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Renal SB > Biochemistry and Microbiology > Flashcards

Biochemistry and Microbiology Flashcards

1
Q

from what is GFR calculated

A

from 4 parameters

  • serum creatinine
  • age
  • gender
  • race
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2
Q

where does the urea cycle occur

A

in the liver

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3
Q

what is the down fall of using serum creatinine to calculate GFR

A

is not useful for showing mild renal impairment

i.e. Creatinine will rise but not greatly.
Small change despite steep fall in GFR.

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4
Q

what is ‘clearance’

A

the volume of plasma that is theoretically cleared of a substance per minute.

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5
Q

how is urinary creatinine clearance calculated

A

[creatinine]urine x urine volume / [creatinine]serum x duration of collection

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6
Q

what are confounders of serum creatinine

A

muscle mass&raquo_space; bigger your muscle mass is the more production of creatinine than a smaller person

diet

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7
Q

what normally happens to plasma proteins in the kidney

A

they are normally retained

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8
Q

Ix for proteinuria

A

albumin/creatinine ratio or

protein/creatinine ratio

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9
Q

what levels of protein in the urine is suggestive of significant glomerular damage

A

Protein >150mg/day in the urine

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10
Q

what are the different causes of proteinuria

A

Overflow

Glomerular

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11
Q

what happens in overflow proteinuria and what can cause this

A

problem is that you are overproducing one particular protein, glomerular basement cannot handle protein load, leak protein into the filtrate, ability to reabsorb is diminished as it cannot handle volume of protein

multiple myeloma

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12
Q

what happens in glomerular proteinuria and what can cause this

A

normal amount of protein, but glomerulus not working as well, protein let through, overwhelms tubules again

albuminuria

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13
Q

in multiple myeloma, what causes kidney impairment

A

light chain deposition

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14
Q

what is seem on an x-ray in multiple myeloma

A

Pepper pot appearance/punched out lesions in the skull

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15
Q

what is nephrotic syndrome

A

triad

  • proteinuria
  • hypoalbuminaemia
  • oedema
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16
Q

what causes the nephrotic syndrome

A

pouring out protein in the urine in severe cases
body cannot make enough protein to replace what you are losing
balance of osmotic forces changes
more fluid in interstitial space
» nephrotic syndrome

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17
Q

what does microalbuminuria mean

A

excretion of albumin in abnormal quantities but still below the limit of protein detection by dipstick

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18
Q

what is microalbuminuria the earliest expression of

A

diabetic nephropathy

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19
Q

why is microalbuminuria treated

A

to reduce risk of progression

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20
Q

Tx of microalbuminuria in DM

A

ACE-i or ARB
irrespective of blood pressure

manage CV risk factors - stop smoking, reduce cholesterol, consider aspirin

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21
Q

what is the target BP in DM with kidney problems but NO proteinuria

A

130/80

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22
Q

what is the target BP in DM with kidney problems WITH proteinuria

A

125/75

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23
Q

what are the 3 categories of problem in tubular function in oliguric patient

A

pre-renal
post-renal
renal

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24
Q

what mechanism and example of pre-renal problem

A

reduced renal perfusion, kidney’s fine but not perfused properly

e.g. Blood loss, hypovolaemia

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25
Q

what mechanism and example of post-renal problem

A

an obstruction to urinary outflow tract, ureter to urethra

e.g. stones, malignancy

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26
Q

what mechanism and example of renal problem

A

intrinsic kidney tissue damage

e.g. glomerulonephritis

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27
Q

what does the kidney produce and where do these products work

A

erythropoietin&raquo_space; bone marrow

1,25 Dihydroxycholecalciferol&raquo_space; gut

renin&raquo_space; converts angiotensiogen to angiotensin I

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28
Q

how can tubular function be calculated

A

urine osmolality v serum osmolality

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29
Q

what is the bacteria in the normal urinary tract

A

Urine in kidneys, ureters and bladder is sterile

Lower end of the urethra is colonised by bowel flora i.e. Coliforms and enterococci

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30
Q

what is definition of UTI

A

The presence of micro-organisms in the urinary tract that are causing clinical infection

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31
Q

what is a lower UTI

A

infection confined to the bladder (cystitis - inflammation of the bladder)

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32
Q

what is a upper UTI

A

infection involving the ureters +/- the kidneys (pyelonephritis - inflammation of the kidney)

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33
Q

why is it important where the UTI is

A

influences the treatment

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34
Q

what is a complicated UTI

A

UTI complicated by systemic sepsis (infection getting into the blood) or urinary structural abnormality or stones

  • have to use longer course of antibiotics
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35
Q

what is Bacteriuria

A

the presence of bacteria in the urine

does not always mean infection, esp. in elderly patients or patients with catheters

36
Q

is cystitis always due to infection?

