Quantitative renal scintigraphy in domestic pigeons (Columbia livia domestica) exposed to toxic doses of gentamicin

Abstract

Objective - To standardize techniques for renal scintigraphy in birds, to use scintigraphy to assess gentamicin nephrotoxicosis in birds, to compare nuclear medicine assessments with histologic assessment of gentamicin nephrotoxicosis and serum uric acid concentrations, and to determine the radiopharmaceutical that best quantifies avian renal function. Animals - 12 domestic pigeons (Columba livia domestica). Procedure - Serum uric acid concentrations were determined for all birds. Renal scintigraphy techniques that used technetium-m99 (99mTc)-dimercaptosuccinic acid (DMSA; 4 hours after injection) and 99mTc-diethylenetriamine pentaacetic acid (DTPA; 15-minute dynamic study) were evaluated in all birds. Renal biopsy specimens were collected following baseline scans. Number and size of renal tubule granules positive for periodic acid-Schiff stain were scored for severity (scale of 0 to 4). Nephrotoxicosis was induced by administration of gentamicin. Serum uric acid concentrations were measured, and 99mTc-DMSA and99mTc-DTPA scans were repeated after gentamicin administration. Birds were euthanatized, and complete necropsies were performed. Results - Standard avian renal scintigraphy techniques were developed for 99mTc-DMSA and 99mTc-DTPA. Decreased renal radiopharmaceutical uptake for 99mTc-DMSA and 99mTc-DTPA indicated nephrotoxicosis. Cloacal accumulation of 99mTc-DTPA was significantly decreased after administration of gentamicin. Histologic grading of renal tissue before and after gentamicin administration confirmed nephrotoxicosis. Inconsistent serum uric acid concentrations could not be used to assess nephrotoxicosis. Conclusions and Clinical Relevance - Renal nuclear scintigraphy is a useful, noninvasive means to determine renal function in birds. Although 99mTc-DMSA may prove useful in the evaluation of renal morphology, 99mTc-DTPA is the radiopharmaceutical agent of choice for the assessment of renal function in avian species.