Hydronephrosis - grading of dilatation of hydronephrosis

Hydronephrosis is commonly divided into four grades according to dilation of the pelvicalyceal system and cortical thinning that can be visualised on ultrasound, CT and MRI.

Grade Description
Grade I dilation of the renal pelvis without dilatation of the calices
Grade II dilation of the renal pevis and calices, that become convex; no signs of cortical thinning
Grade III presence of cortical thinning
Grade IV massive dilation of the real pelvis and calices, severe cortical thinning


1. Beetz R, Bökenkamp A, Brandis M, Hoyer P, John U, Kemper MJ, et al. [Diagnosis of congenital dilatation of the urinary tract. Consensus Group of the Pediatric Nephrology Working Society in cooperation with the Pediatric Urology Working Group of the German Society of Urology and with the Pediatric Urology Working Society in the Germany Society of Pediatric Surgery]. Urologe A. 2001 Nov;40(6):495–507; quiz 508–509
2. Quaia E. Radiological Imaging of the Kidney. Springer; 2011:354
3. Kim S-Y, Kim M-J, Yoon CS, Lee MS, Han KH, Lee M-J. Comparison of the reliability of two hydronephrosis grading systems: the Society for Foetal Urology grading system vs. the Onen grading system. Clin Radiol. 2013 Sep;68(9):e484–490.