Renal Fx

• -bean shaped organ

  -retroperitoneally on either side of spinal column

  Anatomy & Physiology of Kidney
• -outer (cortex)

  -inner (medulla)


  2 regions
• controls RBC production

  Erythropoietin
• -response to decrease in blood flow

  -renin-angiotensin system

  -sodium balance

  Renin
• –the active form of Vitamin D

  1,25-dihydroxycholecalciferol
• -regulates blood pressure, fluid and electrolyte balance

  Prostaglandins
• -1 to 1.5 million nephrons

  -functional unit of kidney

  Nephron
• -cortical means greater than Juxtamedullary, cortex of kidney and outer region

  -Juxtamedullary means the rest Henle, inner region


  2 types of Nephron
• 1. Ascending loop of Henle
  2. Descending loop of Henle
  3. Proximal convoluted tubule
  4. Distal convoluted tubule
  5. collecting duct


  5 basic parts of Nephron
• capillary tuft surrounded by the expanded end of renal tubule known as Bowman’s capsule

  -blocks cells and large molecules but allows water, electrolytes and small molecules like glucose

  Glomerulus
• -branch of renal artery into the glomerulus

  -1200 ml/min TRBF

  Afferent Arterioles
• -carries blood from glomerulus

  Efferent Arterioles
• -blood vessel that surround the PCT and DCT

  Peritubular Capillaries
• -blood vessels located adjacent to ascending and descending loop of Henle

  Vasa Recta
• -receives the cells/protein free filtrate

  -reabsorbs the valuable subtances

  -passes waste products

  Proximal Convoluted Tubule
• -wherein substances are removed from the glomerular filtrate

  Tubular Reabsorption
• -transport the substances like glucose, animo acids, salts (PCT), chloride (ALOH), sodium (DCT)

  -concentration of the subtance being transported

  Active transport/obligatory reabsorption
• -eliminate waste products

  -body through H+ secretion

  Tubular Secretion
• -impermeable of water

  Ascending loop of henle
• concentrating portion freely permeable

  descending loop of henle
• -loops of henle

  -osmotic Gradient of the medulla by selective reabsorption

  Counter Current Mechanism
• -prevented by water impermeable walls of ascending loop while sodium and chloride


  As the ultrafiltrate passes through the Medullary Interstituim
• -almost reached the final composition of the urine

  -hormonal control

  Distal Convoluted Tubule
• -sodium reabsorption by DCT and potassium and hydrogen ion secretion

  -sodium retaining hormone

  Aldosterone
• -final site for either concentrating urine or diluting

  Collecting Duct
• -upper portion - reabsorbs sodium

  Aldosterone
• -increase water reabsorption

  -helps to control blood pressure

  -small amount of water urine

  ADH
• -filtration

  -Reabsorption

  -secretion


  3 Renal Function Tests
• -a timed urine collection to determine how each is cleared from bloodstream

  Clearance Tests
• 1. neither reabsorbed nor secreted
  2. a possible 24 hours of collection period
  3. consistency of plasma level
  4. substances availability to the body
  5. chemical analysis

  Factors to consider in the selection of clearance test substances
• -void first morning specimen

  -collected inti 24hrs container

  -last specimen collected in the first morning specimen on the next day

  -blood samples is also collected sometime within 24hr

  -urine is refrigerated

  -patient can drinks normal amount of fluid

  Urine Collector Procedure
• -natural and produced at a constant rate proportional to individual’s muscle mass

  -filtered easily and excreted only be the kidneys

  -easy and inexpensive to measure

  -only slightly secreted by the proximal tubule

  -normal values : male (85-125 mL/min) ; female (75-112 mL/min)

  Creatinine Clearance
• gold standard;alternative

  Inulin clearance;Creatinine clearance
• -urea: not a true measurement of filtration approximately 40% passively reabsorbed

  -radioisotope

  -B2-microglobulin

  -Sodium (125) iothalamate


  -Cystatin C

  Others glomerular filtration tests
• most sensitive test for early lost of renal function


  Tubular Reabsorption Tests or Concentration test
• -Fishberg Tests: deprived of fluids for 24 hr prior to measuring the SG

  -Mosenthal Test: compares volume and SG of day and night

  -Osmometry: measures osmolarity (colligative properties)


  Concentration Tests
• measure renal plasma flow that requires clearance of dye; most common exogenous and 600-700 mL/min

  Para-Aminohippuric Acid Test (PAH)
• dye proportional to renal tubular mass

  dose: 6mg of PSP, 1200 mL blood flow/min

  Phenol Sulfone Phthalein (PSP) Dye Test
• confirmatory of unilateral kidney disease


  Indigo Carmine Test
• 160-180 mg/dL

  Glucose Renal Threshold