Clinicopathologic Characteristics, Etiologies, and Outcome of Secondary Oxalate Nephropathy.

OBJECTIVE: To report the clinicopathologic characteristics, prognostic indicators, prognosis, and transplant outcome of secondary oxalate nephropathy (ON). PATIENTS AND METHODS: We performed a retrospective analysis of 113 consecutive patients with secondary ON diagnosed at Mayo Clinic in Rochester, Minnesota, between January 1, 2001, and March 1, 2023. RESULTS: The incidence of secondary ON among all native biopsies from Mayo Clinic patients over the study period (n=11,617) was 0.97%. ON was attributed to enteric hyperoxaluria in 60% of the 113 patients (68; most commonly Roux-en-Y gastric bypass), excessive ingestion of foods high in oxalate or oxalate precursors in 23% (26) (most commonly vitamin C), and idiopathic in 17% (19). Most patients presented with acute kidney injury (AKI) (particularly in the ingestion group) or AKI on chronic kidney disease, and 53% (60 of 113) were diabetic. Calcium oxalate crystals were accompanied by acute tubular injury, inflammation, and interstitial fibrosis and tubular atrophy. Concurrent pathologic conditions were present in 53% of the patients (60 of 113), most commonly diabetic nephropathy. After a median follow-up of 36 months, 27% of the patients (30 of 112) had kidney recovery, 19% (21 of 112) had persistent kidney dysfunction, 54% (61 of 112) had development of kidney failure, and 29% (32 of 112) died. The mean kidney survival was worse for patients with a concurrent pathologic lesion (30 months vs 96 months for those without a concurrent pathologic lesion; P<.001). Independent predictors of kidney failure were the degree of interstitial fibrosis and tubular atrophy and nadir estimated glomerular filtration rate but not the degree of crystal deposition. After a median follow-up of 58 months in 23 patients who received kidney transplant, 4 had graft loss (due to ON in 3). The 2-, 5-, and 10-year graft survivals were 90% (18 of 20), 79% (11 of 14), and 50% (6 of 12). CONCLUSION: ON is a rare cause of AKI or AKI on chronic kidney disease. Most patients have comorbid pathologic conditions, particularly diabetic nephropathy, which worsen the prognosis. Recurrence in the renal allograft and graft loss may occur if hyperoxaluria is not controlled.

Characterization of Stone Events in Patients With Type 3 Primary Hyperoxaluria.

PURPOSE: Hallmarks of primary hyperoxaluria type 3 are nephrolithiasis and hyperoxaluria. However, little is known about factors influencing stone formation in this disease. We characterized stone events and examined associations with urine parameters and kidney function in a primary hyperoxaluria type 3 population. MATERIALS AND METHODS: We retrospectively analyzed clinical, and laboratory data of 70 primary hyperoxaluria type 3 patients enrolled in the Rare Kidney Stone Consortium Primary Hyperoxaluria Registry. RESULTS: Kidney stones occurred in 65/70 primary hyperoxaluria type 3 patients (93%). Among the 49 patients with imaging available, the median (IQR) number of stones was 4 (2, 5), with largest stone 7 mm (4, 10) at first imaging. Clinical stone events occurred in 62/70 (89%) with median number of events per patient 3 (2, 6; range 1-49). Age at first stone event was 3 years (0.99, 8.7). Lifetime stone event rate was 0.19 events/year (0.12, 0.38) during follow-up of 10.7 (4.2, 26.3) years. Among 326 total clinical stone events, 139 (42.6%) required surgical intervention. High stone event rates persisted for most patients through the sixth decade of life. Analysis was available for 55 stones: pure calcium oxalate accounted for 69%, with mixed calcium oxalate and phosphate in 22%. Higher calcium oxalate supersaturation was associated with increased lifetime stone event rate after adjusting for age at first event (IRR [95%CI] 1.23 [1.16, 1.32]; P < .001). By the fourth decade, estimated glomerular filtration rate was lower in primary hyperoxaluria type 3 patients than the general population. CONCLUSIONS: Stones impose a lifelong burden on primary hyperoxaluria type 3 patients. Reducing urinary calcium oxalate supersaturation may reduce event frequency and surgical intervention.

