Ultrafiltration Failure and Impaired Sodium Sieving During Long-Term Peritoneal Dialysis: More Than Aquaporin Dysfunction?

Fifteen years ago, our group reported the case of a 67-year-old man on peritoneal dialysis for 11 years, in whom ultrafiltration failure and impaired sodium sieving were associated with an apparently normal expression of aquaporin-1 (AQP1) water channels in peritoneal capillaries. At that time, AQP1 dysfunction was suggested as the cause of impaired free-water transport. However, recent data from computer simulations, and structural and functional analysis of the peritoneal membrane of patients with encapsulating peritoneal sclerosis, demonstrated that changes in the peritoneal interstitium directly alter osmotic water transport. In light of these insights, we challenge the initial hypothesis and provide several lines of evidence supporting the diagnosis of encapsulating peritoneal sclerosis in this patient and suggesting that severe peritoneal fibrosis accounted for the loss of osmotic conductance developed during the course of peritoneal dialysis.