Multicystic dysplastic kidney associated with ipsilateral ureterocele—An imaging finding that may shed light on etiology

Objective: Multicystic dysplastic kidney (MCDK) is a developmental anomaly believed to be a consequence of either early in utero urinary tract obstruction or failure of union between the ureteric bud and the metanephric blastema. Concomitant finding of MCDK and ipsilateral obstructive ureterocele may further support the obstructive theory. We aimed to explore the possible linkage between MCDK and ipsilateral obstructive ureterocele. Materials and Methods: Ultrasonographic imaging and voiding cystourethrography (VCUG) of children diagnosed with MCDK were retrospectively reviewed. Results: A total of 28 children with MCDK were included, all of whom underwent ultrasonography and 16 underwent VCUG. Ten of the 16 children (62%) who underwent VCUG had vesicoureteral reflux, none of which was to the MCDK. Twenty of 28 children (71%) had MCDK replacing the entire kidney, among whom seven (35%) had an ipsilateral ureterocele on bladder imaging. Eight of 28 children (29%) had segmental disease, all involving the upper pole of a duplex kidney (right, 4; left, 4). All four left-sided kidneys with segmental MCDKs had an associated ipsilateral ureterocele. Conclusion: Our data highlight the fact that MCDK is frequently identified with a concomitant finding of an ipsilateral ureterocele, which should be carefully sought whenever MCDK is identified. The reported association strongly supports the theory of MCDK development as a result of an in utero urinary tract obstruction