NAVLE Feline Internal Medicine 4

Question 1

A 10-year-old spayed DSH cat presents with polyuria, polydipsia, and a serum sodium of 168 mEq/L. Urine specific gravity is 1.008. ADH administration fails to concentrate urine. Which diagnosis and underlying mechanism best explains this presentation?

Accepted Answer

Nephrogenic diabetes insipidus due to renal tubular unresponsiveness to ADH

Answer

Failure to concentrate urine after exogenous ADH administration confirms nephrogenic diabetes insipidus (NDI) — the renal tubules are unresponsive to ADH despite its presence. Central DI would respond to ADH administration with urine concentration. Psychogenic polydipsia causes medullary washout but typically responds partially to ADH. The hypernatremia here results from water loss exceeding intake, not pure water deficit with intact concentrating ability.

Question 2

A 7-year-old male castrated Persian cat presents with episodic vomiting, weight loss, and small-intestinal diarrhea. Jejunal biopsy reveals lymphocytic-plasmacytic infiltration with villous blunting. Serum folate is elevated and cobalamin is severely low. Which statement best explains the cobalamin deficiency in this patient?

Accepted Answer

Cobalamin malabsorption due to loss of ileal cubilin/amnionless receptors from mucosal disease

Answer

In cats, intrinsic factor is produced by the pancreas but cobalamin absorption occurs via cubilin/amnionless receptor complexes in the ileum. Diffuse small intestinal mucosal disease (as seen here with IBD/lymphoma) damages ileal absorptive receptors, causing cobalamin malabsorption despite normal pancreatic IF production. Elevated folate suggests proximal small intestinal bacterial overgrowth or intact proximal mucosa with bacteria producing folate. EPI would cause both low folate and low cobalamin. Severe ileal mucosal loss is the direct mechanism here.

Question 3

A 12-year-old cat with known hyperthyroidism controlled on methimazole develops acute azotemia (creatinine 3.8 mg/dL, BUN 58 mg/dL) after 3 weeks of therapy. Pre-treatment creatinine was 1.1 mg/dL. Which pathophysiologic explanation is most accurate?

Accepted Answer

Unmasking of pre-existing chronic kidney disease as GFR normalizes with euthyroid state

Answer

Hyperthyroidism increases cardiac output and causes hyperfiltration, artificially elevating GFR and suppressing serum creatinine. When hyperthyroidism is treated and GFR normalizes, underlying CKD that was masked by the hyperfiltration state becomes apparent. This 'unmasking' phenomenon is well-documented in feline medicine and is why pre-treatment renal biomarkers can be misleadingly normal. The pre-treatment creatinine of 1.1 mg/dL was falsely low due to increased GFR, not because the kidneys were truly healthy.

Question 4

A 9-year-old cat presents with acute collapse, jugular distension, muffled heart sounds, and pulsus paradoxus. Echocardiography confirms pericardial effusion with right atrial collapse. Which etiology is most common for pericardial effusion causing tamponade in cats, and how does it differ from dogs?

Accepted Answer

Feline infectious peritonitis (FIP) causing exudative effusion; dogs more commonly have hemangiosarcoma

Answer

In cats, FIP is the most common cause of pericardial effusion producing cardiac tamponade, causing an exudative high-protein effusion due to coronavirus-mediated vasculitis. In dogs, right atrial hemangiosarcoma and idiopathic pericardial effusion dominate. This species difference is clinically important because treatment, prognosis, and diagnostics differ substantially. FIP effusion in cats characteristically has high protein content (>3.5 g/dL) and a yellow, viscous appearance with Rivalta test positivity.

Question 5

A 6-year-old cat is presented for evaluation of a suspected portosystemic shunt. Fasting ammonia is 210 µmol/L (ref <60). On abdominal ultrasound, multiple tortuous vessels are identified in the splenic and left gastric regions but no single large shunting vessel. Which statement about this cat's condition is most accurate?

Accepted Answer

Multiple acquired portosystemic shunts indicate portal hypertension, most likely from hepatic fibrosis or cirrhosis

Answer

Multiple acquired portosystemic shunts (APSS) develop as a consequence of portal hypertension, typically from hepatic parenchymal disease causing increased sinusoidal resistance — most commonly hepatic fibrosis, cirrhosis, or non-cirrhotic portal hypertension in cats. Unlike congenital shunts (which are typically single large vessels), acquired shunts are multiple small vessels that open as portosystemic pressure gradients increase. In cats, hepatic lipidosis, cholangitis, and inflammatory bowel disease can drive fibrosis. Surgery is contraindicated in APSS; treating underlying hepatic disease is the goal.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Feline Internal Medicine 4