Obstructive uropathy versus nephropathy: compartmental analysis in radioisotopic renography as a new methodology

A study was carried out to determine the spatial-temporal distribution of the radiopharmaceutical, 99mTc-DTPA in the kidney and its compartments during renography and the use of compartmental analysis to improve the diagnostic capability of renography. A total of 60 individuals formed three groups: group A consisted of 30 normals taken as controls, group B consisted of 15 patients with unilateral nephropathy, and group C consisted of 15 patients with unilateral obstructive uropathy. This retrospective study was performed by processing of the frames acquired in the various stages of renography and determination of the time distribution of radioactivity in the aorta, the renal parenchyma and the renal pelvis. The data acquired were used to produce three curves instead of one for each kidney and to study renal function as a system of six compartments (aorta, left and right renal parenchyma, left and right renal pelvis, and bladder). In all the above compartments the differences among the three groups were significant and were quantified using the flow coefficients of the aortorenal compartments. The differences between the aortic flow coefficients (k1) were statistically significant not only between normal controls and patients, but also between individuals with parenchymatic dysfunction and patients with pelvocalyceal obstruction. The same differences were seen comparing the pelvocalyceal coefficients (k3) of all three groups. The parenchymatic coefficient (k2) presented statistically significant differences between normals and patients which were not observed between the two groups of patients (B and C). Compartmental analysis thus increases the sensitivity of renography, is objective by utilizing quantitative parameters, enables the separate analysis of the functional behavior of the various renal compartments, and improves the differential diagnosis between parenchymatic dysfunction and pelvocalyceal obstruction.