We read with interest the article by Gibbs et al1 describing preoperative serum albumin concentration as a predictor of operative mortality and morbidity. The authors are correct in identifying that preoperative hypoalbuminemia reflects preoperative disease severity, and therefore hypoalbuminemia would be expected to be associated with the risk of postoperative organ failures and a poorer outcome. In 1985, Fleck2 showed that trauma, surgery, sepsis, and malignancy were all major causes of hypoalbuminemia owing to increased capillary permeability, which allowed albumin to escape from the vascular space. Preoperative hypoalbuminemia facilitates postoperative edema, which is powerfully associated with sepsis syndrome, acute renal failure, coma, and respiratory dysfunction requiring prolonged mechanical ventilation.3 We write to suggest that monitoring capillary permeability by measuring urine microalbuminuria before and after surgery provides a more sensitive way of predicting and caring for patients who will later develop clinical capillary leak syndrome, of which preoperative and surgically induced hypoalbuminemia is only one feature.4 Microalbuminuria identifies the beginning of a leak, which requires increased vascular volume support; the severity of a leak, which predicts the quantity of fluids needed to provide the increased vascular volume support as well as the risk of later organ failure; and the end of a leak, which identifies the time to begin vigorous removal of iatrogenic edema, edema which is a necessary effect of resuscitation but a hazard that calls for early and vigorous treatment in postsurgical and postshock care.