Hi again Di! I know how worried you are. Many of us here have been in tears and have even had to take anti-depressants and anti-anxiety meds, so you're not alone. But please try not to worry!
I'm not a doctor, so please take everything I say with the appropriate grain of salt. :D
First - "pph" is a kind of surgery for hemorrhoids (Procedure for Prolapsed Hemorrhoids, if I'm not mistaken). It's supposed to be less painful than traditional hemorrhoid surgery, but is still painful nonetheless, from what I've heard.
Second - "LIS" stands for lateral internal sphincterotomy. This is an operation to heal an anal fissure. It involves making a small cut in the internal sphincter muscle so that a fissure can heal. It sounds crazy, but it is quite successful. :D
But, since you don't have hemorrhoids or a fissure, neither of these two surgeries are important right now for your case.
The operation you are thinking about is a fistulotomy. I had that on June 27th and it was a breeze!
If the fistula is low, then that means it doesn't track through the sphincter muscle, or it only tracks through a very small amount of spincter muscle. In these cases, a simple fistulotomy usually solves the problem. The doc just cuts it to lay it open and it heals like an open wound would.
If it's a high fistula, then that means that it tracks through the sphincter muscle. Much of the time in these cases, the doc doesn't want to do a simple fistulotomy because cutting the sphincter muscle could cause continence problems. Instead they insert a seton, which is like a string that slowly cuts through the sphincter muscle, like cutting cheese with a string, but so slowly that the sphincter can heal back again. This usually avoids continence problems. However, sometimes docs will do a fistulotomy for high fistulas instead of a seton - that's what Val had. They make the decision during the surgery, when they can get a better look at what's going on.
As far as the pros and cons of the surgery, I think that depends a lot on your symptoms and what caused the fistula. It won't heal without the surgery. In some cases, fistulas can form secondary tracks and spread, but I believe that's more common when there is an underlying condition, like Crohns, for example. From what I understand, recurrence rates are pretty low for simple fistulas. More complex fistulas (very high ones and those associated with Crohns) can recur.
I really think you should contact your surgeon and ask some more questions so that you are comfortable with the decision you make. A core principle in medical ethics is "informed consent" - you must give your informed consent to a procedure, and that means you are entitled to ask questions.
Many of us have gone to our surgeons (or called them up) with a list of questions to ask, such as:
What does this surgery involve?
What are the possible complications?
What will happen if I don't have the surgery?
How many of these surgeries have you done?
How many complications have you had?
What are the options in case I have a complication?
What will the recovery involve and how long will it be?
Those are some of the questions I asked my surgeon and I felt a lot better about having the surgery after my questions were answered.
There are a few boardies here who have also had a fistulotomy, so hopefully they will chime in. Don't be afraid to ask your doc all kinds of questions. It's your body and you have a right to know what they want to do to it!