Patho 2 test 2: The Renal System
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Questions and Answers

Which of the following is NOT a function of the kidney?

  • Regulation of blood sugar levels
  • Production of hormones
  • Regulation of body fluid volume and osmolality
  • Storage of dietary nutrients (correct)

    • What is the site where the renal artery, nerves, and renal vein enter/exit the kidney?

  • Renal Cortex
  • Renal Papilla
  • Renal Medulla
  • Hilum (correct)

    • What is the name of the process by which the kidney synthesizes glucose from amino acids?

  • Electrolyte regulation
  • Glycolysis
  • Gluconeogenesis (correct)
  • Glycogenesis

    • What is the name of the hormone produced by the kidney that stimulates red blood cell production?

    <p>Erythropoietin</p> Signup and view all the answers

    What is the purpose of the renal papilla?

    <p>To express urine into the urinary collection space</p> Signup and view all the answers

    What is the region between the renal pyramids composed of?

    <p>Renal Columns</p> Signup and view all the answers

    What percentage of cardiac output does the kidney receive?

    <p>25%</p> Signup and view all the answers

    What is the order of blood flow through the kidney?

    <p>Afferent arteriole &gt; glomerulus &gt; efferent arteriole &gt; peritubular capillaries</p> Signup and view all the answers

    What is the function of peritubular capillaries?

    <p>Reabsorption of fluid and solutes</p> Signup and view all the answers

    How many nephrons are present in each kidney?

    <p>1,000,000</p> Signup and view all the answers

    What happens if nephrons are lost?

    <p>The remaining nephrons compensate for the loss</p> Signup and view all the answers

    What is the primary function of tubular secretion in the kidney?

    <p>Eliminating protein-bound substances and toxins</p> Signup and view all the answers

    What is the primary cause of chronic kidney disease?

    <p>Systemic diseases such as hypertension and diabetes</p> Signup and view all the answers

    What is the main difference between acute kidney injury and chronic kidney disease?

    <p>Duration of the disease process</p> Signup and view all the answers

    What is the primary cause of post-renal acute kidney injury?

    <p>Obstruction of the urinary tract</p> Signup and view all the answers

    What is the term for the final stage of chronic kidney disease, where dialysis is necessary?

    <p>End-stage renal disease</p> Signup and view all the answers

    What is the primary mechanism by which NSAIDs can cause acute kidney injury?

    <p>Blocking the synthesis of prostaglandins</p> Signup and view all the answers

    What is the term for the classification of kidney disease based on the location of the damage?

    <p>Location</p> Signup and view all the answers

    What is the primary mechanism by which inadequate renal blood flow can lead to acute kidney injury?

    <p>Decreased renal blood flow leading to ischemia</p> Signup and view all the answers

    What happens to the renal blood flow and GFR when there is high arterial blood pressure?

    <p>Decrease in renal blood flow and GFR</p> Signup and view all the answers

    What is the result of vasoconstriction of the efferent arteriole?

    <p>Increase in GFR</p> Signup and view all the answers

    What is the purpose of using creatinine in measuring GFR?

    <p>Because creatinine is freely filtered in the glomerulus but not reabsorbed in the tubules</p> Signup and view all the answers

    What is the significance of 'transport maximum' in tubular reabsorption?

    <p>The tubules reach a point where they can no longer reabsorb any faster</p> Signup and view all the answers

    What is the result of dilation of the afferent arteriole?

    <p>Increase in GFR</p> Signup and view all the answers

    Why do patients with severe hyperglycemia have glucose in their urine?

    <p>Because the tubules reach a point where they can no longer reabsorb glucose</p> Signup and view all the answers

    What is the order of the tubular pathway?

    <p>Proximal tubule, loop of Henle, distal convoluted tubule, collecting duct</p> Signup and view all the answers

    What is the result of constriction of the afferent arteriole?

    <p>Decrease in GFR</p> Signup and view all the answers

    What is the significance of macula densa in the regulation of GFR?

    <p>It senses an increase in fluid/solute in the distal tubule and constricts the afferent arteriole</p> Signup and view all the answers

    What is the effect of dilation of the efferent arteriole on GFR?

    <p>Decrease in GFR</p> Signup and view all the answers

    What is the primary function of the glomerular capillaries?

    <p>To filter plasma into Bowman's capsule</p> Signup and view all the answers

    What is the main difference between cortical and juxtamedullary nephrons?

    <p>Juxtamedullary nephrons have shorter loops of Henle</p> Signup and view all the answers

    What is the function of the visceral epithelium in the glomerulus?

    <p>To allow filtrate to flow through filtration slits</p> Signup and view all the answers

    What is the purpose of the juxtaglomerular apparatus?

    <p>To regulate renal blood flow</p> Signup and view all the answers

    What is the significance of the presence of large proteins like albumin in a urinalysis?

    <p>It indicates glomerular damage</p> Signup and view all the answers

    What is the main function of the peritubular capillaries?

    <p>To reabsorb sodium and water from the filtrate</p> Signup and view all the answers

    What is the role of the basement membrane in the glomerulus?

    <p>To act as a charge barrier for negatively charged plasma proteins</p> Signup and view all the answers

    What is the primary driving force for filtration in the nephron?

    <p>Mechanical energy from systole creating a pressure wave in the afferent and efferent arterioles</p> Signup and view all the answers

    What type of pressure is responsible for keeping too much fluid from filtering out through a semipermeable membrane?

    <p>Oncotic pressure</p> Signup and view all the answers

    What is the amount of excretion determined by in the nephron?

