Peritoneal equilibration test

Peritoneal function tests should be regularly performed to optimize the treatment and to register changes in the peritoneal membrane. More than 20 years ago Twardowski et al. introduced the peritoneal equilibration test (PET test). This test was performed using a 2.27% glucose solution and was used to measure the clearance rate of small molecular substances. Based on the results of this test the peritoneum is divided into four groups of transport characteristics. In the following years, the PET test was further developed with the aim of obtaining a better characterization of ultrafiltration. As early as the year 2000 it was recommended that the PET test should not be performed with a 2.27% but with a 3.86% glucose solution and that determination of sodium sieving after a 1 h dwell time should be simultaneously carried out. Sodium sieving is a marker for the function of aquaporins. La Milia et al. developed the mini-PET test and with this introduced the determination of free water transport. The modified combined PET test with intermediate complete drainage after 1 h is a combination of the PET test and the mini-PET test. It could be shown that a decline of sodium sieving and of free water transport is currently the best available clinical parameter for early detection of encapsulating peritoneal sclerosis. Furthermore, reduction of free water transport is a good marker for peritoneal fibrosis. As the combined PET test is only slightly more labor intensive compared to the classical PET test but the informative value is much greater, the combined PET test should be routinely used.