Normal functions of the kidneys

Question 1

What are the 5 functions of the kidneys?

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Answer 1

Excretion of salt, water, and waste products of metabolism
Regulate acid - base
Regulate BP
Produce erythropoetin, activates Vit D
Excrete drugs / metabolites

Question 2

How do we measure excretory renal function?

Answer 2

1) PLASMA / SERUM CREATININE - but this is related to muscle mass. It may not be elevated above normal range until 50% GFR lost.
2) ESTIMATED GFR :MDRD FORMULA
3) CREATININE CLEARANCE
4) ISOTOPE GFR

Question 3

How does serum creatinine (Scr) relate to GFR?

Answer 3

If Scr is high but eGFR is low then kidney failure

If Scr high because of high muscle then need high eGFR too

Question 4

What is normal rate of eGFR?

Answer 4

60 - 100 but only need 10 to live so large reserve

Question 5

What is creatinine?

Answer 5

A waste product of muscle metabolism. It will increase or decrease depending on the efficiency of the kidney

Question 6

What does protein in the urine indicate?

Answer 6

Leakage of kidney filters - glomerula disease

Question 7

What are the two types of renal failure?

Answer 7

Acute and chronic:
Acute kidney injury (AKI)
Chronic kidney disease (CKD)

Question 8

What is AKI?

Answer 8

Acute kidney injury - a rapid loss of renal excretory function. Implies reversibility if underlying condition is treated

Question 9

What is CKD?

Answer 9

Chronic kidney disease - slow progressive loss of excretory renal function. Cause often unknown, usually irreversible and so management is aimed at slowing the progression

Question 10

What are the causes of pre renal AKI? (before the kidney)

Answer 10

Salt and water loss (diarrhoea/vomit/diuretics)
Haemorrhage
Hypotension
Renovascular disease

Question 11

What are the causes of renal AKI?

Answer 11

Tubular necrosis
Interstitial nephritis
Acute glomerulonephritis

Question 12

What are the toxic substances that cause AKI?

Answer 12

Antibiotics
Radiographic contrast media
Chemo agents
Rhabdomyolysis
Intravascular haemolysis
Tumour lysis
Solvents
Hepatorenal syndrome

Question 13

What is a hepatonephrotic kidney?

Answer 13

The collecting system dilates, increasing the pressure

Occurs from an obstruction of ureter or bladder

Question 14

What are the causes of post renal AKI? (after the kidney)

Answer 14

Obstruction to outflow from one / both kidneys

Question 15

What are the causes of CKD?

Answer 15

Diabetic nephropathy
Genetic - polycystic kidney disease
Vascular disease
Chronic glomerulonephritis
Chronic outflow urinary obstruction

Question 16

How is CKD classified?

Answer 16

5 stages:
1 = normal kidney funtion with some other evidence of disease
5 = eGFR

Question 17

What are the consequences of renal failure?

Answer 17

Accumulation of K+, urea, creatinine, H+, water,
Deficiency of erythropoetin (anaemia) and Vit D (hyperPTH)
Delayed drug excretion

Question 18

What is renal replacement therapy?

Answer 18

erythropoetin
VIt D
sodium bicarbonate
Dialysis and transplant (to clean blood)
Anticoagulants - heparin, warfarin and aspirin

Question 19

What are the general consequences of immunosuppression?

Answer 19

Infection
Viral transmission with transplant
Malignancy

Question 20

What effects do cyclosporins have?

anti-rejection drug for transplants

Answer 20

nephrotoxicity
tremor
hirsuitism
gingival hypertrophy

Question 21

What drug interactions involve cyclosporins?

Answer 21

Cyclosporins +: macrolides, diltiazem, enzyme inhibitors