Risk factors for developing hyperoxaluria in children with Crohn's disease.

BACKGROUND: For the purpose of a better understanding of enteric hyperoxaluria in Crohn's disease (CD) in children and adolescents, we investigated the occurrence and risk factors for development of hyperoxaluria in those patients. METHODS: Forty-five children with CD and another 45 controls were involved in this cross-sectional study. Urine samples were collected for measurement of spot urine calcium/creatinine (Ur Ca/Cr), oxalate/creatinine (Ur Ox/Cr), and citrate/creatinine (Ur Citr/Cr) ratios. Fecal samples were also collected to detect the oxalyl-CoA decarboxylase of Oxalobacter formigenes by PCR. Patients were classified into 2 groups: group A (with hyperoxaluria) and group B (with normal urine oxalate excretion). The disease extent was assessed, and the activity index was calculated. RESULTS: According to the activity index, 30 patients (66.7%) had mild disease and 13 patients (28.9%) had moderate disease. There was no significant difference in Ur Ox/Cr ratio regarding the disease activity index. O. formigenes was not detected in 91% of patients in group A while it was detected in all patients in group B (p < 0.001). By using logistic regression analysis, the overall model was statistically significant when compared to the null model, (χ2 (7) = 52.19, p < 0.001), steatorrhea (p = 0.004), frequent stools (p = 0.009), and O. formigenes (p < 0.001). CONCLUSION: Lack of intestinal colonization with O. formigenes, steatorrhea, and frequent stools are the main risk factors for development of enteric hyperoxaluria in CD patients. Identifying risk factors facilitates proper disease management in future studies. A higher resolution version of the Graphical abstract is available as Supplementary information.

High Prevalence of Hypocitraturia in Stone Formers from the Maya Region of Yucatan, Mexico.

BACKGROUND: Urinary Stone Disease (USD) arises from an interaction of genetic and environmental factors. Urinary metabolic abnormalities are well described as risk factors. In Mexico, the Maya region holds the highest prevalence of USD. Treatment of these abnormalities lowers the risk of recurrences. AIM: Assess the underlying metabolic abnormalities of patients with USD to provide a rationale to lead further prevention strategies. METHODS: Clinical and demographical data from patients coming to the Stone Clinic were prospectively collected along with a 24 h urinary panel to identify metabolic abnormalities. All participants signed consent and the study was approved by the hospital's institutional review board. RESULTS: A total of 126 patients were included, with a mean age of 47.2 ± 13 years, 75.4% were female. A positive family history of stones was observed in 40 and 87.3% were overweight/obese. The frequency of hypocitraturia, hypercalciuria, hypomagnesuria, hyperoxaluria, and hyperuricosuria was 91.3, 68.5, 42.1, 36.5, and 26.6%, respectively. Median urinary citrate was 79.5 (37.5-160) mg/24 h and was inversely correlated to glycemia. Urine Calcium/Creatinine index was correlated with Hounsfield units (HU) (p = 0.01). Oxalate was correlated with HU and stone burden. Interestingly, dietary distribution of macro- and micronutrients were similar between groups. Patients with a single kidney had lower citrate and higher urinary calcium. CONCLUSIONS: Interestingly, a shortage of inhibitors such as citrate and magnesium are highly prevalent in patients with USD from the Maya region and seems to be influenced by other metabolic conditions as malnutrition next to the genetic component.

Posttransplant recurrence of calcium oxalate crystals in patients with primary hyperoxaluria: Incidence, risk factors, and effect on renal allograft function.

