Urinalysis

Question 1

DDx myoglobinuria:

Answer 1

‘Tea-coloured/ red-brown’ urine = myoglobin/ rhabdo.

Causes toxic ATN/AKI.

DDx:
- Haemoglobinuria
- Porphyria
- Bile pigments/ bilirubin
- Drugs: eg. metronidazole

Question 2

Components of urine dipstick:

Answer 2

Leuks
- >10 = UTI likely

Nitrites
- Most UTI bugs produce
- But, test poorly sensitive (60%)
–> Not good for upper tract
–> Requires hours of stasis
- NOT A RULE-OUT

RCC
- Doesn’t differentiate intact red cells/ haemoglobin/ myoglobin
- If no RCC on the count, think of these.

Protein
- Albumin only

Specific Gravity
- ‘Stuff’ in there
- High: concentrated (SIADH, dehydr), gluc/prot/bili/contrast etc.

Ketones
- Tiny normal

Glucose
- Never normal

Bilirubin
- Never normal

Question 3

Causes of high specific gravity:

Answer 3

More ‘stuff’ in urine

Concentrated (ie. dehydration, SIADH)
Glucose
Bilirubin
Protein
Radiocontrast

Question 4

Causes of haematuria:

Answer 4

Fever
Intense exercise (RCC and myoglobin)
Renal tract infection
Renal pathology (tumour, infarct, trauma)
Glomerulonephritis
Bleeding diathesis
Iatrogenic: IDC
Non-urinary tract (eg. menses)

Red COLOURED: beetroot, metronidazole, food colourings, myoglobin, porphyrins

False +: Old sample, myoglob/Hb/pophyrins

Question 5

Approach to haematuria:

Answer 5

Benign/transient
vs
Structural
vs
Glomerulonephritic.

_____

MACROscopic always needs work up:
–> Urine dip/ cells/ cytology, renal function, coags.
–> Imaging: USS renal tract if young, CT IV pyelogram if older
–> Urology if structural
–> Nephrology if glomerulonephritic: (AKI/proteinuria/HTN/casts)

MICROscopic, +-. If low risk/ transient cause likely –> repeat in 2-4 weeks.

Question 6

Causes of proteinuria:

Answer 6

Overflow:
- High protein diet
- Multiple myeloma
- Rhabdo (myoglobin)
- Haemolysis (Hb)

More filtered
- Febrile illness
- Intense exercise
- Renal disease: glomerular, tubulointerstitial

Post-renal
- UTI
- Neoplasm

Question 7

What is ‘pyruria’? What is ‘sterile pyuria’?

Answer 7

Presence of leuks in urine:
- Positive on dipstick
- >10 x5 on count
- >3 per high-power-field on microsc

Sterile = culture negative.

Question 8

Differential sterile pyuria:

Answer 8

UTI
Recently treated UTI
Non-culturable organism: STI, fungal, TB.
Contained infection: Pyeloabscess, prostatitis

NON-INFECT
Renal colic
Renal malignancy
Interstitial nephritis/ cystitis

SYSTEMIC
Bacteraemia
Acute febrile illness
Steroids

Cervicitis, PID