A Case of Oxalate Nephropathy: When a Single Cause Is Not Crystal Clear

The Beauty and the Beast: Bariatric Surgery and a Case of Oxalate Nephropathy

Oxalate nephropathy is a rare cause of kidney failure. Roux-en-Y gastric bypass surgery is a technique used for surgical treatment of obesity as well as for the treatment of gastric carcinoma. We report the case of a 46-year-old male who was admitted to the nephrology department due to kidney dysfunction eight months after bariatric surgery.

Megadose Vitamin C Prescription Through Alternative Medicine Leading to End-Stage Renal Disease: Case Study and Literature Review

Modern medicine has made tremendous advancements and succeeded in increasing longevity through adequate screening and diagnosis and various new therapeutic approaches. However, alternative medicine is a branch of health care practicing different traditional and unconventional, potentially hazardous therapies to treat commonly known ailments. Standard low-dose vitamin C, ie, 500-1000 mg, is approved in medical conditions like methemoglobinemia, scurvy, burns and also helps iron absorption in anemia. However, toxic doses carry high nephrotoxicity potential like in our case. We present a 74-year-old Caucasian female falling victim to one such alternative therapy leading to acute kidney injury requiring lifelong hemodialysis. She had endometrial cancer and received 100 gm of intravenous vitamin C weekly through a provider for the last 6 weeks as part of this alternate approach to cure her cancer. Upon admission, the serum creatinine level was elevated at 8.2 mg/dl, which subsequently did not improve with conservative management. Renal biopsy revealed diffuse acute tubular injury with polarized microscopy demonstrating calcium oxalate crystals. While her blood vitamin C levels were high, the serum oxalate level was normal. She ended up requiring renal replacement therapy permanently. Alternative medicine continues to be a significant health care hazard with the potential to cause unwanted irreversible nephrotoxicity. Public attention is necessary at various social levels to counter the detrimental outcomes of alternative medicine.

Roux-en-Y gastric bypass surgery induced oxalosis and acute kidney injury: A case report

Introduction and importance

Diabetes mellitus and hypertension are two conditions that can coexist in obese individuals. Roux-en-Y gastric bypass (RYGB) surgery, are used to control obesity. Complications such as steatorrhea, hyperoxaluria, and decreased bone mineral density, may occur after RYGB.

Case presentation

A 58-year-old woman referred to the emergency department complaining of pain on the right side of her lower abdomen. Her past medical history was RYGB surgery, COVID-19 with 40% pulmonary involvement, and Chronic Kidney Disease (CKD). Rapid progressive glomerulonephritis (RPGN) was predicted based on extensive laboratory test results. A kidney biopsy demonstrated oxalate nephropathy. Along with the findings from the kidney biopsy, acute tubulointerstitial nephritis with tubular injury secondary oxalosis was diagnosed.

Clinical discussion

RYGB surgery and chronic kidney disease, can increase the risk of secondary oxalosis. Recent studies introduce enteric hyperoxaluria as an important marker for diagnosing end-stage kidney disease. Renal biopsy is often prescribed for absolute recognition of oxalosis. On the other hand, our patient has a recent history of COVID-19 infection. The use of anti-Covid-19 drugs in patients with renal insufficiency should be considered with caution.

Conclusion

It is important to monitor kidney function following RYGB surgery, particularly in patients with underlying diseases such as diabetes or hypertension.

Dietary Oxalate Intake and Kidney Outcomes

Oxalate is both a plant-derived molecule and a terminal toxic metabolite with no known physiological function in humans. It is predominantly eliminated by the kidneys through glomerular filtration and tubular secretion. Regardless of the cause, the increased load of dietary oxalate presented to the kidneys has been linked to different kidney-related conditions and injuries, including calcium oxalate nephrolithiasis, acute and chronic kidney disease. In this paper, we review the current literature on the association between dietary oxalate intake and kidney outcomes.

The association of calcium oxalate deposition in kidney allografts with graft and patient survival

BACKGROUND

Whether calcium oxalate (CaOx) deposition in kidney allografts following transplantation (Tx) adversely affects patient outcomes is uncertain, as are its associated risk factors.

METHODS

We performed a retrospective cohort study of patients who had kidney allograft biopsies performed within 3 months of Tx at Brigham and Women's Hospital and examined the association of CaOx deposition with the composite outcome of death or graft failure within 5 years.

