularly those involving the ileum): yersinosis, brucellosis, salmonellosis, tuberculosis, amebiasis |
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Vasculitis |
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Appendiceal tumors |
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Psoas abscess |
Young children, for example, often do not express their symptoms clearly; they may present with only lethargy, irritability, and anorexia.78 Elderly patients may have a reduced inflammatory reaction; in such cases, pain may be vague, and there may be less fever or abdominal tenderness.79 Consideration of other diagnoses, such as diverticulitis, may delay surgery.
In patients with AIDS, symptoms may be typical, but concerns about a multiplicity of other diagnoses may delay surgery.
Diagnostic Evaluation
Figure 3 The abscess involves the soft tissues of the abdominal wall (small arrow).
Taking into account the serious consequences of progression to perforation and the relatively low morbidity of appendectomy, most surgeons adopt a relatively aggressive approach to early surgery, accepting a 10% to 15% rate of negative appendectomies.
Some factors that lead to a delay in diagnosis are not under physician control, such as a patient’s delay in seeking medical care. Factors that are under physician control include decisions to perform additional diagnostic studies or to observe the patient for the purpose of improving diagnostic accuracy and reducing the number of unnecessary appendectomies. Clinical scoring systems have generally not been found to improve preoperative diagnostic accuracy.83
This has led some physicians to delay the administration of narcotic analgesics until a surgeon has had the opportunity to examine the patient.
Diagnostic Tests
In cases characterized by a classic presentation, it is standard practice to base the decision to operate primarily on the history and physical examination.The total white blood cell count, the differential count, or both are abnormal in more than 90% of cases, but the decision to perform surgery should not be delayed if the white blood cell count is not elevated.86
In women of childbearing age, a pregnancy test is mandatory. In many cases, no further diagnostic studies are performed. Among women of childbearing age, the rate of negative appendectomy can be as high as 40%.81 In other patients, particularly young children or the elderly, the presentation may be atypical and the diagnosis uncertain. In such patients, additional diagnostic studies may be appropriate and helpful.
Abdominal ultrasound Examination by transabdominal or transvaginal ultrasound or both is useful in pregnant and nonpregnant women of childbearing age to exclude a gynecologic cause of symptoms.81-87 Ultrasound examination is also useful for evaluation of children in cases in which the diagnosis is doubtful. Sonography is widely available, fast, safe, and inexpensive.
On graded compression ultrasonography, the inflamed topic is a noncompressible, aperistaltic tubular structure that is greater than 6 mm in diameter and located in the right lower quadrant. It has a target appearance, and the lumen is filled with anechoic or hyperechoic material.Marked peritonitis or abdominal gas may compromise the examination.
The development of rapid scanning techniques has made CT readily available and practical even in emergency room settings. CT is useful when the diagnosis is unclear, as in elderly patients in whom diverticulitis and perforated colon cancer are important considerations.
Treatment
Preoperative Management
An example of an acceptable regimen for adults is levofloxacin (750 mg I.V. once daily) combined with metronidazole (1 g I.V. every 12 hours).39 If the presence of a phlegmon or abscess is confirmed, antibiotics are customarily continued for 7 to 14 days postoperatively.
Patients with free, unconfined perforation should have abdominal saline lavage during surgery. A prolonged ileus should be anticipated.
Appendectomy
Appendectomy can be performed by a traditional open incision or by laparoscopy. Compared to open appendectomy, lap-aroscopic appendectomy results in decreased wound infections but slightly increased intra-abdominal infections. Postoperative pain is reduced in laparoscopic appendectomy, and patients return to normal activity sooner. Overall, the benefits of laparo-scopic appendectomy over open appendectomy are modest; the greatest benefits occur in women and obese patients.
The most common complications are wound infections, intra-abdominal abscess, intestinal obstruction, and prolonged ileus. Postoperative abscesses are heralded by recurrent malaise, anorexia, and fever, and they are best evaluated by CT.
Interval Appendectomy
Some patients with a contained perforation can be managed by interval appendectomy after treatment with antibiotics or CT-guided percutaneous drainage. The information from preoperative CT or sonography is useful in planning therapy. If imaging shows a phlegmon or small abscess and the patient responds to antibiotic treatment within 48 hours, appendectomy may be postponed for 6 weeks, until the inflammatory process has subsided. If the abscess is large but well circumscribed and accessible, CT-guided percutaneous catheter drainage may be used to reduce the abscess before surgery. The catheter is placed in the abscess and left until drainage from the abscess becomes mini-mal.92 If drainage is successful, appendectomy can be postponed for 6 weeks. However, if a patient with a contained perforation does not respond promptly to antibiotic treatment or drainage, surgery should not be delayed. Catheter drainage is not possible if imaging shows a poorly defined or multilocular abscess or if the abscess is not accessible to percutaneous drainage.
The cecum and terminal ileum should be examined for evidence of Crohn disease or other acute inflammatory bowel disease, for tumor, or for Meckel divertic-ulitis. Lymph nodes in the area should be inspected for evidence of mesenteric adenitis, and biopsies should be performed if the lymph nodes appear abnormal. The gallbladder and duodenum should be palpated. If necessary, the incision should be extended to permit wider exposure. Before closing, the surgeon must feel confident that the cause of the clinical presentation has been explained and that there is no other acute abdominal condition.
Incidental Appendectomy
Incidental appendectomy, performed during surgery for another cause, may be justified in individuals younger than 30 years if the primary surgery would not be compromised. Appendectomy does not increase morbidity when performed under these circumstances.
