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Case 2 > Applied Renal Physiology > Flashcards

Applied Renal Physiology Flashcards

1
Q

Why is renal physiology important

A

Kidneys interact with other organs to maintain homeostasis- heart, lungs, liver. Drug pharmacodynamics and pharmacokinetics depend upon renal mechanisms

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2
Q

What are the kidneys for

A

Fluid and osmotic balance, excretion of waste products, blood manufacture (EPO), acid/ base metabolism, blood pressure, electrolyte metabolism, gluconeogenesis

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3
Q

Where does metabolism of vitamin D occur

A

In the kidneys, this is essential for bones

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4
Q

How much of the total body is water

A

~60%

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5
Q

How much of the body’s water is made up of extracellular fluids

A

1/3 which is exchanged across capillary all, plasma, interstitial composition, kidneys maintain ECF

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6
Q

How much of the body’s water is made up of intracellular fluids

A

2/3, individual mixture but equivalent

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7
Q

What is glomerular filtration rate

A

The volume of fluid filtered by the glomerular capillaries per unit time

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8
Q

What is glomerular filtration rate (GFR) determined by

A

Hydrostatic pressure, oncotic pressure and properties of the barrier

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9
Q

What is oncotic pressure determined by

A

Osmotic relative substances (proteins)

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10
Q

What is net filtration rate

A

Glomerular hydrostatic pressure (60 mmHg)- Bowman’s capsule pressire (18 mmHg)- glomerular oncotic pressure (32 mmHg)

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11
Q

What is Kf determined by

A

Hydraulic properties and surface area

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12
Q

What does GFR equal

A

GFR= Kf x net filtration pressure

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13
Q

What is estimation of GFR used to assess

A

Degree of kidney impairment and follow the disease

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14
Q

How is diagnosis achieved

A

By analysis of urine, measuring protein excretion rate, radiological studies and/or renal biopsy

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15
Q

What do GFR quantitate

A

Effectiveness of renal excretion

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16
Q

What does normal GFR value depend on

A

Age, gender and body size

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17
Q

What is GFR for men

A

Approx 130ml/min/1.73m2

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18
Q

What is GFR for women

A

Approx 120ml/min/1.73m2

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19
Q

What happens to GFR as you get older

A

Definite decline when over 40

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20
Q

What is normal GFR

A

~100ml/min

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21
Q

When can GFR be obtained directly

A

In isolated nephrons

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22
Q

How can GFR be estimated

A

By measuring the rate of excretion of substances that are freely filtered but then are neither absorbed nor secreted by renal tubules

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23
Q

What should substances used to estimate GFR have no influence on

A

Any physiological parameter that may alter renal function such as blood pressure or blood flow

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24
Q

What substance can be used to estimate GFR

A

The plant ploysaccharide inulin which is secreted by the kidneys in direct proportion to its plasma concentration over a very wide range

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25
Q

What is the rate at which a substance is excreted

A

Its concentration in urine (Uinulin) multiplied by the amount of urine produced per minute (V)

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26
Q

What does rate of excretion equal

A

Uinulin x V mg/min-1

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27
Q

For a substance not reasborbed or secreted by the renal tubules what must the rate of excretion by the same as

A

The plasma concentration (Pinulin) multiplied by the rate at which is it filtered

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28
Q

What does rate of filtration equal

A

Pinulin x GFR mg/ml-1

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29
Q

Therefore what does GFR equal when estimating GFR

A

GFR = Uinulin x V / Pinluin ml/min

30
Q

What is the GFR measured rate of inulin excretion called

A

The inulin clearance

31
Q

What is inulin clearance

A

Generally about 120-130 ml/min-1 for adult men and about 10% less for women of a similar body size

32
Q

Why is the use of inulin not very convenient for clinical purposes

A

A steady concentration needs to be maintained in the plasma for measurement and you need to accurately measure flow rate of urine coming out meaning that a person has to be cathaterised

33
Q

What is creatine derived from

A

Skeletal muscle

34
Q

Describe the activity of creatine in the kidney

A

Freely filtered at the glomerulus, not reabsorbed or metabolised, some secretion in the proximal tubule

35
Q

When is plasma creatinine constant

A

If GFR, diet and muscle mass are all constant

36
Q

What can creatine be used for

A

It can be measured in the blood and is related to renal function. It is released at a constant rate so value today and tomorrow should be the same

37
Q

If GFR is less than 60-90 what are you likely to miss

A

The fact that someone has chronic kidney disease as creatinine is relatively unchanged

38
Q

In which stage of chronic kidney disease may you over interpret small changes in creatinine

