An 80-year-old deaf man was treated as if he had dementia by nurses because no-one had written down he had hearing problems, a health watchdog has found.
Staff at Abergavenny's Nevill Hall Hospital also failed to tell him that he may have developed cancer and fitted a catheter when he was not incontinent.
The acting public services ombudsman upheld the complaint by the man's widow that her husband's care was compromised.
Aneurin Bevan Health Board apologised.
But a deaf charity says it knows of many similar cases despite guidelines over NHS care for deaf or blind people.
The Welsh government is bringing in new rules aimed at ensuring people in Wales who are deaf or blind are not at a disadvantage when they need healthcare.
And in February BBC Wales revealed that health boards were breaching equality laws.
In upholding the complaint against Aneurin Bevan Health Board, Prof Margaret Griffiths agreed the health board had failed to follow record keeping procedures.
The man, known as Mr W as his family have chosen to remain anonymous, was admitted to the hospital for a time in September 2011 with a possible chest infection and then again the following month, where he died.
His widow, Mrs W, complained that her husband's care was compromised because staff did not consider his deafness, even though she told them about it.
The family was also not told of a cancer diagnosis while he was in hospital, with them only learning of it later from their GP, she said.
The woman said her husband was given a catheter - something she thought he would consider "humiliating" - even though he was not incontinent.
She complained that she thought her husband was catheterised for the convenience of staff.
Her husband fell while trying to walk to the toilet because he did not like the catheter and there were no rails around his bed to prevent such a fall.
Acting Public Services Ombudsman for Wales Prof Margaret Griffiths found the health board failed to:
- Record a significant clinical discussion with Mr W about scan results
- Complete and record appropriate assessments relating to the risk of falling and the use of bed rails
- Consult Mr W and record his consent for the insertion of a catheter
- Follow national and local guidance on effective discharge planning
- Keep appropriate records related to the discharge process
- Follow relevant guidance on record-keeping
She said: "In any clinical situation it is clearly important to identify whether or not a person is able to hear and, if not, to identify a suitable way to communicate properly with them."
Richard Williams, of Action on Hearing Loss Cymru, said the charity has heard of many similar cases.
He said: "Sadly, there are real problems deaf people in Wales face accessing services.
"We do come across cases similar to this, not necessarily with such horrific outcomes.
"It's very common amongst our members. Access to health services is one of their biggest concerns.
"It's quite routine that the health service is able to communicate with people only by telephone, which is a massive barrier for deaf people."
Aneurin Bevan Health Board has offered an unreserved apology to the family of Mr W and told them of the actions it has taken.
A spokesperson said: "Whilst no specific recommendation was made with regards to deaf awareness training our staff are expected to make "reasonable adjustments" for people who are deaf under the Equality Act (2010).
"We have been setting up specific training for staff to improve their communication skills when caring for patients who are deaf, or may have difficulty with their hearing."