Our pet guinea-pig has been on three different courses of antibiotics recently but he still has a bladder infection. There is still blood in his urine. Why is it not getting better? A Mitchell, Wallingford

Most simple bacterial bladder infections should clear in around seven to 10 days on antibiotics. Your guinea pig may have other complications eg bladder stones. These form from minerals (like calcium and magnesium) in the urine and sometimes they can be as big as marbles – they are sharp and so damage the bladder lining. There are other possibilities as well like bladder tumours. Perhaps having a urine sample analysed, an ultrasound scan or X-ray would help get to the bottom of this problem. Time for another trip to your vet.

My old cat has been diagnosed with kidney failure and my vet wants to put him on a kidney diet. Can I avoid this expense and give him a home diet and do you have a recipe? G Powell, Banbury

Cats with kidney failure can live up to six times longer on kidney diets than those who are not. These diets are designed to reduce the amount of work the kidneys have to do while also providing all the essential nutrients that cats need. It is near impossible to design a home diet which comes anywhere near this. Even though these kidney diets are a bit more expensive than most normal cat foods the benefits to your cat will be well worth the extra cost.

I have a 10-year-old dog that was in heat about two months ago. Last week she started panting and bleeding from her vagina. The blood was a dark colour. She is refusing to eat and drinking lots of water. Is she having a miscarriage? Y Unwin, Oxfordshire

If she was mated when she was in heat then it is possible she got pregnant and is losing the puppies. If pregnant she would show some of the other familiar signs like swelling of the belly and milk glands. It is worrying that she is not eating and drinking lots of water as these are signs that appear when there is a womb infection (pyometra). This can be life threatening and almost all cases need a hysterectomy for a complete cure. A vet examination is essential here and the sooner the better. Your vet may want to take X-rays, blood samples and/or an ultrasound scan to get to the bottom of this problem.