Although most small bowel diverticula are of little clinical significance, approximately 10–20 % will develop complications [1]. Potential sequelae include inflammation, gangrenous change, perforation, peritonitis, bleeding, obstruction, and intestinal stasis leading to blind loop syndrome [11, 12]. Jejunoileal diverticula are more likely to have complications than duodenal diverticula [1, 13]. Of the diverticula that developed complications, jejunoileal diverticula were more likely to perforate and form abscesses, whereas duodenal diverticula were more prone to bleeding [1].

Diverticula in the small bowel are less likely to develop inflammation than those in the colon, probably due to the relative sterility of small bowel contents and the lesser degree of stasis that occurs in the larger diverticula of the small bowel [2]. Stasis of diverticular contents may be promoted by foreign bodies, enteroliths, inspissation of bowel contents, or a smaller diverticular ostium which can reduce the outflow of intestinal fluid from the diverticulum [2, 11, 14]. Because small bowel diverticulitis is more commonly found at the mesenteric side of the bowel, the mesentery can close off the localized inflammatory process from the rest of the peritoneal cavity. As a result, peritonitis and pneumoperitoneum may not be detected clinically or radiologically unless there is rupture of the mesenteric peritoneum that had previously sealed off the abscess [11].

Small bowel diverticulitis presents a diagnostic challenge on clinical exam and can mimic a host of more common abdominal pathologies including acute appendicitis, cholecystitis, perforated peptic ulcer disease, and colonic diverticulitis [12, 15]. A patient with small bowel diverticulitis may present with intermittent abdominal discomfort, acute abdominal pain, fever, chills, and leukocytosis [4, 9, 16–21]. Peritoneal signs may be appreciated on abdominal exam [9, 18].

In the setting of small bowel diverticulitis, barium study may allow detection of air- or contrast-filled diverticula along the mesenteric small bowel wall, thickening of the bowel wall, bowel lumen obstruction, or extraluminal flow of contrast (Fig. 4.3) [12].

The CT findings (Table 4.1) are typically a focal inflammatory mass containing air, fluid, or an air-fluid level adjacent to asymmetrically thickened small bowel wall, with the presence of surrounding inflammation and mesenteric fat stranding [3, 9, 12]. The small bowel wall thickening is most prominent on the mesenteric side. The inflamed diverticulum may be visible along the mesenteric border of the small bowel loop (Fig. 4.4). The differential diagnosis on CT may include a perforated neoplasm, perforation secondary to a foreign body, NSAID-provoked ulceration, intramural hematoma, and local inflammatory bowel disease [3].

CT with multiplanar reconstruction can be employed to identify small bowel diverticula, with excellent visualization of the narrowed diverticular neck [2]. CT with coronal reformatting is especially useful for detecting single diverticula that are difficult to detect on axial views and can allow recognition of additional diverticula [3, 14].

Meckel’s diverticulum is the most common congenital anomaly of the GI tract, seen in approximately 2 % of the population. It is a true diverticulum and is therefore present on the antimesenteric border of the distal ileum. It is most commonly located within 100 cm of the ileocecal junction [22]. It contains hypertrophic gastric mucosa (in 25–50 %) and has a lifetime complication risk of up to 4 %. Heterotropic pancreatic tissue is present in approximately 10 % of the cases.

The majority of cases of symptomatic Meckel’s diverticulum are seen in the pediatric population. Hemorrhage is the most common complication and is most often painless. Bowel obstruction is the second most common complication and is usually seen in older children and adults. The bowel obstruction can be secondary to volvulus, intussusception, or hernia.

Meckel’s diverticulitis most often presents with abdominal pain and fever. It is secondary to obstruction of the mouth of the diverticulum most commonly by an enterolith, fecolith, or foreign body. Littre hernia represents Meckel’s diverticulum which has herniated in a hernia sac.

Meckel’s diverticulum can be seen on barium studies as a blind-ending tubular outpouching arising from the antimesenteric border of the ileum with a triradiate fold pattern at the junction of the diverticulum and ileum.

The heterotopic gastric mucosa present in a Meckel’s diverticulum accumulates and secretes pertechnetate anion and is therefore detected on technetium-99m pertechnetate scan as a focal area of increased radiotracer activity (Fig. 4.5). Technetium pertechnetate scintigraphy has high sensitivity of more than 80 % in the pediatric population and slightly lower sensitivity of 63 % in adult population [23]. CT may show changes of small bowel diverticulitis in the right lower quadrant or may show volvulus or intussusception (Fig. 4.6).

Acute mesenteric ischemia is characterized by inadequate blood flow to the bowel wall, leading to ischemia. Mesenteric arterial occlusion carries a high mortality, unless the patient undergoes emergent vascular surgery.