99mTc-DTPA renal studies for acute tubular necrosis: specificity of dissociation between perfusion and clearance.

In order to evaluate the usefulness of radionuclide renal studies in differentiating acute tubular necrosis from other causes of decreased renal clearance (e.g., rejection) in renal transplant patients, we assumed that acute tubular necrosis would be common during the first 4 days after cadaveric transplantation (group 1) and uncommon 3 weeks or longer after transplantation (group 2). There were 38 renal studies in 34 patients in group 1 and 62 studies in 27 patients in group 2. Each renal study consisted of both a technetium-99m-DTPA and an iodine-131-hippuran study. Perfusion, clearance, and transit time in the 99mTc-DTPA study, and clearance and transit time in the 131I-hippuran study were visually graded on a 5 point scale without knowledge of the time of study or clinical diagnosis. There were 19 studies in group 1 and 25 studies in group 2 with clearance decreased two or more gradations. Eleven 99mTc-DTPA studies had perfusion 2 or more gradations better than clearance; all 11 were in group 1 (p less than 0.01). Other dissociations within the 99mTc-DTPA and 131I-hippuran studies, or between them, did not distinguish the two groups. Data support the hypothesis that decreased clearance with relatively well preserved perfusion in 99mTc-DTPA studies is common in acute tubular necrosis and uncommon in other causes of decreased renal clearance.