Primary hyperoxaluria (PH) is a metabolic defect that results in oxalate overproduction by the liver and leads to kidney failure due to oxalate nephropathy. As oxalate tissue stores are mobilized after transplantation, the transplanted kidney is at risk of recurrent disease. We evaluated surveillance kidney transplant biopsies for recurrent calcium oxalate (CaOx) deposits in 37 kidney transplants (29 simultaneous kidney and liver [K/L] transplants and eight kidney alone [K]) in 36 PH patients and 62 comparison transplants. Median follow-up posttransplant was 9.2 years (IQR: [5.3, 15.1]). The recurrence of CaOx crystals in surveillance biopsies in PH at any time posttransplant was 46% overall (41% in K/L, 62% in K). Higher CaOx crystal index (which accounted for biopsy sample size) was associated with higher plasma and urine oxalate following transplant (p < .01 and p < .02, respectively). There was a trend toward higher graft failure among PH patients with CaOx crystals on surveillance biopsies compared with those without (HR 4.43 [0.88, 22.35], p = .07). CaOx crystal deposition is frequent in kidney transplants in PH patients. The avoidance of high plasma oxalate and reduction of CaOx crystallization may decrease the risk of recurrent oxalate nephropathy following kidney transplantation in patients with PH. This study was approved by the IRB at Mayo Clinic.

Subsequent urinary stone events are predicted by the magnitude of urinary oxalate excretion in enteric hyperoxaluria.

Data directly demonstrating the relationship between urinary oxalate (UOx) excretion and stone events in those with enteric hyperoxaluria (EH) are limited. Therefore, we assessed the relationship between UOx excretion and risk of kidney stone events in a retrospective population-based EH cohort. In all, 297 patients from Olmsted County, Minnesota were identified with EH based upon having a 24-h UOx ≥40 mg/24 h preceded by a diagnosis or procedure associated with malabsorption. Diagnostic codes and urologic procedures consistent with kidney stones during follow-up after baseline UOx were considered a new stone event. Logistic regression and accelerated failure time modeling were performed as a function of UOx excretion to predict the probability of new stone event and the annual rate of stone events, respectively, with adjustment for urine calcium and citrate. Mean ± standard deviation age was 51.4 ± 11.4 years and 68% were female. Median (interquartile range) UOx was 55.4 (46.6-73.0) mg/24 h and 81 patients had one or more stone event during a median follow-up time of 4.9 (2.8-7.8) years. Higher UOx was associated with a higher probability of developing a stone event (P < 0.01) and predicted an increased annual risk of kidney stones (P = 0.001). Estimates derived from these analyses suggest that a 20% decrease in UOx is associated with 25% reduction in the annual odds of a future stone event. Thus, these data demonstrate an association between baseline UOx and stone events in EH patients and highlight the potential benefit of strategies to reduce UOx in this patient group. BACKGROUND: Data directly demonstrating the relationship between urinary oxalate (UOx) excretion and stone events in those with enteric hyperoxaluria (EH) are limited. METHODS: We assessed the relationship between UOx excretion and risk of kidney stone events in a retrospective population-based EH cohort. In all, 297 patients from Olmsted County, Minnesota were identified with EH based upon having a 24-h UOx ≥40 mg/24 h preceded by a diagnosis or procedure associated with malabsorption. Diagnostic codes and urologic procedures consistent with kidney stones during follow-up after baseline UOx were considered a new stone event. Logistic regression and accelerated failure time modeling were performed as a function of UOx excretion to predict the probability of new stone event and the annual rate of stone events, respectively, with adjustment for urine calcium and citrate. RESULTS: Mean ± SD age was 51.4 ± 11.4 years and 68% were female. Median (interquartile range) UOx was 55.4 (46.6-73.0) mg/24 h and 81 patients had ≥1 stone event during a median follow-up time of 4.9 (2.8-7.8) years. Higher UOx was associated with a higher probability of developing a stone event (P < 0.01) and predicted an increased annual risk of kidney stones (P = 0.001). Estimates derived from these analyses suggest that a 20% decrease in UOx is associated with 25% reduction in the annual odds of a future stone event. CONCLUSIONS: These data demonstrate an association between baseline UOx and stone events in EH patients and highlight the potential benefit of strategies to reduce UOx in this patient group.

Increased Prevalence of Nephrolithiasis and Hyperoxaluria in Paget Disease of Bone.