A

no, there are a number of causes but is commonly due to UTI

37
Q

why do women get UTI more than men

A
  • short wide urethra
  • proximity of urethra to anus
  • increased risk with sexual activity
  • pregnancy (many women presenting with first UTI when pregnant)
38
Q

who gets UTIs

A

common
W > M
Catheterised patients
Patients with abnormalities of the urinary tract (e.g. horseshoe kidney)

39
Q

what are the routes of infection for UTI

A

Ascending infection (more important/commoner)

From the bloodstream (descending route of infection)

40
Q

how does ascending infection work

A

bacteria from bowel → perineal skin → lower end of urethra → bladder → ureters → kidneys

41
Q

how does UTI via the bloodstream occur

A

patient with bacteraemia / septicaemia from another focus of infection → bacteria in blood → seeded into kidneys → multiple small abscesses → bacteria in urine

42
Q

what commonly cause UTI

A

‘Coliforms’:

E.coli - commonest cause
Klebsiella sp.
Enterobacter sp.

Proteus sp.
Other coliforms

43
Q

what is the commonest cause of UTI

A

E.coli

44
Q

how do coliforms appear on gram stain

A

gram -ve bacilli

45
Q

what is Proteus sp. associated with

A

formation of stone (calculi)

46
Q

features of Proteus sp. and how it causes stones

A

foul smelling

Produces urease which breaks down urea to form ammonia, which increases urinary pH - precipitation of salts

47
Q

what are enterococcus spp.

A

types of “streptococci” that live in the GI tract that can also cause UTI

e.g.
Enterococcus faecalis
Entercoccus faecium

48
Q

what staph is the most common staph to cause UTI and features of it

A

Staphylococcus saphrophyticus

  • a type of coagulase negative staph
  • usually affects women of child bearing age
49
Q

can staph. aureus cause UTI?

A

yes but it is less common than coliforms and Staphylococcus saphrophyticus

50
Q

why is Pseudomonas aeruginosa difficult to treat

A

resistant to most oral antibiotics except ciprofloxacin

51
Q

features of Pseudomonas aeruginosa

A

Gram negative bacillus but not a coliform

Associated with catheters and UT instrumentation

52
Q

Sx of UTI

A

dysuria (pain passing urine)
frequency of urination / nocturia
haematuria

fever } suggest involvement
loin pain} of
rigors } upper urinary tract

53
Q

what is ciprofloxacin associated with

A

C. Diff infection

54
Q

what are problems with collecting a urine sample for UTI Ix

A

want to test bladder urine, not the lower end of the urethra which has bacteria normally

first urine passed is most likely to be contaminated with bacteria normally in the urethra

55
Q

how should a urine sample for UTI Ix be collected

A

Collecting a mid-stream specimen of urine (MSSU)

  • Wash perineum / urethral meatus with sterile saline (not antiseptic - could be passed into urine and kill bacteria of UTI)
  • Give patient a sterile foil bowl
  • First urine passed into toilet
  • Next part collected in foil bowl
  • Last urine passed in toilet
56
Q

what are other ways urine can be obtained

A

“Clean catch” urine
- children, elderly; nurse tries to catch midstream urine.

Bag urine (babies)

  • often contaminated with bowel flora
  • negative culture result useful

Catheter specimen of urine (CSU)

Suprapubic aspiration
- normally used after Bag urine in children if bag urine is +ve

57
Q

what in a dip stick urine testing can indicate infection

A

Leukocyte esterase
- Indicates the presence of leukocytes (WBC) in the urine

Nitrites

  • Nitrites indicate the presence of bacteria in the urine
  • Some bacteria can reduce nitrates to nitrites – mainly coliforms – Enterococcus spp. do NOT give positive test

Protein

Blood

58
Q

when is microscopy of the urine down

A

only done on selected (urgent) cases

look for presence of polymorphs (pus cells), bacteria +/- red cells

59
Q

what is Kass’s Criteria

A

> 10 to the power of 5 organisms / ml

significant =probable UTI

60
Q

what is ESBL-producing bacteria

A

Makes bacteria resistant to ALL cephalosporins and to almost all penicillins
Carried on a plasmid, which often carries genes for other resistance too (e.g gentamicin, ciprofloxacin)

61
Q

what can be used to treat ESBL-producing bacteria

A 
Nitrofurantoin (oral), pivmecillinam (oral) 
fosfomycin (oral),
temocillin (IV)
meropenem(IV)
ertapenem (IV)
62
Q

where is ESBL-producing bacteria found

A

imported chicken

63
Q

what is Carbapenemase-producing Enterobacteriaceae (CPE)

