[Embryology and genetics of primary vesicoureteral reflux and associated renal dysplasia].

Objectives: The main reasons of this review are: To determine some of the embryological and genetic mechanisms of vesicoureteral reflux (VUR) and associated congenital reflux nephropathy (NR); recognize different patterns of familiar clustering and identify appropriate cases where genetic counselling and investigations might be indicated; and finally, to establish the association of these phenomena (VUR and NR).

Methods: Bibliographic search of related articles until June 2007.

Results: There are two kinds of primary VUR: isolated VUR and syndromic VUR; the last one has an inherited Mendelian transmission and we know the mechanisms. Epidemiological studies seem to demonstrate that isolated VUR also presents familiar clustering and its inheritance pattern is the main object of interest in some studies; most authors support the hypothesis that VUR is genetically heterogeneous and is caused by a number of different genes acting with random environmental effects. There are lots of candidate implicated genes. The characteristics of VUR (incomplete penetrance, variability of expression, spontaneous resolution...) make difficult to configure a selection of patients subsidiary of genetic study. Despite different treatment options, the incidence of renal chronic failure secondary to VUR has not decreased. Some of the candidate genes identified regulate the position of ureteral budding, a critical step in both kidney and urinary tract development. Analysis of data from humans and mice suggests that some of the renal damage associated with VUR is congenital and is due to a kidney malformation. Therefore, in these cases, the association of VUR and renal failure may be caused by a genetic defect affecting the formation of the kidney and the urinary tract and not by evolution of VUR. Investigation in animals is fundamental to know more about this issue (candidate genes and VUR-NR association).

Conclusion: It is important to learn patterns of familiar clustering of isolated and syndromic VUR to offer genetic counselling if possible. For this reason, we should be screening carefully all patients suffering from VUR. It is known that limitations in actual indications of genetic study exist. Prenatal diagnosis may be realized if there is a syndromic VUR with known mutation, invariable expressivity or if clinical manifestations involve risk of death. Epidemiological data and laboratory studies may give us guidance to elicit new cases of nephropathy associated to severe VUR.