CONTEXT: Nephrolithiasis (NL) and primary hyperparathyroidism (HPTH) are metabolic complications of Paget disease of bone (PDB), but recent data regarding their prevalence in PDB patients are lacking. OBJECTIVES: Study 1: To compare the prevalence of primary HPTH and NL in 708 patients with PDB and in 1803 controls. Study 2: To evaluate the prevalence of NL-metabolic risk factors in 97 patients with PDB and NL, 219 PDB patients without NL, 364 NL patients without PDB, and 219 controls, all of them without HPTH. DESIGN: Cross-sectional multicentric study. SETTING: Italian referral centers for metabolic bone disorders. PARTICIPANTS: Patients with PDB from the Associazione Italiana malati di osteodistrofia di Paget registry. Participants in the Olivetti Heart and the Siena Osteoporosis studies. MAIN OUTCOME MEASURES: HPTH; NL; NL-metabolic risk factors. RESULTS: Patients with PDB showed higher prevalence of primary HPTH and NL compared with controls (P < 0.01). The NL recurrence occurs more frequently in patients with polyostotic PDB. About one-half of patients with PDB but without NL showed 1 or more NL-related metabolic risk factors. The hyperoxaluria (HyperOx) prevalence was higher in patients with PDB and NL compared with patients with NL but without PDB and in patients with PDB without NL compared with controls (P = 0.01). Patients with PDB and HyperOx showed a longer lapse of time from the last aminobisphosphonate treatment. CONCLUSIONS: NL and HPTH are frequent metabolic complication of PDB. The NL occurrence should be evaluated in patients with PDB, particularly in those with polyostotic disease and/or after aminobisphosphonate treatment to apply an adequate prevention strategy.

The association of dietary inflammatory index with urinary risk factors of kidney stones formation in men with nephrolithiasis.

OBJECTIVE: Inflammation plays a leading role in the pathogenesis of nephrolithiasis. The association of the dietary inflammatory index (DII) with urinary lithogenic factors is unclear. This study aimed to evaluate the relation of DII to urinary risk factors of kidney stones formation. RESULTS: Of 264 participants, 61.4% (n = 162), 72% (n = 190), 74.6% (n = 197), 68.6% (n = 181), and 80.3% (n = 212) had hyperoxaluria, hypercreatininuria, hypercalciuria, hyperuricosuria, hypocitraturia, respectively. There was a significant increasing trajectory in urinary calcium, uric acid, and creatinine as well as a decreasing trend in urinary citrate across tertiles of DII score (all P = ≤0.001). After multivariate adjustment for energy intake, age, physical activity and body mass index, high DII scores were associated with elevated odds of having hypercreatininuria (OR = 2.80, 95%CI: 1.10-7.12, Ptrend = 0.04), hypercalciuria (OR = 7.44, 95%CI: 2.62-21.14, Ptrend ≤ 0.001), hyperuricosuria (OR = 2.22, 95%CI: 1.001-4.95, Ptrend = 0.05), and hypocitraturia (OR = 5.84, 95%CI: 2.14-15.91, Ptrend ≤ 0.001). No association was identified between DII and hyperoxaluria.

Rising occurrence of hypocitraturia and hyperoxaluria associated with increasing prevalence of stone disease in calcium kidney stone formers.

OBJECTIVE: To evaluate metabolic risk factors in calcium kidney stone formers from two different decades, comparing changes in metabolic profiles over time. METHODS: A retrospective analysis was performed of calcium kidney stone formers who underwent metabolic evaluation of urolithiasis with 24-hour urine collections at a single institution. There were 309 patients evaluated from 1988 to 1994 (Group A), and 229 patients from 2007 to 2010 (Group B). A comparison between both groups was performed to assess changes in demographics and in metabolic stone profiles. RESULTS: Comparing Group A to Group B, the percentage of females increased from 43 to 56%, obese patients (BMI ≥ 30) increased from 22 to 35%, and patients ≥ 50 years increased from 29 to 47% (all p < 0.005). A greater percentage of patients had hypocitraturia in the recent cohort (46-60%, p = 0.001), with hypocitraturia significantly more frequent in obese patients (p = 0.005). Hyperoxaluria was also increased in Group B compared to Group A (23-30% p = 0.07), a finding that was significant in males (32-53%, p = 0.001). CONCLUSIONS: Urolithiasis has increased in females, obese, and older patients, consistent with population-based studies. We report a rising incidence of hypocitraturia and hyperoxaluria in the contemporary cohort, particularly in obese patients and in males, respectively. Further studies are needed to better characterize the metabolic changes corresponding to the increase in stone disease.

