Function of the Kidneys Nephrology Fernando Vega, M.D. Seattle Healing Arts Center Remove Wastes Regulate Blood Pressure Regulate Blood Volume Regulates Electrolytes Converts Vitamin D to active form Produces Erythropoetin Symtpms of Kidney Disease Feeling Generally Sick Fluid Retention Anemia Some causes of Kidney Disease Diabetes Hypertension Glomerulonephritis Lupus Pyelonephritis Toxicities Kidney Picture Kidney and Nephron Fermamdo Vega, M.D. 1
Kidney and Nephrons Nephron Picture Structure and Function of the Kidney The functional unit of the kidney is the nephron The major functions of the kidney are to maintain extracelular fluids, to eliminate wastes resulting from normal metabolism, and to excrete xenobiotics and their metabolites Mammalian kidneys have 10,000-1,000,0001,000,000 nephrons per kidney Structure and Function of the Kidney (cont) The glomerulus yields an ultrafiltrate of plasma that represents 20% of the renal blood flow, ie. 2-3% of cardiac output Endothelial surface is negatively charged and contains fenestrae The glomerular basement membrane is sandwiched between the epithelial cells and contains anionic sailoglycoproteins, glycoproteins and collagen IV The mesangium provides support The outer capsuleis Bowman s capsule Structure and Function of the Kidney (cont) The tubule resorbs greater than 99% of the glomerular filtrate The proximal tubule has extensive resorption and selective secretion (convoluted -S1 and S2, straight -S3) Thin loop of Henle - resorption of fluids Distal tubule - resorption of fluids and acid-base balance Collecting duct - resorption of fluids, antidiuretic hormone and acid-base balance Structure and Function of the Kidney (cont) Produces erythropoietin, which regulates RBC production Hydroxylates 25-OH-cholecalciferol (vitamin D metabolite), to promote bone resorption and calcium and phosphorus absorption from the gut Releases renin to regulate the peripheral renin- angiotensin-aldosterone aldosterone system (juctaglomerular apparatus) Fermamdo Vega, M.D. 2
Assessment of Kidney Function: Urinalysis Proteinuria - indicates glomerular damage Glycosuria - indicates tubular damage Urine volume and osmolarity ph Enzymes - indicates tubular damage Microscopic examination - casts, crystals, bacteria, etc. Assessment of Kidney Function: Blood Chemistries Blood urea nitrogen (BUN) Creatinine Electrolytes -Ca, Mg, K, P Glomerular filtration rate - determines the clearance of inulin Renal clearance - measures the clearance of p- aminohippuric acid by filtration and secretion Assessment of Kidney Function: Morphologic Evaluation Water regulation in the kidney Ultrasound CT scans MRI/MRA IVP Biopsy The loop of Henle The descending limb of the loop of Henle is permeable to water The ascending limb is impermeable. Na + and Cl - ions are actively transported out of the ascending limb and passively move into the descending limb. This creates a concentration gradient across the medulla. There is a lower ion concentration gradient at the top of the ascending limb and a much higher ion concentration gradient at the bottom. Fermamdo Vega, M.D. 3
The Role of ADH The water potential of the tissue fluid in the medulla is always more negative than that of the filtrate in the collecting duct. Whether the water actually leaves the collecting duct (by osmosis) is determined by the hormone ADH (anti-diuretic hormone) Osmoreceptors in the hypothalamus detect the low levels of water,so the hypothalamus sends an impulse to the pituitary gland which releases ADH into the bloodstream. ADH makes the wall of the collecting duct more permeable to water. Therefore, when ADH is present more water is reabsorbed and less is excreted. Infections Stones Glomerular Diseases Diabetic Kidneys Hypertensive Kidneys Tubular Diseases Trauma kindneys Congenital Diseases Neoplastic Diseases Acid-Base Problems Toxicities Renal Failure Infections Childhood, reflux, VCU Pyelonephritis Stones nephrolithiasis Type of Pain Symptoms Signs Diagnosis, pain strainer Types of stones Treatment Fermamdo Vega, M.D. 4
Glomerular Diseases Damage to the Glomerulus the filter Can be caused by Diabetes Hypertension Autoimmune Diseases Toxins Diagnostic Clues Protein Blood Nephron pix Bowman s Capsule Bowman s Capsules and Tubules Tubular Diseases] Beta lactam antibiotics NSAIDs Reflux, obstruction, radiation Infections Toxins (heavy metals) Vascular Nephron Rash, fever, eosinophillia Fermamdo Vega, M.D. 5
Trauma kindneys Direct injury Rhabdomyolysis Congenital Diseases Polycystic Kidneys Extra kidney Solitary kidney Neoplastic Diseases Willm s Tumor Renal Cell carcinoma Acid-Base Problems Diuretic use vs CHF Respiratory Metabolic Blood Gas Equation Renal Failure Caused by all the above Treatment to preserve renal function Maintain metabolic balance Hyperkalemia, acidosis Hyperphosphatemia Hypermagnasemia Anemia acute renal failure: definition ARF is an abrupt decline in glomerular and tubular function, resulting in the failure of the kidneys to excrete nitrogenous waste products and to maintain fluid and electrolyte homeostasis. Fermamdo Vega, M.D. 6
Azotemia is a consistent feature of acute renal failure (ARF), oliguria is not. anuria ::: urine output < 0.5 ml/kg/h acute renal failure: common clinical features azotemia hypervolemia electrolytes abnormalities: K+ phosphate Na+ calcium metabolic acidosis hypertension oliguria - anuria Polycystic Kidney Disease Wilms Tumor Ways To Check Kidney Health Urine Tests Blood Tests Ultrasound Kidney Biopsy Fermamdo Vega, M.D. 7
Treatment Options Transplanted Kidney Transplant Dialysis Hemodialysis i Peritoneal Dialysis No treatment Peritoneal Dialysis Hemodialysis Kidney Specialists Internist Endocrinologist Nephrologists Transplant Surgeon Dialysis Specialist Fermamdo Vega, M.D. 8