QoL in Patients with Stones
Kidney Stone Prevention: 'Fact versus Fiction'
Nephrolithiasis is a common disorder. In the United States, the lifetime risk of developing a kidney stone is approximately 12% in adult men and 6% in adult women (Kidney Int. 2003;63:1817-1823).
While some kidney stones are detected incidentally on x-rays obtained for unrelated reasons and many stones remain asymptomatic for long periods of time, others are associated with hematuria, pain, infection, or obstruction that may necessitate physician evaluation, emergency department visits, hospitalization, or surgical therapy.
Furthermore, following an initial stone event, upward of 50% of patients will experience a recurrence within five years (J Urol. 2005;173:848-857). Although minimally invasive treatments have reduced the morbidity of surgical stone management, lifelong medication and/or dietary modification to prevent recurrence is often necessary. In addition, there is an emotional burden related to living with stones caused by the uncertainty of when or if a stone will become symptomatic.
Clearly, stone disease can substantially impact health-related quality of life (QoL), particularly in patients with a history of recurrent stones who are at risk of needing repeated surgical procedures or office visits. Surprisingly, few studies have assessed QoL in stone patients despite ample literature describing QoL in patients with a variety of other urologic diseases.
When considering QoL of stone formers, several significant questions arise that have not been adequately addressed in the literature:
- How are patients experiencing an acute stone event best managed—with observation or surgery?
- Is there a QoL advantage associated with a particular surgical intervention, such as ureteroscopy (URS) or shock wave lithotripsy (SWL)?
- How do ureteral stents impact QoL?
- Should patients with a history of kidney stones receive prophylactic medical therapy to prevent recurrence? Or should they be managed expectantly, using surgery only when necessary to treat recurrences?
A generic measureIn other diseases, QoL has been considered when weighing treatment options. However, no prospective studies of stone disease have addressed QoL issues in the decision-making process. Indeed, only two recently published studies have specifically evaluated QoL concerns in stone disease. Both studies utilized the SF-36 questionnaire to measure QoL since no disease-specific questionnaires for patients with stone disease have been developed.
The SF-36 is a validated, generic measure of health-related QoL that has been used to assess the impact of a variety of chronic illnesses (Eur Spine J. 2006;15 Suppl 1:S44-S51). Because the SF-36 is applicable to individuals with or without disease, it can be used to compare patients with a disease to healthy controls.
The SF-36 comprises 36 items relating to eight dimensions of health: physical functioning, role limitation caused by physical health problems, bodily pain, general health perception, energy/fatigue, social functioning, role limitation caused by emotional problems, and emotional well-being.
The eight domains are scored from 0 (worse) to 100 (optimal QoL). According to the SF-36 Health Survey Manual and Interpretation Guide, two composite summary scores—one physical (PCS) and one mental (MCS)—can be derived from the eight domains and standardized to the general U.S. population, with a normative mean of 50 and a standard deviation of 10.
In the first report on QoL in stone formers, Penniston and Nakada surveyed by mail 189 adult stone formers, using the SF-36. The researchers found that stone formers scored lower in bodily pain and general health compared with the U.S. population.
Furthermore, women scored significantly lower than men in all domains (J Urol. 2007;178:2435-2440). On multivariate analysis, however, only vitality retained a significant difference between genders. The investigators also found that obesity and other comorbidities had a significant impact on QoL measures.
Interestingly, they found no independent association between QoL and age or number of stone surgeries or SWL procedures.
In the only other QoL study in stone formers, Bensalah and colleagues evaluated 155 first-time and recurrent stone formers in a cross-sectional study in which the SF-36 was administered at the time of patient visits (J Urol. 2008;179:2238-2243). The results showed that stone patients' perception of their QoL was lower than that of the general U.S. population.
Although the differences were small (mean difference 2, range 0-4.8), they were statistically significant in five domains (four physical and one mental). Age and BMI, factors known to impact QoL in general, were also shown to correlate with QoL in stone formers.
Unlike the Penniston and Nakada study, however, the number of surgical procedures (total or specific) to which a patient was subjected was a strong predictor of mental and physical QoL domains. Stent placement, in particular, proved to be an independent predictor, portending a poor MCS.
Although concerted efforts to improve stent tolerance through medication or new stent design continue, ureteral stents are commonly associated with significant discomfort and have been shown to alter QoL (Eur Urol. 2005;48:673-678). Furthermore, the clinical advantage of ureteral stents in cases of uncomplicated URS remains in question (BMJ. 2007;334:572 and Urology. 2008;71:796-800).