Blunt and Penetrating Injury to the Bowel: A Review

Abstract

Traumatic injuries to the small and large bowel are common and can be highly morbid. Identifying these injuries, especially in stable patients who suffer blunt trauma, can be challenging. It is critical that traumatic bowel injuries are diagnosed in a timely fashion as delays in diagnosis and treatment are associated with worse outcomes. The literature outlining the management of traumatic bowel injuries is mostly comprised of retrospective data and case reports/series. We have compiled the existing literature and relevant guidelines into a single resource for providers who care for traumatically injured patients.

Patients suffering traumatic injuries to the small and large bowel are initially evaluated and resuscitated according to Advanced Trauma Life Support principles. ¹ They undergo primary and secondary surveys as well as appropriate adjuncts designed to assess for immediate life-threatening conditions. The abdomen should be specifically inspected for asymmetry, ecchymosis, lacerations, abrasions, distention, peritonitis, or evidence of injury/impalement. ² Peritoneal signs suggest the leakage of intestinal contents, bile, or urine into the abdominal cavity but may take several hours to develop. This delayed presentation can occur when there is vascular injury that leads to bowel ischemia, followed by necrosis. The Focused Assessment with Sonography for Trauma (FAST) exam is a useful adjunct for detecting intraabdominal fluid but requires an average of over 600 mL to be positive and is limited by operator experience. ³

For those suffering penetrating abdominal trauma, immediate indications for operation include impalement, evisceration, peritonitis, blood on digital rectal examination, and hemodynamic instability. In blunt trauma, the combination of hemodynamic instability and a positive FAST examination suggests intraabdominal hemorrhage and is typically treated with laparotomy. Stable blunt patients do not require immediate operation and can be further evaluated with computed tomography (CT). ⁴ Injury to the bowel is relatively rare with an incidence of 1% in blunt trauma and 17% in penetrating trauma. ⁵ These injuries often occur in concert with other injuries and can be challenging to diagnose. They also confer significant morbidity. This review was compiled to consolidate the existing literature governing the identification and management of small and large bowel injuries.

Duodenum

The duodenum is a well-vascularized segment of proximal small bowel extending from the pylorus to the ligament of Trietz. Injuries to the duodenum are relatively rare, affecting only 2 to 5% of patients who suffer abdominal trauma. ^{6 7 8} The most frequently affected demographic is young males. ^{8 9} Nearly 80% of duodenal injuries occur after blunt mechanisms, classically involving direct anterior force to the abdominal wall, such as a steering wheel or bicycle handlebar, which compresses the duodenum against the spinal column. ^{6 8}

Duodenal trauma is often challenging to diagnose since much of the duodenum lies in the retroperitoneum. Thus, duodenal injuries do not always produce classic physical exam findings, such as peritonitis, or radiographical clues, such as free air. ¹⁰ These challenges with physical exams contribute to the nearly 30% incidence of delayed diagnosis for duodenal injury. ^{4 8} Historically, this was associated with a mortality rate of up to 40%. ^{6 11} CT is the most frequently used imaging modality to assess abdominal trauma and has a sensitivity of 64% and specificity of 97% for bowel injury. ^{12 13 14 15} CT findings commonly associated with duodenal injury include duodenal mesenteric hematoma (37%) and free fluid not explained by solid organ injury (30%). ^{12 13} Focal thickening of the duodenal wall, pneumoperitoneum, or pneumoretroperitoneum may also be seen. Laboratory tests are not typically helpful in diagnosing duodenal injuries at presentation. ⁶

Duodenal trauma can be highly morbid as the duodenum lies nestled in between many critical organ systems such as the biliary system, liver, head of pancreas, and multiple major blood vessels. Therefore, the duodenum is often injured concomitantly with other vital structures, most commonly the liver (17%) and colon (13%). ^{16 17} Associated vascular injury can result in hemorrhagic shock, while injuries to the pancreas can lead to devastating local inflammation and necrosis. Even once these injuries are repaired, they are at high risk for failure which can be catastrophic as the duodenum regularly handles approximately 6 L of gastrointestinal fluid daily. ⁸ Leakage from failed repairs can lead to malabsorption and intraabdominal sepsis. ¹⁸

Management

Duodenal injuries are classified according to severity by the American Association for Surgery of Trauma (AAST; Table 1 ). ⁴ Grade 1 injuries include small hematomas or partial lacerations without perforation, while grade 5 injuries involve massive disruption of the duodenopancreatic complex or devascularization of the duodenum. Management of duodenal injuries depends on injury grade as well as the total injury burden and physiology of the patient. The Eastern Association for the Surgery of Trauma and the Western Trauma Association offer guidance for the management of duodenal injuries. ^{8 17} The remaining literature is comprised of several case reports with no prospective studies. ^{19 20 21 22 23 24}

Table 1. AAST classification of duodenal injuries.