RESULTS

Biopsies from 67 of 346 patients (19.4%) had CaOx deposition. In a multivariable logistic regression model, higher serum creatinine [odds ratio (OR) = 1.28 per mg/dL, 95% confidence interval (CI) 1.15-1.43], longer time on dialysis (OR = 1.11 per additional year, 95% CI 1.01-1.23) and diabetes (OR = 2.26, 95% CI 1.09-4.66) were found to be independently associated with CaOx deposition. CaOx deposition was strongly associated with delayed graft function (DGF; OR = 11.31, 95% CI 5.97-21.40), and with increased hazard of the composite outcome after adjusting for black recipient race, donor type, time on dialysis before Tx, diabetes and borderline or acute rejection (hazard ratio 1.90, 95% CI 1.13-3.20).

CONCLUSIONS

CaOx deposition is common in allografts with poor function and portends worse outcomes up to 5 years after Tx. The extent to which CaOx deposition may contribute to versus result from DGF, however, cannot be determined based on our retrospective and observational data. Future studies should examine whether reducing plasma and urine oxalate prevents CaOx deposition in the newly transplanted kidney and whether this has an effect on clinical outcomes.

Association of Urinary Oxalate Excretion With the Risk of Chronic Kidney Disease Progression

IMPORTANCE

Oxalate is a potentially toxic terminal metabolite that is eliminated primarily by the kidneys. Oxalate nephropathy is a well-known complication of rare genetic disorders and enteric hyperoxaluria, but oxalate has not been investigated as a potential contributor to more common forms of chronic kidney disease (CKD).

OBJECTIVE

To assess whether urinary oxalate excretion is a risk factor for more rapid progression of CKD toward kidney failure.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study assessed 3123 participants with stages 2 to 4 CKD who enrolled in the Chronic Renal Insufficiency Cohort study from June 1, 2003, to September 30, 2008. Data analysis was performed from October 24, 2017, to June 17, 2018.

EXPOSURES

Twenty-four-hour urinary oxalate excretion.

MAIN OUTCOMES AND MEASURES

A 50% decline in estimated glomerular filtration rate (eGFR) and end-stage renal disease (ESRD).

RESULTS

This study included 3123 participants (mean [SD] age, 59.1 [10.6] years; 1414 [45.3%] female; 1423 [45.6%] white). Mean (SD) eGFR at the time of 24-hour urine collection was 42.9 (16.8) mL/min/1.73 m2. Median urinary excretion of oxalate was 18.6 mg/24 hours (interquartile range [IQR], 12.9-25.7 mg/24 hours) and was correlated inversely with eGFR (r = -0.13, P < .001) and positively with 24-hour proteinuria (r = 0.22, P < .001). During 22 318 person-years of follow-up, 752 individuals reached ESRD, and 940 individuals reached the composite end point of ESRD or 50% decline in eGFR (CKD progression). Higher oxalate excretion was independently associated with greater risks of both CKD progression and ESRD: compared with quintile 1 (oxalate excretion, <11.5 mg/24 hours) those in quintile 5 (oxalate excretion, ≥27.8 mg/24 hours) had a 33% higher risk of CKD progression (hazard ratio [HR], 1.33; 95% CI, 1.04-1.70) and a 45% higher risk of ESRD (HR, 1.45; 95% CI, 1.09-1.93). The association between oxalate excretion and CKD progression and ESRD was nonlinear and exhibited a threshold effect at quintiles 3 to 5 vs quintiles 1 and 2. Higher vs lower oxalate excretion (at the 40th percentile) was associated with a 32% higher risk of CKD progression (HR, 1.32; 95% CI, 1.13-1.53) and 37% higher risk of ESRD (HR, 1.37; 95% CI, 1.15-1.63). Results were similar when treating death as a competing event.

CONCLUSIONS AND RELEVANCE

Higher 24-hour urinary oxalate excretion may be a risk factor for CKD progression and ESRD in individuals with CKD stages 2 to 4.

Combining Acute Kidney Injury with Gastrointestinal Pathology: A Clue to Acute Oxalate Nephropathy

Acute oxalate nephropathy (AON) is an increasingly recognized cause of acute kidney injury (AKI). Herein, we present two cases of biopsy-proven acute oxalate nephropathy in patients with gastrointestinal malabsorption, coincidentally both stemming from cholangiocarcinoma. The first is a 73-year-old male who presented with syncope and was found to have severe, oliguric AKI in the setting of newly diagnosed, nonresectable cholangiocarcinoma. The second is a 64-year-old man with remote resection of cholangiocarcinoma who presented after routine laboratory monitoring showed significant AKI. Temporary dialysis was required in both cases before renal recovery occurred. Together, these cases should increase physicians' suspicion of AON in the presence of malabsorption. By doing so, the workup of oxalate nephropathy can be expedited with prompt initiation of treatment.