Foreign-body response to sterile catheters is variable over 20 weeks.

We hypothesized that placement of sterile catheter material into the peritoneal cavity results in a foreign-body response that varies with exposure duration. Sterile medical Silastic catheter material was aseptically implanted into the abdomens of 42 anesthetized Sprague-Dawley rats. Controls (n = 18) underwent sham operations without catheter implantation. After 4, 8, or 20 weeks, the animals were anesthetized, the abdomen was opened, and the catheter material was recovered and processed to separate the cells adhering to the catheters. The cells, abdomen, and catheter material were all cultured to demonstrate sterility, and transport experiments were carried out. After euthanasia of the animals, abdominal wall tissue was examined for submesothelial thickness and vascular density, and immunohistochemistry (IHC) for cytokines was performed. Cells from the catheter material were processed for immunocytochemistry (ICC). The catheter, adherent cells, and abdomen were free of bacteria. Inflammatory changes in peritoneal thickness and angiogenesis were highest at 4 weeks and declined thereafter to 20 weeks. Transport of mannitol was higher at 4 weeks in treated animals than in controls, and albumin transport was higher at 8 weeks in treated animals than in controls. The IHC for cytokines demonstrated changes paralleling the structural alterations (p < 10(-5)). The ICC of the catheter cell layer demonstrated mesothelial cells, macrophages, fibroblasts, and T cells. Over 20 weeks, the foreign-body response to polymer catheters placed intraperitoneally in rats without injection of solution depends on exposure time, with an initial immune response evident at 4 weeks and decreasing thereafter.