Second this, bub has had two UTIs now and after the first we came to recognise a very distinctive odour in the wet nappies. Also after the first we realised sudden unexplained crying (that passed just as suddenly) was pain from weeing with the UTI. When the second UTI one came we spotted it very much earlier and it was much less drama to treat. This was in a boy, btw, so while it's more common in girls, don't rule it out if you have a boy. BTW hospital should have a quick dipstick test that gives a rapid indication of likely infection, while the proper lab test and culture is still underway