Theoretical approach to optimum exposure time intravenous pyelography in intravenous pyelography

Abstract

In order to make clear the optimum time of getting good roentogenograms after injectionof urographic contrast medium in intravenous pyelography (IVP), a theoretical approach was carried out using two-compartments kinetics model of excretion and distribution of sodium iothalamate in a man. Amounts of contrast medium (x) accumulated in a renal pelvis were calculated in a normal man with normal kidney function and patients with various kidney diseases. The optimum time of getting X-rays was considered to be the time when x became maximum values. The results are summarized as follows.1) In a patient with normal sized pelvis and normal kidney function, the optimum time is within 30 minutes after injection of contrast medium (Fig. 4).2) In a unilateral hydronephrosis with reduced GFR whose contralateral kidney is hypertrophied with increased GFR, the optimum time is about 2 to 4 hours (Fig. 5 and 8 to 11).3) In a bilateral hydronephrosis with reduced GFR, the optimum time is remarkably prolonged showing about 10 to 20 hours (Fig. 6, 12 and 13).4) In a normal sized pelvis with unilaterally reduced kidney function, the optimum time is the same as in normal kidney function. However, in a normal sized pelvis with bilaterally reduced kidney function, the optimum time is slightly prolonged showing about 1 hour (Fig. 7).