Congenital megacalycosis managed with observation only: A case report

Congenital megacalycosis (CM) is one of the rarest congenital renal anomalies. It typically presents with significant calyceal dilatation resembling severe pelvi-ureteric junction obstruction (PUJO) in a kidney with an intra-renal pelvis. Normal drainage on mercaptoacetyltriglycine (MAG3) renogram confirms the CM diagnosis. A male infant presented antenatally with significant unilateral calyceal dilatation and presumed diagnosis of severe PUJO. Growth scans at 32, 36 and 39 weeks showed an increasingly dilated renal pelvis with normal liquor volume. He was delivered at 39 weeks By emergency caesarean due to fetal distress. Postnatal ultrasound (USS) was consistent with the antenatal scans with an anteroposterior diameter (APD) of 21mm but a MAG3 showed normal drainage and equal split function, confirming the diagnosis of megacalycosis rather than classic PUJO. The patient therefore avoided surgery and has been managed with active observation with 3 monthly USS. Repeat USS at 15 months shows improvement in dilatation (APD 13mm), and no deterioration of drainage or drop of function on repeat MAG3 at 12 months. Congenital megacalycosis should be ruled out with MAG3 in children with suspected pelviureteric junction obstruction as the two conditions may have a similar USS appearance but have a significantly different management strategy.