Hi Paula
water retention is a very common problem in cancer patients, as Lyn has said it is very important to establish if it is Oedema or steroid bloating. Judging by previous information I would be inclined to think that it is Oedema.
There are several causes of this, Lyn has mentioned and explained Lymphodema and how to tell the difference between this and steroidal bloating.
If your Dad has swollen legs or arms it is a really good idea to ask your medical team if he should slightly elevate these whenever possible, so legs on a footstool or, if you have a recliner,raise the lower support. Keep his arms up on the arm rests of the chair away from his sides.
At night in bed he may need to put a small pillow below his legs or arms.
There are also special elasticated stockings, or bandages that can be used to gently push the water back from the area just below the skin back into the blood vessesls so that it gets transported away.
It is vital that he continues to take in fluids and as Lyn also says checking his urinary output is an indicator of how well Dad is processing fluids. Your medical team can advise you how best to do this and what quantities you should be aiming for.
One of the later stage issues is when protein levels (albumin) become very low this is another potential cause of water retention.
If Dad is retaining water he probably will be finding that standing and moving about is harder, try to encourage him to do a little but often.
Right now just having you nearby to give him and your Mum as much love and support as you can will be the best tonic you can give.
You are in my thoughts
warmest wishes
xxx
Mo