Abdominal Stab Wound Exploration 

In the 19th century, penetrating abdominal wounds were managed nonoperatively. The associated morbidity and mortality rates were greater than 70%.^[1] Experience gained during World War I, World War II, and the Korean Conflict led to an aggressive approach of operative management for all penetrating abdominal wounds.^[2] This approach resulted in an unacceptably high frequency of laparotomy with findings negative for trauma. In 1960, Shaftan developed an approach of selective conservatism for penetrating abdominal injury and revolutionized abdominal stab wound management.^[3]

Investigators in this field continue to study various protocols and investigative tools. Despite impressive advances in investigative techniques, the optimal method to determine the need for laparotomy has yet to be definitively established.

The objective is to reduce the number of patients with trivial or no intraperitoneal injury who are subjected to laparotomy. However, a high degree of diagnostic accuracy must be maintained to limit the frequency of missed injury. A reduction in unnecessary hospitalization is also targeted.

In asymptomatic patients with stab wounds to the anterior abdomen, the following 2 methods are widely used to help determine the need for laparotomy:

• Abdominal stab wound exploration (subsequent diagnostic peritoneal lavage [DPL], serial clinical evaluation, or both are used to further assess patients in whom an exploration cannot definitively exclude peritoneal penetration.)
• Serial clinical evaluation

Other modalities that have been studied include DPL alone, CT, laparoscopy, and ultrasonography.^{[4, 5]} These strategies of selection for laparotomy are explored in greater detail below.

Abdominal stab wound exploration forms part of a strategy developed by surgeons to allow a more selective approach. It is a safe, rapid, and cost-effective tool in the management of asymptomatic patients who present with an anterior abdominal stab wound.^{[6, 7]} This approach has no place in the treatment of patients who are unstable, who have peritonitis, or who have evisceration. Patients with peritonitis and those who are hemodynamically unstable should undergo mandatory laparotomy.

The authors advocate abdominal stab wound exploration in asymptomatic patients who present with an anterior abdominal stab wound. An exploration with negative findings is reliable and highly sensitive.^{[8, 9]} More than 25% of anterior abdominal stab wounds do not penetrate the peritoneal cavity.^{[7, 10, 11]} A wound exploration that demonstrates an intact posterior rectus fascia (superior to the arcuate line) or transversalis fascia (inferior to the arcuate line) allows the safe discharge of these patients from the emergency department.^[12]

Only half of the wounds that penetrate the peritoneum cause damage that requires surgical intervention.^{[1, 8, 13]} Abdominal stab wound exploration combined with further investigation, such as DPL or serial evaluation, achieves acceptable specificity rates. The organs most commonly injured with anterior abdominal stab wounds are the small bowel, the liver, and the colon. Missed hollow viscus injuries are associated with significant morbidity and mortality. Minimizing the time taken to control ongoing intraperitoneal contamination is critical in penetrating stab wounds, and local exploration is a valuable first step in speeding up the decision-making process. When combined with DPL, abdominal stab wound exploration allows significant injuries that are not immediately apparent to be identified early.

Wound exploration can be performed successfully by surgeons or ED personnel, provided they are trained in the procedure. This strategy aids with patient flow through a busy emergency department.

Abdominal stab wound exploration is indicated in a patient who presents with a stab wound to the anterior abdomen, normal vital signs, no signs of peritonitis, and no evidence of evisceration (see the image below).

Some authors advocate local exploration of wounds only anterior to the midaxillary line. If the wound tracks anteriorly and the end point of the tract is not accurately determined, the patient undergoes diagnostic peritoneal lavage (DPL). If the wound tracks posteriorly and is not obviously superficial, the patient is investigated as for a penetrating flank wound. This often involves a triple-contrast CT scan.^[14]

Special circumstances involve patients with additional injuries that require operative intervention and cases in which the offending weapon or object is retained.

• If the patient has additional injuries that require operative intervention, a wound exploration may be performed in the operating room before the other procedure is commenced.
• If the object has been retained and the surgeon strongly suspects that the peritoneum has not been breached, the object may be removed in the operating room and the wound locally explored. In such cases, the surgeon should be prepared to immediately convert to laparotomy, if necessary.

Abdominal stab wound exploration is contraindicated if immediate laparotomy is indicated. The situations in which immediate laparotomy is indicated include the following:

• Unstable patient
• Peritonitis
• Evisceration (This remains controversial; see paragraph 2 in Selecting Candidates for Laparotomy section.)
• Blood on rectal examination or blood in nasogastric tube aspirate suggests intra-abdominal injury (A low threshold for operative intervention is suggested.)

