Clinical renal failure

Question 1

Define clinical renal failure

Answer 1

A reduction in GFR

Question 2

What is normal GFR

Answer 2

100 ml/min

Question 3

What are the two main classifications of renal disease

Answer 3

Acute or chronic

Question 4

What are the two main blood tests used in measuring renal function

Answer 4

Serum creatinine and serum urea

Question 5

How is urea formed

Answer 5

When amino acids are catabolised the nitrogen that is released is further catabolised to ammonia which is converted into urea by the liver.

Question 6

What are urea levels dependant on

Answer 6

dietary protein intake, protein catabolism which is increased in infection trauma and immobilisation

Question 7

Describe renal handling of urea

Answer 7

Urea is easily filtered. When GFR is slow there is greater reabsorption from tubules increasing serum urea.

Question 8

Why is serum urea less reliable as a marker of GFR?

Answer 8

Because levels are related to protein intake, hydration status, intestinal bleeding

Question 9

Where is creatinine derived from

Answer 9

From creatine in muscles, solely a waste product

Question 10

What is the rate of creatinine formation proportional to

Answer 10

Muscle mass

Question 11

Why is creatinine clearance rate proportional to GFR and what is it’s effect on GFR

Answer 11

Because it is freely filtered and there is no tubular reabsorption, plasma creatinine rises as GFR falls

Question 12

Why is plasma creatinine an insensitive index of renal function and what is it useful for

Answer 12

It is insensitive as an index marker due to the variety on muscle mass across the population. It is useful as a measurement of the course of renal disease.

Question 13

When can plasma creatinine artificially rise?

Answer 13

After a protein rich meal.

Question 14

What are factors to consider when measuring serum creatinine

Answer 14

Things that effect muscle mass. Weight, age, gender.

Calculations should be done on populations norms for demographic groups

Question 15

What is the difference between eGFR and serum creatinine for measurement of GFR

Answer 15

eGFR also takes into account plasma creatinine, age and sex

Question 16

Describe acute kidney failure including basic aetiology

Answer 16

A sudden rapid reduction in GFR, usually reversible, 70% due to non renal causes i.e. pre-renal and post-renal

Question 17

Describe causes of pre renal failure

Answer 17

Low BP, reduced kidney perfusion from dehydration, septic shock, haemorrhage, cardiogenic shock, severe renal artery stenosis

Question 18

What other serum markers might you get in acute renal failure

Answer 18

Hyperkalaemia (reduced kidney excretion), high phosphate (reduced kidney excretion), low calcium (kidneys turn Vitamin D into calcitriol which increases calcium absorption from intestines to the blood).

Question 19

Treatment of pre-renal causes

Answer 19

Fix underlying problem, rehydrate, fix bleeding, antibiotics, fix heart

Question 20

What are the two possible outcomes from pre-renal kidney failure?

Answer 20

Get better or develop acute tubular necrosis.

Question 21

What is the main cause of renal kidney failure

Answer 21

Acute tubular necrosis, 80% most of this is a progression of pre-renal.

Question 22

Signs and symptoms of acute tubular necrosis

Answer 22

Abnormal creatinine, phosphate, calcium, potassium, persistant oligouria after treating underlying cause.

Question 23

Treatments of acute tubular necrosis.

Answer 23

First ret underlying pre-renal cause. Patient may need dialysis to help filter blood/ maintain osmolality/ acid-base balance etc while tubules heal. Prevents death from hyperkalaemia.

Question 24

What percentage of patients recovers from Acute tubular necrosis

Answer 24

95%

Question 25

Another less common aetiology of acute tubular necrosis and what do patients with this typically present with

Answer 25

Glomerularnephritis | Proteinuria and haemataturia

Question 26

What are post-renal causes of kidney failure

Answer 26

Kidney stones, prostate, tumour, urinary retention

Question 27

Describe chronic kidney disease

Answer 27

Happens over months/ years. Irreversible. Considered in stages dependant on GFR

Question 28

List consequences of chronic kidney failure

Answer 28

Increased PTH (to release Ca as serum Ca low due to reduced Vit D metabolism to calcitriol) Anaemia- low EPO (manufactured in the kidneys) High phosphate Acidosis Hyperkalaemia Uraemia

