The response to surgery and critical illness is a complex process designed to provide energy and other essential compounds for reparative processes. This process also serves to protect the host from microbial invasion and optimize the function of vital organs. Compounds are released from the periphery and taken up by visceral organs for use in these functions, which often expedite recovery. The flow of substrates is initiated and maintained by a variety of mediators and neural signals. The catabolic process appears well orchestrated but errs on the side of abundant substrate delivery. Hence, the physiologic and metabolic alterations that characterize the surgical response may be deleterious when prolonged or severe. There is degradation of total body protein and an increase in systemic metabolism, which can result in death if nutritional and cardiopulmonary reserves are exhausted. While these metabolic changes are usually well tolerated on a short-term basis, prolonged catabolic illness may be harmful even if appropriately managed by the attending clinician. The primary goal of nutritional support is to enhance those salutary processes of the response to surgical stress while minimizing the adverse affects of this response (1). This chapter focuses on nutritional support of the urology patient and those with pathological conditions of the urinary system.