Clinical Significance of Hepatobiliary Localization of Tc-99m EC in Diuretic Renography.

Technetium-99m ethylene dicysteine (Tc-99m EC) is a well-established, tubular tracer for diuretic renography. Few occasional cases have been reported in literature regarding visualization of liver, gallbladder (GB), or bowel due to increased hepatobiliary route of excretion of Tc-99m EC on diuretic renography. This study aimed to retrospectively review the incidence of visualization of liver, GB, or bowel and its clinical significance in Tc-99m EC diuretic renography.  Data of all patients who underwent diuretic renography in the department from January 24, 2022 to March 31, 2023 was included in the study. The data was analyzed to assess the incidence of visualization of GB or bowel loops, correlation of the hepatobiliary localization with factors like age of the patient, concentration of 99m TcO4 solution, quality control parameters, presence of renal stone disease, serum creatinine, relative renal function, and effective renal plasma flow. Effect of hepatobiliary localization on scan interpretation and reporting was assessed.  The retrospective analysis of 437 diuretic renograms revealed the hepatobiliary localization of tracer in 34 patients. Out of these 34 patients, 14 patients had only faint visualization of tracer at 4 hours delayed image. Twenty scans had visualization of both GB and bowel. Out of these 20 scans, GB and bowel were visualized during dynamic imaging in one scan, after initial 20 minutes in two scans and in 2 to 4 hours delayed images in rest of the 17 scans. Two out of 20 patients had increased serum creatinine, 16 patients had either single kidney or relative renal function less than 26%, and 12 patients had renal stone disease. Out of the four patients in whom relative renal function was more than 25%, one patient had raised serum creatinine and three patients had renal stone disease. Interpretation of images was affected only in three patients, in which reporting of the scans required single-photon emission computed tomography imaging and correlation with other imaging modalities.  Hepatobiliary excretion of Tc-99m EC usually does not usually affect the scan interpretation and quantitative renogram analysis, but reader should be cognizant of the potential pitfalls during scan interpretation. In this study, we reviewed the possible causes of this hepatobiliary clearance and importance of additional views and correlation with other imaging modalities to clarify the suspicion arises for accurate reporting.