Renal Biochemistry

Question 1

AKI definition

Answer 1

Rise in creatinine OR fall in urine output over hours to days

Question 2

Pre-renal causes of AKI

Answer 2

Hypovolaemia (eg. sepsis)

Pump failure

Question 3

Renal causes of AKI

Answer 3

Ischaemia
Glomerulonephritis
Nephrotoxins - drugs, metals

Question 4

Post renal causes of AKI

Answer 4

Stones
Tumour
Prostate

Question 5

Ischaemic AKI stages

Answer 5

Stage 1 (Pre renal uraemia)
Stage 2 (Acute Tubular Necrosis)

Question 6

Stage 1 AKI (Pre-renal uraemia)

Answer 6

Reversible by fluid resus
Low plasma volume
Low renal perfursion
Low GFR

Question 7

Stage 2 AKI

Answer 7

Worse by fluid resus

Acute Tubular Necrosis

Question 8

Tests to differentiate stage 1 and stage 2 AKI

Answer 8

1) Urea:Plasma osmolality
- Stage 1 > 2:1
- Stage 2 1:1

2) Urine Na
- Stage 1 < 20
- Stage 2 > 20

Question 9

Clinical features of AKI

Answer 9

1) Failure to remove nitrogenous waste - nausea, confusion
2) Fluid overload - cardiac failure, oedema
3) Acidosis
4) Hyperkalaemia

Question 10

Life threatening pH

Answer 10

< 7.0

Question 11

Life threatening hyperkalaemia

Answer 11

> 8 mmol/L

Question 12

Proximal tubule functions

Answer 12

Solute reabsorption:
1) ~70% Na, K, Ca, Cl

2) ~100% HCO3, Glucose, Urate, Amino acids
3) Isosmotic water reabsorption (~70%)

Question 13

Fanconi syndrome

Answer 13

Glomerular tubule defect

Ion channels defective for reabsorption of solutes

Question 14

Countercurrent system components

Answer 14

1) Countercurrent multiplication

2) Countercurrent exchange

Question 15

Countercurrent multiplication

Answer 15

• Active
• In Loop of Henle
• Dilutes urine (by removing solutes in thick ascending limb)
• Generates hypertonic medulla

Question 16

Countercurrent exchange

Answer 16

• Passive
• In Distal tubule and collecting duct
• Concentrates urine via ADH

Question 17

Site of aldosterone action

Answer 17

Distal tubule

Question 18

Action of aldosterone

Answer 18

Activates channels

Reabsorption of Na ions leading to water absorption

Question 19

eGFR formula

Answer 19

GFR = creatinine production rate /serum [creatinine]

x 0.742 if female
(x 1.21 if African)

Question 20

Causes of CKD

Answer 20

1. Diabetes mellitus
2. Hypertension
3. Polycystic Kidney Disease
4. Glomerulonephritis, pyelonephritis, interstitial nephritis
5. Multisystem disease
6. Drugs

Question 21

Stages of CKD

Answer 21

Stage 1. >90 GFR
Stage 2. 60-90 GFR
Stage 3a. 45-60
= Hypertension / ↑ CVD risk
Stage 3b. 30-45
= Low calcium 2º ↑ PTH
Stage 4. 15-30
= + anaemia + anorexia + high phosphate
Stage 5. <15 GFR mL/min
= + salt &amp; water retention + acidosis + ↑ K+

Question 22

Urine albumin associated with CKD staging

Answer 22

A1. normal to mildly raised
A2. Moderately raised
A3. Severely raised