What is the diagnosis? Case study from eMedicicne-Medscape
Hint: Look closely at the distal segment of ileum containing pooled contrast in Figure 2.
In this case, the cause of the small-bowel obstruction was clinically obscure. The partial relief of symptoms following medical management indicated an incomplete bowel obstruction. The enteroclysis supported the diagnosis of a giant ileal diverticulum, which was later confirmed at laparotomy.
Giant ileal diverticulum is traditionally a disease found in middle-aged and older persons; it remains a rare cause of subacute intestinal obstruction in young individuals. A preoperative, contrast-enhanced computed tomography (CT) scan is useful in making the diagnosis because it provides direct visualization of the diverticulum and detection of any resultant complications.
A diverticulum is an out-pouching from the wall of the gastrointestinal tract, and it can occur from the stomach to the rectosigmoid colon. There are 2 varieties of diverticula: In the congenital variety, all layers of the bowel are present on the wall of the diverticulum (eg, Meckel diverticulum); in the acquired variety, the wall on the diverticulum consists of mucosa and submucosa only and lacks a muscular layer. The majority of small bowel diverticula are thought to be of the latter variety. These diverticula are usually situated on the mesenteric border of the intestine in mesenteric fat. Acquired jejunoileal diverticulosis was first described by Sommering in 1794 and later in 1807 by Sir Astley Cooper.The true prevalence rate of this rare disease is not known. Autopsy studies report a prevalence rate less than 5% for the jejunoileal variety and 6%-22% for duodenal lesions. Diverticula are usually multiple and tend to be larger and higher in number in the proximal jejunum, whereas distal to the proximal jejunum they tend to be smaller and found in lesser numbers. Simultaneous involvement of both the jejunum and ileum is rare. Males are affected slightly more than females, and the disease is most often seen in adults in the fifth to seventh decades of life.
Current hypotheses regarding the etiology of jejunoileal diverticula focus on the abnormalities of smooth muscle and the myenteric plexus. Careful microscopic evaluation of resected specimens indicates 3 types of abnormality in the bowel wall: fibrosis and decreased number of normal muscle cells consistent with progressive systemic sclerosis; visceral myopathy as evidenced by the presence of fibrosis and degenerated smooth muscle cells; and neuronal and axonal degeneration indicative of a visceral neuropathy. Any of these abnormalities alone or in combination could lead to disordered and nonpropulsive smooth muscle contractions, resulting in increased intraluminal pressure and herniation of mucosa and submucosa through the weak mesenteric margin, which is penetrated by blood vessels. These pulsion diverticula (diverticula formed by pressure from within) usually have a narrow mouth with a thin or absent muscle layer. When the muscularis becomes weak or abnormal, the muscle wall of the diverticulum is thinned and fibrosed and the diverticulum are wide-mouthed.
Diverticula are silent in the majority of cases (60%-70%) and are incidentally found following a radiologic study or during laparotomy for another disease. Nonspecific chronic abdominal complaints, including crampy pain, postprandial bloating, flatulence and diarrhea, malabsorption, and vitamin B12 deficiency occur as a result of bacterial proliferation inside the diverticulum. Acute complications (8%-30%) are dangerous and often result in urgent or emergent laparotomy. Diverticulitis can occur (2%-6% of cases), wherein inflammation is usually the result of a foreign-body inspissation or the presence of an enterolith. If the inflammation is severe, ulceration and hemorrhage may occur and may present as either melena or hematochezia. Small-intestine diverticula should be considered as a cause of severe lower gastrointestinal bleeding in a patient in whom no other source of bleeding is readily identified. In extreme cases, the wall of the diverticulum may undergo ischemic necrosis and become gangrenous. Perforation of a diverticulum results in generalized peritonitis, a localized abscess, or a fistula formation between the adjacent loops of bowel.
