The problem of peritoneal membrane area and permeability

Currently there is high interest in determining the pathophysiologic importance of molecules of intermediate molecular weight (500 to 5000) in the clinical syndrome of uremia [1, 2]. For extracorporeal hemodialysis, the efficiency with which these solutes are removed depends on the area and permeability characteristics of the dialysis membrane, as well as the time spent on dialysis [3, 4]. When contrasting peritoneal with extracorporeal hemodialysis, it becomes important to know how the area and permeability characteristics of the peritoneal membrane compare with conventional cellulosic hemodialysis membranes. It is widely held from the anatomical work of Wegner (1877) [5], cited by Boen [6] in his monograph on peritoneal dialysis, that peritoneal membrane area approximates skin surface area. Applying the nomogram of Dubois [7] for determining the skin surface area for a standard 70kg (154 lb) body weight, 170cm (5' 7”) height patient would yield a 1.8 m2 area; that for an 80kg (175 lb), 183cm (6') patient would yield a 2.0 m2 area. A similar but unestablished estimate is provided by Miller and Tassistro, in an unreferenced comment [8], indicating that peritoneal membrane area is “approximately that of the glomerular capillaries.” Pappenheimer [9] estimates the latter area to be between 0.5 and 1.5 m2/100 g of kidney. Given an average single kidney weight of 150 g, peritoneal membrane area according to this method of estimation would be between 1.5 and 4.5 m2