An adult with a dilated renal pelvis on ultrasound is scheduled for a diuretic renogram to separate true obstruction from a system that simply drains slowly. The patient arrives after a dry morning with a full bladder, and the order specifies a diuretic after peak uptake. Which preparation sequence will give the most interpretable washout curve?

Hydrate the patient to support steady urine production, then have them void before imaging so a distended bladder is less likely to impede upper-tract drainage. After peak tracer uptake, administer the ordered diuretic to increase urine flow and challenge the collecting system; the resulting washout curve is more useful for distinguishing true obstruction from slow drainage. Repeat imaging after voiding: reduced residual activity may reflect improved drainage after bladder emptying, while persistent retention supports impaired washout. Giving the diuretic immediately after injection uses an early-diuretic approach rather than the specified post-peak timing; it changes the relationship between tracer uptake and the drainage challenge, making the requested protocol’s curve less interpretable. Imaging with voiding but no diuretic is a gravity/voiding-only assessment and omits the ordered pharmacologic challenge, so it cannot provide the intended diuretic washout assessment. Giving the diuretic without hydration may leave urine flow inadequate; slow clearance could then reflect low flow rather than obstruction. Exam caveat: diuretic timing varies among established renogram protocols, so no single timing should be treated as universal; follow the protocol specified for the study. Practical check: confirm adequate hydration, pre-imaging voiding, the ordered post-peak diuretic timing, and post-void imaging are all documented.