ASSESSMENT OF DRAINAGE IN PUJ DILATATION - PELVIC EXCRETION EFFICIENCY AS AN INDEX OF RENAL-FUNCTION

Renal function is important when assessing the response of a dilated r enal pelvis to a diuretic stimulus. Yet there is little in the literat ure to suggest how this should be undertaken. Our aim was to develop a model which we have called pelvic excretion efficiency (PEE). The PEE , which may be used to assess drainage, is a mathematical model of the ratio of the total kidney excretion to the total amount of isotope ex tracted from the blood by the kidney. Thirty-three children with a pre natal diagnosis of unilateral renal pelvic dilatation (PUJ) were treat ed conservatively after birth. As a group, they underwent a total of 1 64 diuretic DTPA renograms up to the age of 72 months. Drainage was as sessed as the response to frusemide (defined as the time for the corre cted renal curve to fall to 75% of the maximum value in the frusemide part of the study; T-75), response to bladder emptying, a change of po sture after frusemide (PM), and PEE. The contralateral normal kidney s howed a combination of both 'good' T-75 and PM drainage in 51% of reno grams while the PEE showed drainage in all. The affected kidney with r enal pelvic dilatation showed a combination of both 'poor' T-75 and PM drainage in 42% of renograms. The PEE was low in 99% of these 'poor d rainage' renograms. The PEE, the ratio of the mathematical model of re nal uptake to excretion, is readily calculated and may be a more accur ate and specific technique to assess drainage on diuretic renography.