Faculty Bibliography

PURPOSE OF REVIEW/OBJECTIVE:Men have more kidney stones compared with women; however, the difference is progressively decreasing. The reasons for higher prevalence of stones in men, as well as increasing prevalence in women, is a subject of ongoing speculation. In this review, we summarize the evidence of differences between men and women and expand on the speculative causes. RECENT FINDINGS/RESULTS:Stone incidence is rising in women and adolescent girls. Stone disease is more heritable among men than women, and women demonstrate greater influence of the unique environment. Women under the age of 50 years who have been pregnant, have more than double the odds of kidney stones compared with those who have never been pregnant. Women are more burdened with obesity, bariatric surgery and dieting, all associated with increased stones. Women have higher urinary pH because of greater absorption of dietary organic anions leading to increased urinary citrate, compared with men, and they differ in tubular calcium handling. SUMMARY/CONCLUSIONS:It is obvious that the cause of stones in men and women is complex and requires further study. Potential clues offered are in the change of the female environment, influencing increasing incidence in stones, particularly of younger women and female adolescents.

BACKGROUND:A scarcity of organs has driven the transplant community to broaden selection criteria for both living and deceased donors. Living donor transplants offer better patient and allograft survival when compared with deceased donor transplants. Many transplant centers now allow complex living donors such as those with nephrolithiasis to undergo nephrectomy. METHODS:We conducted a survey of medical and surgical directors of kidney transplant programs in the United States to shed light on current practices pertaining to medical evaluation of living kidney donors with nephrolithiasis. 353 surveys were e-mailed to medical directors and surgical directors of transplant programs after contacts were obtained from UNOS. RESULTS:49 completed surveys were returned (13.9%). 77.7% (38/49) of survey participants said their centers will consider living kidney donor candidates with a history of symptomatic kidney stones, 69.4% (34/49) said their centers will consider candidates who are incidentally found to have kidney stones and 10.2% (5/49) said their centers decline all potential donors with nephrolithiasis. CONCLUSIONS:Several programs are still reluctant to allow potential donors with nephrolithiasis to donate. There is an unmet need to develop evidence-based guidelines to optimize outcomes in this population of kidney donors with nephrolithiasis and their recipients.

Previous studies assumed a uniform relationship between heat and kidney stone presentations. Determining whether sex and other characteristics modify the temperature dependence of kidney stone presentations has implications for explaining differences in nephrolithiasis prevalence and improving projections of the effect of climate change on nephrolithiasis. We performed an aggregated case-crossover study among 132,597 children and adults who presented with nephrolithiasis to 68 emergency departments throughout South Carolina from 1997 to 2015. We used quasi-Poisson regression with distributed lag non-linear models to estimate sex differences in the cumulative exposure and lagged response between maximum daily wet-bulb temperatures and emergent kidney stone presentations, aggregated at the ZIP-code level. We also explored interactions by age, race, payer, and climate. Compared to 10 °C, daily wet-bulb temperatures at the 99th percentile were associated with a greater increased relative risk (RR) of kidney stone presentations over 10 days for males (RR 1.73; 95% CI 1.56, 1.91) than for females (RR 1.15; 95% CI 1.01, 1.32; interaction P < 0.001). The shape of the lagged response was similar for males and females, with the greatest risk estimated for the 2 days following high temperatures. There were weak differences by age, race, and climatic zone, and no differences by payer status. The estimated risk of presenting emergently with kidney stones within 10 days of high daily wet-bulb temperatures was substantially greater among men than women, and similar between patients with public and private insurance. These findings suggest that the higher risk among males may be due to sexually dimorphic physiologic responses rather than greater exposure to ambient temperatures.

The package inserts for products containing 5-aminosalicylic acid, or mesalamine, include the following language regarding the risk of adverse kidney effects: "renal impairment, including minimal change nephropathy, acute and chronic interstitial nephritis, and rarely renal failure, has been reported in patients given products such as mesalamine delayed-release tablets that contain mesalamine or are converted to mesalamine." In this article, we review the data regarding this nephrotoxicity and the recommendations regarding appropriate monitoring. Chronic interstitial nephritis is a rare occurrence in patients treated with these drugs for Crohn disease and ulcerative colitis. Patients often present with asymptomatic reductions in glomerular filtration rate, without accompanying pyuria, skin lesions, or eosinophilia, unlike cases of acute interstitial nephritis. Drug cessation is usually associated with improved kidney function. However, if left undetected, more prolonged exposure to the drug can lead to irreversible kidney failure and end-stage kidney disease. No convincing studies demonstrate efficacy of treatment with corticosteroids. Frequent monitoring of serum creatinine, especially in the first years after initiation of therapy, is recommended.

