Abstract
Intermittent hydronephrosis is notoriously difficult to diagnose but, once confirmed, requires surgery. In contrast, congenital megacalicosis is accepted as a non-obstructive cause of upper urinary tract dilatation for which surgery is inappropriate. Experience with 2 cases and a review of the literature suggest that occasionally the clinical features and radiographic findings in the 2 conditions may overlap, leading to misdiagnosis. Attention to the combination of clinical features and radiography, together with the use of radionuclide techniques and acute pain studies, may help to distinguish between these conditions.