Renal Dysplasia, Unilateral

Unilateral renal dysplasia is a form of renal dysplasia (RD; see this term), a renal tract malformation in which the development of one kidney is abnormal and incomplete. Unilateral RD can be segmental, and of variable severity, with renal aplasia corresponding to extreme RD.

Epidemiology

Given the difficulty to have a clear cut diagnosis on ultrasound between renal dysplasia and other renal conditions (e.g.renal hypoplasia (see this term), renal post-infectious damage), prevalence and incidence are not known. An estimate of the prevalence is set at 1 / 2,300 births.

Clinical description

The classic antenatal presentation of unilateral RD is of either a large bright kidney or a small bright kidney, both with or without cystic spaces at the routine 20-week ultrasound scan. Unilateral RD may be asymptomatic if the other kidney is fully functional. In cases of severe unilateral RD, i.e. renal aplasia, the risk of renal failure in childhood is minimal, however patients may develop hypertension, proteinuria and renal failure as adults.

Etiology

The etiology of RD is unknown. RD can be part of a syndrome, such as Kallmann syndrome, Bardet-Biedl syndrome, Beckwith-Wiedemann syndrome, diGeorge syndrome, Fraser syndrome, renal coloboma syndrome, and renal cysts and diabetes syndrome (see these terms). HNF1B (17q12), PAX2 (10q24.3-q25.1) and uroplakins genes, which are associated with some of these syndromes, may have an important role in the pathogenesis of RD. Renal dysplasia can also be found in cases of urine obstruction in utero, such as posterior urethral valves, vesicoureteral reflux (see these terms), or pelviureteric junction obstruction. Whether the dysplasia is a parallel presentation of these congenital anomalies, or a consequence of the high urine pressure, remains to be determined.