Poor urinary output

Question 1

What is a healthy urine output?

Answer 1

1ml/kg/hour

oliguria = reduced output
anuria =no output

Question 2

Poor urinary output may precipitate acute renal failure. What are the complications of this?

Answer 2

Hyperkalaemia, acidosis, pulmonary oedema

Question 3

What are the 3 general requirements for normal urine output

Answer 3

1. Adequate blood flow to kidneys (pre renal)
2. Functioning kidneys (renal)
3. Good flow of urine from kidneys -> ureters -> bladder -> urethra

Question 4

What are the ddx of poor urine output

Answer 4

1. Pre renal: hypovolaemia (dehydration/haemorrhage), hypotension (sepsis/pancreatitis), heart failure
2. Renal: acute tubular necrosis, glomerulonephritis, interstitial nephritis (due to NSAIDS/Abx), vascular causes, infectious causes
3. Post renal: BPH, blocked catheter, neuropathic bladder, calculi,

Question 5

Name 2 surgical procedures that could cause poor urinary output

Answer 5

Pelvic surgery - damage to urinary tract

Laparotomies - dehydration due to water evaporation in open abdominal cavity

Question 6

Which drugs are nephrotoxic

Answer 6

NSAIDS, ACEi, diuretics and some Abx (gentamicin, vancomycin).

Stop these drugs if patient has oliguria or decreased renal function

Question 7

What is creatinine’s relationship with acute kidney injury

Answer 7

50% increase in baseline creatinine constitutes AKI

AKI indicates renal hypoperfusion (pre renal) or renal aetiology

Question 8

Thirstiness indicates what diagnosis

Answer 8

Dehydrationand hypovolaemia

Question 9

Haematuria may indicate what?

Answer 9

Glomerulonephritis

Question 10

Swollen ankles or frothy urine may indicate?

Answer 10

Nephrotic syndrome

Question 11

Rashes/arthralgies suggest what?

Answer 11

Multisystem vasculitis or SLE

Question 12

What are the signs of HF

Answer 12

Raised JVP, displaced apex beat, gallop rhythm (3rd heart sound), bilateral basal lung crepitations, dependent oedema (sacrum/ankles).

Question 13

Which investigations should be done in someone with poor urinary output

Answer 13

1. Check that catheter has been flushed
2. VBG
3. Bloods - raised urea = hypovolaemia. Creatinine raised = renal injury (e.g. acute tubular necrosis)
4. Fluid challenge
5. USS in non-catheterized patients

Question 14

How can you differentiate between acute obstruction and chronic obstruction

Answer 14

Acute obstruction (or acute on chronic) presents with pain whereas chronic obstruction is painless

Question 15

Lower back pain, urinary retention, LMN lesion affecting both limbs, perianal numbness and lax anal tone are signs of what?

Answer 15

Cauda equina - medical emergency

Question 16

What may indicate that there is a urethral stricture as a cause of poor urinary retention

Answer 16

Repeated trauma to urethra, e.g. through many cytoscopies