Grade	Injury	Description
1	Hematoma, laceration	Involvement of a single portion of the duodenum
2	Hematoma, laceration	Involvement of more than 1 portion, disruption of <50% of the circumference
3	Laceration	Disruption of 50–75% of the circumference of D2, disruption of 50–100% of the circumference of D1, D3 and D4
4	Laceration	Disruption of >75% of the circumference of D2 or involvement of the ampulla or distal common bile duct
5	Laceration, vascular injury	Massive disruption of the duodenopancreatic complex or devascularization of the duodenum

Abbreviation: AAST, The American Association for Surgery of Trauma.

Source: Moore et al ⁴

As discussed above, urgent laparotomy is the treatment of choice for unstable patients with blunt abdominal trauma and penetrating trauma with peritonitis, evisceration, impalement, or blood on digital rectal examination. ²⁵ A full Kocherization of the duodenum is essential if an injury is suspected to clearly delineate the extent of injury and relationship to the critical adjacent structures. Laparoscopy is generally avoided with duodenal injuries as a full Kocher maneuver must be performed and small injuries must be detected. A duodenal injury should be suspected if the surgeon notes biliary-tinged fluid in the abdomen, retroperitoneal hematoma surrounding the duodenum, or succus in the lesser sac. ^{18 26}

Grade 1 and 2 hematomas rarely require operative intervention. The hematoma may cause luminal narrowing and gastric outlet obstruction. As such, the patient is typically made nil per os, and nasogastric decompression is initiated. ²⁷ Hematomas generally self-resolve; however, those that persist beyond 14 days are treated operatively with hematoma evacuation. ^{28 29} Grade 1 and 2 lacerations, which involve <50% of the duodenal circumference, should be repaired in a tension-free manner with absorbable suture in two layers, if possible, without narrowing the lumen. The narrowing can be avoided with closure in transverse orientation.

Grade 3 and 4 lacerations, in which there is a >50% disruption of the duodenum, require a customized approach that depends on the location of the injury within the duodenum, the overall injury burden, and patient physiology. ^{8 28} The surgeon's armamentarium includes tension-free primary repair, resection, Roux-en-Y duodenojejunostomy, or drainage. Primary repair is ideal, if feasible, so long as it can be performed without significantly narrowing the lumen. Injuries in D1 or the proximal aspect of D2 can be treated with antrectomy and gastrojejunostomy. Injuries in D4 can be treated with segmental resection, often requiring a hand-sewn anastomosis.

Injuries to D2 and grade 5 lacerations can be devastating and typically require a damage control approach at the initial operation. As with any patient undergoing surgery for trauma, the surgeon, in concert with the anesthetist, must assess the patient's physiology to determine whether a definitive or damage-control approach is most appropriate. This decision should be made as early as possible. If the team elects to use a damage-control approach, the priority is to control major bleeding first, followed by controlling contamination. This may include maneuvers such as stapling the bowel and ligating the bile duct. In patients with severe physiologic derangements, it may be impossible to control contamination and drain placement with temporary abdominal closure is best. Surviving patients may require pancreaticoduodenectomy if the head of pancreas is involved or Roux-en-Y duodenojejunostomy if the defect cannot be primarily repaired.

All patients with high-risk repairs should have distal feeding access established, typically in the form of a nasojejunal tube or formal jejunostomy. ²⁸ Pyloric exclusion is often considered, although it does not appear to improve patient outcomes. ^{30 31} As expected, mortality increases with injury grade and the best outcomes for pancreaticoduodenectomy occur at high-volume centers with high-volume surgeons. ³²

Small Bowel

Distal to the ligament of Trietz, the small bowel measures between 3 and 8 m and is the primary site of protein, fat, carbohydrate, and vitamin absorption. ³³ It takes up a significant amount of space within the abdomen and, thus, is vulnerable to damage from penetrating mechanisms. ¹ It is also only fixed by its mesentery, making it highly mobile and susceptible to shear injury occurring after rapid decelerations. Injuries to the small bowel from blunt mechanisms are uncommon, with an incidence of 0.3% ^e . However, these injuries are very morbid, with a mortality rate of up to 15%, which may be explained by the high incidence of associated injuries and the high frequency of postoperative complications. ³⁴

