Thumbprinting on abdominal X-ray refers to the appearance of rounded mucosal indentations protruding into the lumen, caused by submucosal edema or hemorrhage. This radiologic sign is classically associated with ischemic colitis, where compromised blood flow leads to mucosal and submucosal swelling. Unlike inflammatory bowel diseases or colon cancer, ischemic colitis predominantly shows this pattern due to acute vascular insufficiency affecting the colon wall, making thumbprinting a hallmark imaging feature in ischemic injury diagnosis.

Reference: Bailey & Love's Short Practice of Surgery, R. C. Russell, 27th Edition.