Peritoneal dialysis (P.D.) was attempted for the treatment of acute renal failure (ARF) in an 880 kg. Pacific pilot whale (see accompanying case report by McBain and Reidarson). The practical lessons learned in this unsuccessful attempt, together with theoretical considerations and knowledge gleaned from decades of successful P.D. in humans, suggest that P.D. might be employed successfully in future cases of ARF in cetaceans.

Average humans (70 kg) with permanent renal failure can be kept alive long-term by P.D. exchanges of 2 to 2.5 liters four times per 24 hours. Sterile P.D. fluid, containing appropriate electrolytes and high glucose content (to cause osmotic ultrafiltration), is infused into the peritoneal cavity and allowed to dwell for 4-6 hours, then is run out. Maximal mass transfer of uremic solutes requires more rapid cycles.

Larger animals have a less favorable ratio of body mass (which generates uremic toxins) to peritoneal surface area (for dialysis). In addition to this problem of scale, cetaceans appear to have thicker peritoneal membranes whose diffusive capabilities are unknown. However, it is unlikely that these limitations will be insurmountable. Failure in the present whale was due to inadequate peritoneal access. Recent improvements in human P.D. have come from better catheter design and placement techniques.

Adequate peritoneal access should be achievable in cetaceans, and large-volume P.D. should be attempted in future cases of ARF.