extenuating circumstances

Hey guys,

I had just received my AS results and did not get the grades I wanted to. I would like to retake the whole year of AS again. However, I would like to apply to Dentistry and understand that they do not accept resit applicants that complete their a levels 3 years unless there was extenuating circumstances. Well. My mother suffers from kidney failure, and has to undergo kidney dialysis 3 days a week, leaving her very weak during her days off. I feel like since I would look after my mother a lot, it would get in the way of properly revising for my subjects, which I feel was ultimately the reason I had not done very well this year. However, my mother has been suffering from kidney failure for 3 years now, and I am not sure if this would count as a 'extenuating circumstance'?

Any help will be greatly appreciated