Cystinuria in the dog: Clinical studies during 14 years of medical treatment

The purpose of this study was to summarize 14 years of clinical experience with medical treatment of 88 cystinuric dogs. Of special interest was evalu ation of recurrence rate of cystine uroliths and adverse effects during lon g-term tiopronin treatment. Twenty-six different breeds were recognized, an d the most common breeds were Dachshunds, Tibetan Spaniels, and Basset Houn ds. In 76 of 88 treated dogs (86%), re-formation of cystine uroliths was pr evented. Recurrence rate of cystine uroliths changed from 7 months before t o 18 months during tiopronin treatment. On 28 occasions, bladder stones wer e found, and in about 60% of the dogs, the uroliths dissolved. Quantitative measurement of the urinary excretion of cystine showed a significantly (P < .03) higher excretion of cystine in dogs with recurrent urolith formation than in dogs with only 1 urolith episode. Another finding was a significan t (P = .02) decrease in urinary cystine excretion in older (> 5 years) than in younger (< 5 years) dogs. Adverse effects were found in 11 dogs, and th e most severe signs were aggressiveness and myopathy. All signs disappeared when tiopronin treatment was stopped. In conclusion, this study emphasizes the importance of an individual strategy for lifelong treatment of cystinu ria. In addition to increasing water intake, chemical modification of the c ysteine molecule into a more soluble form by means of tiopronin is useful. In dogs with re-formed cystine uroliths, dissolution may be induced by incr easing the tiopronin dosage to 40 mg/kg body weight per day. In dogs with a low urolith recurrence rate and low urinary cystine excretion, the tiopron in dosage may be decreased or treatment discontinued.