"Postretirement polydipsia" mimicking prostatism.

water in the citric acid cycle. Peritoneal dialysate contains a racemic mixture of both D and L isomers of lactate and mammals lack D-lactic dehydrogenase and are slower in metabolising D-lactate.' There is only one previously reported case of lactic acidosis in a patient receiving peritoneal dialysis, which like our case was related to metformin.4 Severe lactic acidosis has a mortality of about 80% despite treatment. Acetate and bicarbonate are alternatives to lactate as buffers for peritoneal dialysate. The use of acetate, however, has largely been abandoned because of its association with loss of ultrafiltration and sclerosing encapsulated peritonitis.5 Bicarbonate would be the ideal buffer but solutions containing bicarbonate are difficult to prepare and sterilise because of precipitation of insoluble calcium salts. It is, however, possible to prepare bicarbonate based dialysate for use in patients with lactic acidosis.67 We thank Dr I Broom for reviewing the manuscript and for the lactate assay. The study was supported by a grant from the clinical resource and audit group of the Scottish Home and Health Department.