Efficacy of methylene blue-assisted tract visualization in ultrasound-guided percutaneous nephrolithotomy: a salvage technique for failed renal access.

Abstract

We propose using methylene blue with ultrasound-guided percutaneous nephrolithotomy (US-PCNL) as a salvage method when ultrasonography access is challenging, to prevent the necessity of creating a new tract or access failure. We retrospectively evaluated adult patients who underwent US-PCNL over two years by a single surgeon. Patients were divided into two groups based on methylene blue usage. In cases with challenging renal access, diluted methylene blue was injected via the ureteral catheter, and the nephroscope was used to locate the parenchymal defect by visualizing the blue area. Among 120 patients, 34 (28.3%) required methylene blue for renal access. Recurrent stones (70.6% vs. 47.7%; p-value: 0.023) and previous PCNL (41.2% vs. 18.6%; p-value: 0.010) were more common in these patients. All achieved successful access with a single tract. Although access time (median: 235 vs. 160 s; p-value: < 0.001) and operative duration (median: 90 vs. 85 min; p-value: 0.023) were statistically longer when methylene blue was used, the differences were not clinically significant. Analgesic use, hospital stay, hemoglobin drop, and creatinine rise were similar between groups. Stone-free rates after the first session were 50.0% with methylene blue and 57.0% without it (p-value: 0.489). Residual stone rates requiring ancillary procedures were higher when methylene blue was needed (20.6% vs. 9.4%), but the difference was not statistically significant (p-value: 0.126). Complication rates were similar between the groups. Methylene blue injection into the ureteral catheter is a safe and effective procedure for US-PCNL, reducing access failure and the need for new tracts.