This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genitourinary radiology, Subject name: Radiology
[{'content': 'Rim Sign on Contrast Studies of kidney is seen in? \nSelect and explain. \nA. Chronic Hydronephrosis, B. Renal Coical Necrosis, C. Renal Papillary Necrosis, D. RCC', 'role': 'user'}, {'content': 'Answer: A \nExplanation: RIM SIGN-Chronic Hydronephrosis REVERSE RIM SIGN-Renal Coical Necrosis * RIM sign indicates the markedly thinned out atrophic renal parenchyma surrounding the dilated pelvicalyceal system in Chronic Hydronephrosis', 'role': 'assistant'}]