Jejunal diverticulitis complicated by perforation and abscess
Contrast-enhanced CT of the abdomen and pelvis revealed a 10-cm segment of proximal jejunum with markedly thickened walls and a significant amount of inflammatory stranding of the adjacent mesenteric fat (Figure 1). An extraluminal region of soft tissue attenuation between 2 loops of involved bowel appeared to contain a small amount of gas. Additionally, at least 3 pockets of contrast material were noted outside of the bowel lumen in an intramural location.
The patient was diagnosed with jejunal diverticulitis complicated by perforation and abscess formation. She was subsequently taken to surgery, where 6 inches of proximal jejunum and an associated inflammatory mass were surgically removed. Gross examination of the surgical specimen showed 3 diverticula. A histologic examination revealed multiple small diverticula (approximately 10) with perforation of a singlediverticulum and associated abscess formation. The patient tolerated the procedure well and recovered completely.
A true diverticulum, containing all 3 layers of intestinal wall, is present congenitally in 2% to 3% of individuals. Generally, this is a Meckel's diverticulum, which is located on the antimesenteric side of the ileum.1Acquired small bowel diverticula, however, are thin-walled mucosal herniations through the gaps in the muscular layers along the pathway of visceral vessels and, thus, are considered "pseudodiverticula" because the wallsare composed of only mucosa and submucosa.2Enteroclysis detects acquired small bowel diverticula in 2.3% of adults who are >40 years of age,and autopsy detects them in 1% of all patients.3Diverticula aregenerally larger and more numerous in the proximal jejunum than elsewhere in thesmall bowel. Most jejunal diverticula remain asymptomatic and are incidental findings during small bowel follow-through studies, abdominal CT,surgery, or autopsy.1However, some reports cite jejunal diverticula complication rates as high as 30%.2Acute complications include diverticulitis, perforation, peritonitis, hemorrhage, adhesions, and fistula formation. Pseudo-obstruction, blind loop syndrome, jejunal dyskinesia, chronic diverticulitis complicated by the formation of enterolith, and vitamin B-12 malabsorption secondary to chronic stasis and bacterial overgrowth within thejejunal diverticula have also been reported.1,2,4,5
The pathogenesis of small bowel diverticula unrelated to surgery, Crohn's disease, or scleroderma remains unclear. Akin to the pathogenesis of colonic diverticula, abnormalities in peristalsis, intestinal dyskinesia, and high intraluminal pressures are thought to play a role.2,3 Unlike their counterparts in the colon, jejunal diverticula are less likely to become inflamed. This is presumably due to their larger size and betterintraluminal flow of the relatively sterile contents of the jejunum.1 A lack of pathognomonic signs and symptoms makes the preoperative diagnosis of small bowel diverticulitis very difficult.5,6 Symptoms vary from vague intermittent abdominal pain highly variable in location, to acute abdominal pain, with associated leukocytosis.2 This clinical diagnostic dilemma often yields variable presumptive diagnoses, including, but not limited to, perforated ulcer, appendicitis, and colonic diverticulitis.6 Furthermore, recognition of small bowel diverticula at the time of surgery may be extremely difficult, since they are frequently hidden by the mesentery. The reported mortality for perforated small bowel diverticula ranges from 21% to 40%.1
Radiographic diagnosis of jejunal diverticulitis can be difficult. The identification of a saccular out-pouching presenting as an air- or contrast-filled structure juxtaposed to the mesenteric side of the proximal small bowel is the most significant finding.1Inflamed diverticula are generally deformed, with irregular borders with corresponding rigidity during fluoroscopic compression. Adjacent loops of jejunum are frequently narrowed in response to localized inflammation, edema, or spasm.1 CT typically shows nonspecific changes that are consistent with inflammation and infection. Frequent descriptions include evidence of an inflammatory mass containing gas, wall thickening of the involved segment, and edema of the surrounding tissues, including fat or fascial planes.6 Areas of low attenuation within the mass and rim enhancement after intravenous contrast administration, although nonspecific, may suggest abscess formation. Underlying necrotic tumor or hematoma may also have this appearance and should always be considered.6
The difficulty in diagnosing small bowel diverticulitis certainly contributes to the high mortality associated with this particular disease. Therefore, small bowel diverticulitis should always be considered in formulating a differential diagnosis for an intra-abdominal inflammatoryprocess. Although CT findings in jejunal diverticulitis are by no means specific, they may suggest the correct diagnosis. Consequently, with the appropriate level of clinical suspicion and a suitable imaging study, the correct diagnosis of this uncommon disorder is certainly feasible.