Small bowel injuries most commonly occur following motor vehicle or bicycle crashes, followed by falls. ¹ There are multiple theories to explain how the bowel becomes damaged including compression against the spine, shearing of the lumen off the mesentery following deceleration and bursting of a loop due to rapid changes in pressure. ³⁵ Small bowel injury has been associated with physical exam findings such as a seatbelt sign as well as associated injuries such as Chance fractures. ^{35 36}

Similar to the duodenum, small bowel injuries are typically identified intraoperatively. For hemodynamically stable patients who suffer blunt trauma, CT scan is the most commonly utilized diagnostic modality. CT findings associated with injury to the small bowel include free air, free fluid without solid organ injury, fat stranding, mesenteric hematoma, and bowel wall thickening. ^{8 12 37 38} Fluid in multiple areas of the abdomen increases the likelihood of small bowel injury. ³⁹ Free fluid without a solid organ injury, which often makes clinicians concerned for hollow viscus injury, only correlates with bowel injury in 38% of patients. Overall, the sensitivity of CT scan for small bowel injury is 88% and the specificity is 99%. ⁸

While CT scan is useful for diagnosis, it is not uncommon for hollow viscus injuries to be identified intraoperatively in patients with normal CT scans. These patients are typically managed nonoperatively; therefore, changes in vital signs, development of peritonitis, metabolic acidosis or leukocytosis could indicate a missed bowel injury. Recently, scoring systems have been developed to predict bowel injury based on initial systolic blood pressure, abdominal tenderness, guarding, and select CT findings. ^{40 41} Diagnostic peritoneal lavage has been described to evaluate patients with equivocal findings for small bowel injury, although lavage white blood cell counts do not accurately predict hollow viscus injury. ^{42 43} In fact, in the initial evaluation of trauma patients, laboratory testing generally does not help to determine the presence of small bowel injury. Delays in the identification of small bowel injury can significantly increase mortality, morbidity, and readmission rate. ^{44 45 46} Mortality increases with time to operative intervention, and multiple studies have shown that a delay of >5 hours can significantly increase the risk of mortality. ^{45 47}

As with other areas of surgery, minimally invasive approaches have been proposed in trauma. Specifically, diagnostic and even therapeutic laparoscopy has been advocated in cases of possible bowel injury. Each decade has seen an increased utilization of laparoscopy in trauma as modern surgical graduates become more comfortable with the approach. ⁴⁸ Additionally, laparotomy is not benign and, in the setting of trauma, can be nontherapeutic. Nontherapeutic laparotomy is associated with increased mortality (odds ratio [OR] 4.5), higher rate of complications (OR, 2.2), and longer hospital stay (OR, 2.7). ⁴⁹ For this reason, multiple centers are exploring the feasibility of laparoscopy, especially for stable patients with penetrating abdominal injuries. ^{50 51 52}

Treatment

Whether an open or laparoscopic approach is chosen, the entirety of the small bowel must be evaluated in a systematic fashion from the ligament of Treitz to the ileocecal valve. In penetrating trauma, especially stab wounds, the bowel must be visualized extremely carefully as injuries may be very small ( Fig. 1 ). Conversely, in blunt trauma, the injuries are generally less subtle and often involve larger hematomas. Once all injuries are categorized, the treatment plan should be determined based on the extent of injury and the patient's physiology. This may involve primary repair, diversion, or resection which can be done with or without anastomosis.

Fig. 1.

Through and through bowel injury from blast injury and shrapnel.

In general, the goal is to preserve as much length of bowel as possible with the fewest number of anastomoses. The mesentery should also be carefully evaluated, and any significant bleeding must be controlled. If the mesentery is severely compromised, the bowel it feeds should be resected. In situations where the viability of the bowel is initially unclear, the surgeon may use adjunctive techniques such as indocyanine green, intravenous fluorescein with Wood's lamp, or Doppler flow studies to determine whether resection is warranted. ^{53 54 55} Additionally, a damage control approach and temporary abdominal closure can be employed to allow for additional patient resuscitation and demarcation of bowel ischemia. Ultimately, treatment depends on the grade of injury ( Table 2 ). ⁴ Serosal tears and intramural hematomas can be observed or inverted with the Lembert suture. Grade 2, full-thickness injuries may be amenable to transverse repair to avoid narrowing the lumen, although sometimes resection may be preferable if the laceration is on the mesenteric side, is extensive, or there are multiple lacerations in a small segment of bowel. Grade 3 injuries typically require resection.

