Renal scintigraphy in insulin-dependent diabetes mellitus: early glomerular and urologic dysfunction

Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by intravenous injection of 99mTc-diethylenetriaminepentaacetic acid (DTPA) and 131I-Hippuran in 115 insulin-dependent diabetic patients with albumin excretion rates (AER) less than 200 micrograms/min, and in 45 normal subjects. Separate kidney function and urinary elimination were estimated by renography. GFR was increased in the diabetic patients (152 +/- 24 ml/min/1.73 m2 vs. 128 +/- 15) and correlated significantly with RPF (r = 0.5; p less than 10(-9)). No relationship was found between GFR and the duration of diabetes, blood glucose, HbA1c, or AER. Fifty patients were hyperfiltering with RPF and filtration fraction higher than those in the normofiltering group. Slow intrarenal or pyeloureteral elimination, either unilateral or bilateral, was observed in 3 controls and 60 diabetic subjects (24 hyperfiltering; 36 normofiltering) and did not disappear with the patient in the standing position. In these 60 patients, mean age, duration of diabetes, blood glucose, HbA1c, 24 h albumin excretion rate, and frequency of peripheral or autonomic neuropathy did not differ from patients with normal scintigraphy; GFR was lower in the group with slow elimination, but not significantly so. 99mTc-DTPA renal uptake was symmetric in all the controls; asymmetric renal uptake with asymmetric GFR was observed in 13 patients (7 hyperfiltering; 6 normofiltering) and often associated with slower elimination. No evidence for renal stenotic atheroma or parenchymatous disease was found on the angiopyeloureterography. The results suggest that incipient uropathy is a very common phenomenon that occurs irrespective of glomerular dysfunction.