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CASE SCENARIO

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A 47-year-old woman is the restrained driver in a high-speed motor vehicle crash. She has a prolonged extrication time and is brought to the trauma center boarded and collared. She is hemodynamically stable, but she complains of right lower extremity pain. On examination, she has an obvious deformity of the right femur and bruising on her left shoulder and anterior abdomen superior to the umbilicus. Her abdomen is soft, with mild periumbilical tenderness.

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EPIDEMIOLOGY

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Blunt bowel or mesenteric injury (BBMI) occurs in approximately 1% of blunt traumas and is the third most common intra-abdominal injury, surpassed only by trauma to the liver and spleen. The most common site of gastrointestinal injury involves the proximal jejunum, followed by distal ileum, mid small bowel, colon, duodenum, and stomach, in decreasing order.1 The incidence of blunt small bowel injury rose steeply with the introduction of high-speed travel after WWII, and again spiked with the first seatbelt laws in the 1970s.2,3 Motor vehicle crashes account for 70% to 85% of all BBMIs, followed by other rapid deceleration mechanisms including pedestrians struck by cars, bicycle crashes, assaults, falls, blasts, and horse kicks. In pediatric cases, child abuse should also be considered.

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Blunt bowel injury causing perforation carries a high mortality, which correlates directly with time to repair. Perforation repaired within 8 hours carries a mortality of 4%. A delay of as little as 8 to 12 hours, however, has a mortality of 9%, and at 24 hours it rises to 15%. Morbidity also increases, with the risk of abscess and surgical site infection quadrupled after 24 hours.4,5

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PATHOPHYSIOLOGY

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Deceleration injuries inflict damage via a combination of three types of forces. A crushing injury causes direct tissue damage, including lacerations, perforations, and hematomas. This often occurs when the bowel is compressed between two fixed objects, such as the spine posteriorly and any other anterior object (steering wheel, seatbelt, or bike handlebar). Shearing forces between fixed retroperitoneal structures and free-floating bowel can also tear the bowel wall or its supplying mesentery. This most commonly occurs at the proximal jejunum near the fixed ligament of Treitz, the terminal ileum near the retroperitoneal cecum, or the transverse and sigmoid colons at their retroperitoneal attachments.6 Lastly, bursting injuries occur when intraluminal pressure exceeds the bursting strength of the small bowel wall, generally thought to be 120 to 140 mm Hg. This intraluminal pressure can easily be accomplished by relatively small external forces when the bowel lies in a closed-loop position.7

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CLINICAL PRESENTATION

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Clinical findings of BBMI include abdominal tenderness, rigidity, and absent bowel sounds. Unfortunately, these symptoms are vague, and therefore insensitive and nonspecific to bowel injury. In fact, studies have shown that abdominal tenderness and rigidity are present in less than 50% of BBMI cases.8 Furthermore, ...

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