The woman's ordeal at Maidstone Hospital, Kent, was revealed in a Community Health Council study of waiting times at more than 200 accident and emergency departments in the UK.
The longest wait was in Canterbury, where a 41-year-old woman suffering stomach pains was kept waiting for 54 hours at the Kent and Canterbury Hospital.
The hospital said she was being cared for by a consultant while she waited.
Only last week a damning independent report into the three major Kent hospitals, including the Kent and Canterbury, declared the A&E departments there "fundamentally unsafe" and said it was remarkable "a major clinical catastrophe" had not taken place.
Longest waits
Other cases included a 30-year-old woman who had taken an overdose having to wait 26 hours before being admitted to a hospital ward at Newham General Hospital in East London.
The Casualty Watch survey is carried out each year by the Association of Community Health Councils for England and Wales (ACHEW) and covered the whole of the UK. This year's survey was carried out on Monday.
"These figures show that resources are over stretched in many hospitals and it is the A&E departments that are taking the strain.
"Casualty waits of this length show that the system is now under year round pressure."
CHC's are being scrapped under the government's Health and Social Care Bill, to be replaced with Patients' Forums.
Hospital pressures
Doctors leaders say the snapshot survey shows the pressures hospitals are having to work under.
Dr Peter Hawker, chairman of the BMA's consultant's committee, said: "Long waiting times in accident and emergency departments reflect the pressures throughout the hospital where vacant beds are like gold dust.
"Doctors and nurses feel miserable about the length of time patients have to wait and the anxiety and distress it causes."
Dr Hawker also criticised the Department of Health for not counting waiting times until after a decision to admit the patient to hospital was taken.
He said this was simply a way of "massaging" the figures.
The Department of Health said it was important that only one of the 20 longest waits were left on trolleys and that all of them had been cared for by nursing staff.
A DOH spokesman said: "Casualty Watch only provides a partial picture of A&E.
"It is a snapshot which doesn't compare progress over time and which doesn't always take account of the way A&E departments have modernised in recent years, especially of the introduction of assessment wards in A&E departments since the early 1990's.
"We are cutting long A&E waits at the same time as the NHS sees more A&E patients than ever before.
"Between October and December 1997, 466,000 patients were admitted to an NHS bed from A&E. Between October and December last year that figure had risen to 532,075."