Water Loading Improves Specificity in Renal Imaging

Abstract

In previous renal imaging studies, we had the opportunity to study normal controls. We noted that the iodine-131 (¹³¹I) orthoiodohippurate (OIH) renograms for this group had an abnormal configuration in one half of the subjects. The explanation for these abnormal [¹³¹I]OIH scans was unclear, although the hydration status of the subjects was a suspected cause. The current studies were designed to compare 30-min [¹³¹I]OIH and technetium-99m (^99mTc) DTPA renal studies in water-deprived and water-loaded normal subjects. Each volunteer underwent two sets of OIH and DTPA scans under controlled conditions of hydration. In studies of subjects who were scanned after an overnight fast, only three of eighteen ^99mTc-DTPA studies and twelve of eighteen [^l3,I]OIH studies were considered normal. After an oral water load of 10 ml/kg of body mass, all 30-min renal scans with DTPA and OIH were judged within normal limits. These results indicate that patients should receive oral water loading prior to renal scanning to avoid false-positive renal scans.