    <p>The amount filtered + the amount secreted - the amount reabsorbed</p> Signup and view all the answers

    In advanced cirrhosis, what is the primary factor contributing to increased fluid filtration into Bowman's space?

    <p>Increased hydrostatic pressure from portal hypertension</p> Signup and view all the answers

    What is the function of the macula densa in the juxtaglomerular apparatus?

    <p>To monitor the filtrate composition</p> Signup and view all the answers

    What is the purpose of the glomerular endothelium in the glomerulus?

    <p>To make it highly permeable to water and small molecules</p> Signup and view all the answers

    What is the normal glomerular filtration rate (GFR) in mL/min?

    <p>125 mL/min</p> Signup and view all the answers

    What is the primary mechanism by which the kidneys autoregulate renal blood flow and maintain a constant GFR?

    <p>Myogenic autoregulation</p> Signup and view all the answers

    What is the effect of increased systemic blood pressure on GFR?

    <p>Increased GFR</p> Signup and view all the answers

    What is the primary function of oncotic pressure in the nephron?

    <p>To decrease fluid filtration into Bowman's space</p> Signup and view all the answers

    What is the effect of decreased systemic blood pressure on GFR?

    <p>Decreased GFR</p> Signup and view all the answers

    What is the primary mechanism by which the kidneys maintain a constant GFR despite changes in systemic blood pressure?

    <p>Autoregulation of renal blood flow</p> Signup and view all the answers

    What is the primary determinant of the amount of filtration surface area available in the nephron?

    <p>Amount of functional nephrons</p> Signup and view all the answers

    What is the primary mechanism by which hypertension leads to renal failure in hypertensive nephropathy?

    <p>Microvascular damage from constant exposure to high systemic blood pressure</p> Signup and view all the answers

    Which of the following is a complication of uncontrolled diabetes that contributes to the development of diabetic nephropathy?

    <p>Hypertension</p> Signup and view all the answers

    What is the typical percentage of renal function at which dialysis is usually needed?

    <p>10% of normal</p> Signup and view all the answers

    Which of the following is a characteristic of autosomal recessive polycystic kidney disease?

    <p>Bilateral symmetrical enlargement of kidneys</p> Signup and view all the answers

    What is the primary function of the peritoneal membrane in peritoneal dialysis?

    <p>To filter undesired substances from the blood</p> Signup and view all the answers

    Which of the following is a common feature of autosomal dominant polycystic kidney disease?

    <p>All of the above</p> Signup and view all the answers

    What is the primary mechanism by which the kidneys adapt to chronic insults and maintain normal renal function?

    <p>Compensatory hypertrophy of remaining nephrons</p> Signup and view all the answers

    What is the primary site of damage in diabetic nephropathy?

    <p>Glomerular capillaries</p> Signup and view all the answers

    What is the primary advantage of peritoneal dialysis over hemodialysis?

    <p>Less invasive procedure</p> Signup and view all the answers

    Which of the following is a common complication of autosomal recessive polycystic kidney disease?

    <p>All of the above</p> Signup and view all the answers

    Which of the following is a characteristic of Nephritic Syndrome?

    <p>Inflammatory cells accumulating in the mesangium</p> Signup and view all the answers

    What is the primary mechanism of glomerular damage in Nephritic Syndrome?

    <p>Antigen deposition leading to damage to the endothelial cells</p> Signup and view all the answers

    What is the primary cause of hypertension in Glomerular Disease?

    <p>Volume overload due to sodium retention</p> Signup and view all the answers

    What is the primary distinguishing feature between Nephrotic and Nephritic Syndromes?

    <p>Level of proteinuria</p> Signup and view all the answers

    What is the primary consequence of glomerular damage leading to 'holes' in the glomerular basement membrane?

    <p>Hematuria</p> Signup and view all the answers

    What is the primary factor that determines which syndrome a patient with glomerular damage will manifest?

    <p>Amount and type of damage</p> Signup and view all the answers

    What percentage of patients with Minimal Change Glomerulonephritis recover completely?

    <p>25%</p> Signup and view all the answers

    What is the primary mechanism by which the Juxtaglomerular Apparatus responds to low GFR?

    <p>Increase renin &gt; RAAS &gt; inappropriate increase in systemic BP</p> Signup and view all the answers

    What is the term for the glomerular disease that is characterized by a sudden appearance of proteinuria and edema?

    <p>Minimal Change Glomerulonephritis</p> Signup and view all the answers

    What is the primary cause of nephrotic syndrome?

    <p>Damage to the glomerular basement membrane/podocytes</p> Signup and view all the answers

    What is the primary function of the proximal tubule?

    <p>Reabsorption of nearly every substance that gets filtered in the glomerulus</p> Signup and view all the answers

    What is the characteristic feature of minimal change nephropathy?

    <p>Loss of foot processes in podocytes</p> Signup and view all the answers

    What is the term for the mechanism by which the Loop of Henle concentrates urine?

    <p>Countercurrent mechanism</p> Signup and view all the answers

    What is the term for the process by which tubular epithelial cells reabsorb substances from the filtrate?

    <p>Active transport</p> Signup and view all the answers

    What is the primary difference between nephritic and nephrotic syndrome?

    <p>Nephritic syndrome is characterized by hematuria and hypertension, while nephrotic syndrome is characterized by proteinuria and hypoalbuminemia</p> Signup and view all the answers

    What is the primary mechanism of acute glomerulonephritis?

