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

Acute oxalate nephropathy: A potential cause of acute kidney injury in diabetes mellitus—A case series from a single center

Background

Acute oxalate nephropathy (AON) is an uncommon condition that causes acute kidney injury (AKI), characterized by the massive deposition of calcium oxalate crystals in the renal parenchyma. In previous studies, urinary oxalate excretion has been found to be increased in patients with diabetes mellitus (DM). Here, we report a case series of diabetic patients with AKI with biopsy-proven AON, aiming to alert physicians to the potential of AON as a trigger of AKI in diabetic patients in clinical practice.

Materials and methods

Cases with pathological diagnosis of AON who presented with AKI clinically and had DM between January 2016 and December 2020 were retrospectively enrolled. Their clinical and pathological manifestations, treatment, and prognosis were collected.

Results

Six male patients with biopsy-proven AON out of a total of 5,883 native kidney biopsies were identified, aged 58.3 ± 9.1 years at the time of kidney biopsy. Only one patient who had received Roux-en-Y gastric bypass surgery took oxalate-rich food before the onset of the disease. None of them had clinical features of enteric malabsorption. Three patients were currently on renin-angiotensin system inhibitor treatment for hypertension, and 5 of them received non-steroidal anti-inflammatory drugs. Three patients presented with oliguria and 4 patients needed dialysis at the beginning with none requiring dialysis at discharge. Four patients received a course of corticosteroid treatment empirically. Among them, two patients had estimated glomerular filtration rate (eGFR) recovered to over 60 ml/min/1.73 m2, while the other two patients remained with kidney dysfunction at the last follow-up. In two patients without corticosteroid treatment, one patient fully recovered with eGFR over 90 ml/min/1.73 m2 and the other patient remained with kidney dysfunction at the last follow-up.

Conclusion

AON might be a rare but potentially trigger of AKI in patients with DM. A kidney biopsy could help physicians to make the correct diagnosis. The proper treatment to alleviate oxalate-induced injury needs to be further studied.

Sodium Oxalate-Induced Acute Kidney Injury Associated With Glomerular and Tubulointerstitial Damage in Rats

Acute crystalline nephropathy is closely related to tubulointerstitial injury, but few studies have investigated glomerular changes in this condition. Thus, in the current study, we investigated the factors involved in glomerular and tubulointerstitial injury in an experimental model of crystalline-induced acute kidney injury (AKI). We treated male Wistar rats with a single injection of sodium oxalate (NaOx, 7 mg⋅100 g^-1⋅day^-1, resuspended in 0.9% NaCl solution, i.p.) or vehicle (control). After 24 h of treatment, food and water intake, urine output, body weight gain, and renal function were evaluated. Renal tissue was used for the morphological studies, quantitative PCR and protein expression studies. Our results revealed that NaOx treatment did not change metabolic or electrolyte and water intake parameters or urine output. However, the treated group exhibited tubular calcium oxalate (CaOx) crystals excretion, followed by a decline in kidney function demonstrated along with glomerular injury, which was confirmed by increased plasma creatinine and urea concentrations, increased glomerular desmin immunostaining, nephrin mRNA expression and decreased WT1 immunofluorescence. Furthermore, NaOx treatment resulted in tubulointerstitial injury, which was confirmed by tubular dilation, albuminuria, increased Kim-1 and Ki67 mRNA expression, decreased megalin and Tamm-Horsfall protein (THP) expression. Finally, the treatment induced increases in CD68 protein staining, MCP-1, IL-1β, NFkappaB, and α-SMA mRNA expression, which are consistent with proinflammatory and profibrotic signaling, respectively. In conclusion, our findings provide relevant information regarding crystalline-induced AKI, showing strong tubulointerstitial and glomerular injury with a possible loss of podocyte viability.