ABSTRACT
The kidney fulfills several major functions. First, the organ regulates the excretion of several important inorganic and organic ions and participates in the regulation of acid-base balance. Second, the kidneys work in an integrated manner with the cardiovascular and central nervous systems to regulate body fluid osmolality and volume. The control of body fluid osmolality is central to the maintenance of normal cell volume in virtually all tissues. Third, the kidney excretes metabolic by-products and exogenous substances, including certain drugs. Finally, the kidney is an important endocrine organ, producing key hormones involved in the regulation of blood pressure and erythropoiesis, as well as calcium, phosphate, and bone metabolism. The kidney has remarkable functional reserve and, through adaptive changes, can maintain fluid, electrolyte, metabolic, and acid-base balance as the number of functioning nephrons is reduced by injury or disease. However, in response to significant injury, the kidney may undergo maladaptive changes that lead to acute irreversible and/or progressive renal disease. The incidence of acute and chronic kidney failure continues to rise, and despite extensive investigation into the pathophysiology of these disorders, major preventive or therapeutic advances have been infrequent. This chapter examines the anatomy and physiology of the normal kidney and then reviews the pathophysiology, diagnosis, and management of acute and chronic kidney failure, with special emphasis on clinical scenarios commonly encountered in modern surgical practice.
OVERVIEW OF RENAL PHYSIOLOGY Renal Anatomy and Microanatomy The cut surface of a bisected kidney reveals twomajor regions: the outer region, termed the cortex, in which the glomeruli reside, and the inner region, termed the medulla. The medulla is divided into 8 to 18 renal pyramids, whose bases begin at the corticomedullary junction and form an apex in a minor calyx of the papilla. The minor calyces drain into major calyces and then into the renal pelvis, an expanded region of the ureter. Smooth muscle contractions by the walls of the calyces, pelvis, and ureters drive the urine to the urinary bladder.
