Like Penniston and Nakada, Bensalah and coworkers also identified significant differences in QoL between genders. Female stone formers independently had a lower QoL with respect to energy and physical functioning. Of note, the timing of the questionnaire in relation to the last stone event impacted the SF-36 results; not surprisingly, patients who recently underwent a surgical procedure reported a lower QoL than patients who underwent procedures more remotely.

Interestingly, medication use, which was evaluated by Bensalah et al and might be expected to lower overall QoL, showed little impact. The authors theorized that this finding might reflect the real or perceived effectiveness of medical therapy in preventing stone recurrence and reducing the need for surgical procedures, thereby decreasing patient anxiety.

In addition, there may be a potential bias in that individuals who are currently taking medication are those who are able to tolerate it with fewer side effects.

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Unresolved issues related to QoL in stone patients remain. First, the use of the SF-36 does not substitute for a disease-specific QoL questionnaire in stone patients. Much has been learned and gained by the utilization of specialized questionnaires, such as the American Urological Association symptom index for benign prostatic hyperplasia.

A stone-related QoL questionnaire could facilitate studies evaluating more specific stone-related issues, such as anxiety over currently asymptomatic stones or the impact of chronic medication use. The cross-sectional design of the two current QoL studies is another consideration because it can lead to significant bias.

For example, in the study by Bensalah et al, the use of stone-preventing medications was not found to lower QoL. Does this finding imply that these medications do not lower QoL and therefore should be used more extensively? Or does it reflect the bias that patients who take medications chronically represent the subgroup of patients who experience fewer side effects with medication? Perhaps the patients who experienced intolerable side effects stopped taking the medication and therefore their reduced QoL while on medication was not represented.

These types of biases could be re-solved by prospective, randomized controlled trials (RCTs) of recurrent stone formers treated with or without medical therapy. By following QoL over time in all patients, including those on and off medication, the true impact of medical therapy could be realized.

Another important potential contribution of QoL studies is in optimizing surgical care. Prior RCTs, including studies that compared SWL to percutaneous nephrostolithotomy and SWL to URS for lower calyceal stones would have benefited from a validated, stone-specific QoL assessment (J Urol. 2005;173:2005-2009 and J Urol. 2001;166:2072-2080). This information could al-low consideration of patient preferences to be balanced against stone-free and complication rates in order to determine optimal treatment modalities.

Confounding factors

A number of confounding variables contribute to limitations in understanding QoL of stone patients. For example, some factors that are known contributors to stone formation themselves influence QoL. Obesity is known to be associated with nephrolithiasis and is also a factor in lower QoL (Obes Res. 2001;9:564-571).

Additional chronic conditions, such as diabetes, gout, inflammatory bowel disease, and other metabolic abnormalities associated with stone disease, may themselves lower QoL. Failure to integrate these factors into data collection and outcome analysis risks misinterpretation.

There has been only a preliminary and cursory evaluation of the role of QoL in the care of stone-forming patients. Further prospective studies are necessary to validate the published retrospective findings and to help assess the impact of various medical and surgical interventions on QoL of stone patients.

Drs. Lotan and Pearle are affiliated with the University of Texas Southwestern Medical Center in Dallas. Dr. Lotan is an associate professor of urology and holds the Helen J. and Robert S. Strauss Professorship in Urology. Dr. Pearle is a professor of urology and holds the Dr. Ralph C. Smith Distinguished Chair in Urologic Education.