Prenatal sonographic findings of fetal megacalycosis

Megacalycosis refers to dilatation of the renal calyces without evidence of distension of the renal pelvis or ureter.1 It characteristically involves 1 kidney and does not alter renal function. Because obstructive urinary tract lesions are common, both the American Institute of Ultrasound in Medicine2 and the American College of Radiology have included images of the fetal kidneys in their second- and third-trimester fetal examination guidelines. With severe obstruction the renal architecture becomes distorted and difficult to see. In this instance it may be impossible to distinguish between a dilated renal pelvis and a dilated calyx. Institutional Review Board approval was obtained to report the following case.