The diuretic loading tests for genetic tubulopathy

Abstract

 Batter syndrome (BS) and Gitelman syndorome (GS) are genetic tubulopathy, and BS is classified into four types by genetic studies. But genetic studies are pensive and time-consuming. In addition to that, it is reported that some cases of BS type III show similar symptoms and biochemical abnormalities as GS. In this case, it is difficult to diagnosis only by symptoms and biochemical abnormalities. The diuretic loading test is useful to investigate to examine the main part of dysfunction in tubles. BS type I is caused by the dysfunction of NKCC2. NKCC2 is expressed in the assemble Henle's loop (TAL). BS type II is caused by the dysfunction of ROMK, and ROMK is also expressed in TAL. It is expected that cases with BS type I and type II have no response to furosemide loading. GS is caused by the dysfunction of NCCT, and NCCT is expressed in the part of the distal convoluted tubule (DCT). And it has already proved that cases with GS will have no response to thiazide loading. And BS type III is caused the dysfunction of ClC-Kb, and ClC-Kb is expressed in not only TAL but also DCT. It has been considered that BS type III has NKCC2 dysfunction secondary. But there are few studies that make sure this fact examining with patients with genetically defined by the diuretic loading test. We need to confirm the response to the diuretic loading in a large number of patients who are supported by genetic diagnosis, and the diuretic loading test will easily allow to diagnosis the genetic tubulopathy.