Uremia and Host Resistance to Peritonitis in C.A.P.D-an Experimental Evaluation

Peritonitis is an important complication of CAPD. Because uremia is believed to impair immunity, we sought to determine whether uremia per se predisposes patients on CAPD to peritoneal infection. Using an animal model of CAPD, we have evaluated the effect of severe uremia on host resistance to peritonitis. Intraperitoneal catheters were implanted in severely uremic and sham-operated non-uremic rats, which were then dialysed four times a day for two days. Alternatively, they were infused with dialysis fluid twice daily for eight days without drainage of the dialysate. Peritonitis was induced by direct inoculation of Escherichia coli; the bacteria in the peritoneal cavity and spleen were counted 24 hours after this challenge. Uremia did not impair resistance to experimentally induced peritonitis in either the dialysed or infused host.

Continuous ambulatory peritoneal dialysis (CAPD) is becoming increasingly popular as a method for longteffil treatment of chronic renal failure. The major disadvantage is the risk of infection and peritonitis remains the single most important complication and reason for transfer of patients to another mode of therapy.

Uremia is believed to impair immunity and predispose patients to infection (1, 2). Hence the question arises: Are patients on CAPD predisposed to peritoneal infection by the uremia itself? We developed a model of chronic uremia in rats, which made possible studies uncomplicated by many variabies associated with the clinical management of uremic patients. This paper examines the contribution of uremia to the susceptibility of the dialysed host to peritonitis. In the rats, we found it difficult to maintain dialysis for longer than two days because of rapid blockage of catheters by fibrin and connective tissue. As a consequence, we employed two models: one carried out peritoneal dialysis for two days, and the other involved infusions of dialysate without drainage for a longer period. Uremic and sham-operated animals, either dialysed or infused without drainage, were compared with noffilal controls with respect to their ability to withstand an intraperitoneal challenge with viable Escherichia cali.