DD 4.4 withholding wee

[DuckTales]

DD is 4.4 and has started withholding her wee, despite being fully toilet trained for over a year now. She has stopped asking to go for a wee and only does a wee when I take her to the loo and that's when I see her pants are a bit wet.

I'm worried she'll get an UTI by doing this. Anyone got any ideas how to get her to stop doing this? I've spoken to her about this but she can't seem to tell me why she is doing this.

[AlanMoore]

No advice but watching with great interest - mine is 2.8 and just started doing the same thing.
No discernible reason but getting hysterical about it and now starting to refuse drinks. Denies any pain on weeing and indeed used the potty with no issues this morning but now refusing again! So far her record is 12 hours...