The Association Between 24-Hour Urine and Stone Recurrence Among High Risk Kidney Stone Formers: A Population Level Assessment

Role of Genetic Testing in Kidney Stone Disease: A Narrative Review

PURPOSE OF REVIEW

Kidney stone disease (KSD) is a common and potentially life-threatening condition, and half of patients experience a repeat kidney stone episode within 5-10 years. Despite the ~50% estimate heritability of KSD, international guidelines have not kept up with the pace of discovery of genetic causes of KSD. The European Association of Urology guidelines lists 7 genetic causes of KSD as 'high risk'.

RECENT FINDINGS

There are currently 46 known monogenic (single gene) causes of kidney stone disease, with evidence of association in a further 23 genes. There is also evidence for polygenic risk of developing KSD. Evidence is lacking for recurrent disease, and only one genome wide association study has investigated this phenomenon, identifying two associated genes (SLC34A1 and TRPV5). However, in the absence of other evidence, patients with genetic predisposition to KSD should be treated as 'high risk'. Further studies are needed to characterize both monogenic and polygenic associations with recurrent disease, to allow for appropriate risk stratification. Durability of test result must be balanced against cost. This would enable retrospective analysis if no genetic cause was found initially. We recommend genetic testing using a gene panel for all children, adults < 25 years, and older patients who have factors associated with high risk disease within the context of a wider metabolic evaluation. Those with a genetic predisposition should be managed via a multi-disciplinary team approach including urologists, radiologists, nephrologists, clinical geneticists and chemical pathologists. This will enable appropriate follow-up, counselling and potentially prophylaxis.

Delays in Ureteroscopy and Shockwave Lithotripsy After Ureteral Stent Placement: Impact on Infectious Complications, Resource Use, and Medical Costs

Purpose: To evaluate the effects of ureteral stent duration before ureteroscopy (URS) or extracorporeal shockwave lithotripsy (SWL) on infectious complications, health care resource utilization (HCRU), and costs. Materials and Methods: Patients who underwent URS/SWL within 6months of ureteral stent placement were identified from commercial claims, categorized by time from stent placement to URS (0-15, 16-30, 31-60, and >60 days) or SWL (0-15, 16-30, and >30 days), and followed 1-month postprocedure. The relationship between ureteral stent duration and emergency department (ED) visits, inpatient admissions, infectious complications (pyelonephritis/sepsis), imaging, and costs was evaluated. Results: Mean time to URS (n = 9276 patients) was 21.3 ± 24.4 days and SWL (n = 4689 patients) was 19.0 ± 24.8 days. Compared with patients who underwent URS within 15 days of ureteral stent placement, URS 31 to 60 days after ureteral stent placement was significantly associated with inpatient admissions (odds ratio [OR] 2.56, 95% confidence interval [CI] 2.03-3.22); infectious complications (OR 2.82, 95% CI 2.09-3.81); imaging (OR 2.12, 95% CI 1.82-2.46); and medical costs (OR 1.49, 95% CI 1.40-1.58). Compared with patients who underwent SWL within 15 days of ureteral stent placement, SWL more than 30 days after ureteral stent placement was significantly associated with ED visits (OR 1.79, 95% CI 1.37-2.34); inpatient admissions (OR 3.34, 95% CI 2.38-4.69); infectious complications (OR 3.54, 95% CI 2.20-5.70); imaging (OR 2.65, 95% CI 2.23-3.15); and medical costs (OR 1.45, 95% CI 1.36-1.54). Conclusions: URS or SWL >30 days after ureteral stent placement increased the likelihood of infectious complications, HCRU, and medical costs.

Metabolic stone workup abnormalities are not as important as stone culture in patients with recurrent stones undergoing percutaneous nephrolithotomy

To investigate the association between metabolic urinary abnormalities and urinary tract infection (UTI) and the stone recurrence status in patients undergoing percutaneous nephrolithotomy (PCNL). A prospective evaluation was performed for patients who underwent PCNL between November 2019 and November 2021 and met the inclusion criteria. Patients with previous stone interventions were classified as recurrent stone formers. Before PCNL, a 24 h metabolic stone workup and midstream urine culture (MSU-C) were done. Renal pelvis (RP-C) and stones (S-C) cultures were collected during the procedure. The association between the metabolic workup and UTI results with stone recurrence was evaluated using univariate and multivariate analyses. The study included 210 patients. UTI factors that showed significant association with stone recurrence included positive S-C [51 (60.7%) vs 23 (18.2%), p < 0.001], positive MSU-C [37 (44.1%) vs 30 (23.8%), p = 0.002], and positive RP-C [17 (20.2%) vs 12 (9.5%), p = 0.03]. Other factors were mean ± SD GFR (ml/min) (65 ± 13.1 vs 59.5 ± 13.1, p = 0.003), calcium-containing stones [47 (55.9%) vs 48 (38.1%), p = 0.01], median (IQR) urinary citrate levels (mg/day) [333 (123-512.5) vs 221.5 (120.3-412), p = 0.04], and mean ± SD urinary pH (6.1 ± 1 vs 5.6 ± 0.7, p < 0.001). On multivariate analysis, only positive S-C was the significant predictor of stone recurrence (odds ratio: 9.9, 95% confidence interval [CI] (3.8-28.6), p < 0.001). Positive S-C, and not metabolic abnormalities, was the only independent factor associated with stone recurrence. A focus on preventing UTI might prevent further stone recurrence.