A 
Gram negative (coliform) bacilli that are resistant to meropenem 
This usually means that they are effectively resistant to ALL current antibiotics
64
Q

what microorganisms can be found in the urine after travelling to india

A

Klebsiella pneumoniae

Providencia rettgeri

65
Q

how long does an uncomplicated UTI in women need to be treated for

A

3 days

66
Q

why is amoxicillin a 1st line drug in UTI but what are its drawback

A

Can be given orally or IV
Safe, even in pregnancy

Range of organisms treated

  • Enterococcus faecalis
  • Some coliforms, but >50% E coli now resistant, and many other coliforms also resistant
  • not good for empirical treatment
67
Q

what is given for empirical treatment of UTI

A

Trimethoprim (oral)

68
Q

features of Trimethoprim

A

Safe, but avoid in 1st trimester (3 months) of pregnancy

Can be given as co-trimoxazole (IV or oral) but risk of Stevens-Johnson syndrome

Range of organisms treated:
most coliforms, Staph aureus incl. MRSA but not Pseudomonas sp.

69
Q

when is Nitrofurantoin useful

A

in lower uncomplicated UTI as only reaches effective concentrations in bladder urine

Range of organisms treated:
Most coliforms, Enterococci, Staph aureus incl MRSA, but not Proteus sp and Pseudomonas sp.

70
Q

when should Nitrofurantoin be avoided

A

Avoid in late pregnancy (can cause neonatal haemolysis), breast feeding and children

71
Q

features of Gentamicin

A

Hospital use only (has to be given IV)

Range of organisms treated: Most coliforms, PSEUDOMONAS sp, Staph aureus incl MRSA, but not enterococci

Very effective drug in severe Gram negative (coliform-related) sepsis

Should be prescribed for 3 days ONLY - due to toxicity

72
Q

complications of gentamicin and when is it NOT used

A

risk of toxicity causing renal and VIIIth nerve damage (deafness and balance problems)

Avoid in pregnancy

73
Q

Dose of gentamicin

A

Given once daily – 7mg/kg (ideal body weight) then measure a blood level 6-14 hours later

74
Q

what is Pivmecillinam used for

A

treating lower uncomplicated UTI

often used in elderly in community

75
Q

what antibiotics have some action against coliforms that produce ESBLs

A

Pivmecillinam

Temocillin

76
Q

when is Temocillin given

A

Useful for treating complicated UTI/urosepsis in patients whose renal function is too poor for gentamicin

77
Q

when is Cefalexin used

A

in pregnancy

78
Q

features of Co-amoxiclav

A

associated with C. Diff

BUT safe to use in pregnancy

79
Q

features of Ciprofloxacin

A

risk of C.Diff infection

not used in pregnant women or young children

80
Q

when do you need to use Ciprofloxacin

A

Pseudomonas sp infection

- only oral drug that can treat it

81
Q

Empirical antibiotic treatment for UTI

A

Female lower UTI
- Trimethoprim or nitrofurantoin orally (3 days)

Uncatheterised male UTI
- Trimethoprim or nitrofurantoin orally (7 days)

Complicated UTI or pyelonephritis (GP)
- Co-amoxiclav or co-trimoxazole (14 days)

Complicated UTI or pyelonephritis (Hospital)
- Amoxicillin and gentamicin IV for 3 days (cotrimoxazole and gentamicin if penicillin allergy)

82
Q

what is Asymptomatic bacteriuria

A

Significant bacteriuria (>10 to the power of 5 orgs/mL)

Patient is asymptomatic, condition detected incidentally.

No pus cells in urine

Antibiotic treatment often NOT required, especially in the elderly

May recur even if antibiotic treatment is given

83
Q

when are pregnant women screened for Asymptomatic bacteriuria

A

All pregnant women screened at 1st antenatal visit

84
Q

what can happen is asymptomatic bacteriuria is left untreated in pregnant females

A

Usually treated with antibiotics in pregnancy.
If left untreated:
- 20-30% progress to pyelonephritis
- May lead to intra-uterine growth retardation (IUGR) or premature labour

85
Q

what is Abacterial cystitis/
Urethral syndrome

A

Patient has symptoms of UTI

Pus cells present in urine, but no significant growth on culture

May be an early phase of UTI

May be due to urethral trauma - “honeymoon cystitis”

May be due to urethritis caused by chlamydia, gonorrhoea

86
Q

what can provide symptomatic relief

A

Alkalinising the urine may help

87
Q

when should UTI in catheterised patients be treated

A

> 10 to the power of 5 orgs/mL

ONLY given antibiotics if there is supporting evidence of UTI (fever, symptoms etc.)

Renal SB (15 decks)

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