Emergency approach to abdominal trauma (Proceedings)

Introduction:

Abdominal trauma may result in specific injury of the peritoneal or retroperitoneal structures, diaphragm, or body wall constituents. Pain referred from other sites (especially spine) is also frequently mistaken for abdominal pain. Historical examination and physical examination should allow the clinician to recognize the likelihood that a given patient has sustained trauma. Trauma associated acute abdomen is a unique situation and should prompt an already narrowed list of differential diagnoses. (Table 1) It is critical to recognize that trauma is most often a whole body problem (polytrauma) involving multiple body systems. Similarly, it is also not uncommon for trauma-associated acute abdomen to result from multiple injuries, for example, concurrent uroperitoneum and hemoperitoneum.

Table 1: Etiology of trauma associated acute abdomen

Stabilization & Resuscitation:

Stabilization of the patient with abdominal trauma should initially be focused on restoring abnormalities identified on major body systems assessment to normal thus maximizing the delivery of oxygen to the tissues. Perfusion abnormalities such as hypovolemic shock as well as oxygenation abnormalities due to concurrent pulmonary and / or pleural space injuries are commonly identified in animals with abdominal trauma. Shock is defined as the failure of oxygen delivery (DO2) to the tissues and can result from significant compromise to the cardiovascular, respiratory, central nervous systems, or a combination thereof. Immediately after trauma, we will most often by faced with traumatic / hypovolemic shock. In order to better understand the possible causes of the shock states, we must first consider the factors that will influence delivery of oxygen (DO2) to the tissues:

After significant trauma, DO2 may be compromised via a variety of mechanisms including alterations in both cardiac output (CO) and blood oxygen content (CaO2). We can then utilize knowledge of the determinants of DO2 to help guide resuscitation efforts.

Example: A young (2yr old) intact male mixed breed dog is hit by a car and is presented to your veterinary hospital for immediate care. Upon triage, you note pale mucous membranes, a CRT of 4 seconds, a pulse rate of 220, extremely weak pulse quality, dramatically increased respiratory rate (60bpm) and effort. The dog also has a severely depressed level of consciousness. A gaping wound in the left thorax is noted. You immediately transport the patient to the treatment area for resuscitation efforts. This animal is obviously showing signs of shock (decreased DO2). Applying our knowledge as to possible causes in this patient, you may deduce that CO is depleted due to decreased preload from blood loss. In addition, CaO2 is also likely significantly decreased because of decreased hemoglobin concentration (blood loss), decreased SpO2 (open pneumothorax and pulmonary contusion), and decreased PaO2 (open pneumothorax and pulmonary contusion). You can now consider "attacking" the low DO2 via a number of different routes including provision of oxygen support to maximize SpO2 and PaO2 and thus CaO2, volume resuscitation to improve preload and thus CO, and possibly sanguineous blood product administration also to improve hemoglobin concentration and thus CaO2 and CO. In addition, the wound will need to be sealed with concurrent chest tube placement for decompression of the pneumothorax. Antibiotic therapy should be initiated immediately. Once stable, the patient will require aggressive surgical debridement and exploration of the wound and chest (within hours).

In a serious trauma situation, each member of the team should have specific responsibilities. Resuscitation efforts will proceed optimally when doctors are doing "doctor things", technicians are doing "technician things", and other support staff is performing other tasks. As soon as the triage is complete and the resuscitation effort is underway, a FULL physical examination MUST be performed by the attending veterinarian. The full physical examination will still largely focus on the major body systems, but will serve to better characterize injuries and to identify co-morbidity (such as underlying mitral valve insufficiency in an older trauma patient) that could alter therapy. Concurrently, support staff should be placing an ECG, checking blood pressure, SpO2, placing IV catheter(s), administering oxygen, collecting blood samples, etc.

Detection and Retrieval of Abdominal Fluid Accumulations:

Abdominal effusion is a clinical finding in many traumatized small animal patients. Retrieval and analysis of abdominal effusion (biochemical and cytological) is useful in determining the underlying etiology of the fluid accumulation. A variety of techniques are available for the retrieval of abdominal fluid. These include abdominocentesis, 4 quadrant abdominocentesis, F.A.S.T. (Focused Abdominal Sonogram for Trauma) Scan, abdominal paracentesis with a peritoneal dialysis catheter, and diagnostic peritoneal lavage.

