Peritoneal Equilibration Test Using the Radiopharmaceutical, Diethylene-triaminepentaacetate (DTPA)

Abstract

The inherent characteristics of the peritoneal membrane determine the peritoneal dialysis (PD) prescription. Membrane characteristics are also an important variable affecting patient outcome. The peritoneal equilibration test (PET) described by Twardowski and colleagues in 1987 is the most commonly used test for determination of peritoneal membrane characteristics. A need exists to have simpler and more definitive tests of peritoneal membrane characteristics. In a pilot study, we used a radiopharmaceutical [(99)Tc-diethylenetriaminepentaacetate ((99)Tc-DTPA)] to determine membrane characteristics.We injected (99)Tc-DTPA (370 MBq) intravenously into 20 patients at the end of peritoneal instillation of 2.5% glucose-containing PD fluid as in a standard PET. After a 4-hour dwell, a dialysate sample was collected, and excretion of (99)Tc-DTPA into the dialysate fluid was calculated as a percentage of the injected dose. Depending on the excretion of the radiopharmaceutical into the effluent after intravenous injection, patients were categorized into high, high-average, low-average, and low transporters. An analysis of standard PET characteristics was also conducted for 75 consecutive patients.Excretion of the radiopharmaceutical was found to vary between 8% and 17% of the injected dose, depending on membrane characterization. The patients were categorized into four groups depending on the percentage excretion of the radiopharmaceutical: excretion > 15%, high transporter; 12% - 15%, high-average transporter; excretion 10% - 12%, low-average transporter; and excretion < 10%, low transporter. Standard PET characteristics for 75 patients showed 32% to be high transporters, 40% to be high-average transporters, 23% to be low-average transporters, and 5% to be low transporters. The nuclear PET in 20 patients showed 40% to be high transporters, 35% to be high-average transporters, 15% to be low-average transporters, and 10% to be low transporters. Correlation with the standard PET was good (correlation coefficient: 0.64; p = 0.002).The nuclear PET could be an alternative to the standard PET for assessing peritoneal membrane characteristics. It is reproducible and may have the added advantages of simplicity and a possibility of measuring total clearance (PD + renal) in the same sitting.