Obstructive ureterolith in the cat: medical treatment or SUB
9-year-old female cat with anorexia and vomiting. Creatinine 6.8 mg/dL. Ultrasound shows a ureterolith in the proximal left ureter with hydronephrosis; the right kidney is small and irregular.
What is the most appropriate approach?
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A. Oral treatment at home for two weeks and repeat the ultrasound
With severe azotaemia and a diseased contralateral kidney, every day of obstruction reduces recoverable function. Weeks of waiting are not appropriate.
B. Dissolution diet, since most feline ureteroliths are struvite
The great majority are calcium oxalate, which does not dissolve. Diet has no role in acute obstruction.
C. Stabilise and give medical treatment for 24–72 h with monitoring; if the obstruction and azotaemia do not improve, decompress with a subcutaneous ureteral bypass (SUB) or stent
Correct. A minority of ureteroliths move with medical treatment (fluids while watching for overload, sometimes mannitol). Without improvement, early decompression at an experienced centre is the best option to preserve renal function.
D. Nephrectomy of the left kidney, which is the obstructed one
The obstructed kidney is often the better-functioning one; the contralateral kidney is already diseased. Removing it would leave the cat without enough renal function.
lightbulb Key takeaway
Cat with 'big kidney-little kidney' and severe azotaemia: the big kidney is usually obstructed and is the one to save. Few ureteroliths move with medical treatment; if there is no improvement in 24–72 h, refer for decompression.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.