99mTc-mercaptoacetyltriglycine renal scintigraphy can prevent unnecessary urinary drainage in patients with malignant ureteral obstruction

Abstract Objective: Urinary drainage (ureteral stenting, percutaneous nephrostomy) is a standard treatment for malignant ureteral obstruction (MUO), but its exact indications have yet to be determined. 99mTc-mercaptoacetyltriglycine (MAG3) renal scintigraphy evaluates urinary obstruction using radioisotopes and may help to determine whether there is an indication for urinary drainage in patients with MUO. In this study, we investigated the ability of MAG3 scintigraphy to avoid unnecessary urinary drainage by following up patients who did not undergo urinary drainage after evaluation of residual renal function using this imaging modality. Methods: Fifty patients who received MAG3 scintigraphy for MUO between April 2020 and January 2022 were included. These patients were classified according to the excretion pattern seen on MAG3 scintigraphy and followed up for renal function, development of pyelonephritis, and low back pain after 1, 2, 3, and 6 months. Results: Fifteen patients received conservative treatment after evaluation by MAG3 scintigraphy. The median patient age was 72 years, and the median creatinine level was 0.79 mg/dl. Hydronephrosis was present on the left side in seven cases, the right side in seven cases, and on both sides in one case. The MAG3 pattern on the affected side was non-function in seven cases, delayed voiding in seven cases, and obstruction in one case. Three patients died as a consequence of their primary malignancy during follow-up. There were no instances of decreased renal function or development of pyelonephritis on conservative treatment. However, one patient underwent ureteral stenting for low back pain on the side contralateral to the nonfunctional kidney. Conclusion: Fourteen of 15 patients with MUO who were treated conservatively after MAG3 scintigraphy did not experience troublesome renal events during up to 6 months of follow-up. MAG3 scintigraphy may be a valuable tool for preventing unnecessary urinary drainage. We would recommend conservative treatment for patients with a non-functional pattern.