Poor Urinary Output

Question 1

What is the normal urine output

Answer 1

1/ml/kg/hr

Question 2

What is oliguria and anuria

Answer 2

Oliguria - reduced output = <400ml/day (<0.5ml/kg/hour)

Anuria - complete absence of output

Question 3

Why is anuria important

Answer 3

May be the first and only sign of acute renal failure

=> Death due to hyperkalaemia, profound acidosis, pulmonary oedema

Question 4

What are the most common causes for reduced urinary output

Answer 4

Hypovolaemia (dehydration, haemorrhage)
Hypotension (sepsis, pancreatitis)
Acute tubular necrosis 
BPH 
Blocker catheter

Question 5

What are the pre-renal causes of reduced urinary output

Answer 5

Hypovolaemia (dehydration, haemorrhage)
Hypotension (sepsis, pancreatitis)
Heart failure
Reduced local perfusion of kidneys

Question 6

What are the renal causes of reduced urinary output

Answer 6

Acute tubular necrosis
Glomerulonephritis
Interstitial nephritis (NSAIDs, antibiotics)
Vascular (vasculitides, HUS, TTP, DIC, malignancy hypertension, scleroderma)
Infection (malaria, legionnaire’s, leptospirosis)
Multiple myeloma

Question 7

What are the post-renal causes of reduced urinary output

Answer 7

Abdominal/pelvic mass compressing ureters
Complication of surgery 
Bilateral calculi 
Retroperitoneal fibrosis 
Neuropathic bladder
Drugs (anticholinergics, sympathomimetics)
Bladder stones or tumour 
Uterovaginal prolapse 
BPH 
Blocked catheter
Prostate cancer
Urethral stricture 
Trauma 
Infection

Question 8

What is the required fluid intake for adults of average size

Answer 8

3L per 24 hours

Febrile - 500mL for every degree above 37

Question 9

Which drugs are nephrotoxic

Answer 9

NSAIDs
ACEi
Diuretics
Antibiotics - gentamycin, vancomycin

Question 10

What should be looked for in an inpatients notes if they have reduced urinary output

Answer 10

Fluid balance chart
Surgical operative notes
Drug charts
Bloods: haemoglobin and renal function 
Past medical history

Question 11

What should be looked for on examination of a patient with reduced urinary output

Answer 11

Catheterised => check the catheter bag for urine output and any blood + colour

Signs of dehydration: dry lipids mouth and tongue.
Tachycardia, narrow pulse pressure, hypotension, prolonged CRT (>2s), cool peripheries

Ask patient if they feel dizzy on standing

Fluid overload - signs of heart failure (Raised JVP, ascites, peripheral oedema, hepatosplenomegaly, basal lung creps, S3, displaced apex beat

Urinary retention signs: palpable, distended bladder, dull to percussion

Question 12

Typical presentation for a patient with cauda equina syndrome

Answer 12

Lower back pain
Urinary retention
Lower motor neuron signs affecting the lower limbs
Peri-anal numbness
Lax anal tone

Question 13

Management for cauda equina syndrome

Answer 13

Urgent MRI spine

If confirmed - urgent surgical intervention to decompress the affected roots

Question 14

What are the main complications of urethral bladder catheterisation

Answer 14

UTI (esp. Proteus mirabilis)
Urethral trauma ± creation of a false passage
Urethral scarring + stricture
Bladder perforation

Question 15

What are the main complications of chronic urinary retention

Answer 15

Urinary incontinence due to overflow
UTI due to stasis
Bladder stones due to stasis
Hydroureters and hydronephrosis
Renal failure
Acute-on-chronic urinary retention (painful)
Bladder wall hypertrophy and outpouchings

Question 16

Which drugs commonly cause urinary retention

Answer 16

Antimuscarinics e.g. Tolterodine, oxybutynin
Antihistamine e.g. chloerpheniramine, cetirizine
TCAs e.g. amitryptiline, imipramine

Question 17

What are the indications for dialysis in the acute setting

Answer 17

Acute renal failure (oliguria or anuria with deranged renal function)
Severe hyperkalaemia >6.5
Severe acidosis <7.2
Severe pulmonary oedema 
Urea >30 Cr >1000
Uraemic encephalopathy

Question 18

At what level of PSA elevation suggests a risk of prostate cancer

Answer 18

> 10 = high risk
40 = high risk of mets
100 = almost certain mets