Hi Emily, I hope you see this post and I hope you are feeling a lot better by now.
I have IC too and am treating it successfully using diet and supplements without the help of a doctor. I've had this with chronic pain for at least ten years, but have been mostly symptom free since I started looking into diet - (about 6 months on an alkalizing diet - 4 months symptom free). It is a horrible thing to live with and 4 years is 4 years too long.
I'll get onto the specific question about the acidic fruit for the Liver Flush but first want to give you some general info I have found about IC.
In a nutshell the diet I follow is about eating an alkalizing diet and finding foods that trigger you bladder to flare and eliminating them.
People with IC generally have sores and ulcers inside their bladder, eating acidic food like fruit, sodas, refined foods or even meat is like pouring acid onto an open wound! Ouch!
Also food allergies play a big part, there are cells in the bladder that release histmines, when you eat certain trigger foods it causes these histmines to go into overdrive, again causing much pain.
Animal protein is both acidic and causes lots of problems for people with IC as it can trigger of the release of histamine in the bladder.
There is an excellent site for people who are working on healing IC naturally, you might want to check out http://groups.yahoo.com/group/icpuzzle/
The lady who runs this site is a nurse and has written a book about her experience of healing her IC naturally. I hav't been able to get hold of her book yet as she's currently woring on the 2nd edition but her site has been enough to get me started.
If you go to 'files' there is an article that explains more about the diet a lot better than I could. it also explains about protein and how it is possible to get all your protein requirements from veggies (broccoli is actually very high in protein), grains and nuts and seeds and give some tips on how to help with IC symptoms whilst you work on healing from this. The file is called 'getting started on your alkalizing program'
There is also a message board, everyone is so lovely and helpful at the site and will answer any questions you have, its been a huge life saver for me to be able to speak to people who are having good results treating their IC.
More specifically regarding the liver flush.
After 6 months of being on the alkalizing diet I was able to tolerate apples and pink grapefruit for the flush no problem and know other people with IC who also were fine with it.
There are a few things that you might try though as you probably need to do the flush sooner.
I picked red apples instead of green as they are less acidic. I didn't eat apples prior to the flush (didn't want to push my luck too far!), just used them with the Epsom Salts . I made sure I drank lots of water as the Epsom Salts are very dehydrating. my kidneys did ache slightly through the night, (though a lot of people report this) but I found it a bit worrying with having IC, I was fine in the morning though. Just to warn you to keep hydrated with plenty of water.
Have you come accross prelief? This is something you can take with food to take the acidity out of food, you could consider taking this with the fruit juices. I think it will mean that the apples aren't doing their job of helping to soften the stones as effectively but it should prevent your bladder from flaring too horribly. If you are in America you can buy this most drugstores or supermarkets or you can get it from the internet, not sure I'm allowed to post the site but you can do a search in google to find it. I know people who have used this in a successful flush.
As regards softening the stones, I drink breakstone tea which helps to break down both gall and kidney stones gently. My bladder can tolerate this. You make this up from a herb called chanca piedra (or quebra pedra). It works slowly over several months but again, I know people who did struggle with the flushes who have used this successfully treating their gall stones long term. As I couldn't eat the apples, I took it for 3 weeks, 3 times daily before the flush but in all honesty am not sure if this was long enough to break up any stones.
You take it 3 weeks on then have a break for one week, not to be taken if pregnant of planning on getting pregnant.
Hope some of this helps, please free to ask any more questions.