- Score the AFAST exam, with 1 point for each quadrant that has free fluid identified. Perform serial FAST exams every 4-6 hours and compare scores. MWDs with increasing scores should be monitored closely and prepared for URGENT evacuation or surgery, as exploratory surgery may be necessary for MWDs with scores of 3/4 or 4/48 or with clinical deterioration.
4- Quadrant Abdominocentesis
Perform a 4-quadrant abdominocentesis in any patient with free fluid in the abdomen.9 This technique is quick and easy to perform, and usually differentiates abdominal hemorrhage or biliary or urinary tract injury. The general rule of thumb is that a positive peritoneal tap is a reliable indicator that some hemorrhage has occurred or that free urine or bile is in the abdominal cavity, but that a negative tap does not rule these out.
- Place the dog in lateral recumbency. Clip the abdomen of hair and prepare for aseptic procedure.
- “Divide” the abdomen into 4 quadrants, and tap each quadrant sequentially, unless a positive yield is obtained in a quadrant. Perform abdominocentesis on the “down” quadrants, rolling the dog over for the opposite quadrants.
- A large bore needle (18 or 20 gauge) is quickly inserted perpendicular to and through the body wall approximately 2 inches off the midline in each quadrant. Alternatively, a large bore over-the-needle catheter can be aseptically fenestrated and inserted into the abdomen. This increases the likelihood for higher yield because the fenestrations are less likely to occlude.
- The presence of blood suggests intra-abdominal hemorrhage, and the presence of clear or yellowish fluid suggests urine.
- As much sample is collected by gravity drip or slight suction with a 3 cc syringe and saved in serum tubes and EDTA tube. The fluid is analyzed cytologically, and for glucose, lactate, hematocrit, total protein concentration, BUN or creatinine, bilirubin, amylase or lipase, ALT, and ALKP.
- Assess cytology for the presence of bacteria or other organisms, or fecal or food material that would suggest gastrointestinal rupture and contamination.
- The peritoneal fluid glucose and lactate concentrations can be measured and compared to serum levels to aid in differentiating possible septic peritonitis in the absence of cytological evidence. An increased abdominal fluid lactate >2.5 mmol/L or an abdominal fluid-to-peripheral blood lactate difference of >2 mmol/L strongly suggests a septic peritonitis.10,11 An abdominal fluid glucose concentration that is >20 mg/dL lower than peripheral blood glucose concentration strongly suggests a septic peritonitis.10,11
- The hematocrit and total protein concentration are compared to a simultaneously collected peripheral blood sample. If the hematocrit and total protein concentration are similar, significant hemorrhage into the abdomen is probable, and surgical intervention may be necessary, but base this decision on the patient’s status more than the actual number. If the hematocrit and total protein concentration of the abdominal fluid are very low, minor hemorrhage is more likely, and a more conservative approach – based on the patient’s status – is recommended.
- The presence of bilirubin suggests gall bladder injury, although this may not be present for several days after trauma.9 Amylase or lipase with values higher than systemic circulation suggests pancreatic trauma. A ratio of 1.4:1 in comparing abdominal fluid potassium with peripheral blood potassium concentrations has 100% sensitivity and specificity for uroperitoneum.12 Comparison of abdominal fluid creatinine to peripheral blood creatinine concentrations shows 86% sensitivity and 100% specificity for ratios >2:1.12 Elevated ALT suggests direct liver injury, and elevated ALKP suggests bowel injury or ischemia, but these are non-specific and can rarely be used to guide management decisions.
Diagnostic Peritoneal Lavage (DPL)
Consider DPL in any MWD in which major abdominal trauma is suspected, but AFAST and abdominocentesis are unrewarding.9 If available, CT or MRI may be better modalities.
- Use a specialized DPL catheter or aseptically fenestrate a large bore over-the-needle (OTN) catheter.
- Sedate the patient if necessary and locally anesthetize the site of catheter insertion using 20 mg lidocaine.
- Percutaneously insert the catheter; a small stab incision may be needed if a larger catheter is used.
- Immediately after entering the abdominal cavity, remove the needle and advance the catheter in a caudodorsal direction to avoid the omentum and cranial abdominal organs.
- Infuse 20 mL/kg warmed, sterile saline aseptically over 5-10 minutes.
- Aseptically plug the catheter and gently roll the MWD from side to side for several minutes to allow the infusate to mix.
- Either aspirate effluent or allow gravity-dependent drainage to collect a sample for analysis.
- Analyze the sample for the same parameters described for abdominocentesis.