Traumatic Small Bowel Injury

In summary, in a patient who underwent blunt abdominal trauma, Focused Abdominal Sonography for Trauma (FAST) should be performed as an adjunct to the primary survey. A hemodynamically unstable patient with a positive FAST should be taken to the operating room for exploration for possible life-threatening intrabdominal pathology.^{[1, 2]}

If FAST is not available or the exam is limited (may be limited by body habitus, subcutaneous emphysema, small bowel gas, or user variability), a diagnostic peritoneal lavage (DPL) may be considered.^{[1, 2]}

If more than 10cc of blood, succus, or bile is found on DPL, this is considered a positive result and should also trigger abdominal exploration in the operating room.^[1] A hemodynamically stable patient with a positive fast should undergo a CT scan with IV contrast.^[1-3] Signs of hollow viscous injury or mesenteric injury include fat stranding, hematoma of the mesentery, contrast extravasation, extraluminal air, >4mm thick bowel wall, and free fluid in the absence of solid organ injury.^[4]

If there are no definitive signs of bowel injury requiring exploration, then the patient should be monitored for 24-48 hours with serial abdominal exams, as CT scan can be normal in 4-20% of patient with documented blunt rupture of a hollow viscous.^{[2, 4]} A partial thickness injury with or without a devascularized segment of bowel from a mesenteric injury may also evolve into full thickness necrosis and perforation over the subsequent few days.^[2]

Gunshot wounds (GSW) to the abdomen should be evaluated with a FAST exam as part of the primary survey, with the addition of X-rays to map the track of the projectile.^[1] In the case of abdominal GSW, abdominal, chest, and pelvis films can help locate any retained bullets and map the trajectory of each wound. If the patient is hemodynamically unstable, they should be taken directly to the operating room.^[1]

Almost all patients with abdominal GSWs, the exception being patients without violation of the peritoneum on CT, should be taken to the operating room for exploration.^[2] Another example of a patient who may not require exploration is a patient with an isolated GSW to the RUQ. If the bullet is lodged in the liver on CT and the patient is stable, they may not need exploration, however they should be monitored closely for any change in hemodynamics.^[5]

Blast injuries are similar to gunshot wounds in that projectiles enter the body at a high velocity, and therefore X-rays to map the track and identify retained objects can be useful. Management is similar to gunshot wounds, however there is an additional component of blunt force involved, thus patients without any obvious injuries should be monitored with serial exams as partial thickness injuries may necrose and evolve over the first few days.^[2]

In any stab wound, hemodynamic instability, peritonitis, and evisceration all necessitate exploratory laparotomy. Otherwise, CT imaging with contrast is recommended. This can help evaluate if the fascia has been violated in an anterior stab wound, and if no violation is found then the patient may be safely discharged.^{[1, 2]}

Local wound exploration is another way of determining fascial violation, depending on surgeon comfort level. If the fascia was violated, then the patient should be monitored and any concerning CT scan findings, worsening of abdominal exam, or signs of bleeding should prompt exploratory laparotomy.^[2]

If there is an isolated injury to the left upper quadrant without concerning findings on CT, then diagnostic laparoscopy might be considered to evaluate the diaphragm as this is often missed on imaging.^[1]

Exploratory laparotomy is preferred over laparoscopy due to the high rate of missed injuries in laparoscopy.^[4] After packing each quadrant and evaluating for bleeding as is done in every trauma exploratory laparotomy, the bowel should be run to look for injuries.^[3] The small bowel should be eviscerated to the right, the ligament of treitz (LOT) identified, and the bowel examined from there to the ileocecal valve.^[4]

Blunt ruptures of the small bowel (often related to seat belt injuries) most commonly occur near the ligament of Treitz or ileocecal valve or at the site of adhesions.^[4] Small bowel injuries are often associated with mesenteric bleeding and hematomas following blunt injury, but may be subtle in penetrating trauma. Areas of concern should be marked with suture or clamp; the whole bowel should be examined before repair attempted.^[2] Bleeding in the mesentery can be controlled with figure of eight sutures or the suture ligation.^[4]

Once all injuries have been identified, repair versus resection may be planned based off the principle of avoiding short gut syndrome which occurs when the patient is left with <60-100 cm of small bowel.^[3] Questionably perfused bowel may be reassessed throughout the operation, and adjuncts such as doppler may be considered.^[2]

If the patient is unstable, a temporary abdominal closure device may be used and the bowel re-examined during a second look operation in about 24 hours when physiologic derangements may be improved.^{[2, 4]} If there is suspicion to injury in the distal duodenum or proximal jejunum, takedown of the LOT can assist in evaluation and repair, however care should be taken not to damage the SMA.^[4]

Grade 1 injuries (partial thickness or hematoma) can be repaired using seromuscular sutures (3-0 or 4-0 recommended), with inversion of a hematoma.

Grade 2 injuries (full thickness injury involving <50% of the bowel circumference), may be repaired with s single or two-layer suture repair, taking care not to overly narrow the bowel lumen.^{[2, 4]}

Once the injury involves >50% of the circumference of the bowel (Grade 3), then the segment should be resected.^{[1, 4]}

Grade IV injuries (full transection of the bowel) and Grade V injuries (transection with tissue loss) should both be repaired by resection and anastomosis.^[4]  Devascularized segments of bowel that occur when the mesentery is avulsed off bowel segments (“bucket handle injury”) should be repaired by resection and anastomosis. 

When resecting and creating an anastomosis of small bowel in the trauma setting, either hand-sewn or stapled anastomosis is appropriate based on the operator experience. There is no strong data to support a difference in complication rates between the techniques in non-edematous bowel.^[4] However, in the setting of very edematous bowel, the thickened wall may lead to a higher leak rate in stapled anastomosis.^{[2, 3]} Therefore surgeon experience may be used to decide which type of anastomosis to make.

Perioperative antibiotics such as cefoxitin or ampicillin-sulbactam should not be given for more than 24 hours. Nasogastric decompression may be used to avoid emesis and aspiration while awaiting return of bowel function in people with extensive or multiple repairs, per surgeon preference.^[4] In the immediate post-operative period, patients who underwent aggressive fluid resuscitation should be closely monitored for abdominal compartment syndrome.^[3]

The most common complications following traumatic SBR involve anastomotic failure. Anastomotic failure may present as a worsening abdominal exam, abscess, or a new fistula. An anastomotic leak may be contained or cause diffuse peritonitis. Risk factors include massive transfusion and resuscitation, concomitant pancreatic injuries, abdominal compartment syndrome, hypoperfusion in the early post-operative period requiring vasopressors, and failure to close fascia in 5 days for those left with an open abdomen.^[4] Anastomotic leaks (most often identified by CT scan around 4-5 days post-op) are best addressed with either re-operation and re-anastomosis if within the first few days post-operatively, or, after 10-14 days, creation of a controlled fistula via percutaneous drainage.^[4]

Missed injuries, delayed perforations, or leaks may cause enterocutaneous fistulas. This is also more likely to occur in patient’s with open abdomen, therefore early closure is of utmost importance. Good wound care and nutritional supplementation are key tenants in the management of fistulas. Closure of fistulas is best done in about 3-6 months after the initial operation.^[4]