Colon and rectal injuries

Incidence and mechanism of injury

Mechanisms of colon and rectal injuries can be classified as direct penetration of the bowel wall by a foreign body as with stab or gunshot wounds, high-pressure blowout of the bowel wall as occurs in blunt trauma, or devascularization injury secondary to avulsion of the supporting mesentery. The vast majority of colon injuries are caused by penetrating trauma. Firearms account for 75% to 90% of penetrating colon injuries. The colon is second only to the small bowel in the frequency of organs injured in penetrating trauma. The high incidence of colon injuries in penetrating trauma relative to other organs is a reflection of the size and distribution of the colon within the abdominal cavity. In contrast, blunt colon injuries are rare, occurring in less than 5% of patients with abdominal injuries. Most occur following high-energy motor vehicle crashes and present as blowout disruptions of the colonic wall or mesenteric avulsions. Approximately 80% of rectal injuries are caused by firearms, 10% by blunt trauma, 6% by transanal or impalement injuries, and 3% by transabdominal stab wounds.

Diagnosis

Colon injuries are most often diagnosed during operative exploration. Although it is rare to make an organ-specific diagnosis preoperatively, free intraperitoneal air may occasionally be seen on chest radiograph or abdominal computed tomography (CT) scan. Blood or a positive occult hemoglobin test on digital rectal examination may also be seen. Suspicion of enteric injury should be raised in all patients with evidence of fever, tachycardia, peritonitis, and leukocytosis. CT scan evidence of intra-abdominal fluid in the absence of solid organ injury warrants further investigation. This may consist of diagnostic peritoneal lavage, serial abdominal examinations, diagnostic laparoscopy, or exploratory laparotomy. A triple-contrast CT scan may be helpful in patients who have penetrating flank injuries with no clear evidence of intraperitoneal injury.

Blunt colon injuries are evenly distributed around the colon and usually present as large blowout disruptions of the colon wall or avulsion injuries in which the mesocolon is stripped from the adjacent colon. Although penetrating colon injuries are usually obvious, missed injuries are often the result of small-caliber gunshot wounds or stab wounds to areas that are difficult to examine, such as the splenic flexure and rectosigmoid junction. If a perforation is not obvious, feculent odor, hematoma, or mesenteric staining may suggest an area that requires further evaluation. The suspicious area should be completely mobilized. Division of one or two terminal mesenteric vessels may be necessary to adequately evaluate potential injuries at the mesenteric border. A final diagnostic maneuver is to create a closed loop of colon by proximal and distal manual compression and gently milk the bowel contents toward the suspected injury. The extrusion of fecal material or gas is diagnostic, and its absence effectively rules out colonic injury.

Patients with penetrating injuries to the abdomen, pelvis, buttocks, perineum, or upper thighs and any history of lower abdominal or pelvic pain should be suspected of having a rectal injury. Evaluation begins with a digital rectal examination, in which the presence of gross or occult blood should trigger further investigation. However, it is important to note that a negative digital rectal examination or absence of blood does not rule out a rectal injury. Rigid proctoscopy should be performed in all patients with suspected rectal injury. Unstable patients who have undergone laparotomy for hemorrhage control should have the abdomen temporarily closed and should undergo proctoscopy once stable. Palpation or visualization of a perforation is definitive evidence of an injury. However, intraluminal blood or a submucosal hematoma is often the only evidence of rectal injury. In such cases with distal rectal injuries, transabdominal exploration and rectal mobilization does not improve the chance of definitive diagnosis and may increase the chance of iatrogenic vascular, urologic, or neurologic injury. Therefore, these patients should be treated in the same manner as patients with confirmed rectal injuries.