    <p>Immune complex deposition in the glomeruli</p> Signup and view all the answers

    What is the term for the disease that is characterized by significant fibrous scar tissue, hypercellularity, and obliteration of the glomerular capillaries?

    <p>Chronic Glomerulonephritis</p> Signup and view all the answers

    What is the primary characteristic of post-streptococcal glomerulonephritis?

    <p>Cross-reactivity of antibodies to streptococcal antigens</p> Signup and view all the answers

    What is the most common cause of chronic renal failure?

    <p>Diabetic Nephropathy</p> Signup and view all the answers

    What is the term for the cells that connect the proximal tubule to the glomerulus?

    <p>Podocytes</p> Signup and view all the answers

    What is the primary difference between acute and chronic glomerulonephritis?

    <p>Acute glomerulonephritis is reversible, while chronic glomerulonephritis is irreversible</p> Signup and view all the answers

    What is the primary function of the glomerulus?

    <p>Filtration of the blood</p> Signup and view all the answers

    What is the term for the process by which the kidneys concentrate urine?

    <p>Urine concentration</p> Signup and view all the answers

    What is the term for the disease that is characterized by uniform and diffuse effacement of podocytes?

    <p>Minimal Change Glomerulonephritis</p> Signup and view all the answers

    What is the primary mechanism of proteinuria in nephrotic syndrome?

    <p>Increased permeability of the glomerular capillary wall</p> Signup and view all the answers

    What is the primary cause of hyperlipidemia in nephrotic syndrome?

    <p>Increased synthesis of lipids in the liver</p> Signup and view all the answers

    What is the typical duration between the original infection and the onset of symptoms in post-strep glomerulonephritis?

    <p>7-10 days</p> Signup and view all the answers

    What is the characteristic pattern of antibody deposition in Goodpasture's syndrome?

    <p>Linear pattern</p> Signup and view all the answers

    What is the primary mechanism of damage in Type II Rapidly Progressive Glomerulonephritis (RPGN)?

    <p>Immune complex deposition</p> Signup and view all the answers

    What is the characteristic feature of the glomerular injury in Membranous Glomerulonephritis?

    <p>Immune complex deposition and complement activation</p> Signup and view all the answers

    What is the most common type of Rapidly Progressive Glomerulonephritis (RPGN)?

    <p>Type III</p> Signup and view all the answers

    What is the typical rate of decline in glomerular filtration rate (GFR) in untreated Rapidly Progressive Glomerulonephritis (RPGN)?

    <p>50% per 3 months</p> Signup and view all the answers

    What is the hallmark of Goodpasture's syndrome?

    <p>Both alveolar and glomerular involvement</p> Signup and view all the answers

    What is the typical presentation of Rapidly Progressive Glomerulonephritis (RPGN)?

    <p>Nephritic syndrome</p> Signup and view all the answers

    What is the primary function of the ascending limb in the loop of Henle?

    <p>Reabsorption of sodium but not water</p> Signup and view all the answers

    Which of the following is a function of anti-diuretic hormone (ADH)?

    <p>Promoting water retention at the level of the renal distal tubule</p> Signup and view all the answers

    What is the effect of loop diuretics on the nephron?

    <p>Inhibition of sodium reabsorption in the ascending limb of the loop of Henle</p> Signup and view all the answers

    What is the primary function of aldosterone in the distal tubule?

    <p>Regulation of sodium and potassium levels</p> Signup and view all the answers

    What is the effect of thiazide diuretics on the nephron?

    <p>Inhibition of sodium reabsorption in the distal tubule</p> Signup and view all the answers

    What is the primary cause of obstructive uropathy?

    <p>Complete or partial blockage of the urinary system</p> Signup and view all the answers

    What is the primary function of the collecting duct?

    <p>Fine-tuning of sodium and water reabsorption</p> Signup and view all the answers

    What is the effect of potassium-sparing diuretics on the nephron?

    <p>Inhibition of potassium secretion in the distal tubule</p> Signup and view all the answers

    What is the primary function of the descending limb of the loop of Henle?

    <p>Reabsorption of water but not sodium</p> Signup and view all the answers

    What is the result of constriction of the efferent arteriole?

    <p>Decreased GFR</p> Signup and view all the answers

    What triggers the growth of new tissue in the ureters in obstructive uropathy?

    <p>Collecting system dilation</p> Signup and view all the answers

    What is the primary cause of Acute Tubular Necrosis (ATN)?

    <p>Ischemia or nephrotoxicity</p> Signup and view all the answers

    What is the result of elevated hydrostatic pressure in Bowman's Capsule?

    <p>Decreased GFR</p> Signup and view all the answers

    What is the timeline for glomerular damage in obstructive uropathy?

    <p>4 weeks</p> Signup and view all the answers

    What is the effect of fibrosis in the tubules and interstitial space?

    <p>Tissue damage</p> Signup and view all the answers

    What is the common symptom of glomerular disease in obstructive uropathy?

    <p>Edema</p> Signup and view all the answers

    What is the primary cause of Ischemic Acute Tubular Necrosis (ATN)?

    <p>Renal hypoperfusion</p> Signup and view all the answers

    What is the hallmark of the Initiation Phase of ATN?

    <p>Drastic decrease in GFR coupled with a big jump in BUN/creatinine levels</p> Signup and view all the answers

    What is the most common indication for Hemodialysis in the acute setting of ATN?

    <p>All of the above</p> Signup and view all the answers

    What is the primary reason why we care about ATN?

