Introduction

Abstract

Hydronephrosis is the dilatation of renal pelvis and calyces. It can be classified into obstructive and nonobstructive hydronephrosis. The typical intravenous urogram (IVU) findings of acute obstruction include increasingly dense nephrogram, modest renal enlargement, delayed calyceal opacification, minimal to moderate dilatation of the collecting system, forniceal rupture, and pyelosinous extravasation. In the case of chronic obstruction, IVU findings include negative pyelogram, calyceal crescents, dilated papillary duct, soap bubble nephrogram, and ball pyelogram. Ultrasonography (US) is a noninvasive, excellent method to evaluate obstructive uropathy. Color Doppler and pulsed wave Doppler can help in the diagnosis of obstruction. CT has advantages over other examinations in evaluating the etiology of obstruction. However, contrast-enhanced CT in early cortical phase may cause confusion in the diagnosis of hydronephrosis. Magnetic resonance (MR) urography has advantages of optimal noninvasive evaluation of urinary tract abnormalities including urinary tract obstruction, hematuria, congenital anomalies and evaluation of pediatric or pregnant patients.