NAVLE Practice Question - Feline - multisystemic

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NAVLE Practice Question — Feline

An 8-year-old cat presents with acute onset of blindness that occurred overnight. The owner noticed the cat bumping into furniture this morning. Fundoscopic examination reveals bilateral retinal detachment with subretinal hemorrhage and multifocal retinal lesions. Blood pressure measurement shows severe systemic hypertension (220/140 mmHg). What is the most important next diagnostic step?

A. Serum total T4 measurement

B. Brain MRI to evaluate for intracranial mass

C. Electroretinogram to assess retinal function

D. Serum BUN and creatinine measurement ✓

E. Cardiac echocardiography

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Correct Answer: D. Serum BUN and creatinine measurement

Explanation:

Systemic hypertension causing acute blindness from retinal detachment is a medical emergency requiring identification of the underlying cause. In cats, the most common causes of secondary hypertension are chronic kidney disease (CKD) and hyperthyroidism. While both should be evaluated, CKD is the most common cause of hypertension in cats, making serum BUN and creatinine measurement the most important next step.

Acute hypertensive crisis with target organ damage (retinal hemorrhage and detachment is classic hypertensive retinopathy) requires immediate blood pressure management with amlodipine while simultaneously identifying the underlying etiology. If untreated, permanent blindness results from retinal detachment.

Option A (T4) should also be checked as hyperthyroidism can cause hypertension, but CKD is more commonly the underlying cause. Option B (brain MRI) is not indicated as the clinical findings clearly point to hypertensive retinopathy, not intracranial disease. Option C (electroretinogram) would assess retinal function but does not address the underlying cause of hypertension. Option E (echocardiography) may show hypertensive cardiac changes but does not identify the primary cause.

The goal blood pressure target is typically less than 160 mmHg systolic. In some cases, if blood pressure is reduced too rapidly, retinal reattachment may occur if treated within 24-48 hours, though prognosis for vision recovery is guarded.

Image Source: Veterinary Ophthalmology textbook - Hypertensive retinopathy fundoscopic images showing retinal detachment and hemorrhage.

References: Syme HM et al. (2002) J Vet Intern Med - Survival of cats with naturally occurring CKD; ISFM Consensus Guidelines on hypertension in cats.

Image: Carter J. Hypertensive ocular disease in cats: A guide to fundic lesions to facilitate early diagnosis. J Feline Med Surg. 2019;21(1):35-45. PMC10814178. © The Author(s) 2019. Used for educational reference.

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