Week 4 - Kidney Failure

Question 1

What are the 2 types of nephrons?

Answer 1

Cortical nephrons

Juxtamedullary nephrons

Question 2

What is the funciton of the renal corpuscle and tubular system of nephron?

Answer 2

Renal corpuscle = site of initial blood filtration

Tubular system = controls concentration and content of urine

Question 3

What are the blood supplies to the nephron?

Answer 3

Glomerulus capillary bed - in Bowman’s capsule - high hydrostatic pressure - FILTRATION

Peritubular capillary bed - aroudn tubular system - low hydrostatic pressure - REABSORPTION AND SECRETION

Question 4

What is GFR?

Answer 4

Volume of fluid entering Bowman’s capsule per unit time

Question 5

What does the glomerular filter look like?

Answer 5

Question 6

What is the organisatino of golumerular capillary membrane?

Answer 6

Question 7

What are the effects of afferent arteriole constriction, efferent arteriole constriction and hypoproteinaemia on GFR?

Answer 7

Afferent constriction = - GFR

Efferent constriction = + GFR

Hypoproteinaemia = + GFR

Question 8

What are the benefits of using inulin to estimate GFR?

Answer 8

• Freely filtered
• Not reabsorbed, secreted or metabolised by kidney
• No effect on renal function
• Easily measured in urine

Question 9

What is RPF?

Answer 9

Renal plasma flow = amount of plasma that perufses kidney per unit time

Question 10

How do you derive renal bloodflow using RPF?

Answer 10

RBF = RPF / 1 - haematocrit

Question 11

What is the filtration fraction?

What does high FF indicate?

Answer 11

The proportion of plasma that forms filtrate

+ FF = + colloid osmotic pressure in peritubular capillaries

Question 12

What are the ways autoregulation alters GFR?

Answer 12

Myogenic - afferent arteriole contraction

Tubuloglomerular feedback - NaCl concentration in filtrate sensed by macula densa of JGA and singal produced, contractin afferent arterioles

Question 13

What is the juxtaglomerular apparatus?

What is its role?

Answer 13

Macula densa + granular cells

Autoregulation and renin release

Question 14

What effect do vasodilators and NSAIDs have on RBF and GFR?

Answer 14

Vasodilators = increase RBF and GFR (prostaglandins)

NSAIDs = block prostaglandin synthesis = + vasoconstriction and ischaemia = actue renal tubular necrosis

Question 15

What is glycosuria?

What causes it?

Answer 15

When renal glucose threshold (RTG) is exceeded, glucose excreted in urine

• Untreated diabetes
• Hyperthyroidism
• Pregnancy
• Familial
• Drugs

Question 16

What happens in the proximal tubule?

Answer 16

• Bulk reabsorption of filtered ions and solutes
• Reabsorption of organic solutes, ions and water is coupled with sodium reabsorption
• • water permeability means so significant osmotic gradient
• Tubular fluid = isosmotic with plasma

Question 17

How is sodium trnasported in proximal tube?

Answer 17

Readily enters epithelial cells across apical membrane

Question 18

How is bicarbonate transported in proximal tube?

Answer 18

Indirectly reabsorbed via carbonic anhydrase as apical membrane impermeable to bicarbonate

Question 19

How is water transported and reabsorbed in proximal tubes?

Answer 19

+ permeability

Occurs paracellularly across tight junctions and transcellularly via water channels on apical and basolateral membranes

Reabsorption:

• Osmotic pressure gradient + low hydrostatic pressure = water passively moves down gradient

Question 20

How is sodium, chloride, potassium and water processed in thick ascending limb of loop of Henle?

Answer 20

• Is impermeable to water
• 1 Na+, 1 K+ and 2 Cl- enter cell via symporter protein in apical membrane
• Cl- leaves via passive diffusion
• Most K+ leaks back into lumen
• Tubular lumen becomes + charged
• Sodium enters cell via Na+/H+ antiporter
• Sodium pumped out by sodium pump
• Low sodium = electrochemical gradient = drives Na movement into cell

Question 21

What is the role of the thick ascending limb?

Answer 21

• Reduces tubular fluid osmolality
• Is diluting segment
• Makes interstitial fluid of medulla hyperosmotic
• • role in creating medullary interstitium and regulating urine osmolality

Question 22

What are the effects of aldosterone in the late distal tube?

Answer 22

• Enhances sodium reabsorption in principal cells
• Enhances K+ secretion in principal cells
• Enhances H+ secretion in intercalated cells

Question 23

What happens in hyperaldosteronism and hypoaldosteronism?

Answer 23

Hyper = + aldosterone, metabolic alkalosis, hypokalaemia, hypertension, oedema

• DUE TO SODIUM AND WATER RETENTION

Hypo = type 4 renal tubular acidosis = hyperkalaemia

Question 24

What are the effects of ADH on inner medullary collecting duct?

Answer 24

• • urea permeability
• Water diffuses out of tubule lumen, into medullary interstitium
• Urea recycling occurs –> urea diffuses into ascending and descending limbs of loop of Henle

Question 25

What happens to body during excess sodium and sodium defecit?

Answer 25

**_Excess:_** * - Weight gain * - Oedema * - Hypertension * - Nocturia **_Defecit:_** * - Weight loss * - Change in skin tugour * - Syncope * - Orthostatic hypotension

Question 26

What happens during chronic kidney disease?

Answer 26

* Slow function loss overtime * Decreased ability to remove waste products * Treat with dialysis, transplant or supportive care * Clinically = \< 60 ml/min

Question 27

How does chronic kidney failure present?

Answer 27

* Asymptomatic serum biochemical abnormaility * Asymptomatic proteinuria or haematuria * Hypertension * Oedema * Primary renal disease symptoms * Uraemia symptoms * Complications of CKD * Tiredness * Salt and water retention * Itching

Question 28

How can you treat CKD?

Answer 28

* ACE inhibitors * Lifestyle change * Monitor BP, creatinine and GFR * Haemodialysis * Peritoneal dialysis

Question 29

What is acute kidney injury?

Answer 29

* Rapid decline in kidney function * + serum creatinine conc. * Fall in urine output * Uraemia * Due to haemodynamic, septic, immunological, nephrotoxic or obstructive insults

Question 30

What are causes of pre-renal AKI?

Answer 30

Intravascular volume depletion - cardiac output Systemic vasodilatation

Question 31

What are the causes of intrinsic AKI?

Answer 31

Diseases or toxins damaging small renal vessels and glomeruli Acute tubular necrosis Miscallaneous renal diseases Toxins

Question 32

What causes post-renal AKI?

Answer 32

Acute obstruction of urine flow