Oxalate Balance in Peritoneal Dialysis Patients: A Potential Role of Dialysis-related Peritonitis

Abstract

Background: Little evidence is available on oxalate balance in peritoneal dialysis (PD) patients. Patients and Methods: We performed a cross-sectional observational pilot study with 62 adult PD patients to document oxalate balance and explore its association with PD-related peritonitis. Plasma oxalate concentration, levels of oxalate excretion in 24-h urine, and peritoneal dialysis effluent were evaluated. The peritoneal oxalate transport status and renal and peritoneal oxalate clearances were calculated according to the PD-related peritonitis history. Results: PD patients with a history of peritonitis had a statistically significantly lower peritoneal oxalate clearance, daily peritoneal oxalate excretion, and overall oxalate removal rate compared with the peritonitis-free PD patients. They had a 4-fold risk of plasma oxalic acid increase, and even a single episode of dialysis-related peritonitis resulted in plasma oxalate elevation. Conclusion: Peritoneal oxalate clearance plays an important role in oxalate balance in PD patients and, therefore, dialysis-related peritonitis is a significant predictor for hyperoxalemia. Further well-designed clinical trials need to be undertaken before the association between peritonitis and oxalate balance in PD patients is more clearly understood.Oxalate is an ionized form of a potentially toxic oxalic acid formed from endogenously synthesized and exogenously ingested oxalates (1, 2). In physiological conditions, the bulk of circulating oxalate (90-95%) is excreted through the kidneys, whereas the remainder (5-10%) through the terminal parts of the small intestine and colon (1-4). A decline in kidney function leads to decreased oxalate clearance and, ultimately, hyperoxalemia in end-stage kidney disease (ESKD) (1, 5-7). The accumulation of oxalate is associated with oxidative stress and systemic inflammation (1, 8, 9), high cardiovascular risk (9-11), and increased mortality rate (1, 11) in patients with kidney stones and ESKD. Nevertheless, little evidence is available on oxalate balance in ESKD patients in general and peritoneal dialysis (PD) patients in particular; almost all scientific data on this issue were published during the 1980s and 1990s (6,(12)(13)(14).Worldwide, PD is a key element of kidney replacement therapy (15-17). Nonetheless, peritonitis remains one of the major challenges associated with severe clinical complications of PD despite technological advances (17,18). Detrimental effects of dialysis-related peritonitis on the characteristics of peritoneal transport and the alterations of the peritoneal membrane have been documented (19-21). However, the potential effect of dialysis-related peritonitis on oxalate balance in PD patients has never been evaluated before. We hypothesized that the alteration of the peritoneal membrane due to dialysis-related peritonitis could decrease the peritoneal clearance of oxalate and, consequently, its removal levels. To test this hypothesis, the present study aimed to define oxalate balance and explore its association with dia...

Oxalate Homeostasis in Non-Stone-Forming Chronic Kidney Disease: A Review of Key Findings and Perspectives

“…However, POx concentrations increase rapidly after dialysis and typically return to predialysis levels within two hours [ 114 ]. In PD, oxalate removal is achieved through the combination of dialysate and urine clearance, which is comparable to the 24 h excretion of oxalate in healthy subjects [ 122 , 123 ]. However, the rate of oxalate removal is influenced by the balance between the peritoneal and kidney routes, with peritoneal clearance being more significant than residual kidney function in controlling POx levels [ 122 , 123 ].…”

“…In PD, oxalate removal is achieved through the combination of dialysate and urine clearance, which is comparable to the 24 h excretion of oxalate in healthy subjects [ 122 , 123 ]. However, the rate of oxalate removal is influenced by the balance between the peritoneal and kidney routes, with peritoneal clearance being more significant than residual kidney function in controlling POx levels [ 122 , 123 ]. This means that even a single episode of peritonitis or other complications that impact the function of the peritoneal membrane can increase POx levels in patients treated with PD [ 123 ].…”

“…However, the rate of oxalate removal is influenced by the balance between the peritoneal and kidney routes, with peritoneal clearance being more significant than residual kidney function in controlling POx levels [ 122 , 123 ]. This means that even a single episode of peritonitis or other complications that impact the function of the peritoneal membrane can increase POx levels in patients treated with PD [ 123 ]. Therefore, although DKRT is the only effective option for significantly reducing POx concentrations, it alone is insufficient to maintain oxalate homeostasis in patients with ESKD.…”

Peritoneal dialysis and peritoneal fibrosis: molecular mechanisms, risk factors and prospects for prevention

“…На жаль, на відміну від сечової кислоти, дослідження щодо безпосередньої участі оксалової кислоти у розвитку перитонеального фіброзу ще не проводились. Проте, за нашими клінічними спостереженнями, концентрація оксалової кислоти крові ПД пацієнтів зворотно асоціювалась з перитонеальним кліренсом оксалату та мала прямий кореляційний зв'язок з марекрами oксидативного стресу, прозапальними та профіброгенними цитокінами [34,44]. Більше того, низька оксалат-деградувальна активність кишкової мікробіоти у ПД пацієнтів асоціювалась з підвищенням перитонеального кліренсу оксалату, підвищенням IS сироватки та концентрації профіброгенних медіаторів запалення в ексфузаті [44,45], що опосередковано підтверджує участь оксалату у перитонеальному фіброзі.…”