Overview of the kidney : Introduction

Hello everybody. This is Professor Lee of Taipei Medical University. Today’s topic is renal excretion in end-stage renal disease.

Learning objectives : To determine renal function by GFR, renal plasma flow and serum biomarker. To describe filtration, secretion and reabsorption functions of the kidneys. To estimate creatinine clearance using C-G equations, MDRD equation and other commonly used formula. To estimate creatinine clearance for pediatric patients using Schwartz formula. and to define the stages of chronic kidney disease. To discern between renal excretion, renal clearance and urinary drug recovery. To derive renal clearance by excretion rate method. and last but not the least derived renal clearance by urinary recovery method. Let’s first review renal physiology a little bit. This slide shows the longitudinal view of the urinary system. We have two kidneys. The right kidney and the left kidney.

Since we only need one to survive. and that’s why you heard about the horrible stories of selling kidneys in the third world. This is the cross-section view of the kidneys. Each kidney consists of millions of nephrons. and each nephron consists of glomerulus, the proximal tubule, the loop of Henle, the distal tubule and the ureters. Physiology data of the kidneys. Each kidney contains 1 to 1.5 million nephrons. It weighs about 0.5 percent of total body weight. It received 20 to 25 percent of cardiac output. that is about one-quarter of cardiac output. And therefore the renal plasma flow is 1.5 liters per minute. or in terms of plasma flow is 0.6 to 0.75 liters per minute.

Normal GFR is 100 to 125 milliliters per minute. and urine flow is 1 to 2 milliliters per minute. Functions of the kidney. First to regulate body fluid osmolality and volume. To regulate electrolyte balance. To maintain acid-base balance. To produce and secrete hormones such as renin and erythropoietin. Excretion of endogenous metabolic wastes. And excretion of drug and metabolites. Functions of the nephron. There are three functions here. Filtration by the glomereulus. Secretion in the proximal tubules and reabsorption in the distal tubules