Question 29

Commonest cause of CKD

Answer 29

Diabetes (70%)

Question 30

Other causes of CKD

Answer 30

Glomerulonephritis, hypertension, loads of others

Question 31

Microscopic pathology seen in chronic kidney disease

Answer 31

Scarring of glomeruli and interstitium

Question 32

What are symptoms of uraemia

Answer 32

Anorexia, nausea, vomiting, pruritis, SOB due to anaemia or fluid overload, cold intolerance, swelling, seizures, coma

Question 33

Why would bone disease ensue in chronic kidney failure

Answer 33

Because the kidneys convert vitamin D to calcitriol which help to absorb Calcium from the intestines. In the presence of low serum Ca PTH is stimulated which causes excessive bone resorption of Ca. Causes fractures, and extra osseous calcification.

Question 34

What blood test readily distinguishes between chronic and acute kidney injury

Answer 34

Hb. The kidneys produce erythropoietin, a hormone necessary for RBC production. In chronic injury production of erythropoietin is reduced and thus fewer RBC. This takes time to manifest as the life span of RBC is 120 days... so not evident in acute.

Question 35

Describe principles of treatment in chronic kidney injury

Answer 35

``` Treat underlying cause of kidney injury Treat hypertension Treat anaemia Monitor blood glucose Monitor electrolytes May need dialysis ```

Question 36

Why does K+ increase in kidney failure

Answer 36

Reduced renal excretion

Question 37

Describe the five mechanism for regulation of glomerular filtration

Answer 37

1) Tubuloglomerular feedback: 2) Myogenic 3) Renin-angiotensin-aldosterone 4) Sympathetic stimulation. 5) ANP and BNP

Question 38

Describe tubuloglomerular feedback for GFR regulation

Answer 38

MD cells sense NaCl and stimulate the JG cells to release NO if NaCl low- causing vasodilation of afferent arteriole, increased flow. If NaCl is high the MD cells release adenosine which causes the afferent arteriole to constrict decreasing flow.

Question 39

Describe Myogenic feedback for regulation of GFR

Answer 39

Increased stretch on the afferent arteriole cause it to constrict reducing flow

Question 40

Describe the RAAS for regulation of GFR

Answer 40

MD sense low NaCl causing JG to release renin, renin cleaves angiotensinogin to angiotensin I, ACE converts angiotensin I to angiotensin II. Angiotensin II causes constriction of efferent arteriole back pressure increases GFR. It also causes the adrenal gland to release aldosterone.Aldosterone results in NaCl retention, fluid retention,increased volume, increased flow.

Question 41

Describe sympathetic regulation of GFR

Answer 41

Peripheral baroreceptors detect low pressure decreased firing from these causes sympathetic stimulation resulting in vasoconstriction of the afferent arteriole decreasing flow (shock)

Question 42

Describe ANP and BNP in relation to regulation of GFR

Answer 42

Decreased stretch in atria of heart result in release of ANP causes dilatation of afferent arteriole increasing GFR

Question 43

Chronic kidney disease stage 1

Answer 43

Normal GFR >90

Question 44

Chronic kidney disease stage 2

Answer 44

GFR 60-89 | Increased PTH

Question 45

Chronic kidney disease stage 3

Answer 45

Moderate absorption | GFR 30-59 decreased Ca,low EPO, increased CV risk

Question 46

Chronic kidney disease stage 4

Answer 46

Severe High phosphate, acidosis, Hyperkalaemia, malnutrition GFR 15-29

Question 47

Chronic kidney disease stage 5

Answer 47

ESRF GFR <15 Uraemia

Question 48

Describe the actions of ANP

Answer 48

ANP release inhibits release of ADH from the posterior pituitary gland, More water loss from collecting ducts. Inhibits aldosterone, more Na+ secretion and K+ retention (fluid loss), vasodilation of arteries, Vasodilation of afferent arteriole causing increased GFR.

Question 49

Name a drug that inhibits aldosterone and its mechanism of action

Answer 49

Spirolactone. Blocks aldosterone is a weak K+ sparing diuretic