    <p>It is associated with a higher chance of death</p> Signup and view all the answers

    What is the result of ischemia in the tubular cells in ATN?

    <p>They stop producing their own vasodilators</p> Signup and view all the answers

    What is the characteristic appearance of urine in ATN?

    <p>Muddy</p> Signup and view all the answers

    What is the primary mechanism of Nephrotoxic ATN?

    <p>Exposure to toxic agents</p> Signup and view all the answers

    What is the final stage of the phases of ATN?

    <p>Recovery Phase</p> Signup and view all the answers

    What is the primary function of aquaporins in the tubules?

    <p>To form a 'hole' in the cellular membrane to allow water through</p> Signup and view all the answers

    What is the main organ involved in osmoregulation, along with the kidneys?

    <p>Brain</p> Signup and view all the answers

    What is the primary mechanism by which vasopressin (ADH) regulates water reabsorption in the collecting ducts?

    <p>By stimulating the release of aquaporins from vesicles in the collecting duct cells</p> Signup and view all the answers

    What is the normal range of plasma osmolality?

    <p>280-300 mOsm/kg</p> Signup and view all the answers

    What is the primary function of the proximal tubules in the nephron?

    <p>To reabsorb water and electrolytes into the bloodstream</p> Signup and view all the answers

    What is the effect of vasopressin (ADH) on the collecting ducts?

    <p>It increases water reabsorption into the bloodstream</p> Signup and view all the answers

    What is the primary function of the descending limb of the loop of Henle?

    <p>To concentrate the urine by removing excess water</p> Signup and view all the answers

    What is the primary effect of hypernatremia on the body's cells?

    <p>Cellular shrinkage and altered mental status</p> Signup and view all the answers

    What is the term for the concentration of solutes in body fluids?

    <p>Osmolality</p> Signup and view all the answers

    What is the most common cause of hypovolemic hypernatremia?

    <p>Dehydration due to hypovolemia</p> Signup and view all the answers

    Why is phosphorus essential for normal body function?

    <p>It is essential for ATP production</p> Signup and view all the answers

    What is the term for the loss of free water leading to hypernatremia?

    <p>Diabetes insipidus</p> Signup and view all the answers

    What is the consequence of rapid changes in plasma osmolality on the brain?

    <p>Cerebral damage</p> Signup and view all the answers

    What is the primary mechanism by which sodium homeostasis is maintained?

    <p>Renal function and reabsorption of sodium</p> Signup and view all the answers

    What is the direct effect of decreased body fluid osmolarity on vasopressin secretion?

    <p>Decreased vasopressin secretion</p> Signup and view all the answers

    What is the primary mechanism by which decreased plasma volume leads to increased vasopressin secretion?

    <p>Decreased atrial and carotid baroreceptors</p> Signup and view all the answers

    In diabetes insipidus, what is the primary defect that leads to increased water excretion?

    <p>Decreased vasopressin secretion or faulty response to vasopressin</p> Signup and view all the answers

    What is the primary consequence of SIADH (Syndrome of Inappropriate ADH) on plasma osmolarity?

    <p>Hypo-osmolar plasma</p> Signup and view all the answers

    What is the mechanism by which sodium reabsorption in the kidney generates an electrochemical gradient?

    <p>Active transport of sodium through Na+/K+ ATPase</p> Signup and view all the answers

    What is the primary function of the 'conveyor belt' mechanism in sodium reabsorption?

    <p>Passive diffusion of sodium into the epithelial cells</p> Signup and view all the answers

    What is the effect of decreased vasopressin secretion on water reabsorption in the collecting ducts?

    <p>Decreased water reabsorption</p> Signup and view all the answers

    What is the primary cause of hypernatremia in diabetes insipidus?

    <p>Inadequate water reabsorption</p> Signup and view all the answers

    What is the primary consequence of SIADH on urine osmolarity?

    <p>Increased urine osmolarity</p> Signup and view all the answers

    What is the primary mechanism by which the kidneys respond to changes in plasma osmolarity?

    <p>Vasopressin secretion and regulation</p> Signup and view all the answers

    What is the primary function of the juxtaglomerular apparatus?

    <p>Regulation of blood pressure through renin release</p> Signup and view all the answers

    What happens when potassium levels are high in the adrenal gland?

    <p>Aldosterone release is increased, leading to potassium excretion</p> Signup and view all the answers

    What is the primary mechanism of potassium regulation in the distal tubule and collecting duct?

    <p>Aldosterone stimulates Na+/K+ ATPase, leading to potassium secretion</p> Signup and view all the answers

    What is the main source of potassium gain in the body?

    <p>Diet</p> Signup and view all the answers

    What is the effect of massive cellular breakdown on potassium levels?

    <p>Hyperkalemia</p> Signup and view all the answers

    What is the role of the macula densa in the juxtaglomerular apparatus?

    <p>Chemoreceptors that sense changes in sodium concentration of the filtrate</p> Signup and view all the answers

    What is the primary determinant of resting membrane potential?

    <p>Potassium levels</p> Signup and view all the answers

    What is the function of Na+/K+ ATPase in potassium regulation?

    <p>Pumps sodium out of cells and potassium into cells</p> Signup and view all the answers

    What is the primary cause of hyperkalemia in a patient with acute renal failure?

    <p>Decreased filtration of potassium at the glomerulus</p> Signup and view all the answers

    What is the effect of acidic pH on potassium levels?

    <p>Increased potassium levels due to increased cell membrane permeability</p> Signup and view all the answers

    What is the primary mechanism of potassium removal in the treatment of hyperkalemia?

