Abstract
A 23-day-old Japanese Black female calf presented with distension of the lower abdomen. Abdominal ultrasonography revealed a cystic structure with fluid accumulation and moderate echoluminance in the right abdominal cavity. Ultrasonography and contrast-enhanced computed tomography revealed congenital hydronephrosis due to narrowing of the intrarenal ureter, and right kidney resection was performed. Blood urea nitrogen and serum creatinine levels, which were within reference values preoperatively, peaked on the third postoperative day and gradually decreased afterward until reaching preoperative values on the tenth day. In bovine hydronephrosis, nephrectomy may provide a favorable prognosis if one kidney is intact. Moreover, this case suggests that blood tests immediately after surgery are not suitable for evaluating residual kidneys.