Poor urinary output (oxford clin cases)

Question 1

What should you do when informed a catheterised patient in hospital has stopped passing urine?

Answer 1

Ask about the history of urine output- if it suddenly stopped check if the catheter is blocked by flushing
Look at the patients obs- blood pressure, resp rate, oxygen sats, temperature to get an idea of whether the patient is unwell

Question 2

What is an adults normal urine output?

Answer 2

1 mL/kg/hour

Question 3

What is oliguria numerically defined as?

Answer 3

<0.5 mL/kg/hour urine output

Question 4

How serious of a symptom is anuria and why

Answer 4

Very serious- it can be the first sign of acute kidney failure and this may result in patient death by hyperkalemia, acidosis or pulmonary oedema if the kidney is unable to carry out its usual role

Question 5

What 3 things does normal urine output require?

Answer 5

Adequate blood supply to the kidney
The kidney to be functioning normally
Adequate flow of urine from the kidney to the bladder and then from the bladder out the body

Question 6

What differentials might you have if someone presents with reduced urine output? Class your differentials anatomically

Answer 6

Pre renal- hypovolemia, hypotension, reduced local blood supply due to obstruction
Renal- acute tubular necrosis, glomerulonephritis, interstitial nephritis, vascular causes, infection of kidneys
Post renal- obstruction of the ureter (bilateral calculi, masses, fibrosis), bladder (neuropathic bladder, stones, tumor), urethra (BPH, blocked catheter)

Question 7

What might you look at in the patients notes to gain an idea of why there is reduced urinary output?

Answer 7

Fluid balance chart
Recent surgery
Blood count
Renal function
Existing conditions
Drug chart

Question 8

Why is looking at a patients fluid balance chart important when they have reduced urinary output and what can it tell you?

Answer 8

Fluid balance- is the patient intaking fluid more/ equal to what they are excreting? Is the fluid balance positive

Question 9

How much fluid does an adult require per day?

Answer 9

3L

Question 10

How much extra fluid do febrile patients require?

Answer 10

500 mL extra per day for every degree above 36 their temperature is

Question 11

Why might surgery result in reduced urinary output?

Answer 11

There may be damage to the urinary tract or fibrosis.
If the patient underwent a laparotomy there may be fluid that evaporated from their peritoneal cavity which will not be documented in their fluid chart
There may have been a loss of blood which wasn’t replaced resulting in hypovolemia

Question 12

What may be relevant on the drug chart of a patient with reduced urinary output?

Answer 12

Nephrotoxic drugs like NSAIDs, ACE inhibitors, diuretics, antibiotics (that increase risk of kidney infection)

Question 13

What might be relevant on bloods when someone has reduced urinary output?

Answer 13

Haemoglobin- will show if someone is anaemic but note if there was recent high volume blood loss it will take for haemoglobin to be reduced because it is measured as a % of serum and in blood loss serum is lost too
Renal function- compare peri and post op

Question 14

What % rise in creatinine constitutes acute kidney injury?

Answer 14

Over 50%

Question 15

How does acute kidney injury usually arise?

Answer 15

Usually hypoperfusion

May also be renal aetiology

Question 16

Patients with what condition are predisposed to kidney failure?

Answer 16

Cardiac conditions

Question 17

What symptoms might you want to ask someone to assess whether they might have kidney damage/injury?

Answer 17

Do they have hematuria
Is their urine frothy
Do they have any rashes or vasculitis

Question 18

When is postrenal obstruction very unlikely?

Answer 18

When someone is catheterised

Question 19

How should you check if obstruction is the cause of poor urinary output?

Answer 19

Exclude pre renal causes and once this is done catherise them