    <p>Increased potassium binding in the gut</p> Signup and view all the answers

    What is the effect of thiazide diuretics on potassium levels?

    <p>Decreased potassium levels due to increased potassium secretion</p> Signup and view all the answers

    What is the primary cause of hypokalemia in a patient with diarrhea?

    <p>Excess potassium loss in the stool</p> Signup and view all the answers

    What is the effect of insulin on potassium levels?

    <p>Decreased potassium levels due to increased potassium uptake by cells</p> Signup and view all the answers

    What is the primary mechanism of action of calcium gluconate in the treatment of hyperkalemia?

    <p>Stabilizes the cardiac membrane</p> Signup and view all the answers

    What is the primary cause of hyperkalemia in a patient with hypoaldosteronism?

    <p>Decreased potassium excretion due to decreased aldosterone</p> Signup and view all the answers

    What is the effect of alkalosis on potassium levels?

    <p>Decreased potassium levels due to increased potassium uptake by cells</p> Signup and view all the answers

    What is the primary mechanism of action of IV sodium bicarbonate in the treatment of hyperkalemia?

    <p>Only beneficial in acidotic patients</p> Signup and view all the answers

    What is the primary mechanism by which the kidneys regulate serum pH?

    <p>By regulating the amount of H+ and HCO3 ions in the blood</p> Signup and view all the answers

    What happens to the bicarbonate ions in the tubule during renal compensation for acidosis?

    <p>They are reabsorbed into the bloodstream</p> Signup and view all the answers

    What is the effect of hyperventilation on serum pH?

    <p>It increases serum pH by reducing H+ ions</p> Signup and view all the answers

    What is the primary source of H+ ions in the body?

    <p>All of the above</p> Signup and view all the answers

    What is the role of the kidneys in maintaining acid-base homeostasis?

    <p>To maintain a balance of H+ and HCO3 ions in the blood</p> Signup and view all the answers

    What is the effect of alkalosis on the body?

    <p>It leads to an increase in HCO3- ions in the blood</p> Signup and view all the answers

    What is the role of the lungs in maintaining acid-base homeostasis?

    <p>To exhale CO2 and regulate the respiratory rate</p> Signup and view all the answers

    What is the effect of respiratory acidosis on the body?

    <p>It leads to a decrease in serum pH</p> Signup and view all the answers

    Study Notes

    The Renal System

    • The kidney is the main organ responsible for maintaining homeostasis, controlling the composition of body fluids and excretion of metabolic waste and foreign substances.
    • The kidney regulates body fluid volume, osmolality, and acid-base balance, and also produces hormones such as erythropoietin and activates vitamin D.

    Gross Anatomy of the Kidney

    • The kidney is a retroperitoneal organ located alongside the vertebral column at T12-L3.
    • The kidney is divided into the outer cortex and inner medulla, with the hilum being the point where the renal artery and nerves enter and the renal vein exits.
    • The ureter exits the kidney to drain urine into the bladder.

    Renal Perfusion

    • The kidney is one of the most well-perfused organs in the body, receiving 25% of cardiac output.
    • The right and left renal arteries branch off the abdominal aorta and enter the kidney through the hilum.
    • The blood flow through the kidney is divided into two capillary beds: glomerular and peritubular.

    The Nephron

    • The nephron is the functional unit of the kidney, with approximately 1 million nephrons per kidney.
    • The nephron is divided into the glomerulus, proximal tubule, loop of Henle, and distal tubule.
    • The nephron is responsible for filtering plasma, reabsorbing and secreting substances, and regulating the amount of substance excreted in the urine.

    Glomerular Filtration

    • Glomerular filtration is a passive process that occurs through the glomerular capillaries, driven by hydrostatic and osmotic pressures.
    • The filtration rate is influenced by the surface area available for filtration, membrane permeability, and net filtration pressure.
    • The glomerular filtration rate (GFR) is the volume of plasma filtered per unit time, with a normal rate of 125 mL/min.

    Autoregulation of Renal Blood Flow

    • The kidney can autoregulate blood flow in response to changes in systemic blood pressure, maintaining a constant GFR.
    • Autoregulation occurs through two mechanisms: myogenic autoregulation and feedback from the juxtaglomerular apparatus.

    Regulation of Renal Blood Flow and GFR

    • The kidney can regulate GFR by adjusting the diameter of the afferent and efferent arterioles.
    • The kidney can increase GFR by dilating the afferent arteriole and constricting the efferent arteriole, and decrease GFR by constricting the afferent arteriole and dilating the efferent arteriole.

    Clinical Correlations

    • Estimating GFR is an important indicator of kidney function.
    • Creatinine is a commonly used substance to estimate GFR, as it is freely filtered in the glomerulus but not reabsorbed in the tubules.
    • GFR can be influenced by age, gender, and muscle mass.

    Tubular Pathway Review

    • The tubular pathway consists of the proximal tubule, loop of Henle, and distal convoluted tubule.
    • Transport (reabsorption and secretion) occurs in every part of the tubule.
    • The proximal tubule is responsible for reabsorbing most of the filtered sodium, water, and other solutes.

    Tubular Reabsorption

    • Tubular reabsorption is the process of transporting substances from the tubular lumen back into the peritubular capillaries.
    • Transport can be active or passive.
    • The tubules have a transport maximum, beyond which they cannot reabsorb any more substances.

