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
[{'content': 'Stipple sign in transitional cell carcinoma of the renal collecting system is best demonstrated by – \nSelect and explain. \nA. Intravenous urography, B. Retrograde pyeloureterography, C. Radionuclide scan, D. Ultrasound scan', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The\xa0stipple sign\xa0refers to tracking of contrast into the interstices of a papillary lesion. This is seen in\xa0Intravenous urography (intravenous pyelography)\xa0of transitional cell carcinoma of renal collecting sysym. Other signs on IVP are filling defect; Calyceal obliteration & amputation; hydronephrosis with soap bubble nephrogram.', 'role': 'assistant'}]