Rim sign in IVP is seen in –: (A) Polycystic kidney, (B) Hydronephrosis, (C) Chronic pyelonephritis, (D) Hypemephroma
Answer is B. Two most important causes of rim sign on nephrogram are -
	(i) Hydronephrosis (chronic obstruction), and
	(ii) Renal artery occulusion.