Consideraciones acerca de las bases moleculares de algunas tubulopatías en relación con la endogamia y los desplazamientos poblacionales / Considerations about the molecular basis of some kidney tubule disorders in relation to inbreeding and population displacement

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What Factors Drive Staghorn vs Nonstaghorn Pattern Growth in Patients with Metabolic Stones?

Purpose: There has been an increase in the number of staghorn calculi that form in the absence of infection (metabolic staghorns). It is unknown why some large metabolic calculi form as solitary or multiple separate, nonbranching caliceal stones, whereas others develop as staghorn stones forming a cast of the collecting system. We sought to compare these two groups of metabolic stone formers (SFs) in an attempt to shed light on these disparate stone-forming phenomena. Materials and Methods: From January 2017 to September 2018, 190 patients underwent percutaneous nephrolithotomy for stones >2 cm. We identified 86 (45%) patients with a metabolic stone, defined as ≥80% calcium oxalate monohydrate or dihydrate and/or calcium phosphate. Exclusion criteria included stones composed of cystine, >20% uric acid, or any infectious element (struvite or carbonate apatite). Metabolic staghorn and nonstaghorn SFs were compared with respect to medical comorbidity, 24-hour urine parameters, stone and urine microbiology, stone compositions, and intraoperative findings. Statistical differences were assessed using chi-square analysis, Fisher's exact test, and Student's t-test. Results: In total, 25 (29%) staghorn and 61 (71%) nonstaghorn SFs were included for analysis. The groups were statistically similar in age, sex, body mass index, and medical comorbidity. Staghorn SFs had larger stone burdens (p < 0.0001), but did not require more punctures (p = 0.783). Staghorn SFs were more likely to have hyperoxaluria (p = 0.041) and higher mean 24-urine oxalate levels (p = 0.040). There were no other significant differences in 24-hour urine profiles, rates of metabolic abnormalities, stone compositions, stone or urine cultures, presence of collecting system obstruction, or pelvicaliceal anatomy. Conclusions: Although potentially driven by urinary oxalate, whether a metabolic stone will form into a staghorn configuration or not does not appear significantly influenced by standard determinants of stone development, including metabolic profile, cultures, hydronephrosis, and pelvicaliceal anatomy, among others. Further work is needed to elucidate the physicochemical factors that govern the pathogenesis of this increasingly prevalent entity.

Urine kidney injury markers do not increase following gastric bypass: a multi-center cross-sectional study.

INTRODUCTION: To determine if markers of kidney injury correlate with urinary oxalate excretion. If so, such biomarkers might be early predictors of oxalate nephropathy. Gastric bypass surgery for obesity is known to be associated with postoperative hyperoxaluria, which can lead to urolithiasis and kidney damage. MATERIALS AND METHODS: Patients were recruited from four large academic centers > 6 months following completion of gastric bypass surgery. Patients provided a spot urine sample for analysis of three markers of kidney injury: 8-iso-Prostaglandin F2 α, N-acetyl- ß -D-Glucosaminidase, and Neutrophil gelatinase-associated lipocalin. Patients also provided 24 hour urine samples for stone risk analysis. RESULTS: A total of 46 study patients provided samples, the average age was 48.4 +/- 11.3. There were 40 women and 6 men. There was no difference in the level of any of the three inflammatory markers between the study group and the reference range generated from healthy non-hyperoxaluric subjects. Neither oxalate excretion nor supersaturation of calcium oxalate correlated with any of the injury markers. There was no difference noted between those with hyperoxaluria (n = 17) and those with normoxaluria (n = 29) with respect to any of the injury markers. CONCLUSIONS: Though hyperoxaluria was common after bypass surgery, markers of kidney injury were not elevated after surgery. No correlation was found between urine oxalate excretion and any of the injury markers.

