What is the most appropriate next step for the 65-year-old man with right flank pain and diagnostic findings suggesting right-sided hydronephrosis?

In the scenario presented, the 65-year-old man with right flank pain and diagnostic findings indicating right-sided hydronephrosis likely has an obstruction causing urine to back up in the kidney, leading to swelling (hydronephrosis). The most appropriate next step is cystoscopy, as it allows for direct visualization of the urinary tract and can help identify any intra-luminal obstruction, such as calculi (stones) or tumors that may be causing the hydronephrosis.

Cystoscopy would enable the clinician to visualize the urethra, bladder, and potentially the ureters if the scope is advanced appropriately. Identifying and addressing the cause of the obstruction through this procedure is crucial for preventing further renal damage. Furthermore, it may allow for immediate therapeutic interventions, such as the removal of a stone, if identified.

In this context, referral for nephrology consultation is premature before directly investigating the source of the obstruction. Imaging follow-up could be relevant but won’t provide an immediate solution or diagnosis regarding the obstruction. Antibiotic treatment may be necessary if there’s an underlying infection or at risk of infection due to the urinary obstruction, but it would not address the obstruction itself. Therefore, cystoscopy stands out as the most definitive and appropriate next step