brain injury should be maintained at an incline of approximately 20 degrees to promote adequate venous drainage (after appropriate volume resuscitation). Fluid therapy should be instituted to maximize cerebral perfusion pressure by maintaining an adequate peripheral mean arterial pressure, and oxygen therapy instituted as described earlier to maximize blood oxygen content and oxygen delivery.
Abdominal Examination
As soon as the major body systems are assessed and stabilization is in progress, a complete physical examination with focused abdominal examination should be performed. Initial examination may reveal abdominal distension, obvious signs of penetrating trauma or other wounds, and bruising. Periumbilical bruising (Cullen's sign) is suggestive of intra‐abdominal hemorrhage. Bruising in the inguinal region is suggestive of retroperitoneal or pelvic hemorrhage. Abdominal palpation should then proceed carefully and methodically to reveal whether pain is focal, regional, or diffuse, and to aid in localizing the source of pain. Focal abdominal pain is more likely in cases of foreign body obstruction, intestinal intussusception, prostatic disease, or mild pancreatitis. Regional abdominal pain may be present in cases of more severe pancreatitis and pyometra. Diffuse abdominal pain is found in diseases that affect the entire peritoneum, including septic peritonitis and diffuse gastroenteritis. Gentle ballottement of the abdomen should then be performed to aid in the detection of gas or fluid distension as found in cases of gastric dilatation and volvulus and hemoabdomen, respectively. Rectal examination may also prove helpful to pinpoint the underlying cause of acute abdomen. Rectal palpation of the pelvis, pelvic urethra, prostate, intrapelvic lymph nodes, and feces can provide key information including the presence of pelvic fractures, distal urethral obstruction, prostatomegaly, neoplasia, and changes in feces such as melena, hematochezia, acholic feces, and ingested foreign material. Imaging studies, including abdominal radiography and ultrasound, are recommended to confirm and/or help further differentiate between these causes of acute abdomen. In recent years, following the trend of human medicine, computed tomography (CT) has gained significant attention for its ability to rapidly and accurately diagnose various acute abdominal pathologies in dogs and cats. In the authors' practice, CT is used equally as often or more commonly than ultrasound for the diagnosis of acute abdominal pathology.
Minimum Database Interpretation and Management
Emergency data collection from PCV, total solids, blood glucose, blood gas analysis, lactate, BUN, creatinine, and electrolyte levels is critical for rapid metabolic assessment of the patient. This information will aid in identifying the underlying cause of acute abdomen and may help guide initial treatment.
PCV and total solids measurements should always be assessed together. These values will be increased in a parallel manner in cases of dehydration, and will be decreased in a parallel manner in the case of hemorrhage. It is important to note that PCV and total solids may in fact be normal in cases of acute hemorrhage before fluid replacement. A normal PCV with decreased total solids indicates protein loss, but can also be found in the acute phase of hemorrhage when splenic contraction slows the decrease in PCV compared with total solids, or it may also be supportive of peritonitis, which causes increased vascular permeability and leakage of proteins [6].
Blood glucose levels can be measured with a cage‐side glucometer, with hypoglycemia (blood glucose < 60 mg/dl) often associated with sepsis. Hyperglycemia instead may be found in patients with diabetes, or transiently in cases of severe acute pancreatitis or severe stress.
Venous blood gas analysis provides insight into the pH and the metabolic side of an acid–base equation and may also include electrolyte status of the patient. Hypochloremic metabolic alkalosis is a common finding in animals with vomiting, due to pyloric or proximal duodenal obstruction [7]. Animals with severe hypoperfusion may instead show evidence of metabolic (lactic) acidosis.
Patients with urinary tract obstruction or rupture are often hyperkalemic, which is dangerous due to its effects on the heart. Bradyarrhythmias, characterized by a prolonged P–R interval, widening of the QRS complex, increased T‐wave amplitude, and loss of P waves, can eventually progress to atrial standstill and asystole if untreated. Aggressive medical treatment with intravenous fluids and calcium gluconate (20–60 mg/kg administered over 1–3 minutes with concurrent ECG monitoring) is indicated if ECG changes are significant. These patients should be monitored closely with ECG during and after treatment. Dextrose (0.5 g/kg) and regular insulin (0.1 iu/kg) may also be used to drive potassium intracellularly. Bicarbonate will result in a redistribution of potassium to the intracellular space and will also help manage metabolic acidosis. Bicarbonate therapy is generally reserved for patients with severe hyperkalemia coupled with life‐threatening metabolic acidosis (pH < 7.2).
Peritoneal Fluid Analysis and Indications for Emergency Laparotomy
Free peritoneal fluid is common in animals with acute abdominal pain. Analysis of free peritoneal fluid is important for both determining the cause of acute abdomen and guiding the decision to take a patient to surgery. A FAST scan is very useful in identifying peritoneal fluid accumulations in small animal patients. Abdominocentesis (Video 3.1) can be performed with or without ultrasound guidance. Abdominal fluid samples should be examined for gross appearance, and analyzed for PCV, total solids, glucose, and cytology. Additional biochemical testing for creatinine and potassium, and bilirubin levels are also measured in cases of suspected uroperitoneum and bile peritonitis, respectively.
The presence of hemoabdomen is confirmed by a PCV of peritoneal fluid similar to that of peripheral blood. This finding in a patient with no history of trauma and a normal coagulation profile is an indication for emergency laparotomy to identify and control the source of hemorrhage, often identified as a bleeding splenic or liver mass.
Septic peritonitis is confirmed by the cytologic presence of toxic neutrophils with intracellular bacteria and is also supported by an abdominal glucose measurement 20 mg/dl lower than that of the peripheral blood [8]. These findings are also an indication for emergency laparotomy to identify and control the source of sepsis, which is commonly a gastrointestinal perforation or rupture.
In cases of suspected bile peritonitis, intracellular bile pigment is found cytologically, and is noted to have a green or brown mucinous appearance [9]. In addition, if the total bilirubin measured in an abdominal fluid sample is greater than that in peripheral blood, bile peritonitis may be present. This also warrants emergency surgery following appropriate stabilization.
Uroperitoneum is confirmed by comparing levels of creatinine and potassium in abdominal fluid and serum. An abdominal fluid to serum ratio of creatinine greater than 2.0, and a fluid to serum ratio of potassium of greater than 1.4 (dogs) or 1.9 (cats) indicates uroperitoneum [10]. Following imaging studies to localize the source of uroperitoneum (retrograde urethrocystogram and, in patients with evidence of retroperitoneal pathology, excretory urography or pyelography), urinary diversion and/or emergency surgery is indicated.
Other types of abdominal fluid include pure transudates, proteinaceous effusions (modified transudates), neoplastic effusions, and chylous effusion. Patients with these types of effusions are less likely to require surgical intervention on an emergency basis.
Independent of abdominal fluid analysis, other indications for emergency exploratory laparotomy include any penetrating abdominal injuries such as from bite wounds or other trauma, the radiographic evidence of free gas in the peritoneum, small‐bowel obstruction, or gastric dilatation/volvulus syndrome.
Diagnostic Imaging for the Acute Abdomen
The use of radiographs, ultrasound, and/or CT is indicated in all cases of acute abdomen to guide the diagnostic workup and decision to treat medically or surgically.