No abstract

The incidence of both symptomatic and asymptomatic kidney stones has increased dramatically. The increased utilization of computed tomography during this period may have improved stone detection and contributed to the increased kidney stone incidence.

Objective To determine the variation in kidney stone composition and its relationship to risk factors and recurrence among first-time stone formers in the general population. Patients and Methods Medical records were manually reviewed and validated for symptomatic kidney stone episodes among Olmsted County, Minnesota residents from January 1, 1984 to December 31, 2012. Clinical and laboratory characteristics and the risk of symptomatic recurrence were compared between stone compositions. Results There were 2961 validated first-time symptomatic kidney stone formers. Stone composition analysis was obtained in 1508 (51%) at the first episode. Stone formers were divided into the following mutually exclusive groups: any brushite (0.9%), any struvite (0.9%), any uric acid (4.8%), majority calcium oxalate (76%) or majority hydroxyapatite (18%). Stone composition varied with clinical characteristics. A multivariable model had a 69% probability of correctly estimating stone composition, but assuming calcium oxalate monohydrate stone was correct 65% of the time. Symptomatic recurrence at 10 years was approximately 50% for brushite, struvite, and uric acid, but approximately 30% for calcium oxalate and hydroxyapatite stones (P<.001). Recurrence was similar across different proportions of calcium oxalate and hydroxyapatite (P-trend=.10). However, among calcium oxalate stones, 10-year recurrence rate ranged from 38% for 100% calcium oxalate dihydrate to 26% for 100% calcium oxalate monohydrate (P-trend=.007). Conclusion Calcium stones are more common (94% of stone formers) than has been previously reported. While clinical and laboratory factors associate with the stone composition, they are of limited utility for estimating stone composition. Rarer stone compositions are more likely to recur.

Background Several registry-based studies, using diagnostic codes, have suggested that preeclampsia is a risk factor for end-stage renal disease (ESRD). However, because the two diseases share risk factors, the true nature of their association remains uncertain. Our goals were to conduct a population-based study to determine the magnitude of the association between preeclampsia and ESRD and to evaluate the role of shared risk factors. Study Design Population-based, nested case-control study Setting & Participants The US Renal Data System was used to identify women with ESRD from a cohort of 34,581 women who gave birth in 1976–2010 in Olmsted County, Minnesota. Forty-four cases of ESRD were identified and each one was matched to 2 controls based on year of birth (± 1 year), age at first pregnancy (± 2 years), and parity (± 1 or ≥ 4). Predictor Preeclamptic pregnancy, confirmed by medical record review. Outcome End-stage renal disease. Measurements Pre-pregnancy serum creatinine and urine protein measurements were recorded. Comorbidities existing prior to pregnancy were abstracted from medical records, and included kidney disease, obesity, diabetes, and hypertension. Results There was evidence of kidney disease prior to the first pregnancy in 9 of 44 cases (21%) and 1 of 88 controls (<1%). Per chart review, 8 of 44 (18%) cases vs 4 of 88 controls (5%) had preeclamptic pregnancies (unadjusted OR, 4.0; 95% CI, 1.21–13.28). The results were similar after independent adjustment for race, education, diabetes, or hypertension prior to pregnancy. However, the association was attenuated and no longer significant after adjustment for obesity (OR, 3.25; 95% CI, 0.93 −11.37). Limitations The limited number of ESRD cases and missing data on pre-pregnancy kidney function. Conclusions Our findings confirm that there is a sizable association between preeclampsia and ESRD; however, obesity is a previously unexplored confounder. Pre-existing kidney disease was common, but not consistently coded or diagnosed.

The higher risk for ESRD in recurrent symptomatic compared with incident symptomatic kidney stone formers suggests that stone events are associated with kidney injury. The clinical indication for imaging in asymptomatic stone formers, the correct diagnosis in miscoded stone formers, and the cause of a bladder outlet obstruction in bladder stone formers may explain the higher risk for ESRD or death in these groups.