Cytological and Biochemical Examination of Abdominal Fluid Accumulations after Trauma:

Table 2: Characteristics of common causes of abdominal effusion after abdominal trauma

Table 2 illustrates fluid characteristics resulting from various injuries to the abdomen after trauma.

Diagnostic Imaging of the Patient with Abdominal Trauma

Radiography is an accessible diagnostic tool to most veterinary practitioners and abdominal radiography is a valuable tool in the examination of the trauma patient. Table 3 includes a list of common radiographic findings in animals with abdominal trauma and their possible causes.

Thoracic radiographs are indicated for all dogs and cats with abdominal trauma that are to undergo any anesthetic procedure such that concurrent thoracic injuries such as pneumothorax and pulmonary contusion may be identified.

Table 3: Common radiographic findings and their diagnostic significance in the dog and cat with abdominal trauma

Ultrasound is useful for the detection of free peritoneal or retroperitoneal fluid and occasionally for the identification of injury to parenchymatous organs. Integrity of urinary and gall bladder cannot be determined consistently using abdominal ultrasound. The author uses ultrasound in the trauma situation primarily to identify abdominal fluid accumulations as described above.

Computed Tomography (CT) is a widely utilized tool for evaluation of people with a history of abdominal trauma. At this point, utilization of CT for assessment of canine and feline abdominal trauma patients and its value in comparison to other diagnostic tests in the dog has not been prospectively evaluated.

Treatment of Specific Abdominal Injuries

Hemoperitoneum: Traumatic hemoperitoneum represents one of the most common injuries to the abdomen after trauma and most often results from parenchymatous organ injury (spleen, liver, or kidney). Keys to the successful management of dogs and cats with traumatic hemoperitoneum include judicious volume resuscitation and stabilization of concurrent injuries. Recently, low volume fluid resuscitation to prevent "rebleeding" has been advocated in the veterinary literature, however, additional work evaluating more long term outcomes will be necessary to be able to definitely recommend this method over more traditional volume expanding methods in clinical patients. It is the author's practice to administer 20-30mL/Kg of isotonic crystalloid solution over 15-20minutes to the poorly perfused patient and then reevaluate vital signs, blood pressure, etc. Use of hypertonic solutions and colloids may complement standard resuscitation methods. Goals of fluid therapy for the patient with hemoperitoneum should include restoration of euvolemia while providing for maintenance requirements and ongoing losses and avoiding fluid overload.

Abdominal counterpressure techniques increase intraabdominal pressure in an effort to tamponade venous bleeding. Abdominal counterpressure can be applied using bandaging material wrapped snuggly up the limbs, over the abdomen, and over the 13th rib or just from the pelvic inlet to the 13th rib. Abdominal counterpressure has fallen somewhat out of favor due to deleterious effects on end-organ perfusion due to high intraabdominal pressures and due to effects on the respiratory system. If an abdominal counterpressure bandage is applied, it should be left on for no more than 6 hours and then it should be gradually removed over the following 3-4 hours. The author currently does not use abdominal counterpressure bandages.

Surgical management of traumatic hemoperitoneum is rarely necessary as most patients will respond to volume expansion and transfusion of blood or blood products. Surgical intervention should be considered when resuscitation efforts fail and hemorrhage is ongoing. Clinicians planning to explore the patient with traumatic hemoperitoneum should be comfortable with splenectomy, liver lobectomy, nephrectomy, vascular, and gastrointestinal surgical procedures.

