Renal Disease

Question 1

What is the function of the kidney?

Answer 1

o Excretion waste products e.g. creatinine, urea, metabolites of xenobiotics (chemical constituents foreign to animal life – drugs, plants, food additives, industrial chemicals, & environment pollutants)
oMaintain water balance.
oMaintain Blood Pressure water & Na retention/excretion.
oMaintain cardiac function K excretion.
oMaintenance of pH excretes H+.

Question 2

What is a nephron?

Answer 2

microscopic structural & functional unit of kidney (1-1.5 million/kidney)

Question 3

What are the parts of the nephron?

Answer 3

Renal corpuscle glomerulus & Bowman’s capsule Renal tubule epithelial cells with lumen

Question 4

Describe the Bowman’s Capsule

Answer 4

2 layers – parietal layer simple squamous epithelium & visceral layer podocytes (highly specialized cells that wrap around capillaries) -Filtrate enters Bowman’s capsule for transportation along renal tubules.

Question 5

What is the glomerulus?

Answer 5

o Capillary tuft – filters blood - surrounded by Bowman’s capsule.
o Diameter of the afferent arteriole > diameter of the efferent arteriole – induces pressure – force some molecules with small molecular weight into ultrafiltrate.
o Albumin too large to be filtered – low albumin conc. In urine – sign of glomerular damage.

Question 6

What are the 3 stages of excretion in the nephron?

Answer 6

1st Glomerular Filtration remove solutes from blood (water, salts, area, uric acid, glucose, amino acids) 180 L/day (140 ml/minute)
2nd Tubular Reabsorption water & most nutrients (all glucose, amino acids, most Na & Cl) via active & passive transport
3rd Tubular Secretion waste products resecreted.

Question 7

What is the glomerular filtrate?

Answer 7

ultrafiltrate similar to plasma (without most proteins).

Question 8

Describe the adrenal glands.

Answer 8

Endocrine glands – messenger system – feedback loops of hormones – released by internal glands into circulatory system – regulate distant target organs.

Question 9

What are the functions of the adrenal glands?

Answer 9

o Osteogenesis/ossification – synthesise Vitamin D – needed for Ca absorption.
o Erythropoiesis - erythropoietin (EPO) synthesis – commits haematopoietic stem cells to differentiate to make RBC.
o Salt/water balance via aldosterone synthesis(mineralocorticoid) – Na+ absorbed & K+ excreted – hyperkalaemia (renal disease)
o Regulate body’s stress – cortisol(glucocorticoid) & adrenaline (glucocorticoid)
o Corticosteroids – stress response, immune response, regulation of inflammation, CHO metabolism, protein catabolism, blood electrolyte levels, behavior.

Question 10

How does the adrenal gland regulate electrolyte balance and blood volume?

Answer 10

o Antidiuretic Hormone (ADH)/Vasopressin/Arginine Vasopressin (AVP) – secreted from posterior pituitary– insert aquaporin channels at collecting ducts – control water reabsorption.
o Aldosterone – exchange of Na+ and K+
o Hypovolaemia – stimulates ADH & aldosterone production – RAAS activation.

Question 11

What does RAAS stand for

Answer 11

Renin-Angiotensin-Aldosterone System

Question 12

Explain RAAS

Answer 12

o Hormone system – regulate blood pressure, electrolyte balance, & systemic vascular resistenace
o Hypovolaemia- juxtaglomerular cells in kidneys convert prorenin into renin - secreted into bloodstream.
o Renin converts angiotensinogen (from liver) to angiotensin I (decapeptide)
o Angiotensin converting enzymes (ACE) (found on surface of vascular endothelial cells e.g. lungs) – convert angiotensin I to angiotensin II (octapeptide)
o Angiotensin II binds to hypothalamus – stimulate thirst, increasing water intake – stimulate release of ADH
o Angiotensin II stimulate aldosterone secretion from adrenal glands (increase Na reabsorption, increase k excretion)
o Blood pressure increases

Question 13

What is nephropathy?

Answer 13

renal disease

Question 14

What is nephritis/nephritic syndrome?

Answer 14

Inflammatory kidney disease

Question 15

What is nephrosis/nephrotic syndrome?

Answer 15

non-inflammatory kidney disease?

Question 16

What is end stage kidney disease?

Answer 16

kidney failure

Question 17

Pre-renal causes of renal disease?

Answer 17

o Reduced blood flow (severe blood/fluid loss, dehydration, vomit, diarrhoea, congestive heart failure, cardiovascular disease, abnormalities, ineffective endocarditis)
o Haemolytic anaemia – porphorin pigment in haemoglobin – toxic to kidneys
o Hypertension
o Liver disease
o Diabetes Mellitus – too much sugar – toxic – damage vessel walls

Question 18

What are renal causes of kidney disease?

