Late-onset polyvinylpyrrolidone allergy in a long-term hemodialysis patient: a case report of dialysis hypotension and gastrointestinal symptoms.

Polysulfone membranes are widely used in hemodialysis due to their excellent biocompatibility, with polyvinylpyrrolidone (PVP) serving as a key hydrophilic component. While PVP-related allergic reactions typically occur during initial exposure, delayed reactions in long-term dialysis patients present a unique diagnostic challenge due to their unexpected nature and similarity to routine complications. We report a case of delayed PVP allergy in a 69-year-old male who developed severe intradialytic hypotension and gastrointestinal symptoms after 13 months of stable hemodialysis treatment. Blood volume monitoring revealed a rapid 15% decrease within 30 min of dialysis initiation despite the absence of ultrafiltration, accompanied by marked eosinophilia (absolute eosinophil count: 13,266/μL) and elevated white blood cell count (19,800/μL). These symptoms persisted despite dry weight adjustments but resolved completely after switching from a polysulfone membrane to a PVP-free cellulose triacetate membrane. The patient's condition improved significantly, with eosinophil counts normalizing over nine months following the membrane change. This case contributes to the limited literature on delayed PVP allergic reactions, highlighting that such reactions can occur even after extended periods of stable dialysis. The successful use of blood volume monitoring and eosinophil tracking for early detection, combined with the effectiveness of PVP-free membrane substitution, provides valuable insights for managing similar cases. Recognition of this phenomenon may help improve the diagnosis and management of unexplained dialysis reactions in long-term patients.