Collection and quantification of urine during anesthesia in small animals

This note describes a simple method for collecting urine and quantification of urine production during anesthesia in small animals. It offers two advantages, especially important for procedures requiring lengthy anesthesia: 1) The animals are kept dry, and 2) fluid balance can be maintained more accurately. The method, which we have applied to rats, is to rest the animal on an absorbent pad of known weight and to weigh the pad after urine has been collected. The note describes the performance characteristics of a preferred pad type and contrasts them with those of other readily available types of absorbent pads. The preferred pad keeps the animal dry while facilitating quantification of urine production, a refinement of animal use.