Abstract

Renolithiasis occurs uncommonly in cetaceans. The uroliths that occur in the Atlantic Bottlenose Dolphin (Tursiops truncates) are typically composed of uric acid. The etiology is unknown. Diagnosis can be difficult in that pure uric acid stones a radiolucent but gradual incorporation of impurities make larger stones (>2 cm. diameter) faintly radiopaque. Ultrasonography was used to diagnose the renal calculi and follow response to the therapy in the case presented. Serum uric acid levels of affected cetaceans are usually within normal limits. The most significant diagnostic clue is found in the urinalysis. Urine samples from affected dolphins have significant hematuria from time to time without other abnormalities. However, an advanced case of uric acid urolithiasis had severe proteinuria.

Therapy may include three strategies. First, an increase in daily fluid intake. Second, an attempt should be made to alkaline the urine. Third, excessive uric acid excretion should be reduced. An attempt to increase daily fluid intake was made by injecting the daily fish ration with water. Also using a low fat fish when compared to a high fat fish can result in a three to four liter increase in daily water intake despite a reduction in metabolic water from fat. The adult female Atlantic bottlenose dolphin in this report prior to beginning alkalinization with oral sodium bicarbonate was consistently pH 6, at the maintenance dose of 32 grains/day increased the urine pH 6.5-7.0. The third therapeutic strategy of reducing excessive uric acid excretion can be addressed from two areas, endogenous production within the tissues of the body and exogenous dietary sources. The endogenous sources of uric acid can be reduced after administration of allopurinol. This drug was not used in this case report, but should be considered in the therapeutic plan.

Periodic ultrasound graphy studies revealed a gradual dissolution of stone over a three year period while the dolphin was maintained on 8 grains of sodium bicarbonate orally four times daily, low fat diet, and injecting the daily fish ration with water.