    Tubular Secretion

    • Tubular secretion is the process of transporting substances from the peritubular capillaries into the tubular lumen.
    • Important for disposing of drugs and drug metabolites, eliminating undesirable substances, removing excess potassium, and controlling pH.

    Pathophysiology of the Kidney

    • Each function of the kidney can be compromised, leading to various disorders.
    • The result of the compromised function will depend on the location, etiology, and chronicity of the damage.

    Classifying Renal Disease

    • Renal disease can be classified based on chronicity, location, and etiology.
    • Acute kidney injury (AKI) and chronic kidney disease (CKD) are two common classifications.

    Causes of Kidney Injury

    • Prerenal causes: inadequate renal blood flow, leading to decreased GFR.
    • Intrarenal causes: nephron damage, glomerulotubular diseases.
    • Postrenal causes: obstruction or structural defects blocking urine from draining.

    Chronic Kidney Disease

    • Slow, progressive loss of renal function and decrease in GFR.
    • Causes: systemic diseases, intrinsic kidney disease, and obstructive uropathies.
    • Defined in stages based on GFR and whether the patient is dialysis-dependent.

    End-Stage Renal Disease

    • Dialysis is needed to sustain life.
    • Can be caused by various diseases, including hypertension, diabetes, and autoimmune conditions.

    Hypertensive Nephropathy

    • Can affect both glomerular and peritubular capillaries.
    • Microvascular damage from constant exposure to high systemic blood pressure.
    • Leads to tissue fibrosis, ischemia, and small/fibrotic glomeruli.

    Diabetic Nephropathy

    • Hyperglycemia over time causes microvascular damage to renal arteries and direct glomerular damage.
    • Leads to decreased GFR, proteinuria, and eventually end-stage renal disease.

    CKD and Renal Adaptation

    • The kidney has a remarkable ability to adapt to chronic insults, allowing for preservation of renal function.
    • However, eventually, the kidneys can no longer compensate, and dialysis may be needed.

    Dialysis

    • Hemodialysis and peritoneal dialysis are two common methods of dialysis.
    • Hemodialysis uses an external glomerular membrane and tubule system to filter undesired substances, remove volume, and maintain a normal balance of solutes.
    • Peritoneal dialysis uses the peritoneal membrane to filter plasma and remove waste products.

    Glomerular Diseases

    • Impairment of glomerular filtering properties leads to decreased GFR
    • Can be primary or secondary
    • Molecules like blood cells and Albumin can pass into urine and be excreted

    Nephrotic and Nephritic Syndromes

    • Syndromes are constellations of signs and symptoms with multiple causes
    • Depend on amount and type of damage
    • Not all glomerular damage causes syndromes, and some diseases can cause both

    Nephritic Syndrome

    • Inflammatory cells accumulate in the mesangium
    • Caused by antigen deposition, leading to damage to endothelial cells
    • Damage thins the glomerular basement membrane and podocytes, allowing proteins and red cells through into the filtrate
    • Signs: Hematuria, Hypertension, Oliguria, Edema, RBC casts and red blood cells, Protein (to a lesser degree), White blood cells
    • Associated with: Infection-related Glomerulonephritis, Rapidly Progressive Glomerulonephritis (RPGN)

    Nephrotic Syndrome

    • Damage to the glomerular basement membrane/podocytes leads to loss of negative charge and increased permeability
    • Plasma proteins are lost, decreasing plasma oncotic pressure
    • Can be primary or secondary
    • Diabetic nephropathy is the most common cause of secondary, HTN is the second most common
    • Signs: Proteinuria (>3.5 gm/day), Hypoalbuminemia, Ascites and peripheral edema, Hyperlipidemia, Lipiduria

    Glomerulopathy

    • Disease of the glomeruli
    • Group of autoimmune disorders involving inflammation of glomerular capillaries
    • Present with various combinations of hematuria, proteinuria, oliguria, hypertension

    Types of Glomerulonephritis

    • Acute Glomerulonephritis: Primary glomerular injury from immunologic responses, ischemia, drugs, toxins, infection
    • Post-Streptococcal Glomerulonephritis: One of the causes of Acute Glomerulonephritis
    • Rapidly Progressive Glomerulonephritis (RPGN): Autoimmune, can be secondary to post-strep GN or unknown causes, always autoimmune
    • Membranous Glomerulonephritis: One of the most common causes of Nephrotic syndrome in adults
    • Minimal Change Glomerulonephritis: One of the most common causes of Nephrotic syndrome in children
    • Chronic Glomerulonephritis: Slow progression, can be asymptomatic, often an incidental finding on a routine physical
    • Secondary Glomerulonephritis: Most common cause of chronic renal failure, often due to DM, HTN, or both

    Path of Damage in Obstructive Uropathy

    • Collecting system dilates, triggering smooth muscle hypertrophy in the ureters
    • Flow slows down or stops, decreasing GFR and elevating hydrostatic pressure in Bowman's Capsule
    • Collecting system stretches and enlarges, damaging tubular cells and leading to fibrosis
    • Fibrosis signals tissue repair, bringing in cytokines, proteases, and causing cell damage and apoptosis
    • Irreversible tubular damage can result

    General Timeline

    • < 1 week: Hydronephrosis and hydroureter are present
    • ~ 1 week: Distal tubules show evidence of damage
    • ~ 2 weeks: Proximal tubule damage
    • ~ 4 weeks: Glomeruli are damaged
    • > 4 weeks: Cell death begins to occur
    • > 3 months: Doubtful that any function can be regained

