Our neighbour (before she moved) use to do this all the time with her 2 dogs. Would sod off to Shrewsbury for the weekend, leave the dogs after her grand children gave false promises that they'd come in and look after the dogs a few times a day.
On many occasions Margaret, the neighbour, would return to a house full of dog crap and the stentch of pee would emit from the house when she opened the windows.
RSPCA as has been mentioned will not do anything unless it's been for a long period of time, neither will the council.
What you could do however if it's REALLY that bad and stopping you sleeping or what have you is, say, call the police, say you've heard a 'thud', not seen the neighbour since and the dogs have been barking and you're worried if the dogs are barking to alert others of a possible problem