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Classification of Normal and Diseased Exit Sites

The classification of healed exit sites into seven categories evolved from the accompanying study presenting methods and results of 565 evaluations of 61 healed exit sites in 56 patients ( 1). Detailed attrib utes and differential diagnosis for these seven categories are presented in this paper. A brief discussion of the anatomy of the sinus and pathomechanism of inflammation helps to explain the presence and importance of various attributes. A recent study of catheter tunnels removed from patients showed that in almost all human peritoneal catheter tunnels the epithelium does not reach to the cuff, but stops a few millimeters from the exit in the sinus tract (2). The remaining sinus is covered by granulation tissue (Figure A). The outer cuff limits spreading of granulation tissue and/or epithelium when it reaches the cuff (2). Well-healed, uninfected exits and sinus tracts are usually colonized by bacteria. The part of the sinus tract covered with epithelium constitutes an excellent barrier to bacterial invasion in the same way as the rest of the body integument. The part of the sinus covered with granulation tissue appears to respond to bacteria by constant exudation of serum with white blood cells. The serum and white blood cells suppress bacterial proliferation and curb penetration of bacteria into the deeper sinus. This small amount of exudate becom-es desiccated and forms a crust, which may be seen in the external part of the sinus or around the sinus rim. This crust is easily washed away during routine exit care but may be visible if the exit care has been performed some time before examination of the exit. Such a crust is easily