Pathogenesis of nephrolithiasis post-partial ileal bypass surgery: case-control study. The POSCH Group

Area of Science:

• Nephrology
• Gastroenterology
• Metabolic Disorders

Background:

• The Program on the Surgical Control of Hyperlipidemias (POSCH) trial investigated partial ileal bypass (PIB) surgery for hyperlipidemia.
• An increased incidence of kidney stone formation was observed in patients who underwent PIB surgery compared to controls.

Purpose of the Study:

• To investigate the causes of increased kidney stone formation in patients following partial ileal bypass (PIB) surgery.
• To compare metabolic and urinary parameters between PIB patients with and without kidney stones and control subjects.

Main Methods:

• A matched triplet case-control study was conducted with 146 patients.
• Three groups were analyzed: PIB stone-formers (S), PIB non-stone formers (N), and non-PIB controls (C).
• Serum vitamin D metabolites and urinary parameters (volume, pH, citrate, magnesium, oxalate, ammonia, supersaturation) were measured.

Main Results:

• PIB patients (S and N) exhibited significantly lower serum vitamin D metabolites and urinary citrate, magnesium, and sulfate.
• PIB patients also had lower urine volume and pH, but higher urinary oxalate and ammonia.
• Elevated relative supersaturation for calcium oxalate and uric acid was noted in PIB patients compared to controls.

Conclusions:

• Partial ileal bypass (PIB) surgery is associated with an increased risk of kidney stone formation.
• Reduced urinary volume, decreased levels of stone inhibitors, and increased urinary supersaturation contribute to nephrolithiasis in PIB patients.
• All patients undergoing PIB surgery should be considered at risk for kidney stone development.