An outpatient with a dilated right collecting system is referred for a diuretic renogram because clinicians cannot tell whether the dilation is a true obstruction. The camera is positioned and the tracer is drawn up. Which study plan answers the obstruction question most directly?

A diuretic renogram evaluates drainage by observing tracer handling and the response to a diuretic challenge. Protocols vary: the diuretic may be administered before, with, or after the tracer, so follow the department's protocol and the authorized user's prescription. Dynamic imaging and assessment of washout help distinguish a dilated system that drains from one with impaired drainage, though poor washout must be interpreted in context, including renal function, hydration, and bladder status. Delayed static imaging shows tracer distribution at one moment but does not demonstrate the response to increased urine flow. Serum creatinine and estimated GFR assess renal function but do not directly answer whether drainage is impaired. Cortical binding imaging evaluates parenchymal uptake and scarring rather than drainage.