[Two Cases of Ammonium Acid Urate Urinary Stones That Could Not Be Diagnosed by Dual-Energy Computed Tomography].

We report two cases of ammonium acid urate stones that could not be diagnosed by dual-energy computed tomography (CT). Case 1: A 37-year-old female was referred to our hospital for a left kidney stone. She had a medical history of anorexia nervosa, Basedow's disease and hypoparathyroidism. Her height was 167 cm, weight 38 kg and body mass index (BMI) 13. 6. CT showed a left kidney stone measuring 18×12 mm. Dual-energy CT showed that the left kidney stone was composed of uric acid. Chemolysis by oral administration of alkaline citrate was attempted. Six months later, CT showed no improvement, and endoscopic combined intrarenal surgery (ECIRS) was performed. Stone analysis revealed pure ammonium acid urate. Case 2: A 42-year-old female was referred to our hospital because of right back pain. She had a medical history of ventricular septal defect and urolithiasis. Her height was 158 cm, weight 37 kg, and BMI 14.8. CT showed a right kidney stone measuring 16×12 mm. Dual-energy CT showed that the right kidney stone was composed of uric acid. Chemolysis by oral administration of alkaline citrate was attempted. Two months later, CT showed no improvement, and ECIRS was performed. Stone analysis revealed pure ammonium acid urate. It is difficult to differentiate uric acid stones and ammonium acid urate stones by dual-energy CT. Even when dual-energy CT suggests uric acid stones, ammonium acid urate stones should also be considered in thin young women and women with a history of anorexia nervosa.

[Retrograde Ureteroscopic Lithotripsy with Ureteral Access Sheath Via Cutaneous Ureterostomy after Urinary Diversion : A Case Report].

A 65-year-old man presented with a history of rectal cancer 20 years prior that led to the development of a cutaneous ureterostomy and a colostomy. Subsequently, the patient was diagnosed with acute complicated pyelonephritis due to a right ureteral stone. After the placement of a single J ureteral stent in the right ureter for therapeutic management, the patient was referred to our institution for treatment of the right ureteral stone. An abdominal computed tomography (CT) revealed an 11×8 mm stone in the upper right ureter. A 10/12 Fr ureteral access sheath was inserted through the cutaneous ureterostomy and retrograde ureteroscopic lithotripsy was performed. Although a febrile urinary tract infection appeared postoperatively, the patient was discharged on the sixth postoperative day. At postoperative 1-month, CT showed no residual stones and no hydronephrosis. The use of a ureteral access sheath in performing retrograde ureteroscopic lithotripsy effectively managed the ureteral stone with cutaneous ureterostomy.

[Ureteral Access Sheath Assisted Percutaneous Antegrade Ureteroscopic Lithotripsy for Impacted Ureteral Calculus].

We retrospectively evaluated the safety and effectiveness of ureteral access sheath-assisted percutaneous antegrade ureteroscopic lithotripsy in treating ureteral calculus. Between January 2016 and April 2022, 28 patients with ureteral calculus received ureteral access sheath-assisted percutaneous antegrade ureteroscopic lithotripsy. At postoperative 1 month, a plain computed tomography (CT) and kidney ureter bladder X-ray (KUB) were performed to assess stone fragmentation and hydronephrosis. According to postoperative imaging, stone-free was defined as residual fragments 4 mm or less on KUB and 2 mm or less on CT. The mean stone size was 16.3 mm (3-43 mm). The mean stone volume was 1.91 ml (0.13-6.1 ml). The mean operative time was 140 min (60-222 min). Stone-free rate (SFR) was 89.3% on KUB, and 82.1% on CT. Three patients (10.7%) had postoperative fever greater than 38.5°C. There were no complications of grade III or higher according to the modified Clavien-Dindo classification. In the Ellenbogen classification, improvement was observed in hydronephrosis of Grade II or lower. Improvement was also observed in cases with Grade III hydronephrosis. However, due to the presence of residual renal atrophy, there was no change in the classification. The preoperative eGFR was 63 ml/min/1.73 m² (36-101 ml/min/1.73 m²) and the postoperative eGFR was not improved. We conclude that ureteral access sheath-assisted percutaneous antegrade ureteroscopic lithotripsy is effective for treating impacted ureteral calculus.