Study of Urine Composition of Patients With Recurrent Nephrolithiasis in Lorestan, Iran.

INTRODUCTION: Nephrolithiasis is one of the most common urinary tract diseases. After the first episode of urinary calculus, the risk of recurrence is nearly 40% to 50% at 5 years. Nephrolithiasis is a systemic disease that is associated with some metabolic disorders. This study aimed to provide a picture of the frequency of metabolic abnormalities in patients with nephrolithiasis from west part of Iran. MATERIALS AND METHODS: Patients with recurrent urinary tract calculi referred to the Nephrology-Urology Clinics in Khorramabad city were recruited. After collection of demographic data of all the patients, 24-hour urine and blood samples were taken to measure biochemical factors. RESULTS: Of the 232 participants, 125 were males and 107 were females. Hyperoxaluria was seen in 93 (40.1%) of the participants, hypercalciuria in 55 (23.7%), hypocitraturia in 58 (25%), and hyperuricosuria in 33 (14.9%). Hyperoxaluria in the males was significantly more frequent than in the female patients. There were no significant differences between the two groups in other urinary metabolic disorders. CONCLUSIONS: Patients with nephrolithiasis from Lorestan province may have metabolic characteristics varying from those of regions; ethnicity may be a possible reason. Variation of dietary regimens, such as the amount of meat or vegetable in the diet that can change oxalate, calcium, or citrate of urine, might have influenced the results. Time of sampling is another factor. Population-specific studies are helpful to health care providers for preventive planning for nephrolithiasis.

Determinants of calcium and oxalate excretion in subjects with calcium nephrolithiasis: the role of metabolic syndrome traits.

BACKGROUND: The association of metabolic syndrome (MetS) traits with urinary calcium (UCE) or oxalate excretion (UOE) is uncertain in calcium stone formers (CSFs). Our aim was to investigate this association in a large group of Caucasian CSFs. METHODS: We retrospectively reviewed data of CSFs evaluated at our Kidney Stone Clinic from 1984 to 2015. Data on body mass index (BMI), MetS traits defined according to international consensus, family history of urolithiasis, anti-hypertensive treatments, calcemia, renal function, and 24-h urinary profile of lithogenic risk were collected. The association between MetS traits and UCE or UOE was tested with multivariate linear regression models accounting for a long list of potential confounders. RESULTS: We included 3003 CSFs, aged 44 ± 14 years. The prevalence of hypertension, diabetes, overweight (BMI ≥ 25 kg/m2) and dyslipidemia was 17, 2, 42 and 38%, respectively. Median values of UCE and UOE were 211 mg/24 h (IQR 143-296) and 28 mg/24 h (IQR 22-34), respectively. At a multivariate model, including age, sex, date of examination, drug treatments, family history, renal function, blood calcium and urinary factors as covariates, hypertension was a significant positive determinant of UCE (ß ± SE 0.23 ± 0.07, p = 0.003), but overweight, dyslipidemia and diabetes were not. No MetS trait was significantly associated with UOE in multivariate models. CONCLUSIONS: In a large group of Caucasian CSFs, hypertension was the only MetS trait significantly associated with UCE, while no MetS trait was associated with oxalate excretion.

Age, Body Mass Index, and Gender Predict 24-Hour Urine Parameters in Recurrent Idiopathic Calcium Oxalate Stone Formers.