Answer 18

o Damage to renal tissue (glomerular basement membrane & tubules)
o Tubular damage toxin exposure/ingestion
o Autoimmune disease
o Hereditary e.g. polycystic hormone disease

Question 19

What are post-renal causes of renal disease?

Answer 19

obstruction to urine outflow – urolithiasis, metastatic carcinomas, UTIs (cystitis (lower urinary tract-bladder) & pyelonephritis (upper urinary tract-kidney))

Question 20

What is Acute Renal Disease/Acute Kidney Injury (ARD/AKI)?

Answer 20

temporary failure of kidney (hours/days)

Question 21

What is chronic renal disease?

Answer 21

progressive, irreversible destruction of kidney – dialysis & treatment

Question 22

What are the lab findings that indicate renal disease?

Answer 22

hyperkalaemia, hypocalcaemia, normocytic normochromic anaemia, metabolic acidosis, proteinuria (chronic renal disease), rising serum urea (waste product – protein & liver breakdown) & creatinine (waste product – muscle metabolism)

Question 23

Signs & symptoms of kidney disease?

Answer 23

Nausea, vomiting, anorexia, fatigue & lethargy, insomnia, oedema, puritis, high blood pressure, SOB (increase H+ ions)

Question 24

Complications of renal disease?

Answer 24

Metabolic acidosis, hyperkalaemia, heart disease, oedema, anaemia, bone weakness

Question 25

How does renal disease cause bone weakness?

Answer 25

o Calcitriol activated Vit. D – 1st hydroxylation occurs in liver – 2nd hydroxylation occurs in kidneys
o Synthesis of cholecalciferol (Vit. D3) – lower layers of the epidermis through photochemical reactions with UV-B
o Ergocalciferol (Vit D2) ingested.
o Calcitriol – increase intestinal absorption of Ca (Mg, PO4)
o Low Vit D. – hypocalcaemia – compensatory increase in PTH (hyperparathyroidism) – increase serum calcium via increased intestinal & renal absorption, osteoclast activity

Question 26

How does renal disease cause oedema?

Answer 26

build up of fluid in body – tissue becomes swollen.
oProteinuria & renal disease – loss of albumin (maintains colloid osmotic pressure/oncotic pressure)
oWater moves out of blood into intestinal fluid to maintain osmolality.
oImpaired ability to excrete water.

Question 27

How does renal disease cause anaemia?

Answer 27

Erythropoietin synthesized in adrenal glands – anoxia & hypoxia stimulate EPO function – decreased RBC – normocytic normochromic anaemia

Question 28

How does renal disease cause

Question 29

How does renal disease cause heart disease?

Answer 29

oReduced glomerular filtration – excess fluid – cause hypertension – damage arteries – coronary artery disease.
oHyperkalaemia causes muscle weakness, cardiac arrhythmia, cardiac arrest.
oHeart disease – leading cause of death for dialysis patients

Question 30

How does renal disease cause hyperkalaemia?

Answer 30

oaldosterone levels decreased (mineralocorticoid deficiency CKD) – K+ not excreted.
oK+ essential for maintaining resting potential & generating action potential.
oVentricular fibrillation – arrhythmia

Question 31

How does renal disease cause metabolic acidosis?

Answer 31

oImpaired excretion of H+
oSOB – hyperventilation – decrease CO2 – increase plasma pH to treat acidosis – bicarbonate buffer system (homeostatic pH balance)
oCO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
oLe Chatelier
oCarbonic anhydrase catalyse the conversion of CO2 to H2CO3

Question 32

Pathogenesis of renal disease (DM)?

Answer 32

Diabetes mellitus – poor management – hyperglycaemia – thickening & scarring of nephron – angiopathy of glomerular capillaries – nephrotic syndrome, proteinuria – causes dialysis.

Question 33

Risk factors of renal disease?

Answer 33

Smoking, diet, obesity, genetic factors, family history, abnormal kidney structure, certain medications, high BP, older age, uncontrolled DM

Question 34

Treatment of renal disease?

Answer 34

Dialysis, transplantation, diet (low, protein, fat, cholesterol)

Question 35

Diagnosis of renal disease?

Answer 35

> Test of Tubular Function
Test of Glomerular Function
oSerum urea – nitrogenous end product of protein & AA catabolism – urease assay – AA & proteins deminated in liver – ammonia is liberated (urease) – ammonia measured via Nesseler’s or Bertelot Reaction
oSerum creatinine – muscle & protein metabolism - modified Jaffe procedure – formed in liver & pancreas - transported to liver cells – creatine kinase phosphorylates creatine to form creatine phosphate (muscle energy source) – creatinine waste product
oProteinuria
oInsulin/creatinine clearance test – determine glomerular filtration rate – 24 hour urine collection – ideal marker = insulin – freely filtered & not reabsorbed, or secreted in the tubules
oEstimated GMR – Crockcroft-Gault & Modification of Diet in Renal Disease (MDRD) equations – age, gender, race, weight, serum creatinine