Other contraindications to abdominal stab wound exploration include the following:

• Lower chest wounds: Exploration of these wounds carries a high risk of iatrogenic pneumothorax.
• Flank and back wounds: Some authors advocate exploration of these wounds if they are suspected to be superficial. However, this expectation may be unreliable, and the strong musculature makes the tract difficult to predict or to follow. Local wound exploration may result in further injury or a restart of hemorrhage that had stopped.
• Patient refusal or uncooperative patient.

Relative contraindications include the following:

• Obesity
• Multiple abdominal stab wounds

Complication Prevention

Complications of abdominal stab wound exploration are rare (rate is approximately 1%). Complications include local wound infection and bleeding.

Published papers report no false-negative exploration findings.^{[7, 10, 15]}

An appreciation of the anatomy of the anterior abdominal wall at different levels is essential to understanding the procedure. The differences are highlighted in red on the diagrams below.

Boundaries of the anterior abdomen (see image below) are as follows:

• Costal margins (superior)
• Inguinal ligaments (inferior)
• Anterior axillary lines (lateral)Boundaries of the anterior abdominal wall.

No debate exists about the management of patients who are hemodynamically compromised or who exhibit peritonitis upon abdominal examination. These patients are immediately transferred to the operating room and undergo laparotomy.

No consensus has been reached regarding the treatment of patients with evisceration of omentum or an abdominal organ. Many still opt for operative intervention in this group and cite a high incidence of organ injury as the reason for their standpoint.^{[9, 16, 17]} Demetriades and others have shown that these patients can also be successfully managed nonoperatively, provided that they are stable and that the findings of their abdominal examination remain benign.^{[18, 19]}

The optimal management for an asymptomatic patient with an anterior abdominal stab wound remains controversial. Routine laparotomy was once advocated but is no longer accepted practice. The universally accepted practice is now selective management of asymptomatic patients with stab wounds. However, the best method to select those who will benefit from laparotomy is still debated.^{[12, 20, 21, 4, 22]}

Institutional approaches to stab wound evaluation are determined not only by patient physiological status, examination findings, and stab wound location, but also by staffing logistics, cost of investigation, and local experience. Each method has its merits and shortfalls, and combinations of techniques are not uncommon.

The 2 most commonly used selective approaches are abdominal stab wound exploration (combined with DPL or serial clinical evaluation) and serial clinical evaluation. Results from the available studies show comparable patient outcomes (see image below).

Abdominal stab wound exploration

Abdominal stab wound exploration allows for safe and immediate discharge of approximately 25% of patients with an abdominal stab wound. When performed by trained operators, this procedure is 100% sensitive.^[15] If one considers patients who mandate laparotomy and those who have an exploration with negative findings, local wound exploration can guide an early, clear, and safe decision in more than half of patients who present with an anterior stab wound.^[15]

Unfortunately, positive local wound exploration findings carry a poor specificity for significant intra-abdominal injury. If all patients with positive abdominal exploration findings were to undergo laparotomy, more than 40% would do so unnecessarily.^{[1, 9, 15]} Patients with positive or equivocal local exploration findings, therefore, undergo DPL or serial clinical evaluation to further select those who are likely to have an intra-abdominal injury that requires surgical intervention. This strategy successfully reduces the number of unnecessary laparotomies.^[23]

Diagnostic peritoneal lavage

DPL was initially developed as a tool to help assess for intra-abdominal injury in patients who had sustained blunt trauma. Its value in penetrating trauma is accepted, but its application is less clear. No consensus exists concerning what constitutes a positive result, and protocols vary from one institution to the next. Pre-lavage aspiration of 10-20 mL of blood is generally accepted as a positive result. The lavage fluid is assessed for red blood cells, white blood cells, bile, feces, and vegetable matter.

