Successful Treatment of Obstructive Ureterolithiasis with Medical Expulsive Therapy Including Tamsulosin in a Dog

Ureterolithiasis is a common cause of ureteral obstruction in dogs, often leading to kidney injury. Medical expulsive therapy (MET) using α-adrenergic antagonists has been proposed as a nonsurgical treatment option in selected cases and is thought to facilitate ureteral stone passage by reducing ureteral smooth muscle tone. A 9-year-old castrated male Chihuahua weighing 1.78 kg was presented with anorexia. Physical examination revealed 7% dehydration and pale mucous membranes. Serum biochemistry demonstrated severe azotemia, with markedly elevated symmetric dimethylarginine (>100 μg/dL; reference interval [RI], 0-14 μg/dL), blood urea nitrogen (157.9 mg/dL; RI, 7-25 mg/dL), and creatinine (2.2 mg/dL; RI, 0.5-1.5 mg/dL). On day 4 of hospitalization, ultrasonography revealed dilation of the renal pelvis (16.1 mm), ureteral distention (3.74 mm), and multiple ureteroliths (maximum diameter, 3.31 mm) at the ureterovesical junction. Antegrade pyelography confirmed a right ureteral obstruction. As the owner declined surgical intervention, MET including tamsulosin, was initiated with close clinical monitoring. After 3 days, improvement in azotemia and resolution of ureteral obstruction were observed. Although concurrent medical treatments were administered, this case provides clinical insight into the potential role of tamsulosin as part of medical management of obstructive ureterolithiasis in a dog with small distal ureteral stones.