Your next patient is a 4 yo who has a UTI and his mother tells you that he hasn’t passed urine for more than 10 hours. Your nurse does a bladder scan…. but you’re not sure what to do when she tells you that the volume is 130 mls.

As always, you’re saved by a formula!

The normal bladder capacity for children 0–8 years = (age + 2)
x 30mL

And to remind you, urinary retention is defined as inability to empty the bladder for more than 12 hours with a volume of urine greater than expected for age or a palpably distended bladder.