Cauda equina: measure the residual

Question 1When should you scan the bladder in suspected cauda equina syndrome?

1. aWithin about 10 minutes after the patient has tried to pass urine
2. bAfter a catheter has been inserted
3. cOnly before the patient voids
4. dThe next morning

Question 2How do you estimate bladder volume from three diameters in centimetres?

1. aWidth × height × length × 0.52
2. bWidth + height + length
3. cWidth × height × length × 2
4. dLength × 0.52 only

Question 3A patient with back pain and saddle numbness has a post-void residual of 40 mL. What next?

1. aRepeat the bladder scan in a week
2. bUrgent MRI is still needed, because a normal residual does not exclude the syndrome
3. cCauda equina syndrome is excluded
4. dDischarge with analgesia

Question 4Which finding is most worrying?

1. aA full bladder before voiding
2. bA large residual which the patient cannot feel
3. cA bladder which empties completely
4. dA small residual after voiding

Question 5Which of these can also cause a large post-void residual?

1. aOpioids, anticholinergic drugs and prostate enlargement
2. bDehydration alone
3. cA recent meal
4. dOnly cauda equina syndrome