Small-bowel obstruction can occur as a result of postinflammatory adhesions, bands, or by volvulus of the diverticulum bearing a loop of intestine. Incomplete bowel obstruction may be caused by enteroliths that form in the diverticula, which subsequently become dislodged and obstruct the distal intestine. The clinical picture of intestinal diverticula may be confused with other causes of an acute abdomen (eg, acute appendicitis, cholecystitis, peptic and enteric perforations). Metabolic blind-loop syndrome/small intestine stasis syndrome may occur, along with pernicious anemia (in extreme situations) resulting from vitamin B12 deficiency. Other complications of giant diverticulum include infestation with roundworms or threadworms, neoplastic changes, and pneumatosis cystoids. There is no single confirmatory diagnostic test for small-bowel diverticulum. A plain abdominal x-ray and/or chest x-ray may demonstrate pneumoperitoneum indicating perforation, or multiple air-fluid levels indicating obstruction. A barium swallow follow-through examination may show filling of the diverticula with oral contrast. In the case of mesenteric abscess formation, small bowel loops are displaced by the mass. On enteroclysis (the most sensitive contrast examination of the small bowel), contrast may be seen to pass back and forth from the intestinal lumen into the diverticulum. This condition may be associated with hypertrophy and dilatation of the portion of bowel proximal to the diverticulum. Findings on abdominal CT scans include jejunoileal wall thickening, mesenteric thickening and inflammation, free gas, and fluid collection. A phlegmon can be identified in the retroperitoneal space, providing an initial clue to a possible small-intestine diverticular disease. Direct visualization of the diverticulum is also possible using CT. An esophagogastroduodenoscopic examination is not useful in acute diverticulitis of the small bowel, as jejunal or ileal diverticulum are not accessible by this approach. A colonoscopic examination is useful in evaluating the source of bleeding and excluding other diagnoses; however, small-bowel diverticula are generally not accessible to colonoscopy. These diverticula can be investigated by enteroscopic examination using capsule enteroscopy and double-balloon enteroscopy. The limitation of capsule enteroscopy lies in its inability to localize with accuracy the region of the small bowel involved. In double-balloon enteroscopy, an experienced operator is required to accurately recognize these lesions. Both investigations are of limited value in emergent situations, such as is depicted in this case. As a result, the diagnosis depends on exclusion; therefore, it is seldom made before a laparotomy. In nonacute but symptomatic conditions, diagnostic laparoscopy plays an important role in ensuring an accurate diagnosis in most cases and avoiding unnecessary laparotomy.
The mere presence of a diverticulum does not justify its surgical removal. If the diverticula are large and found in an isolated, dilated, and hypertrophied segment, and if they are the cause of intestinal obstruction, hemorrhage, adhesions, perforation, or intra-abdominal or retroperitoneal abscess formation, then they should be removed. Patients with steatorrhea or pernicious anemia should be treated initially with a course of antibiotics as well as vitamin B12 and folate supplementation plus correction of the anemia. If a patient fails to respond to medical therapy, laparotomy for removal of the diverticula should be considered. A single diverticulum is best treated by diverticulectomy. Inversions of small lesions are best avoided because these can give rise to a lead point for intussusception. When the diverticula are confined to a segment of the intestine, resection with restoration of bowel continuity should be the goal. Multiple diverticula scattered throughout the small bowel present a difficult treatment scenario. Resection should be restricted to those segments containing the largest diverticula or those producing complications such as perforation, abscess, and bowel adhesions.
In the case above, the patient underwent an exploratory laparotomy which revealed a single, giant, wide-mouthed diverticulum of 15 cm in diameter in the distal ileum with patent proximal and distal lumen (Figure 3). The ileal and distal jejunal loops were distended and aperistaltic. The diverticulum was thick-walled and inflamed, and it adhered to an adjacent loop of bowel. It did not show any evidence of perforation or gangrene. A segmental ileal resection including the diverticulum was performed, with end-to-end anastomosis. A thorough search of the peritoneal cavity did not reveal any other abnormalities. The postoperative period was uneventful. The histopathological examination of the resected diverticulum demonstrated small-intestine mucosa with mucus gland metaplasia, areas of ulceration, and acute inflammatory cell infiltration in the bowel wall with nerve plexus not recognizable in wider areas, all of which were suggestive of a heavily inflamed diverticulum with early infarction. After 1 year of follow-up, the patient was symptom free.
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