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Purpose: The assessment of hydronephrosis due to chronic partial ureteral obstruction is controversial. We determined whether a new radiographic technique for assessing kidney function, electron beam computerized tomography (CT), can detect altered renal physiology due to chronic partial ureteral obstruction. We also compared and contrasted electron beam CT with standard well tempered diuretic mercaptoacetyltriglycine (MAG-3) urography. MATERIALS ANDS METHODS: Six pigs underwent creation of unilateral partial ureteral occlusion or sham operation. Three weeks after surgery diuretic enhanced MAG-3 renal scan was done and 48 hours later contrast enhanced electron beam CT was performed., Results: Mean differential function plus or minus standard error of mean of the obstructed kidney was 5.6% +/- 2.4% on MAG-3 renography. In contrast, electron beam CT revealed significantly preserved mean renal function at 24.5% +/- 2.7% (p <0.01). Electron beam CT analysis of tubular function revealed persistent glomerular filtration and filtrate flow through the proximal tubules and loop of Henle with a selective decrease in distal tubular flow, which were findings suggestive of proximal tubular sparing that were not demonstrated by nuclear renography., Conclusions: Renal function on MAG-3 renography is primarily determined by measuring kidney perfusion and tubular secretion of the isotope. In contrast, electron beam CT determines renal function via quantifying the in vivo single kidney glomerular filtration rate and by assessing renal tubular function. This study documents that electron beam CT of differential renal function is significantly different from that of MAG-3 renography. To our knowledge which of these 2 radiographic studies is most clinically applicable is unknown to date.

We undertook a study to determine the value of gallium imaging of the kidneys in patients who had primary amyloidosis that was manifest clinically by nephrotic syndrome. We studied 28 patients with gallium-67 (67Ga) citrate scans performed 48 hr after injection. Intense (3+ to 4+) uptake was noted in both kidneys in 25 of 28 patients. Renal amyloidosis should be considered in the differential diagnosis when diffuse bilateral renal uptake of [67Ga]citrate is seen in the setting of nephrotic syndrome. Gallium uptake did not differentiate amyloid nephrotic syndrome from other causes of nephrotic syndrome. Renal gallium uptake showed a weak correlation with 24-hr urine protein excretion (p = 0.06).