Enzyme assays, including alkaline phosphatase (ALP) and amylase, have achieved limited clinical value. Some authors have used a red blood cell count of greater than 100,000/μL and a white blood cell count of greater than 500/μL as the threshold. At these relatively high values, the incidence of missed injury increases and, consequently, even patients with negative lavage findings are further assessed and observed.^{[6, 11, 24]} These cell count cutoff values are the same as those used for blunt trauma. When applied, these values achieve an accuracy rate of 90-91%.^{[6, 25]}

Isolated injuries to hollow organs often cause little bleeding. These injuries are commonly associated with lavage red blood cell counts of less than 100,000/μL or even of less than 10,000/μL. However, red cell counts of less than 1,000/μL are almost never associated with significant intra-abdominal injury.^{[6, 15, 26]}

The white blood cell count threshold is not without problems, either. An elevated count raises suspicion of a hollow visceral injury. The intraperitoneal contents do not reliably produce a white cell response to injury until approximately 3 hours after the injury occurs. Hence, the timing of the lavage becomes important. Lavages performed soon after injury may reflect relatively low white cell counts despite significant injury. If significant delay occurs before the lavage is performed, even a simple breach of the peritoneum may produce a significantly raised white blood cell count.^[6]

No threshold for DPL achieves 100% accuracy. The clinician must determine the relative weight of missed injury (false-negative findings) versus that of unnecessary laparotomy (false-positive findings). Up to 60% of visceral injuries involve the small bowel or colon.^{[1, 27]} Injuries to these organs are still the leading cause of morbidity and mortality in patients with abdominal stab wounds.^[15] Surgeons are aware that the risk of morbidity and mortality of missed hollow visceral injury far outweighs that of unnecessary laparotomy; therefore, many have elected to lower their threshold for operative intervention. DPL is increasingly considered a quantitative assay that merely serves to provide further information to assist in decision-making and should no longer be used blindly with absolute cutoff values.

DPL is not organ-specific and may be unhelpful in patients with retroperitoneal injury. A lower threshold increases the sensitivity of the investigation but results in an increase in unnecessary surgery.^[28] Wound complications, technical error and intraperitoneal injury have been reported in less than 1% of patients subjected to DPL.^{[15, 29]}

Some authors who no longer recommend DPL in the assessment of patients with abdominal stab wounds cite the residual risk of missed injury and unnecessary laparotomy as their reasons.^[9] Despite a noticable decrease in the use of DPL at training institutions, some authors continue to advocate its use in the assessment of abdominal stab wounds.^[30]

Serial clinical evaluation

Serial clinical evaluation is a method used by many surgeons as a selective approach to abdominal stab wound management. Approximately 30% of patients with a significant abdominal injury have initial benign abdominal examination findings.^[1] Furthermore, up to 10% of injuries are initially overlooked, even in the more advanced trauma centers.^[31] These statistics clearly demonstrate the value of serial evaluation. Unfortunately, studies have also shown that 14-28% of patients without an injury that penetrates the peritoneum have misleading positive abdominal examination findings.^{[11, 24, 32]}

The length of hospital stay in patients whose injuries are managed conservatively varies among institutions. One study showed that no significant injuries were discovered in any patients who were asymptomatic after 12 hours of observation.^[33] Most protocols, however, recommend evaluation of the patient over 24-72 hours.^{[18, 34, 35]} The delay in laparotomy inherent in such an approach has not been associated with adverse outcome.^[18] This is, possibly, because most severe injuries are obvious early. Degree of contamination is likely more important than the delay in surgery, provided the delay is not excessive. However, few would argue with the principle that the time taken to control contamination should be minimized.

An audit conducted across 3 hospitals in Pietermaritzburg (South Africa) warns of the morbidity associated with delayed recognition of the need for laparotomy.^[36] Martin et al found a 6-fold increase in complications in patients with colonic injury who were not operated on within 12 hours.^[37]

A retrospective study at a level-1 trauma center highlights a reduction in the therapeutic and unnecessary laparotomy rate over a 17-year period.^[38] Serial clinical evaluation has been central to a selective nonoperative approach at their institution. Their results demonstrate safety and efficacy, but the logistical challenges of such a service may not be feasible in resource-constrained environments. A recent review by Como et al recommends that the same team of experienced clinicians be responsible for repeat examinations over a period of 24 hours.^[21]

Other methods of selection

Other methods of selection have been advocated, but few claim advantage over the 2 selective approaches discussed above.

Some authors advocate DPL alone without prior local wound exploration as particularly useful in patients who are difficult to assess clinically because of drugs or alcohol or who are to be anesthetized for another procedure. A study successfully used a red blood cell lavage count of less than 1,000/μL as a criterion for immediate discharge from the emergency department.^[26] The authors claim that DPL is a simple procedure with few complications and that the complications, when they occur, are usually immediately evident. This view is certainly not shared by all.

