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Module 104: Theme 3 > Measurement of renal function > Flashcards

Measurement of renal function Flashcards

- Renal clearance - Measurement of creatinine clearance - Measurement of renal blood flow

1
Q

Risk factors for kidney failure

A

The extremes of age: Very young and very elderly.

Polypharmacy

Specific disease:
Hypertension
Diabetes
Chronic HF
UTIs

Long term analgesia treatment

Transplant patient- rejection and anti-rejection drugs

Drug theraphy

Imaging procedures- radiocontrast can be nephrotic

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2
Q

Clinical signs and symptoms of fluid imbalance

A

Sign- oedema

Symptoms- breathlessness

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3
Q

Clinical signs and symptoms of electrolyte imbalance/ dysregulation

A

Signs:

Abnormal ECG- Absent P waves, broad QRS, Peaked T waves

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4
Q

Clinical signs and symptoms of EPO production dysfunction

A

Signs:
Pallor

Symptoms:
- Fatigue

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5
Q

Clinical signs and symptoms of Vitamin D3 dysfunction

A

Sign:
Osteomalacia- softening of bones

Symptoms:
Bone pain

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6
Q

Clinical signs and symptoms of Excretion dysfunction

A

Signs:

  • Uremia
  • Raided blood creatinine

Symptoms:

  • Nausea/ vomitting
  • Pruritus: severe itching of skin
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7
Q

Clinical signs and symptoms of acid-base imbalance

A

Signs:

  • Low/high blood pH
  • Low/high bicarbonate levels

Symptoms:

  • Tachypnea
  • Deep breathing
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8
Q

Bedside clinical data to assess patient’s clinical condition

A

Weight charts- rapid weigh gain/ loss

Fluid balance charts

Degree of oedema

Urine dipstick results

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9
Q

Imaging techniques for assessing renal function

A

Renography- macroscopic views of renal blood flow, filtration of excretory function

Gamma camera planar scintigraphy

PET scan

SPECT - single photon emission computerised tomography

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10
Q

Plasma creatinine

A

End product from the breakdown of creatine phosphate in the muscles

Filtered at the glomerulus

Secreted at the PT

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11
Q

Normal range of plasma creatinine

A

40-120 micro-mol/L

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12
Q

Factors that show increased plasma creatinine

A

Increased muscle mass

Dietary intake

Drugs that interfere with analysis- cephalosporins, dexamethasone

Drugs that inhibit tubular secretion

Ketoacidosis

Ethnicity- higher creatine kinase activity in black population

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13
Q

Factors that show decreased plasma creatinine

A

Low muscle mass

Cachexia/ starvation

Immobility

Pregnancy

Sever liver disease

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14
Q

Drugs that inhibit tubular secretion of creatinine

A

Cimetidine

Trimethoprim

Aspirin

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15
Q

Classifications of plasma creatinine concentrations as an indicator for renal function:

  • Normal
  • Mildy reduced
  • Moderately reduced
  • Severely reduced
  • Very severely reduced
A

Normal: 120-150 [40-150]

Mildly reduced: 150-300

Moderately reduced: 300-500

Severely reduced: 500-700

Very severely reduced: >700

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16
Q

Plasma urea

A

Waste product of protein digestion- produced in the liver

Filtered in the glomerulus, secreted and reabsorbed in the tubule

17
Q

Normal range of plasma urea

Range that indicates moderate- severe renal failure

A

Normal: 2.5-7.5 mmol/L

Renal failure: >20mmol/L

18
Q

Factors that increase blood urea nitrogen

A

High protein diet

Hypercatobolic conditions: severe infection, burns, hyperthyroidism

GI bleeding

Muscle injury

Drugs: gluccorticoids, tetracycline

Hypovolaemia

19
Q

Factors that decrease blood urea nitrogen

A

Malnutrition

Liver disease

Sickle cell- increased GFR

SIADH- syndrome of inappropriate ADH

20
Q

Examples of renal clearance

A
  • Filtered and not reabsorbed or secreted
  • Filtered and some reabsorbed: electrolytes
  • Filtered and completely reabsorbed: glucose, amino acids
  • Filtered and primarily secreted into the tubule: PAH
21
Q

Substance that is filtered and not reabsorbed or secreted

A

Inulin

The excretion rate is equal to the rate at which it is filtered

22
Q

Inulin

A

Inulin is a plant polysaccharide filtered and not secreted/ reabsorbed.

Inulin filtration rate = GFR

Inulin is injected into the blood through an IV.

If a substance filtration rate > inulin clearance, then it is being secreted

23
Q

Renal clearance

A

The volume of plasma completely cleared of a given substance in a unit time.

Clearance of X = Urine concentration of (X) x Volume of urine in a given time / Concentration of X in plasma

24
Q

GFR

A

The rate at which filtrate is produced in the kidneys
- roughly 125mL/min (inulin filtration rate)

Used to measure renal function

25
Q

Drawbacks of using inulin to measure GFR

A

Has to be given IV

Analysis of inulin in the blood and urine is technically demanding

26
Q

Creatinine clearance

A

Creatinine is filtered and secreted in the PT

Creatinine clearance gives overestimation by 20%
- This is cancelled out by using colorimetry which underestimates by 20%.

Can be adjusted to take into account body surface area

27
Q

Advantages of creatinine clearance over inulin clearance

A

Creatinine avoids IV infusion as it is endogenous.

Easy to analyse compared to inulin.

28
Q

Formulas used to estimate GFR using creatinine clearance

A

Cockcroft-Gault

Modification of Diet in Renal disease [MDRD]- used more in the UK and takes into account ethinicity

29
Q

GFR classifications for:

  • Normal kidney function
  • Mildy reduced
  • Moderately reduced
  • Severely reduced
  • Very severely reduced
A

Normal- 90+ (stage 1 kidney disease)

Mildly reduced: 60-89 (stage 2)

Moderately reduced:
45-59 (3A)
30-44 (3B)

Severely reduced:
15-29 (4)

Very severely reduced:
<14 (stage 5)

30
Q

PAH

A

Para-aminohippuric acid

  • substance that is completely cleared from the plasma
  • Its clearance rate= renal plasma flow
31
Q

PAH clearance

A

90% of PAH is secreted into the PT.

10% left in the plasma in venous renal blood.

  • Used to calculate effective renal plasma flow
  • The 90% of PAH in urine is corrected to find total renal plasma flow by weighing it to 100%.

Total renal blood flow is calculated by adding haemocrit (extra 45%)

32
Q

Biomarkers of renal disease

A

Urinary albumin/ protein secretion- indicator of chronic kidney disease

  • Kidney injury molecule-1: KIM-1 in urine
  • IL-18 in urine
  • Fatty-acid binding proteins in urine
  • Neutrophil gelatinase-associated lipocalin (in plasma and urine
  • Cystatin C in plasma

Module 104: Theme 3 (13 decks)

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