Hi Mandypink,
This link should help with the basics,
http://www.kidneypatientguide.org.uk/contents.php, whilst PKD is a specific condition the resultant kidney failure , and it's consequences are pretty much the same.
Some common questions answered: - It is not possible to predict just when your kidneys will fail or even if they actually will.
There is no such thing as a, 'kidney diet', until you are actually on dialysis, the only useful diet is the one pushed by the medical world, i.e. 'five a day' - five portions of fruit or vegetables per day, along with a portion of first class protein (usually meat/fish).
This should keep you healthy.
You will find there is a common misunderstanding about diet, the diet mentioned is for patients on dialysis, because dialysis doe's not remove Potassium and Phosphates very well.
To counter this dialysis patents have to take over one of the kidneys functions, controlling the levels of Potassium and Phosphate in the body. Most of our normal foods have both these elements in them to differing levels, so when on dialysis, we have to pick and choose the foods we eat to keep them at safe levels.
If you make changes to your diet you must remember to tell your nephrologist/dietician about it.
Calcium - the kidneys are involved in the control of calcium, again our 'normal' foods tend to supply more than is needed, as the condition progresses it may become necessary to reduce calcium intake, usually by cutting out cheese, and reducing milk.
If any dietary adjustments are required your nephrologist will tell you.
There has been research going on looking for a cure, the result to date is a drug said to slow down the progress of PKD in some patients, however NICE has said the benefits do not justify the cost so it is not in use at the moment in the UK.
As the condition progresses, you can become anaemic (low haemoglobin or low red cell count) due to the kidneys not producing a hormone called EPO (short name), this should be dealt with, usually by iron infusions, and/or EPO injections, over the counter iron pills are a waste of money.
Blood Pressure (PB) - this needs to be kept down as high PB destroys kidneys, target is 120/80.
Take care with anything you find on the internet, there is a lot of dangerous rubbish out there.
Best wishes.