History: An eight-year-old, spayed female Labrador retriever presented for evaluation of acute onset of diarrhea and collapse. The owner reported that the dog was completely normal until 3 hours prior to presentation when the dog developed profuse bloody diarrhea. There was no history of toxin exposure, and current medications included prednisone 1 mg/kg orally BID, famotidine 0.5mg/kg orally SID, and azathioprine 10mg/kg orally SID for immune-mediated hemolytic anemia diagnosed 4 weeks prior.
On initial physical examination the dog was recumbent with tacky, muddy mucus membranes and a capillary refill time of approximately 3 seconds. The rectal temperature was 98.9° F, pulse 180 beats per minute, and respiratory rate 60 breaths per minute. A large bore over the needle catheter was placed in the cephalic vein and the following minimum data base was obtained: PCV 34%, TP 5.4 g/dl, venous lactate 7.4 mmol/L. The dog had severe pain on abdominal palpation and there was a palpable abdominal fluid wave. An abdominocentesis was performed and the abdominal effusion was found to be a transudate. The remainder of the physical examination was non-remarkable. An emergency abdominal ultrasound was performed.
Describe the lesion outlined in the ultrasound image:
List 5 differential diagnoses for a dog presenting with an acute abdomen and abdominal effusion.
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Portal vein thrombosis is being recognized with increased frequency in small animals due to greater awareness of hypercoagulable states and greater use of abdominal ultrasound in animals with gastrointestinal signs. The veins of the hepatic portal system drain the digestive organs, spleen and pancreas and deliver blood to the liver via the hepatic portal vein. The portal vein is responsible for delivering close to 75 percent of the hepatic blood supply, the remaining being provided by hepatic arteries. Obstruction of the portal vein occurs most commonly secondary to thrombus formation, or due to neoplastic infiltration and secondary thrombus formation.
Clinical investigation of hemostasis in dogs and cats with naturally-occurring disease processes is facilitated by the state-of-the-art equipment housed in the coagulation laboratory at the Foster Hospital for Small Animals at Tufts University. A recent study performed at Tufts (JAVMA: Fenty et al.) used thromboelastography to document hypercoagulability in dogs with immune-mediated hemolytic anemia prior to therapy with prednisone. Certainly this population of dogs is known to experience severe thrombotic complications, at times despite aggressive anticoagulation.