    Clinical Correlation: Signs/Symptoms

    • Flank pain
    • Fever
    • Nausea/vomiting
    • Hematuria (especially in intrinsic causes like stones)
    • Symptoms of glomerular disease like edema if the obstruction persists

    Acute Tubular Necrosis (ATN)

    Ischemic ATN

    • Hypoperfusion leads to hypoxia, causing cell death
    • Cellular debris of dead cells (casts) fall into the tubules, causing physical obstruction
    • Obstruction lowers GFR more due to initial hypoperfusion
    • Ischemia in tubular cells stops production of vasodilators, leading to more vasoconstriction
    • Tubules are affected in an interrupted and "patchy" way
    • Debris from dead tubular cells can be seen as granular "casts" in the urine, which looks "muddy"

    Etiology of Ischemic ATN

    • Renal hypoperfusion
    • Tubule cell injury
    • Tubule cell death
    • Cellular debris → Tubular occlusion
    • Lowered GFR
    • More vasoconstriction

    Nephrotoxic ATN

    • Occurs due to exposure to toxic agents
    • Nephrotoxic drugs (e.g., antibiotics, chemotherapy, contrast dye)
    • Bacterial toxins
    • Large amounts of circulating hemoglobin or myoglobin
    • Toxic non-drug substances (e.g., antifreeze, mercury, arsenic)

    Phases of ATN

    Initiation Phase

    • Drastic decrease in GFR
    • Big "jump" in BUN/creatinine levels
    • Clinically, suspect ATN if creatinine rises sharply in the first 24-48 hours

    Maintenance Phase

    • GFR remains low
    • BUN/Cr continue to rise
    • Oliguria or anuria
    • Hemodialysis may become necessary

    Clinical Correlation: Indications for HD in the Acute Setting

    • Volume overload
    • Hyperkalemia
    • Severe acid-base disturbances
    • Uremic encephalopathy
    • Toxin/medication removal

    Recovery Phase

    • Tubule cells begin regenerating
    • Tubular function can slowly recover
    • First indication is usually increasing urine output and then gradual decrease in BUN/Cr
    • Similar to obstruction, there can be "post-ATN diuresis" due to dilute urine from regenerating tubular cells
    • Recovery can be complete, partial, or never, and some patients end up with life-long ESRD and remain dialysis-dependent

    Clinical Correlation: Why should we care about ATN?

    • 22.7% incidence of AKI in hospitalizations
    • AKI is associated with a more than fourfold increased likelihood of death
    • ATN is the most common cause of AKI

    Body Fluid Compartments

    • Total body fluid is divided into ⅔ intracellular fluid (fluid within cells) and ⅓ extracellular fluid
    • Extracellular fluid is further divided into ¾ interstitial fluid (between cells) and ¼ plasma fluid (in capillaries)
    • Plasma fluid is responsible for transporting materials between cells and capillaries through interstitial fluid

    Osmoregulation

    • Osmolality is the concentration of solutes in body fluids, critically important for organ function
    • Normal plasma osmolality is maintained by:
      • Excreting excess water
      • Replenishing lost water
      • Maintaining normal amounts of solutes in the body
    • The brain and kidneys are the main organs involved in osmoregulation

    Maintaining Body Water

    • Water reabsorption occurs passively through osmosis, but is ultimately determined by the movement of sodium and the presence of aquaporins
    • Sodium is the most abundant extracellular cation
    • Aquaporins are surface proteins that form "holes" in the cellular membrane, allowing water to pass through
    • Aquaporins are present throughout the tubules, with high concentrations in the proximal tubules and descending limb of the loop of Henle
    • No aquaporins are present in the collecting ducts unless vasopressin (ADH) is present, making water reabsorption dependent on ADH

    Vasopressin/ADH Control of Water Reabsorption

    • Vasopressin is released by the posterior pituitary in response to elevated osmolarity and stimulates water reabsorption in the collecting ducts
    • Decreased osmolarity inhibits vasopressin secretion, leading to decreased water reabsorption
    • Baroreceptors in the atria and carotid arteries also affect vasopressin production, with low blood pressure stimulating release of vasopressin

    Disorders of Vasopressin

    • Diabetes Insipidus (DI):
      • Central DI: brain produces too little ADH, often due to pituitary or hypothalamic damage
      • Nephrogenic DI: kidneys don't respond to circulating ADH, often due to chronic lithium use or hypercalcemia
    • SIADH (Syndrome of Inappropriate ADH):
      • Body is unable to suppress ADH secretion, leading to excessive water reabsorption and hyponatremia
      • Caused by CNS issues, malignancy, or certain medications

    Sodium Homeostasis

    • Sodium reabsorption from tubule cells to interstitial fluid is almost always active transport
    • Active transport generates an electrochemical gradient, allowing for the reabsorption of other substances like glucose
    • Na+/K+ ATPase is the enzyme responsible for active sodium reabsorption

    Sodium Reabsorption

    • Sodium is actively pumped out of the tubule and back into the blood, allowing other substances to be reabsorbed
    • Energy is expended to "pull" sodium from the tubular lumen into the cell, creating an electrochemical gradient
    • Sodium is then actively transported out of the cell to maintain low intracellular Na+ concentrations

    Disorders of Sodium Regulation

    • Hypernatremia: too much sodium (Na >145 mg/dL), causing fluid to shift from intracellular fluid to extracellular fluid
    • Causes of hypernatremia:
      • Hypovolemic hypernatremia: dehydration, osmotic diuresis
      • Hypervolemic hypernatremia: excessive sodium intake, iatrogenic administration of normal saline
      • Diabetes Insipidus: loss of free water
    • Hyponatremia: too little sodium (Na <135 mg/dL), often caused by SIADH, heart failure, or liver disease

    Juxtaglomerular Apparatus

    • JG cells around the afferent arteriole are specialized smooth muscle cells that secrete renin and control blood flow into the glomerulus.
    • Mechanoreceptors in JG cells sense changes in the vessel diameter, and when blood pressure is low, they release more renin.
    • Macula densa, located in the distal convoluted tubule, senses changes in sodium concentration of the filtrate and signals to the JG cells to release more renin when sodium levels are low.

