Question: What is a Whitaker test and how should I code for it? Illinois Subscriber Answer: Interventional radiologists perform this procedure when they need to measure the pressure gradient between the kidney and bladder. The Whittaker test is coded and billed once per kidney and includes the pressure measurements in the kidney and the bladder, full and empty. The code is 50686 (Manometric studies through ureterostomy or indwelling ureteral catheter). The Whittaker test does not include the renal pelvic puncture, the bladder catheterization, the antegrade pyelogram or any imaging monitoring or guidance.