Background: The COVID-19 pandemic was associated with a greater incidence of AKI than expected. At the NY Harbor VA we faced an overwhelming number of AKI patients who were critically ill with multi-organ failure. We needed to invoke new mechanisms of providing kidney replacement therapy (KRT).
Method(s): We obtained 3 Tablo systems in late March, 2019. The machines have selfcontained reverse osmosis capabilities and so do not require other equipment to operate. They can make dialysate from concentrate and tap water and so do not require special plumbing adaptation. Their self-contained step-by-step procedures are relatively simple to follow and allow rapid training of previously unskilled personnel. Tablo generates 300 ml dialysate per minute, and blood flow was increased to up to 400 ml/min as tolerated.
Result(s): Training was completed by 2 nephrologists and 2 RNs without previous dialysis experience. We used the Tablo Hemodialysis System to provide KRT to critically ill patients. In the first week we demonstrated that water cultures and endotoxin testing were negative, and that AAMI water tests were acceptable. We used the machines to provide KRT for ICU patients with double-lumen dialysis catheters. In addition we used the machines on hospital wards where KRT had not been provided before because of a lack of the plumbing needs of conventional HD machines. We provided multiple treatments 3-6 times per week for 15 AKI patients, mean age 65 years. The mean of the best urea reduction ratio achieved in the first 1-4 treatments, if available, was 41% (often limited by hypotension and fulfillment of ultrafiltration, UF, needs). Most treatments were successful and were slowed for hypotension or tachycardia. Some were aborted because of water pressure alarms if sediment filters needed replacement, or lines clotted due to hypercoagulability associated with COVID-19. Personnel availability dictated that most treatments were 3-4 hours (and up to 8h), and generally achieved UF goals. Later HD nurses cannulated arteriovenous fistulas in ESKD patients and left treatment to non-HD nurses to complete.
Conclusion(s): By incorporating a user-friendly platform and an accelerated training program including nephrologists and RNs without previous dialysis experience, we were able to nearly double our capacity to deliver KRT during the surge

Background: Our previous study showed that PH without a transplant (tx) had worse HRQoL compared to the US Standard Population and worsened with increased stone frequency. We now show the first longitudinal HRQoL profiles for PH patients with transplants.
Method(s): PH participants were enrolled from the Rare Kidney Stone Consortium registry. HRQoL was measured with a generic non-disease specific instrument (SF-36v2). Results were calculated as norm-based scores (NBS) based on US Standard Population (Mean domain score = 50). We created three groups based on the time of last stone event (<= 30 days, 31 - 365 days, >;366 days). The study compared HRQoL for participants with a kidney and/or liver transplant over 5 different time points.
Result(s): This sub-sample included 100 surveys of 32 PH participants (16 males and 16 females) with a tx. The mean age was 47 years for both males and females. This subsample includes 24 participants with liver/kidney tx (75%) and 8 with kidney tx only (25%). Participants with only a kidney tx reported significantly more stone events within a year (26% vs 13%, X2 =0.028). Two way ANOVA did not find a change in HRQoL profiles over time for PH participants with kidney or kidney/liver tx (figure). Most mean domain scores are 50 or above, except for the domain of General Health which was less. Participants with only a kidney tx scored significantly lower in role physical, bodily pain, general health, social function, and physical component score (data not shown) than participants with kidney/liver tx. There was no difference between male and female participants over time.
Conclusion(s): PH participants with kidney/liver tx achieve better HRQoL, measured with a non-disease specific generic instrument, than those with kidney alone; both are better when compared to the US Standard Population. The majority of PH participants with a tx are stone-free, with a direct beneficial impact on their HRQoL

It is a question many patients ask in stone clinic - does it matter what water I drink? Often patients cite scaling up of their water pipes or kettles as demonstrating the influence that the hardness of the water has on stone formation. This article is protected by copyright. All rights reserved.

Appropriate dosing of cystine-binding thiol drugs in the management of cystinuria has been based on clinical stone activity. When new stones form, the dose is increased. Currently, there is no method of measuring urinary drug levels to guide the titration of therapy. Increasing cystine capacity, a measure of cystine solubility, has been promoted as a method of judging the effects of therapy. In this study, we gave increasing doses of tiopronin or D-penicillamine, depending on the patients' own prescriptions, to ten patients with cystinuria and measured cystine excretion and cystine capacity. The doses were 0, 1, 2, 3 g per day, given in two divided doses, and administered in a random order. Going from 0 to 1 g/day led to an increase in cystine capacity from - 39.1 to 130.4 mg/L (P < 0.009) and decreased 24 h cystine excretion from 1003.9 to 834.8 mg/day (P = 0.039). Increasing the doses from 1 to 2 to 3 g/day had no consistent or significant effect to further increase cystine capacity or decrease cystine excretion. Whether doses higher than 1 g/day have additional clinical benefit is not clear from this study. Limiting doses might be associated with fewer adverse effects without sacrificing the benefit of higher doses if higher doses do not offer clinical importance. However, trials with stone activity as an outcome would be desirable.

PURPOSE OF REVIEW/OBJECTIVE:The effect of the intestinal microbiome on urine chemistry and lithogenicity has been a popular topic. Here we review the evidence for exposure to antibiotics increasing the risk of nephrolithiasis. RECENT FINDINGS/RESULTS:Studies of the intestinal microbiome have focused on Oxalobacter formigenes, an anaerobe that frequently colonizes the human colon. As a degrader of fecal oxalate its presence is associated with lower urinary oxalate, which would be protective against calcium oxalate stone formation. It also appears capable of stimulating colonic oxalate secretion. A recent study showed that antibiotics can eliminate colonization with O. formigenes. In a case-control study, exposure to sulfa drugs, cephalosporins, fluoroquinolones, nitrofurantoin/methenamine, and broad spectrum penicillins prospectively increased the odds of nephrolithiasis. The effect was greatest for those exposed at younger ages and 3-6 months before being diagnosed with nephrolithiasis. SUMMARY/CONCLUSIONS:Recent evidence suggests a possible, causal role of antibiotics in the development of kidney stones. A possible explanation for this finding includes alterations in the microbiome, especially effects on oxalate-degrading bacteria like O. formigenes. Ample reasons to encourage antibiotic stewardship already exist, but the possible role of antibiotic exposure in contributing to the increasing prevalence of kidney stones in children and adults is another rationale.