    Potassium Regulation

    • Potassium is the major intracellular cation, and its distribution is maintained by Na+/K+ ATPase pumps.
    • K+ sensors in the adrenal gland respond to changes in potassium levels, and high potassium levels stimulate the release of aldosterone, which promotes potassium excretion and sodium retention.
    • Low potassium levels lead to decreased aldosterone release, resulting in potassium retention and sodium excretion.
    • Normal intracellular potassium levels are crucial for maintaining resting membrane potential, and changes in potassium levels can affect muscle contraction and neuronal activity.

    Renal Regulation of Potassium

    • Bulk reabsorption of potassium occurs in the proximal tubule and the loop of Henle.
    • The distal tubule and collecting duct are responsible for regulating potassium levels in response to aldosterone.
    • Aldosterone stimulates the production of proteins that activate the Na+/K+ ATPase, leading to sodium reabsorption and potassium secretion.

    Factors Affecting Plasma K+

    • Factors that increase plasma potassium levels include:
      • Dietary intake
      • Cellular breakdown
      • Acidosis
    • Factors that decrease plasma potassium levels include:
      • Stool losses
      • Increased cellular uptake
      • Insulin and acid-base status

    Potassium and Serum pH

    • Potassium is an important buffer in the intracellular fluid.
    • When there is high plasma H+ (acidosis), H+ ions move into the cell, and potassium ions move out of the cell, leading to increased plasma potassium levels.
    • Alternatively, when there is high plasma pH (alkalosis), H+ ions move out of the cell, and potassium ions move into the cell, leading to decreased plasma potassium levels.

    Pathophysiology of Hyperkalemia

    • Hyperkalemia is typically defined as plasma potassium levels > 5.5 mmol/L.
    • Causes of hyperkalemia include:
      • Decreased renal excretion due to decreased filtration or secretion
      • Acute renal failure
      • Hypoaldosteronism
      • Medication effects
      • Cellular breakdown
    • Clinical correlations:
      • Treatment of hyperkalemia includes calcium gluconate, insulin + D50, Kayexalate, and IV sodium bicarbonate.
      • Patients with end-stage renal disease on hemodialysis must be mindful of dietary potassium intake.

    Pathophysiology of Hypokalemia

    • Hypokalemia is not as life-threatening as hyperkalemia.
    • Causes of hypokalemia include:
      • Excess urinary losses
      • Excess stool losses
      • Increased cellular uptake
      • Alkalosis
      • Pregnancy
    • Treatment of hypokalemia includes potassium replacement, either orally or intravenously.

    Renal Acid-Base Buffering

    • Acids tend to give up hydrogen ions, while bases combine with hydrogen ions to neutralize them.
    • The shape of a protein determines its action, and protein shape is dependent on pH.
    • Derangements in serum pH can lead to significant dysfunction throughout the body and ultimately death.

    Hydrogen Ion Buffering

    • The lungs and kidneys work together to maintain a balance of H+ and HCO3 ions to maintain normal pH.
    • Excess hydrogen in the blood is buffered by bicarbonate, which combines with hydrogen to form carbonic acid.
    • Not enough hydrogen in the blood leads to the dissociation of carbonic acid into hydrogen and bicarbonate ions.

    Acidosis and Alkalosis

    • Acidosis pushes the equation towards the left, forming more carbonic acid, while alkalosis pushes it towards the right, promoting the dissociation of carbonic acid into hydrogen and bicarbonate ions.
    • Respiratory compensation occurs quickly, while renal buffering takes more time.
    • The kidneys and lungs work together continuously to regulate serum H+ concentrations.

    Bicarbonate Reabsorption

    • Bicarbonate is freely filtered in the glomerulus and must be reabsorbed in the tubule.
    • The majority of bicarbonate reabsorption occurs in the proximal tubule.
    • Within a tubule cell, water and CO2 combine to form carbonic acid, which dissociates into bicarbonate and hydrogen ions.
    • H+ moves into the tubular lumen, and bicarbonate moves out of the cell and back into the plasma.

    Renal pH Control

    • To increase serum pH, the kidneys reabsorb more bicarbonate.
    • To decrease serum pH, the kidneys excrete more bicarbonate.

    Renal Compensation for Acidosis

    • If the plasma is too acidic, the kidneys reabsorb more bicarbonate, but the bloodstream still wants more.
    • This leads to the renal compensation for chronic respiratory acidosis.
    • Within a tubule cell, water and CO2 come together to form bicarbonate, which is reabsorbed.
    • H+ moves into the tubular lumen, where it binds to an anion, usually phosphate, and is excreted into the urine.

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    Day 1: The Renal System: Structure and Function & Overview of Renal Pathophysiology ppt Day 2: Glomerular & Tubular Disorders ppt Day 3: The Renal System: Osmoregulation Acid-base Homeostasis ppt

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