This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
Which is the most sensitive imaging modality to detect early renal tuberculosis? 
Select and explain. 
A. Ultrasound, B. Intravenous urography, C. Computed tomography, D. Magnetic resonance imaging
B: Intravenous urography
Answer: B: Intravenous urography 
Explanation: The most sensitive imaging modality to detect early renal tuberculosis is intravenous urography. Earliest urographic findings in renal TB is irregular calyceal contour which occur secondary to papillitis. Characteristic urographic finding in renal TB is 'phantom calyx' which refers to an obstructed, nonfunctional calyx proximal to an infundibular stricture. Early signs of ureteral TB includes dilation, ulceration and mucosal irregularity. Ref: Diagnosis of Genitourinary Disease By Main I. Resnick, 2nd Edition, Pages 289-90