Struvite Urolithiasis in a Dog

INTERNAL MEDICINE CASE STUDIES Struvite urolithiasis in a 6 year old entire male Cocker Spaniel A 6 year old male entire cocker spaniel was examined at the R(D)SVS Internal Medicine Service for investigation of stranguria, pollakuria and haematuria of one months’ duration. Urethral catheterisation had been required on three occasions to relieve a distended and uncomfortable bladder. On presentation, the dog was bright, alert and responsive. Body condition score was 5/9, at a weight of 14.9 kg. A number of small, firm, gritty structures were palpated within the bladder. There were no other significant findings on physical examination. Rectal examination revealed a symmetrical, non-painful prostate, of a standard size for an entire dog. Routine haematology and serum biochemistry revealed no significant abnormalities. Abdominal ultrasound revealed moderate thickening of the bladder mucosa, with multifocal polypoid lesions. There were also multiple calculi within the bladder, ranging in size from 312 mm. The majority were freely mobile within the bladder lumen, 2 were located within the bladder neck, and one (1cm diameter) appeared lodged within the prostatic urethra. A 6Fr catheter was passed into the bladder, encountering only mild resistance at the level of the prostate. Urine was collected for analysis and the bladder was emptied. Urinalyses revealed USG 1.023, pH 8, + protein and ++ blood. Sediment examination revealed large numbers of red blood cells and sperm, accompanied by occasional epithelial cells and neutrophils. Small numbers of struvite crystals were identified. Bacteria were not seen. Bacterial urine culture was negative; however antibiotics had already been administered, potentially masking infection. The dog was diagnosed with multiple cystic calculi and partial obstruction of the prostatic urethra. He was transferred to the Soft Tissue Surgery service for cystotomy and stone retrieval. A full thickness bladder biopsy was obtained for histopathology, and calculi were submitted for mineral analysis and culture. Histopathology showed moderate to marked, diffuse, chronic polypoid cystitis with haemorrhage and haemosiderosis. Urolith culture results were negative. Urolith analysis revealed 100% magnesium ammonium phosphate (struvite). Polypoid cystitis usually represents a hyperplastic inflammatory reaction to chronic irritation of the bladder, most commonly as a result of recurrent urinary tract infection, or urolithiasis1. In this case, a combination of struvite urolithiasis and chronic urinary tract infection was suspected as the underlying cause. Post operatively, the dog was started on Hills c/d ® diet, and recommendations were made to increase his water intake and frequency of urination. Meloxicam was prescribed for the page 1 of 2 anti-inflammatory effect and associated potential benefit in polypoid cystitis. At re-evaluation 4 months later, the dog was asymptomatic and doing well. Recheck ultrasound of the urinary tract and prostate revealed a large amount of echogenic sediment within the urinary bladder, but no evidence of discrete urolithiasis. There were several areas of localised bladder wall thickening (up to 3.5 mm). The bladder wall thickness and layering was otherwise normal, representing a marked improvement since the previous ultrasound scan. Urinalysis was unremarkable and follow up urine culture was negative. Meloxicam was discontinued, and the dog continues to do well at this time. Reference 1 Martinez et al (2003) Polypoid cystitis in 17 dogs (1978-2001). JVIM. 17, 499-509 page 2 of 2