Urine, Urea, Creatinine Flashcards

1
Q

Renal causes for haematuria

A
Congenital: PCK
Trauma
Infection: pyelonephritis
Neoplasm
Immune: GN, TIN
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2
Q

Extra-renal causes of haematuria

A

Trauma: stones, catheter
Infection: cystitis, prostatitis, urethritis
Neoplasm: bladder, prostate
Bleeding diathesis
Drugs: NSAIDs, frusemide, cipro, cephalosporins

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3
Q

False positive for haematuria

A

Myoglobin, porphyria

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4
Q

Proteinuria levels

A

30mg/dL = 1+
300mg/dL = 3+
PCR < 20mg/mM is normal, >300 = nephrotic

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5
Q

Causes of proteinuria

A

DM
Minimal change Membranous
Amyloidosis
SLE

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6
Q

False -ve proteinuria

A

Bence-Jones protein

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7
Q

Microalbuminuria

A

Albumin 30-300mg/24h

Causes: DM, ↑BP, minimal change GN

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8
Q

Casts in the urine

A

RBC: glomerular haematuria
WBC: interstitial nephritis or pyelonephritis
Tubular: ATN

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9
Q

Creatinine - determinants of levels, when does plasma Cr increase

A

Creatinine is synthesised during muscle turnover.
Freely filtered and small proportion secreted by PCT
↑ muscle → ↑ creatinine: age, sex, race
Plasma Cr doesn’t ↑ above normal until 50% ↓ in GFR

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10
Q

Urea - production, high levels, low levels, absorption

A

Produced from ammonia by liver in ornithine cycle ↑ ̄c protein meal (e.g. upper GI bleed, supplements) ↓ ̄c hepatic impairment
10-70% is reabsorbed: depends on urine flow.
↓ flow → ↑ urea reabsorption (e.g. in dehydration)

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11
Q

Isolated high urea vs high urea and creatinine

A

Isolated ↑ urea = ↓ flow (i.e. hypoperfusion / dehydration)

↑ U and ↑ Cr = ↓ filtration (i.e. renal failure)

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12
Q

Creatinine Clearance

A

Vol of blood that can be cleared of a substance in 1min
CrC roughly approximates GFR as it is freely filtered and
only a small proportion secreted (~10%) Slightly overestimates GFR
Requires urine concentration from 24h collection
Can use radiolabelled EDTA: very rarely done

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13
Q

eGFR

A

Modifiation of Diet in Renal Disease (MDRD) equation
Serum Cr, sex, age, race
Obviates need for urine collection

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14
Q

Problems - eGFR

A

Validated for patients ̄c established renal failure: ?applicable to general population.
Most elderly people are in ≥ stage 3 CRF by eGFR: may not progress or impinge on their health.
eGFR is too pessimistic in mild renal impairment

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