Scanning Electron Microscopy


Patients with end stage renal failure may be treated by continuous ambulatory peritoneal dialysis. The transcutaneous portion of the catheters used in this treatment is covered with porous expanded polytetrafluoroethylene (PTFE) to provide a surface suitable for tissue infiltration. Following some instances where catheters failed to become fixed in the abdominal wall, a scanning electron microscopical study was carried out to compare the infiltration of catheters having successful or unsuccessful implantation.

The porous layer of a well-fixed catheter, removed after successful renal transplantation, was infiltrated with collagen fibrils and overlain by layered connective tissue composed of fibroblasts and collagen fibre bundles, sometimes linking to surrounding muscle fibres. The examination of four unsuccessful catheters revealed no evidence for infection being the cause of implantation failure. However the porous surface of these catheters was filled with blood components and products, sometimes apparently laid down in layers, suggesting that frequent bleeding resulting from repeated trauma may be responsible for the failure of catheter fixation.

These findings led to two changes in clinical practice with apparent patient benefit. The implantation site has been relocated to reduce chafing by clothing and the post-operative wound dressing technique has been altered to minimise catheter movement.

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