Frequently Asked Questions about Nutritional Management of Feline Lower Urinary Tract Disorders

Q

A

A cat presents with hematuria and inappropriate urination. There are no bacteria seen on the urinalysis. Should I treat the cat with antibiotics and see if he responds to therapy or should I recommend radiographs or other diagnostic procedures?

Urinary tract infections (UTIs) are very uncommon (<1%) in healthy cats and the routine use of antibiotics is not recommended. Idiopathic cystitis or urolithiasis is more common than UTIs in cats and a radiograph is indicated. Struvite and calcium oxalate uroliths are the two most common uroliths in cats and they are both radiodense. Note: urate and cystine stones are usually radiolucent, and require positive contrast studies or ultrasound for determination.

If I see a urolith on a radiograph, is it most likely to be struvite or calcium oxalate?

In some regions of the world, struvite predominates in cats; in other regions, calcium oxalate uroliths are more common. Therefore, rather than predict what the urolith is, it is appropriate to retrieve a urolith and perform quantitative analysis. The urolith can be retrieved via free catch using an aquarium net, via catheter assistance, voiding urohydropropulsion, cystoscopy or cystotomy. Urine pH and sediment examination may or may not be helpful as crystals may not be passed at all or the crystals that are present could be different than the underlying urolith that is present. If struvite is suspected, dissolution therapy may be attempted. Failure to dissolve the uroliths within six weeks suggests the urolith is of a different mineral composition and surgical removal is indicated.

Are kidney stones in cats more likely to be struvite or calcium oxalate?

In cats, approximately 70% of nephroliths are calcium oxalate. Calcium oxalate nepholiths are present in up to 50% of cats with renal disease. Therefore, all cats that have renal disease should have abdominal radiographs. It is important to recognize if nephroliths are present and to monitor for obstruction and a decline in renal function.

How should nephroliths and ureteroliths be managed in cats?

If the nephroliths are causing complete obstruction or progressive deterioration in renal function, surgical removal is indicated. However, because of the unavoidable destruction of nephrons during nephrotomy, surgical removal is not recommended unless it can be established that the uroliths are the cause of clinically significant disease. If not, the patient should be monitored for indications of disease progression or ureteral obstruction. In many cases, ureteroliths will migrate into the bladder so it is appropriate to obtain serial radiographs to monitor for urolith movement.

How often should the cat be reexamined after a urolith has been removed? What diagnostic tests are recommended to monitor the patient?

Because many uroliths have a high risk of recurrence, it is recommended to obtain radiographs every three to six months. For metabolic uroliths (urate, cystine), contrast radiography or ultrasound examination may be necessary as these stones are typically radiolucent. Urine pH and urine specific gravity should be performed every three months to ensure owner compliance and diet efficacy.