In a patient with a history of renal stones, what should be monitored to assess their condition?

Monitoring urinary calcium excretion is crucial for patients with a history of renal stones, particularly if they are predisposed to calcium oxalate stones, which are the most common type. Increased urinary calcium excretion can indicate a metabolic disorder such as hypercalciuria that may contribute to stone formation. By assessing this parameter, clinicians can tailor dietary and therapeutic interventions to prevent recurrence, such as advising on calcium intake or considering thiazide diuretics, which help lower urinary calcium levels.

Evaluating other markers, such as serum potassium levels and blood urea nitrogen (BUN), does not specifically address the underlying causes of stone formation. While urinary pH can provide insights into certain types of stones, such as struvite or uric acid stones, it does not give a comprehensive overview of the metabolic state that contributes to calcium stone formation. Hence, monitoring urinary calcium excretion is the most relevant and actionable measurement in managing a patient with a history of renal stones.