To analyze and summarize the ultrasonographic features of intestinal and periintestinal lesions in small intestinal Crohn's disease (SICD).

Twenty-five patients with SICD who were admitted to Suzhou Hospital Affiliated to Nanjing Medical University from June 2009 to June 2019 were selected retrospectively, of whom 42 underwent transabdominal intestinal ultrasound examination. The ultrasound images of the diseased intestinal wall, abdominal complications, and activity assessment results of SICD were analyzed and summarized.

The main manifestation of diseased small intestines was intestinal wall thickening (41/42), which was mostly annular and full-layered. Approximately 83.3% (30/36) of thickened segments of the intestines were located in the right lower quadrant (30/36). In active and severe cases, the layers of the intestinal wall disappeared (16/42), and the stiffness of the bowel increased, and peristalsis disappeared. In 26 of the diseased intestinal walls, deep ulcerations can be found in different layers of the wall. Fifteen patients had stenosis, and the image features were intestinal wall thickening and intestinal lumen narrowing with the expansion of the proximal intestine; 8 developed fistula, and the images showed linear echogenic or hypoechoic bands between the intestinal wall and other tissues, with or without strong gas echo; 30 had creeping fat, which manifested as hyper-echogenic mass-like fat around the diseased intestines; 20 developed mesenteric lymphadenitis, 90% of whom had lesions<20 mm in length; 16 had ascites; 9 developed an abdominal mass, including 5 cases of abscess, and the image feature was localized fluid area in the inflammatory mass or mesenteric region, without blood flow signal; 1 developed perforation, and the image features were continuity interruption of a thickened bowel wall, and hypoechoic inflammatory area near the interruption area, with free fluid possibly found inside the abdominal cavity; 8 had inflammatory polyps, which manifested as one or more regular hypoechoic or iso-echoic masses protruding into the bowel lumen; and 3 had diverticulum, manifesting as thinning and swelling of local intestinal wall, mostly located at the mesangial margin. The incidence of stenosis, creeping fat sign, mesenteric lymphadenitis, and peritoneal effusion in the active phase (by ultrasound evaluation) was significantly higher than that in the remission phase (P=0.002, 0.000, 0.024, and 0.025, respectively). The mean maxium thickness of the intestinal wall and creeping fat in the active stage was significantly higher than that in the remission stage (P=0.000). There was a good consistency between ultrasound and Harvey Bradshaw index in assessing the activity of SICD (Kappa=0.897, P<0.05).

Transabdominal bowel ultrasound can accurately show the classic features of Crohn's disease as well as the complications frequently associated with the disease. The addition of color Doppler imaging may allow differentiation of chronic from active bowel wall thickening. Transabdominal bowel ultrasound can be used as a routine imaging assessment tool for SICD.