A 67 year old man presented initially after a single episode of gross painless haematuria. An excretory urogram demonstrated a 1.5 mm round filing defect in the right lower renal infundibulum.The best study to obtain next is -: (A) Urinary cytology, (B) Cystoscopy, (C) Ultrasonography, (D) Retrograde pyelography
Answer is C. None