Expected white blood cell counts and differentials in a rat model of peritoneal dialysis

The purpose of this study was to establish baseline dialysate white blood cell (WBC) counts and differentials in noninfected rats on peritoneal dialysis (PD).

Sixteen male Sprague-Dawley rats underwent PD in the first protocol, and eight from the 16 continued PD in the second through fourth protocols. At the beginning of the experiments, all animals had a PD catheter implanted and were initiated on PD with 1.5% dextrose dialysis solution twice daily. In the first protocol, WBC counts and differentials were assessed from day 4 to day 15 of dialysis in noninfected animals to establish "normal values" for such a rat model. In protocol 2, WBC counts and solute concentrations in small aliquots of dialysate obtained from the catheter were compared to values in well-mixed total drainage. Protocol 3 was designed to assess effects of dwell time on WBC counts. Protocol 4 examined the effect of glucose concentration of dialysis solution on WBC counts.

In the first protocol, the mean dialysate WBC counts were significantly higher on the fourth day of dialysis, but stabilized below 2500 cells/mm3 by the eighth day. The percentage of neutrophils was stable around 20%-25%. In the second protocol, we found aliquots < 1 mL might underestimate the dialysate WBC count compared to the complete drainage. In the third protocol, WBC counts increased as cycle time became longer, but the percentage of neutrophils remained below 50%. In the fourth protocol, we did not find any effects of glucose concentration of instilled solutions on WBC counts and differentials.

This study of WBC counts and differentials in noninfected rats on peritoneal dialysis establishes the range above which infection should be suspected. WBC counts increase with cycle time. Small dialysate aliquots may underestimate WBC counts. Glucose concentration does not effect WBC counts.