Alterations in intestinal transport of oxalate in disease states.

Normally, absorption of oxalate from dietary sources can occur in all segments of the intestinal tract. However, alterations in both the magnitude and direction of oxalate fluxes across the intestine can occur in disease states. In enteric hyperoxaluria, enhanced absorption of oxalate by the large intestine is caused by increased permeability of a shunt conductance induced by malabsorbed bile salts and fatty acids. In this condition, the contribution of a paracellular passive flux of oxalate moving along its electrochemical gradient will predominate when intraluminal concentrations of free oxalate are high. In contrast, in chronic renal failure, secretion of oxalate can occur across both small and large intestine thereby facilitating extrarenal elimination with subsequent degradation by mucosal substrate-specific microorganisms. Clearly, in recent studies of oxalate transport, the intestine has emerged with an integral role in mass balance of oxalate in health and disease.