Hi My Wife Has Problems With Dehydration, And This Has

Hi
My wife has problems with dehydration, and this has been going on for at least 2 years.
She has an Ileostomy, the large bowl, and the rectum, has been removed.
This was not a cancer related operation, the reason was that the rectum did not function anymore.
Most off the time the discharge, is jet black, and thin as water, on the odd occasion, it is off a semmy solid matter.
Have been admitted to hospital last year 4 times, with severe dehydration, no one has come up with a positive explanation.
She also had the bag function taking over from the urine production, and for a scary time, that she did not pass any urine, except for a few drips, no explanation from the hospital.
Her condition at the moment is, that she has absolutely no energie, even the simple task off having a shower, is an effort.
I have kept as short as possibly, and any advise would be appreciated.
Regards Jack Willems 77 Years Wife Bella Willems 73 Years
1 Waikana Street Broad Bay Dunedin
Medicine List Omeprazol / Metformin / Diltiazem / Atorvastation / Levothyroxine / Dilatrend / Dicarz / Aspirin