Acute mesenteric lymphadenitis and its associated CT and MRI features
Acute mesenteric lymphadenitis is a self-limited condition resulting from inflammation of ileal mesenteric lymph nodes, sometimes with associated terminal ileal and cecal inflammation. It often manifests with right lower quadrant pain and diarrhea and most often occurs in children and young adults. The most common causative agents include the bacteria Campylobacter jejuni and Yersinia species, although viruses may also be causative.
Characteristic CT and MRI findings include a cluster of three or more enlarged ( ≥ 5 mm) right lower quadrant mesenteric lymph nodes, sometimes with associated thickening of the cecum or terminal ileum, and a normal-appearing appendix.
CT and MRI findings of segmental omental infarction include a large (5 to 10 cm) well-circumscribed focus of fat attenuation/signal intensity with associated inflammatory fat stranding. Typically, the infarction is located in the right anterolateral aspect of the abdomen between the colon and parietal peritoneum at or above the umbilical level (in the expected location of the greater omentum).