The risk of associated urological abnormalities in children with pre and postnatal occasional diagnosis of solitary, small or ectopic kidney: is a complete urological screening always necessary?

OBJECTIVE: Voiding cystourethrogram (VCUG) and radionuclide scan is recommended for patients with solitary (secondary to aplasia or multicystic dysplasia), hypoplasic or single ectopic kidney, to detect associated anomalies (vesicoureteric reflux, obstructive uropathies). With the increase of occasional diagnosis, mainly by fetal ultrasound (US), the possibility of an unjustified extension of diagnostic work up must be prevented. Aim of this paper was to estimate the incidence of associated anomalies in asymptomatic cases without associated US signs of hydronephrosis.
MATERIALS AND METHODS: Among 158 Patients examined there were 81 solitary kidneys (26 multicystic dysplasia), 27 small kidneys, 50 single ectopic kidneys); prenatal diagnosis was recorded in 86%. Incidence of associated anomalies was compared with figures resulting when symptomatic cases or with hydronephrosis were excluded.
RESULTS: Vesicoureteral reflux or obstruction were found in 17% of solitary kidneys, 70% of hypoplasic kidneys and 2% of single ectopic kidneys. Among those (120 cases) without infection or hydronephrosis, incidence decreased, respectively to 5, 60 and 0%.
CONCLUSIONS: Associated anomalies are reported to affect up to 48% of solitary kidneys and about 30% of single ectopic; 80% of severe reflux are usually associated to small kidneys. In our series of solitary and ectopic kidneys incidence of abnormalities was significantly less and fell to negligible values when occasionally detected, undilated cases were considered. On this basis, indiscriminate urological screening simply based on the occasional pre or postnatal detection of undilated solitary or ectopic kidney appears to be unjustified. Small kidneys deserve special attention and VCUG is always indicated.