INTRODUCTION AND OBJECTIVE: Despite guidelines, routine 24-hour urine testing is completed in <10% of high-risk, recurrent stone formers. Using surrogates for metabolic testing, such as key patient characteristics, could obviate the cost and burden of this test while providing information needed for proper stone prevention counseling. METHODS: We performed a retrospective study of 392 consecutive patients from 2007 to 2014 with ≥2 lifetime stone episodes, >70% calcium oxalate by mineral analysis, and ≥1 24-hour urine collection. We compared mean 24-hour urine values by age in decades. We used logistic regression and receiver operating characteristic (ROC) curve analysis to assess the predictive ability of age, gender, body mass index (BMI), and comorbidities to detect abnormal 24-hour urine parameters. RESULTS: The mean age of the cohort was 51 ± 16 years. Older age was associated with greater urinary oxalate (p-trend <0.001), lower urinary uric acid (UA) (p-trend = 0.007), and lower urinary pH (p-trend <0.001). A nonlinear association was noted between age and urinary calcium or citrate (calcium peaked at 40-49 years, p = 0.03; citrate nadired at 18-29 years, p = 0.001). ROC analysis of age, gender, and BMI to predict 24-hour urine abnormalities performed the best for hyperuricosuria (area under the curve [AUC] 0.816), hyperoxaluria (AUC 0.737), and hypocitraturia (AUC 0.740). Including diabetes mellitus or hypertension did not improve AUC significantly. CONCLUSIONS: In our recurrent calcium oxalate cohort, age significantly impacted urinary calcium, oxalate, citrate, and pH. Along with gender and BMI, age can be used to predict key 24-hour urine stone risk results. These data lay the foundation for a risk prediction tool, which could be a surrogate for 24-hour urine results in recurrent stone formers, who are unwilling or unable to complete metabolic testing. Further validation of these findings is needed in other stone populations.

Fourier Transform Infrared Analysis of Urinary Calculi and Metabolic Studies in a Group of Sicilian Children.

INTRODUCTION: Prevalence of urinary calculi in children has been increasing in the past years. We performed an analysis of the chemical composition of stones formers of the pediatric population in our geographical area over the years 2005 to 2013. MATERIALS AND METHODS: Fourier transform infrared spectroscopy was employed for the determination of the calculus composition of a group of Sicilian children, and metabolic studies were performed to formulate the correct diagnosis and establish therapy. RESULTS: The prevalence of stone formation was much higher for boys than for girls, with a sex ratio of 1.9:1. The single most frequent component was found to be calcium oxalate monohydrate, and calcium oxalates (pure or mixed calculi) were the overall most frequent components. Calcium phosphates ranked 2nd for frequency, most often in mixed calculi, while urates ranked 3rd. The metabolic disorder most often associated with pure calcium oxalate monohydrate calculi was hypocitraturia, while hyperoxaluria was predominantly associated with calcium oxalate dihydrate calculi. CONCLUSIONS: Mixed calculi had the highest prevalence in our pediatric population. Our data showed that Fourier transform infrared spectroscopy was a useful tool for the determination of the calculi composition.

Enteric hyperoxaluria in chronic pancreatitis.

Chronic pancreatitis may lead to steatorrhea, enteric hyperoxaluria, and kidney damage. However, the prevalence and determinants of hyperoxaluria in chronic pancreatitis patients as well as its association with renal function decline have not been investigated.We performed an observational study. Urine oxalate to creatinine ratio was assessed on 2 independent random urine samples in consecutive adult patients with chronic pancreatitis followed at the outpatient clinic from March 1 to October 31, 2012. Baseline characteristics and annual estimated glomerular filtration rate (eGFR) change during follow-up were compared between patients with hyper- and normo-oxaluria.A total of 48 patients with chronic pancreatitis were included. The etiology of the disease was toxic (52%), idiopathic (27%), obstructive (11%), autoimmune (6%), or genetic (4%). Hyperoxaluria (defined as urine oxalate to creatinine ratio >32 mg/g) was found in 23% of patients. Multivariate regression analysis identified clinical steatorrhea, high fecal acid steatocrit, and pancreatic atrophy as independent predictors of hyperoxaluria. Taken together, a combination of clinical steatorrhea, steatocrit level >31%, and pancreatic atrophy was associated with a positive predictive value of 100% for hyperoxaluria. On the contrary, none of the patients with a fecal elastase-1 level >100 µg/g had hyperoxaluria. Longitudinal evolution of eGFR was available in 71% of the patients, with a mean follow-up of 904 days. After adjustment for established determinants of renal function decline (gender, diabetes, bicarbonate level, baseline eGFR, and proteinuria), a urine oxalate to creatinine ratio >32 mg/g was associated with a higher risk of eGFR decline.Hyperoxaluria is highly prevalent in patients with chronic pancreatitis and associated with faster decline in renal function. A high urine oxalate to creatinine ratio in patients with chronic pancreatitis is best predicted by clinical steatorrhea, a high acid steatocrit, and pancreatic atrophy. Further studies will need to investigate the mechanisms of renal damage in chronic pancreatitis and the potential benefits of therapies reducing oxaluria.