A

Stage 5

39
Q

How can you improve on creatinine

A

By encorporating demographic changes

40
Q

What do you used in Wales to incorporate demographic changes and what does it include

A

MDRD. Includes 4 variables- age, gender, creatine and ethnicity

41
Q

What happens to creatinine as you get older

A

There is muscle mass atrophy therefore a decrease in creatine production

42
Q

Why do women have a lower creatine productionq

A

They have a lower muscle mass

43
Q

Why is ethnicity important in relation to creatinine

A

Afro-Caribbean people have a different body muscle ratio

44
Q

What is eGFR

A

Estimated GFR

45
Q

Where does the MDRD formula come from

A

A population of patients in the USA that had renal kidney impairment

46
Q

Describe the performance of the MDRD eCFR vs GFR graph

A

Performs well in the mid-range of GFR but less well as higher GFR levels. At the top of the graph the scatter of data is much greater meaning that your confidence that measured GFR= MDRD GFR is much less

47
Q

What is pyelonephritis

A

A cortex infection

48
Q

What is pyonephrosis

A

An infection in the pelvis of the kidney

49
Q

What is rigors

A

An exaggerated response to infection and means that someone shales

50
Q

What are the symptoms of a lower tract infection

A

Dysuria, frequency, haematuria, nocturia, suprapubic pain, urgency, foul urine

51
Q

What are the symptoms of acute pyelonephritis

A

Fever, malaise, nausea, vomitting, abdominal pain

52
Q

What are the symptoms of pyonephrosis or perinephric abscess

A

Rigors, loin pain, scoliosis, loin swelling, weight loss, night sweats

53
Q

What is ‘honeymoon’ cystitis due to

A

Women first becoming sexually active

54
Q

Why are you more likely to get an infection during pregnancy

A

Due to physiological changes that occur

55
Q

What does ureteric reflux mean

A

That urine usually only flows in one direction

56
Q

What happens if the valve between the ureter and bladder is incomplete

A

Urine goes back up from the bladder to the kidneys as sits as a static pool- vesico-ureteric reflux

57
Q

Describe primary vesico-ureteric reflux

A

Incompetent ureterovesicle junction, shortening of intravsicle ureter (if ureter is shorter then reflux is more likely), spontaneous resolution with growth

58
Q

Describe secondaet vesico-ureteric reflux

A

High pressure bladder, dysfunctional voiding or neurogenic bladder (distended= abnormal)

59
Q

What can cause a functional obstruction during pregnancy

A

The pressure in the uterus causes pressure in the pelvis which can cause a functional obstruction in the ureter

60
Q

What is acute pyelonephritis

A

An inflammatory process occurring within the renal parenchyma caused by bacterial infection

61
Q

What does acute pyelonephritis most commonly result from

A

Ascending infection within the urinary tract

62
Q

What is the definition of pyelonephritis

A

Fever (>38.5), loin pain and cystitis. Frequently associated with vomiting and dehydration. Significant and potentially life threatening infection

63
Q

Why do you get vomiting in pyelonephritis

A

Sympathetic response to pain and fever

64
Q

Describe the pain associated with pyelonephritis

A

Localised pain tends to be in the back but can also be in the front of the abdomen. Remember anatomical location of the kidney retroperitoneal but inflammation-peritoneal irritation

65
Q

What are host factors of acute pyelonephritis

A

Congenital abnormalities of the tract- vesicoureteric reflux, anatomical abnormalities, dilation +/- obstruction (incomplete fusion of the kidneys). Acquired abnormalities- prostatic enlargement. Calculi (kidney stones). Haematuria- increased Fe (blood loss into urinary system)

66
Q

What are the symptoms of acute pyelonephritis

A

High urinary luekocyte count, high bacterial count, haematuria, high systemic leukocyte count, malaise, fever, rigors, loin pain +/- nausea or vomiting

67
Q

Sequelae to acute pylenephritis

A

Rarely leads to acute renal failure (ANT). Modern imaging techniques= small defects or scars not uncommon. Very rare for long term renal problems but co-morbidity will increase the possibility. Most patients with acute pyelonephritis get better with antibiotics, it is very rare to cause long term renal problems

68
Q

How many women get a recurrent UTI within 6 months of their first UTI

A

27%, more common with E.Coli

69
Q

What does recurrent mean

A

That it is a different organism

70
Q

What does relapse mean

A

Same organism within 2 weeks of treatment

71
Q

What is the marker of choice to assess GFR

A

Creatinine

Case 2 (8 decks)

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