Breaking the Cycle of Recurrent Calcium Stone Disease

Calcium stones are common and recurrent in nature, yet few therapeutic tools are available for secondary prevention. Personalized approaches for stone prevention have been informed by 24-hour urine testing to guide dietary and medical interventions. However, current evidence is conflicting about whether an approach guided by 24-hour urine testing is more effective than a generic one. The available medications for stone prevention, namely thiazide diuretics, alkali, and allopurinol, are not always prescribed consistently, dosed correctly, or tolerated well by patients. New treatments on the horizon hold the promise of preventing calcium oxalate stones by degrading oxalate in the gut, reprogramming the gut microbiome to reduce oxalate absorption, or knocking down expression of enzymes involved in hepatic oxalate production. New treatments are also needed to target Randall's plaque, the root cause of calcium stone formation.

Urinary supersaturation in a Randomized trial among Individuals with Nephrolithiasis comparing Empiric versus selective therapy (URINE): design and rationale of a clinical trial

Clinical guidelines disagree on whether the identification of abnormal urine chemistries should occur before starting diet and medication interventions to prevent the recurrence of kidney stone events. We describe the rationale and design of the Urinary supersaturation in a Randomized trial among Individuals with Nephrolithiasis comparing Empiric versus selective therapy (URINE) study, a randomized trial comparing two multi-component interventions to improve urinary supersaturation. Participants are randomized (1:1 ratio) to the empiric or selective arm. The target sample size is 56 participants. Adults ≥ 18 years of age with idiopathic calcium stone disease and two symptomatic stone events within the previous 5 years. Exclusion criteria include systemic conditions predisposing to kidney stones and pharmacologic treatment for stone prevention at baseline. Participants in the empiric arm receive standard diet therapy recommendations, thiazide, and potassium citrate. Participants in the selective arm receive tailored diet and nutrient recommendations and medications based on baseline and 1-month follow-up of 24-h urine testing results. The primary endpoints are urinary supersaturations of calcium oxalate and calcium phosphate at 2 months of follow-up. Secondary endpoints include side effects, diet and medication adherence, and changes in 24-h urine volume, calcium, oxalate, citrate, and pH. Short-term changes in urinary supersaturation may not reflect changes in future risk of stone events. The URINE study will provide foundational data to compare the effectiveness of two prevention strategies for kidney stone disease.

Comparison of empiric preventative pharmacologic therapies on stone recurrence among patients with kidney stone disease

OBJECTIVE

To compare the frequency of stone-related events among patients receiving thiazides, alkali citrate, and allopurinol without prior 24 h urine testing.  It is unknown whether 1 preventative pharmacological therapy (PPT) medication class is more beneficial for reducing kidney stone recurrence when prescribed empirically.

MATERIALS AND METHODS

Using medical claims data from working-age adults with kidney stone disease diagnoses (2008-2018), we identified those prescribed thiazides, alkali citrate, or allopurinol. We excluded those who received 24 h urine testing prior to initiating PPT and those with less than 3 years of follow-up. We fit multivariable regression models to estimate the association between the occurrence of a stone-related event (emergency department visit, hospitalization, or surgery for stones) and PPT medication class.

RESULTS

Our cohort consisted of 1834 (60%), 654 (21%), and 558 (18%) patients empirically prescribed thiazides, alkali citrate, or allopurinol, respectively. After controlling for patient factors including medication adherence and concomitant conditions that increase recurrence risk, the adjusted rate of any stone event was lowest for the thiazide group (14.8%) compared to alkali citrate (20.4%) or allopurinol (20.4%) (each P < .001). Thiazides, compared to allopurinol, were associated with 32% lower odds of a subsequent stone event by 3 years (OR 0.68, 95% CI 0.53-0.88). No such association was observed when comparing alkali citrate to allopurinol (OR 1.00, 95% CI 0.75-1.34).

CONCLUSION

Empiric PPT with thiazides is associated with significantly lower odds of subsequent stone-related events. When 24 h urine testing is unavailable, thiazides may be preferred over alkali citrate or allopurinol for empiric PPT.

