Background: Ureteral stent placement to localize the ureters during operations is an invasive procedure. The aim of this study was to evaluate the feasibility of using the gamma probe to intraoperatively identify the ureters after intravenous injection of a radiopharmaceutical agent.
Study design: Ten patients undergoing elective abdominal operations were prospectively enrolled in this study. An average dose of 4.5 mCi (range 2.8 to 5.3 mCi) of technetium Tc 99m-labeled diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) was administered intravenously before localization of the ureters. The gamma probe was used to localize the ureters. Correct identification of the ureters was confirmed when gentle manipulation induced a typical ureteral peristaltic pattern.
Results: Gamma counts were significantly elevated in all ureters examined. Compared with background counts, gamma counts were increased over the ureter in all patients, with an average increase of 465%. The technique was modified after use in the first 3 patients and standardized for patients 4 through 10. Data from those seven patients were analyzed. Both ureters were correctly identified using the gamma probe at a mean of 15 minutes (median, 10 minutes) after a single (99m)Tc-DTPA injection (range 4 to 41 minutes). The mean background count was 80 counts per second (cps, range 50 to 130 cps). The mean ureter count was 393 cps (range 128 to 700 cps). The average percent increase of each ureter count compared with its specific background count was 465% (range 256% to 1,077%). The difference was statistically significant for all values (p < 0.001).
Conclusions: This novel technique of gamma probe localization of the ureters may offer a noninvasive approach for ureteral identification.