Steatorrhea and Hyperoxaluria in Severely Obese Patients Before and After Roux-en-Y Gastric Bypass.

BACKGROUND AND AIMS: Hyperoxaluria after Roux-en-Y gastric bypass (RYGB) is generally attributed to fat malabsorption. If hyperoxaluria is indeed caused by fat malabsorption, magnitudes of hyperoxaluria and steatorrhea should correlate. Severely obese patients, prior to bypass, ingest excess dietary fat that can produce hyperphagic steatorrhea. The primary objective of the study was to determine whether urine oxalate excretion correlates with elements of fat balance in severely obese patients before and after RYGB. METHODS: Fat balance and urine oxalate excretion were measured simultaneously in 26 severely obese patients before and 1 year after RYGB, while patients consumed their usual diet. At these time points, stool and urine samples were collected. Steatorrhea and hyperoxaluria were defined as fecal fat >7 g/day and urine oxalate >40 mg/day. Differences were evaluated using paired 2-tailed t tests. RESULTS: Prior to RYGB, 12 of 26 patients had mild to moderate steatorrhea. Average urine oxalate excretion was 61 mg/day; there was no correlation between fecal fat and urine oxalate excretion. After RYGB, 24 of 26 patients had steatorrhea and urine oxalate excretion averaged 69 mg/day, with a positive correlation between fecal fat and urine oxalate excretions (r = 0.71, P < .001). For each 10 g/day increase in fecal fat output, fecal water excretion increased only 46 mL/day. CONCLUSIONS: Steatorrhea and hyperoxaluria were common in obese patients before bypass, but hyperoxaluria was not caused by excess unabsorbed fatty acids. Hyperphagia, obesity, or metabolic syndrome could have produced this previously unrecognized hyperoxaluric state by stimulating absorption or endogenous synthesis of oxalate. Hyperoxaluria after RYGB correlated with steatorrhea and was presumably caused by excess fatty acids in the intestinal lumen. Because post-bypass steatorrhea caused little increase in fecal water excretion, most patients with steatorrhea did not consider themselves to have diarrhea. Before and after RYGB, high oxalate intake contributed to the severity of hyperoxaluria.

Metabolic disturbances in Chinese children with urolithiasis: a single center report.

Urinary stones and urine composition are the first steps in the process of recurrence prevention, but data concerning the association between the two compositions are scarce in Chinese children with urolithiasis. We retrospectively analyzed the records of children (age range 0-18 years) with urolithiasis in our center between March 2004 and December 2013. Stone analysis was carried out in 382 children and 24-hour urine analysis in 80 children. Analysis of both stone and 24-hour urine composition was completed in 56 children. Stone samples were analyzed by Fourier transform-infrared spectrometry. The major stone constituents were calcium oxalate (78.8 %). Of 80 children with 24 h urine analysis, only 2.5 % were without urinary metabolic abnormalities. Hypocitraturia was recorded in 97.5 %, high sodium excretion in 50.0 %, cystinuria in 48.7 %, hypercalciuria in 18.8 %, small urine volumes in 12.5 %, hyperoxaluria in 5.0 % and hyperuricosuria in 1.3 %. Interestingly, higher urine volumes were recorded in girls than in boys (73.2 ± 58.5 vs 51.3 ± 45.3 mL/kg, p = 0.036). Urine sodium (p = 0.002) and oxalate (p = 0.004) were significantly higher in children >9 year old. Moreover, compared with calcium oxalate stone formers, the urine volume (p = 0.040), citrate (p = 0.007) and cystine (p = 0.004) were higher in patients with cystine stones. Hypocitraturia was the common abnormality among Chinese children with urolithiasis. The surprisingly high incidence of cystinuria is of note.