Squatting a lot and dribbling (not mine). UTI or marking?

A client's dog peed the normal amount the first two times she went on our walk and then squatted a whole bunch and just dribbled the rest of the way. I didn't notice any blood and the dog's attitude seems fine, though to be honest I don't know her. My gut tells me that this isn't marking, but something medical.
 
Should I volunteer to take the dog to the vet (with them footing the bill)? Meaning is this urgent? They won't be back until Friday and I don't want the dog to be uncomfortable or in pain until then if it's something medical. Help. This is a first for me.