Sinography ("stabogram") and blind probing of wounds are unreliable procedures.^{[1, 39]}

Despite the instrumental role of CT scan in the assessment of penetrating flank and back wounds, the modality has traditionally been of little help with anterior abdominal wounds. CT scan evidence of intraperitoneal injury does not reliably predict clinically significant injury requiring operative intervention and should not be used as a sole method of assessment.^[9] The presence of free intraperitoneal air has poor specificity for intra-abdominal organ injury. Air can track through a defect in the abdominal wall and enter the peritoneal cavity. As part of a prospective study of 651 patients with abdominal stab wounds, 18 patients with free air under the diaphragm on plain radiograph were managed conservatively by method of serial examination. Only 2 of these patients went on to laparotomy, and no adverse outcomes were reported in the other 16 patients.^[18]

More recent studies assessing the performance of improved CT technology have found fewer missed hollow visceral injuries than previously reported.^{[40, 41]} However, the inability to confidently exclude hollow visceral and diaphragm injuries is well documented.^[42] Serial clinical evaluation, when combined with CT scan, has been shown to be an effective strategy in the selective management of abdominal stab wounds.^{[40, 41]} This approach is only suitable for well-staffed major centers with sufficient experience in abdominal stab wound management.

Few authors advocate the use of laparoscopy in the management of anterior abdominal stab wounds. It may be useful as an adjunct in special circumstances.^[20] Laparoscopy is reliable when used to determine breach of the peritoneum or to assess potential diaphragm injuries in patients with wounds to the left upper quadrant or lower chest. It is unreliable in the assessment of hollow visceral injuries. A protocol of stab wound exploration followed by emergency department awake laparoscopy for equivocal cases has been studied, but it resulted in 31.3% of selected patients being exposed to the risks of unnecessary surgery.^[43] At this stage, despite reports of safety and a reduction in unnecessary laparotomy,^[44] laparoscopy lacks sufficient therapeutic value to be used routinely in abdominal stab wounds.^{[9, 45]}

Ultrasonography, on its own, is inadequate as an investigation of anterior abdominal stab wounds and rarely aids in the management of these cases.^{[12, 21, 46]} Focused abdominal sonography for trauma (FAST) scan has proved to be a reliable method of investigation in blunt abdominal trauma, especially when the scan is repeated.^[47] This type of scan is less helpful in the assessment of patients with penetrating injury.^{[46, 48]} Low sensitivity and low negative predictive value limit its accuracy as an investigation. Positive FAST scan findings are useful predictors of significant intraperitoneal injury and, when performed early, can decrease the time to operation.^[48] To confidently exclude significant intraperitoneal injury in patients with negative FAST scan findings, additional investigations are required.^{[9, 48]}

A small study of 35 patients has suggested a role for fascial ultrasonography to detect fascial penetration in anterior abdominal stab wounds.^[49] As an investigation, fascial ultrasonography had a specificity and positive predictive value of 100%. Positive fascial ultrasonographic findings rule out the need for an abdominal stab wound exploration. Unfortunately, even in more experienced hands, fascial ultrasonography had a sensitivity of only 73%. The resultant drawback, therefore, is that negative fascial ultrasonographic findings do not adequately exclude an intra-abdominal injury, which requires further investigation or observation. Further assessment of the use of fascial ultrasonography may be justified.

Further developments

No meaningful change has occurred in decades in the suggested management of this important and growing group of patients. However, the combination of physical examination and other investigations has allowed a reduction in unnecessary intervention.^[50] Modern approaches have succeeded in limiting the mortality due to anterior abdominal stab wounds to as low as 0-3.6%.^{[1, 24]} Selective approaches have achieved unnecessary laparotomy rates of less than 10%.^{[1, 6, 11, 15, 18, 24]} In abdominal stab wounds, the morbidity rate of a laparotomy with negative findings is in the range of 1.5-8%.^{[24, 32, 51]} Regrettably, a limited number of injuries are still missed.

Further trials or, perhaps, technology may provide the next development in anterior abdominal stab wound management. Computerized penetrating injury prediction models have been retrospectively tested and compared.^[52] No single investigation or technological development is likely to provide all the information necessary to accurately determine which patients are likely to have injuries that require surgical intervention.

For now, abdominal stab wound exploration remains a valid and effective tool that allows safe and early discharge of a significant number of patients. It is also valuable as a first step in a process that limits the time to decision-making in the management of asymptomatic patients with anterior abdominal stab wounds. A multidisciplinary working party recently developed evidence-based guidelines for the management of hemodynamically stable patients with stab wounds to the anterior abdomen. They conducted a systematic review of the available literature and recommended the use of abdominal stab wound exploration.^[12]