Small bowel injury

History

Injuries to the small intestine have been described in the medical literature throughout history. Hippocrates was the first to describe intestinal injury from penetrating trauma. Aristotle is recognized as the first to report a small bowel perforation from blunt trauma. Throughout the Middle Ages and into the early 20th century, physicians have reported on surgical techniques and the nature of these injuries. In 1275, Guillaume de Salicet reported the first successful suture repair of a tangential intestinal wound. In 1686, Bonet described an injury to a hunter thrown against a tree by a stag in which autopsy showed a ruptured terminal ileum and cecum. The slow and insidious nature of small intestinal injuries, which is clinically pertinent in modern times, were described in multiple cases by Morgagni in 1761. Attempted surgical interventions for intestinal injuries were of interest in the medical literature throughout the various military conflicts in the 19th and 20th centuries. Results of surgical intervention remained dismal until the late 19th century, as early operative intervention was recognized to improve outcomes. Dr. Vera Gedroitz, during the Russo-Japanese war, positioned her operative theatre close to the front lines, and by selecting casualties wounded within hours, she was able to improve outcomes. As surgical techniques improved in the early 20th century, there was growing interest in the surgical management of small intestine injuries. However, despite earlier recognition and technological advances, the mortality for a laparotomy for intestinal perforations at the beginning of World War I was equal to the mortality of nonoperative intervention. As the recognition of these injuries improved and casualties were more rapidly evacuated, improvements in anesthesia and the management of shock throughout World War II, Korean War, and Vietnam war continued to improve mortality. The lessons learned in these conflicts were adopted by civilian centers. The awareness of early recognition and repair as well as the improvement in diagnostic technology has led to significant improvement in outcomes.

Incidence

The incidence of small intestine injuries differs by the mechanism of injury. The small intestine occupies the largest portion of the peritoneal cavity and therefore has a higher incidence of injury after penetrating trauma. For stab wounds that penetrate the peritoneum, only 30% of these patients will have a small bowel injury that would require intervention. For gunshot wounds, over 80% of patients will have injuries requiring surgical repair. In blunt trauma, the small intestine is the third most injured organ, after the liver and spleen, but the incidence of injury is lower than previously thought ( Table 1 ). Estimated frequency of small bowel injury in blunt abdominal trauma ranges from 5% to 15%, with perforations occurring in less than 1% of blunt abdominal traumas. Though small bowel injuries are uncommon following blunt injuries, the incidence is thought to be rising. The most common mechanism for blunt abdominal trauma is motor vehicle crashes. With the increase in the use of seat belts and safety features of motor vehicles, fatalities have decreased, but injuries associated with both proper and improper use of these devices have increased.

Mechanism of injury

The small intestine can be injured by both penetrating and blunt forces. Gunshots and shotgun wounds, stabbings, and impalements each have varying probability of clinically significant injuries. Gunshot wounds to the abdomen will have a surgically significant injury in greater than 80% of patients. High-velocity projectiles may also cause a blast effect that may lead to delayed perforations near the wound channel. Shotgun injuries are directly related to the shot size and the distance between the victim and the muzzle of the shotgun. Large shot sizes and close-range shotgun wounds are more damaging. Stab wounds are less lethal as a third of the injuries do not violate the peritoneal cavity. Stab wounds are often managed selectively; therefore, there is increased risk of missed injury compared with often mandatory laparotomy for gunshot wounds to the abdomen.

Blunt injuries to the small intestine are uncommon but are increasing due to high-speed transportation and safety restraints. Fatalities from motor vehicle crashes have decreased with improvements in road safety as well as safety restraints and airbags. Traffic casualties that would have died at the scene or sustained rapidly fatal injuries in the past are now presenting with injury patterns related to restraint devices, which includes small bowel injuries. The presence of a seat belt sign was thought to be significantly associated with small bowel perforations. In a 2003 multi-institutional report by Fakhry et al, however, the follow-up study performed 15 years later did not demonstrate a significant association. Though not significantly associated with small bowel perforations, the presence of a seat belt sign is indicative of changes in potential injury pattern due to the improved safety of modern automobiles.

The pathogenesis of small bowel rupture has been ascribed to crushing, shearing, or bursting forces. A violent force directly applied to the abdomen can crush the intestines between the external force and the spine. This is often associated with other injuries. Shearing injuries occur from sudden deceleration with typical injuries occurring at points of relative fixation such as the ligament of Treitz and terminal ileum or sites of adhesive bands. The small bowel may burst if force is applied to a distended segment, where ends may be temporarily closed. In summary, gaping small bowel disruptions with mesenteric mutilation and extensive small bowel contusion suggest a crush mechanism ( Fig. 1 ). Small bowel injuries with isolated, clearly defined points of rupture may represent burst injuries and shredding injuries, especially if near the ligament of Treitz, cecum, or other points of fixation, and are likely caused by shearing forces ( Figs. 2 and 3 ).