HISTORY / CLINICAL SIGNS: Adopted as a stray 4 mo ago. Hematuria 2 mo ago, worked up as a bladder stone. Prolonged anesthetic recovery from neuter and cystotomy as performed at another clinic; behavioral & visual changes have persisted. One seizure reported 1 mo ago. Intermittent vomiting for several months. Indoor only. UTD vaccines, but not on flea/tick prevention.
PHYSICAL EXAM FINDINGS: BAR. Delayed PLRs and menace response. Otherwise, unremarkable PE.
What is on your differential diagnosis list? What diagnostic tests would you order? Any other questions?
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DIAGNOSTIC TESTS & RESULTS:
- CBC: microcytic, hypochromic RBCs; otherwise, within normal limits
- Chemistry: low normal BUN; otherwise, within normal limits
- Fasting bile acids: elevated
- Blood ammonia: elevated
- Urinalysis: ammonium urate crystals
Any other tests youโd like to perform?
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- Abdominal ultrasound: Extrahepatic portocaval shunting vessel. No current uroliths noted. Focal thickening of cranioventral bladder (due to recent cystotomy)
Based on this patientโs signalment, clinical signs, physical exam findings, and test results, what is your diagnosis, recommended treatment, and prognostic outlook?
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DIAGNOSIS: Extrahepatic portosystemic shunt (PSS).
A portosystemic shunt is when abnormal blood vessels โbypassโ the liver, starving the liver of a proper blood supply and nutrients, causing hepatic damage. In addition to many other functions, the liver normally helps filter out toxins, such as ammonia, which arise from protein in ingested food. Ammonia crystals can accumulate in the urine, forming bladder stones. With a PSS, the liver cannot rid the body of these toxins, so they buildup in the bloodstream and can cause seizure activity due to hepatic encephalopathy. Due to this patientโs young age, a congenital shunt is more likely than an acquired shunt. Shunts may arise from blood vessels either inside the liver (intrahepatic) or on the outside of this organ (extrahepatic). Extrahepatic shunts are more common in cats, and domestic shorthairs are more likely to have shunts vs. other breeds. Cats with PSS tend to respond well to medical management, the goal of which is to reduce the amount of ammonia in the body. It does not, however, improve liver function or prevent future urolith formation.
TREATMENT: Referral for surgery was addressed with the owner, yet medical management was elected instead. This included a low protein diet, oral lactulose, and metronidazole. If seizures resume, Keppraยฎ (levetiracetam) is to be considered. Bloodwork/UA to be repeated in 1 mo (or sooner if seizures, aggression, or other behavioral changes occur).
Any other questions, comments, or suggestions?
Unless otherwise stated, these clinical cases are real-life cases that I have managed as a veterinarian in general small animal veterinary practice or else assisted with as a student in vet school. These cases are a great real-world learning tool for vet students and other veterinary professionals. They shall be used for learning purposes and collaboration of knowledge only. These cases are not intended to diagnose or treat any disease by pet owners. – Maranda Elswick, DVM
