Introduction

Both elevated testosterone and polycystic ovary syndrome (PCOS) have been speculated as possible risk factors for kidney stone formation; however, the details of this potential relationship with regards to 24-hour urine metabolic panels and stone composition have not previously been characterized.

Methods

A total of 74 PCOS patients were retrospectively identified and matched with a cohort of female stone formers at a 3 : 1 ratio (by age and BMI). All patients had 24-hour urinary metabolic panels and stone compositions. These groups were compared using Pearson chi-square and Student t-tests. Additionally, the PCOS group was differentiated based on free testosterone using multivariate analysis.

Results

The case-control cohort showed that PCOS patients had significantly lower sodium excretion (p=0.015) and hypernatriuria rates (28.9% vs 50.9%, p=0.009). The PCOS-testosterone cohort demonstrated that high testosterone patients had significantly higher citrate values (p=0.041) and significantly lower odds of hypocitraturia (36.7% vs 54.2%, OR = 0.2, p=0.042). The high testosterone group also had higher sodium excretion (p=0.058) with significantly higher odds of having hypernatriuria (40.0% vs 13.6%, OR = 13.3, p=0.021). No significant patterns were revealed based on stone composition analysis.

Conclusions

Compared to healthy stone formers, PCOS patients did not demonstrate significant differences in 24-hour urine and stone composition values. Elevated free testosterone in PCOS patients has a significant association with higher urinary citrate and sodium values: findings that in and of themselves do not confirm the hypothesized increased risk of stone formation. This patient cohort may provide deeper insight into the interplay between androgens and stone formation; however, further study is needed to fully characterize the possible relationship between PCOS and stone formation.

Objectives

To determine whether spot urine pH measured by dipstick is an accurate representation of 24 hours urine pH measured by an electrode.

Materials and methods

We retrospectively reviewed urine pH results of patients who presented to the urology stone clinic. For each patient we recorded the most recente pH result measured by dipstick from a spot urine sample that preceded the result of a 24-hour urine pH measured by the use of a pH electrode. Patients were excluded if there was a change in medications or dietary recommendations or if the two samples were more than 4 months apart. A difference of more than 0.5 pH was considered na inaccurate result.

Results

A total 600 patients were retrospectively reviewed for the pH results. The mean difference in pH between spot urine value and the 24 hours collection values was 0.52±0.45 pH. Higher pH was associated with lower accuracy (p<0.001). The accuracy of spot urine samples to predict 24-hour pH values of <5.5 was 68.9%, 68.2% for 5.5 to 6.5 and 35% for >6.5. Samples taken more than 75 days apart had only 49% the accuracy of more recent samples (p<0.002). The overall accuracy is lower than 80% (p<0.001). Influence of diurnal variation was not significant (p=0.588).

Conclusions

Spot urine pH by dipstick is not an accurate method for evaluation of the patients with urolithiasis. Patients with alkaline urine are more prone to error with reliance on spot urine pH.