This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary Tract, Subject name: Surgery
[{'content': 'Following are the sign/s suggestive of obstruction of urinary tract on CT Scan \nSelect and explain. \nA. Hyroureter, B. Perinephric stranding, C. Thickening of the lateroconal fascia, D. All the above', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., All the above CT Scan in Urolithiasis* Nonenhanced CT has been accepted as the imaging modality of choice in the radiologic evaluation of patients suspected of having urolithiasis.* CT is superior to other imaging modalities in the diagnostic accuracy and assessment of their characteristics.* The most direct sign of ureterolithiasis is the stone within the ureteral lumen, with proximal ureteral dilatation and normal distal caliber.* Other favorable secondary signs at CT are: Hydroureter, hydronephrosis, perinephric stranding, periureteral edema and unilateral renal enlargement.* Less reliable findings include unilateral absence of the white renal pyramid, thickening of the lateroconal fascia, and perinephric edema.* Differences in the renal parenchymal attenuation between obstructed and nonobstructed kidneys have also be used as the secondary sign of obstruction.", 'role': 'assistant'}]