OBJECTIVE: Large-bowel obstruction is most often due to primary carcinoma, diverticulitis, or volvulus. In populations of patients in which trauma is prevalent, however, an additional important consideration is traumatic diaphragmatic hernia. We describe the findings on plain radiographs and single-contrast enema in four adults who had vague complaints of abdominal pain days to months after an abdominal stab injury and large-bowel obstruction resulting from herniation of colon or omentum through the left hemidiaphragm. MATERIALS AND METHODS: We retrospectively analyzed plain radiographs of the chest and abdomen that were obtained before confirmation of colonic obstruction by single-contrast enema, surgery, or both in four men. Herniation of colon or omentum through the left hemidiaphragm was confirmed at surgery in all four cases. RESULTS: Posteroanterior and lateral radiographs of the chest obtained as part of the initial evaluation showed, in all four cases, abnormalities of the left hemidiaphragmatic contour. These included elevation of the hemidiaphragm in one case, loss of definition of a portion of the hemidiaphragm due to adjacent confluent opacity in two cases, pleural effusion in two cases, and small cystic lucencies above the diaphragmatic contour in one case. Abdominal radiographs obtained at the same time as the initial chest radiograph showed normal findings in two cases and mild dilatation of gas-filled colon in the upper part of the abdomen in two cases. In three of the four patients, progressive dilatation of the colon to the level of the splenic flexure was seen on serial abdominal radiographs. Large-bowel obstruction was confirmed by single-contrast enema in three cases and surgery in four cases. Minimal dilatation of the large bowel in the fourth patient resolved the day after admission; however, progression to complete obstruction was shown by single-contrast enema the following day. CONCLUSION: Delayed herniation through a trauma-induced defect in the left hemidiaphragm can be an unsuspected cause of large-bowel obstruction. Abnormalities of the left hemidiaphragmatic contour on plain radiographs of the chest should suggest the diagnosis in patients who have abdominal pain, colonic dilatation, and a history of abdominal injury.