Risk factors for kidney stone disease recurrence: a comprehensive meta-analysis

Background

Kidney stone disease (KSD) is a common illness that causes an economic burden globally. It is easy for patients to relapse once they have suffered from this disease. The reported recurrence rate of KSD ranged from 6.1% to 66.9%. We performed this meta-analysis to identify various potential risk factors for the recurrence of KSD.

Methods

The PubMed, Embase and Web of Science databases were searched using suitable keywords from inception to Mar 2022. A total of 2,663 records were collected initially. After screening the literature according to the inclusion and exclusion criteria, 53 articles (40 retrospective studies; 13 prospective studies) including 488,130 patients were enrolled. The study protocol was registered with PROSPERO (No. CRD42020171771).

Results

The pooled results indicated that 12 risk factors including younger age (n = 18), higher BMI (n = 16), family history of kidney stones (n = 12), personal history of kidney stones (n = 11), hypertension (n = 5), uric acid stone (n = 4), race of Caucasian (n = 3), suspected kidney stone episode before the first confirmed stone episode (n = 3), surgery (n = 3), any concurrent asymptomatic (nonobstructing) stone (n = 2), pelvic or lower pole kidney stone (n = 2), and 24 h urine test completion (n = 2) were identified to be associated with KSD recurrence. In the subgroup analysis, patients with higher BMI (OR = 1.062), personal history of nephrolithiasis (OR = 1.402), or surgery (OR = 3.178) had a higher risk of radiographic KSD recurrence.

Conclusions

We identified 12 risk factors related to the recurrence of KSD. The results of this analysis could serve to construct recurrence prediction models. It could also supply a basis for preventing the recurrence of KSD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-022-01017-4.

Comparison of Selective Versus Empiric Pharmacologic Preventive Therapy of Kidney Stone Recurrence with High-Risk Features

OBJECTIVE

To compare the frequency of stone-related events among subgroups of high-risk patients with and without 24-hour urine testing before PPT prescription. While recent studies show, on average, no benefit to a selective approach to preventive pharmacological therapy (PPT) for urinary stone disease (USD), there could be heterogeneity in treatment effect across patient subgroups.

MATERIALS AND METHODS

Using medical claims data from working-age adults and their dependents with USD (2008-2019), we identified those with a prescription fill for a PPT agent (thiazide diuretic, alkali therapy, or allopurinol). We then stratified patients into subgroups based on the presence of a concomitant condition or other factors that raised their stone recurrence risk. Finally, we fit multivariable regression models to measure the association between stone-related events (emergency department visit, hospitalization, and surgery) and 24-hour urine testing before PPT prescription by high-risk subgroup.

RESULTS

Overall, 8,369 adults with USD had a concomitant condition that raised their recurrence risk. Thirty-three percent (n=2,722) of these patients were prescribed PPT after 24-hour urine testing (median follow-up, 590 days), and 67% (n=5,647) received PPT empirically (median follow-up, 533 days). Compared to patients treated empirically, those with a history of recurrent USD had a significantly lower hazard of a subsequent stone-related event if they received selective PPT (hazard ratio, 0.83; 95% CI, 0.71-0.96). No significant associations were noted for selective PPT in the other high-risk subgroups.

CONCLUSIONS

Patients with a history of recurrent USD benefit from PPT when guided by findings from 24-hour urine testing.

Twenty-four-hour Urine Testing and Urinary Stone Disease Recurrence in Veterans

OBJECTIVE

To determine whether 24-hour urine testing in Veterans with USD (urinary stone disease) reduces or delays urinary stone recurrence.

METHODS

Cohort study of national health record data from Veterans Health Administration from 2007 through 2013. We utilized a study population of 130,129 Veterans with USD based on diagnostic or procedural codes and excluded those with USD claims in the 2 years before cohort entry. We then created a propensity-score matched cohort of 14,854 Veterans based on completion of 24-hour urine testing within 6 months of stone diagnosis. Primary outcome was time-to-next clinically significant stone event, defined as an emergency department visit, inpatient admission related to a urinary stone, or urologic stone procedure with 5-year follow up.

RESULTS

Of 14,854 Veterans in the propensity-score matched cohort, 8560 (57.6%) experienced a recurrent USD event. Completion of 24-hour urine testing was associated with a higher risk of developing a second stone event (hazard ratio [HR] 1.17, 95% confidence interval [95% CI] 1.12-1.22). Among Veterans with known recurrent disease, we examined time to a third stone event. In this cohort of 4736 patients, completion of 24-hour urine testing was not associated with a higher risk of developing a third stone event (HR 1.06, 95% CI 0.99-1.12).

CONCLUSION

Completion of 24-hour urine testing was not associated with a reduction in urinary stone recurrence. These findings challenge the validity of a longstanding recommendation in general medicine, nephrology, and urology practice.