Uroperitoneum / Uroretroperitoneum: Uroperitoneum / uroretroperitoneum must be considered as differential diagnoses in all patients with abdominal pain after trauma. Uroperitoneum results from disruption of the urinary system at any level (kidney, renal pelvis, ureter, bladder, urethra). Clinical signs commonly observed in dogs and cats with uroperitoneum include abdominal pain, abdominal distention, decreased or absent urination, lethargy and vomiting. Disruption of a ureter, kidney, or renal pelvis without disruption of the retroperitoneum may result in uroretroperitoneum. Clinical signs commonly observed in dogs and cats with uroretroperitoneum include abdominal pain and distention and hematuria.16

Dogs and cats with uroperitoneum / retroperitoneum may demonstrate bradycardia if hyperkalemia is present. Initial laboratory abnormalities may include acidosis, azotemia, and hyperkalemia. Lactic acidosis may be present due to concurrent perfusion abnormalities. Electrocardiographic evidence of hyperkalemia includes "tenting" of the T waves, flattening or absence of the P waves, prolongation of PR and QT intervals, and bradycardia.

Uroperitoneum or uroretroperitoneum is confirmed based on abdominal fluid evaluation (see table 2 above). After confirmation is made, localization of the lesion(s) must be accomplished through retrograde urethrocystography and / or excretory urography. Bladder disruption is the most common site of urinsary tract injury, however, multiple lesions may be present warranting both studies.

It is critical to recognize that hyperkalemia (not uroperitoneum) kills dogs and cats with urinary tract disruption. Consequently, acute management should NOT include immediate surgical intervention. Tenets of treatment for dogs and cats with uroperitoneum include stabilization of perfusion abnormalities, treating hyperkalemia, and diverting urine with a peritoneal drain +/- urinary catheterization if necessary until stabilization can be achieved and a surgical intervention safely pursued.

Body Wall Hernia: Disruption of the body wall may occur after blunt abdominal trauma. Lesions may include prepubic tendon rupture (cranial pubic ligament), inguinal hernia, and paralumbar and paracostal hernias.17 Hernias may be immediately evident on visual inspection or palpation if there is significant herniation of abdominal viscera, however, some body wall hernias may not become evident until later.17 Concurrent injury should be expected. Traumatic body wall hernias should be considered surgical emergencies if there is evidence of visceral ischemia, gastrointestinal or urinary obstruction, penetrating abdominal injury, or concurrent injuries that warrant emergency surgical intervention. In other scenarios, the hernia should be repaired as soon as possible. Most acute, traumatic body wall hernias can be repaired using autologous materials.

Abdominal Wound Management: Wounds or crushing injury over the abdomen warrant special consideration. Wounds over body cavities frequently follow the iceberg analogy. What is seen on the surface is a small component of what lies beneath. Evaluation of the patient with any wounds over the abdominal cavity should always include surgical exploration of those wounds. It is generally accepted that simple probing of wounds over a body cavity is ineffective in identifying penetrating injury because of the motion of the skin, subcutaneous tissues and muscular layers over one another. All bite wounds should be explored surgically, opened to allow adequate exposure for exploration, debrided, lavaged, closed utilizing appropriate drainage techniques, or left open to heal by second intention. Wounds found to penetrate into the abdominal cavity warrant abdominal exploration through a ventral midline laparotomy followed by local wound care externally. It should be mentioned that even non-penetrating wounds could result in severe intra-abdominal injury. The most common clinical cause of this situation is crushing injury as a result of bite wounds. Abdominal exploration is never an improper diagnostic test in this scenario. DPL may help identify serious intraabdominal injury prior to exploratory laparotomy.

Vomiting after Abdominal Trauma

Vomiting after trauma represents a relatively uncommon and thus somewhat ominous finding. Most injuries that happen as a result of trauma do not result in vomiting. When vomiting is observed in the traumatized patient, a vigilant search for previously unidentified injuries and diseases such as diaphragmatic hernia, mesenteric avulsion, body wall hernia, pancreatitis, bile peritonitis, septic peritonitis, infarction of abdominal viscera, etc. should occur.

Conclusion: Dogs and cats presenting with signs of abdominal trauma can represent one of the most critically ill populations of patients encountered in Emergency Practice. A firm knowledge of the common injuries, their pathophysiology, and mechanisms for rapid diagnosis coupled with the ability to efficiently institute appropriate treatment measures will maximize the likelihood of a positive outcome.

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