Obstructive ureterolith with pyonephrosis in the dog: what to do
8-year-old spayed female Maltese with fever (40.1 °C), lethargy and right lumbar pain for 2 days. Ultrasound: right hydronephrosis with a 14 mm pelvis containing echogenic suspended material, and a ureter dilated down to a radiopaque calculus (probably calcium oxalate) in the distal ureter; normal left kidney. Urine culture positive for E. coli.
| Parameter | Result | Reference |
|---|---|---|
| Neutrophils | 24,000/µL with a left shift | 3,000–11,500 |
| Creatinine | 1.9 mg/dL | 0.5–1.5 |
After stabilisation and starting antibiotics, what is the most appropriate management?
chevron_right Show answer and explanation
A. Antibiotics for 4 weeks and tamsulosin, waiting for the stone to pass
Pyonephrosis is a closed septic focus: antibiotics alone are insufficient and delay endangers the kidney and the patient. Medical expulsive therapy is only considered for stable, non-infected obstructions.
B. Right nephroureterectomy: a kidney with pyonephrosis is already lost
The obstructed kidney may recover function after decompression, and a dog that forms oxalate may develop stones in the other kidney: nephrectomy is a last resort.
C. Drain the kidney and place a ureteral stent, endoscopically if possible
Correct. The infected kidney must be decompressed and drained as soon as possible. In dogs, unlike cats, a ureteral stent (ideally placed cystoscopically under fluoroscopic guidance) is the technique of choice: it drains the pelvis, allows stone passage and has fewer complications than ureterotomy. SUB devices are kept for selected cases.
D. Dissolution diet and potassium citrate to dissolve the stone
Calcium oxalate stones cannot be dissolved by diet, and an infected obstruction cannot wait.
lightbulb Key takeaway
An infected ureteral obstruction is an emergency: antibiotics and immediate decompression. In dogs a ureteral stent is first choice; in cats a SUB is often preferred. Culture urine from the renal pelvis and analyse the stone once retrieved.
References: ACVIM consensus recommendations on the treatment and prevention of uroliths in dogs and cats (2016)
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.