Abstract
Hydrocalyx is the obstruction of a renal calyx resulting from infundibulopelvic stenosis or diminution and can be congenital or acquired. A 37-year-old man with a history of preemptive kidney transplantation in 2007 and transplant rejection underwent another ABO-incompatible transplant. During follow-up four months after transplantation, a transplant biopsy was performed, which revealed acute thrombotic microangiopathy. Seven months after transplantation, the patient was admitted to the hospital because of elevated creatinine levels and dilatation of the upper calyx on ultrasound examination. Upper calyx hydrocalycosis and calyceal neck stenosis were diagnosed. Nephrostomy placement along with an antegrade double-J stent through the upper major calyceal neck was performed. Endoscopic dilatation of the narrowed neck of the upper major calyx 10 days after hydrocalyx decompression was performed without intraoperative or postoperative complications. During follow-up, the patient was asymptomatic, had steady creatinine levels, and showed no signs of obstruction on ultrasound. This case highlights that treatment with balloon dilation of the calyceal neck appears to be an effective solution that respects the renal parenchyma and function.