Table 2. AAST classification of small bowel injuries.

Grade	Injury	Description
1	Hematoma, laceration	Contusion or hematoma without devascularization. Partial-thickness laceration.
2	Laceration	Laceration of <50% of the circumference.
3	Laceration	Laceration of >50% of the circumference.
4	Laceration	Full-thickness laceration.
5	Vascular	Devascularized segment.

Abbreviation: AAST, The American Association for Surgery of Trauma.

Source: Moore et al ⁴

Note: advance one grade for multiple injuries up to grade 3.

Colon

The colon is a partially retroperitoneal organ which spans nearly the entire abdominal cavity and is the primary site of resorption of water and electrolyte exchange. The colon is injured in 0.3 to 0.5% of patients with blunt mechanisms and even more commonly in penetrating trauma. ^{56 57} As with all penetrating ventral injuries, violation of the fascia mandates surgical evaluation during which a stepwise exploration may reveal colonic injuries. When surgeons suspect a missile tract involves the abdomen, the patient should undergo operative exploration. In the setting of blunt trauma, initial evaluation with a FAST exam and/or CT may manifest colon injury with colon wall thickening, extraluminal fluid, and/or air. Any of these findings should prompt expedient evaluation in the operating room. Interestingly, the presence of a seatbelt sign has been associated with large bowel injuries in 39% of patients undergoing laparotomies. ⁵⁸ Patients who cannot be reliably examined, such as those with altered mental status, are a particular challenge as CT scans miss up to 20% of injuries. ^{56 57 59} As described above, scoring systems have recently been developed to predict colon injury and determine who requires operative evaluation. ^{40 41}

Surgical evaluation of the colon can be driven by institutional protocols and the surgeon's own comfort. Both open and laparoscopic techniques are described; however, retroperitoneal injuries may be missed in the setting of laparoscopy due to the challenges of appropriate medialization of the ascending and descending colon. Medialization is especially important in penetrating flank trauma which has been associated with retroperitoneal colon injuries. Notably, complete evaluation of the colon includes visualization of both the mesentery and the serosa proper.

The AAST has created a rating system to create a common language to describe injuries to the colon and is highlighted in Table 3 . ⁴ Low-grade injuries are described as nondestructive injuries and include grade I with contusion or hematoma or partial thickness lacerations. Grade II and III injuries are stratified by < 50% and ≥ 50% circumference injuries, respectively. Grade IV and V injuries occur with transection injuries with grade V including segmental tissue loss and devascularization.

Table 3. AAST classification of colon injuries.

Grade	Injury	Description
1	Hematoma Laceration	Contusion or hematoma without devascularization. Partial thickness laceration without perforation.
2	Laceration	Laceration of <50% of the circumference.
3	Laceration	Laceration of ≥50% of the circumference without transection
4	Laceration	Transection
5	Laceration Vascular	Transection with segmental tissue loss Devascularized segment.

Abbreviation: AAST, The American Association for Surgery of Trauma.

Source: Moore et al ⁴

Note: advance one grade for multiple injuries up to grade 3.

The optimal management of colon injuries has been heavily debated. Initial data from World War II suggested that all patients should undergo diversion. ¹ Even now, with the results of prospective and retrospective data, there is no unified consensus in the WTA and EAST guidelines to identify which patients should be repaired primarily. ^{60 61} A highly referenced 2001 AAST prospective trial showed that primary repair is feasible in appropriately selected patients; however, debate exists over what defines an appropriate patient. ⁶² Clearly patients who are undergoing damage control laparotomy should not undergo definitive anastomosis or ostomy maturation as these contradict the central tenants of damage control, which is to focus on life-threatening hemorrhage and ongoing insult to the patient. It is reasonable and safe to perform debridement of nonviable tissue and primary repair of grade I, II, and III injuries. ^{61 62 63} Destructive injuries, including selective grade III-V, should undergo resection based on injury and anatomic blood supply. Creation of an anastomosis without ostomy, either in a delayed fashion or at the index surgery for stable patients, is the most ideal. The decision to form a colostomy can be individualized based on injury patterns and patient factors.

Rectum

Traumatic injuries to the rectum are covered in detail elsewhere in this issue.

Conclusion

Clinicians caring for traumatically injured patients must maintain a high degree of suspicion for injuries to the small and large bowel as these injuries can be challenging to diagnose and are highly morbid. Once identified, the AAST grading scale provides a framework for management. As with all injured patients, special attention should be paid to the burden of injury and patient physiology. In severely injured patients, damage control surgery may be indicated.