Venous axial CE-CT
A 69-year-old woman presented with abdominal pain, increasing during movement. Clinical examination showed no pressure pain or defense. The body temperature was 37°C. Laboratory results showed a CRP of 182 mg/L (<5.0 mg/L) and a white blood cell count of 14.38 10³/µL (3.65-9.3010³/µL).
Contrast-enhanced CT of the abdomen showed multiple proximal jejunal diverticula at the mesenteric side. Multiple diverticula had a thickened wall with associated surrounding fat stranding and infiltration (Fig. 1a,b, 2) . Free air was seen in the infiltrated mesenterial fat near the diverticula (Fig. 1b). Retrospectively the diverticula were visible on a non-contrast-enhanced CT 3 years before (Fig. 3).
Jejunal and ileal diverticulosis is a rare acquired abnormality, with a reported prevalence of 0.3%-1.3% on autopsy, and an increasing incidence with age. They are far less frequent compared to colon (>50% at the age of 60) and duodenal (around 5%) diverticulosis. Jejunal diverticulitis is a very rare disease (incidence of < 0.02%). [1, 2]
The aetiology of diverticulosis is unclear, they are thought to be outpouchings at weak parts of the intestinal wall, in general the site where an artery enters the muscular layer. Bowel spasms increase the pressure in the intestine and create more diverticula or enlarge existing ones. Diverticulosis of the jejunum and ileum arise at the mesenteric border of the small bowel. They are more frequent at the proximal jejunum. There is an association with intestinal motility disorders (myopathies, progressive systemic sclerosis or visceral neuropathies). 
Most small bowel diverticula are asymptomatic, almost all symptoms are caused by complications.  Complications include inflammation (diverticulitis) with or without perforation, haemorrhage, malabsorption due to bacterial overgrowth or obstruction. When complications occur symptoms are abdominal pain, nausea and/or fever.
Diagnosis of uncomplicated diverticula is usually an incidental finding on CT or MRI imaging, with declining small bowel follow-through examinations. The diverticula appear as lobular outpouchings, they can be filled with bowel fluid or air. Ultrasound is not specific, the diverticula are difficult to diagnose because of superimposed air in the bowel. On CT or MRI diverticulitis presents as thickening of the diverticular wall with adjacent fat stranding. The surrounding small bowel wall can be thickened. When perforation occurs free air is visible in the mesenterium, with possible ascites. Obstruction can show dilated bowel loops with a starting point at an enlarged/filled diverticula, collapsed distal bowel and air-fluid levels. [5, 6]
Management for uncomplicated diverticulitis is conservative, with bowel rest, clear liquid diet and antibiotics. Therapy for perforated diverticulitis is surgical, with resection of the affected segment and anastomosis. 
Small bowel diverticula are easy to overlook on CT examinations, but complications can give symptoms and typical findings on imaging.
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 Krishnamurthy, S., Kelly, M. M., Rohrmann, C. A., & Schuffler, M. D. (1983) Jejunal diverticulosis: a heterogenous disorder caused by a variety of abnormalities of smooth muscle or myenteric plexus. Gastroenterology 85(3), 538-547 (PMID: 6409704)
 Psathakis, D., Utschakowski, A., Müller, G., Broll, R., & Bruch, H. P. (1994) Clinical significance of duodenal diverticula. Journal of the American College of Surgeons 178(3), 257-260 (PMID: 8149017)
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