The lives of thousands of non-cardiac NHS emergency surgery patients are being risked by poor care and delays in treatment, leading surgeons say.
The Royal College of Surgeons says poor access to facilities like theatres and scans in the UK means some abdominal emergencies are not spotted in time.
The RCS also says not enough patients receive critical care after surgery.
NHS managers said they, surgeons and ambulance services needed to work together to achieve "real change".
The RCS adds that junior staff are often left to deal with complications.
A report by the college highlights figures that show that about 170,000 patients undergo non-cardiac emergency operations each year.
Of those, 100,000 will develop complications and 25,000 of these patients will die.
Among the elderly, deaths can climb to 40%.
The report says the non-cardiac category includes most major gastro-intestinal and vascular procedures.
Emergency major gastrointestinal (abdominal) surgery has one of the highest mortalities, which can reach 50% in the over 80s, the report says.
The report also says that while survival rates vary from hospital to hospital, there can even be significant differences from day-to-day within the same institution.
It also highlights other research which shows that the chance of a patient dying in a UK hospital is 10% higher if they are admitted at a weekend rather than during the week.
The report says that poor access to facilities such as scanners and operating theatres means diagnosis is sometimes slow, not enough patients receive critical care after surgery and when they do it is for too short a time.
It also says less experienced junior staff are often left to deal with complex and dangerous cases.
There is also the suggestion that elective or planned surgery has been prioritised over emergency surgery and some may link this to the pressure on hospitals to bring down waiting lists.
The study says hospitals need to provide fast access to operating theatres.
Iain Anderson, the author of the report and a consultant general surgeon at Salford Royal NHS Foundation Trust, said trusts needed to acknowledge that problems exist and review the way their services work.
"Every single emergency patient who comes through the door of an NHS hospital should have an individual risk assessment, diagnosis, treatment plan and post-operative care plan prioritised according to need," he said.
"Instead we have some of the NHS's sickest patients languishing on inappropriate wards, treated by juniors and with no plan in place to deal promptly with unexpected complications.
"These tend to be the patients who end up in intensive care units for lengthy periods of time or, sadly, too sick to be helped."
Mr Anderson told Radio 4's Today programme the high-risk nature of emergency abdominal surgery was not being recognised.
"These are the largest abdominal operations and emergency operations and I think there's been a general failure to understand just how high risk this surgery is, both by the patients - sometimes by the doctors - but certainly by health service managers."
The report suggests improvements but the surgeons say NHS managers in particular need to recognise the problems facing those described as the "forgotten patients" of the health service.
David Stout, deputy chief executive of the NHS Confederation which represents NHS managers, says: "If we want to make a real change to emergency services we need to get everyone - managers, surgeons and ambulances services - working together to ensure patients receive properly planned, quality surgical care."
Bruce Taylor, president of the Intensive Care Society, said: "It is vital that the guidance is initiated as it in the best interest for potentially vulnerable patients who require surgical procedures."
A spokesman at the Department of Health said the NHS was being modernised to improve results for patients and safety was at the heart of the service.
"It is essential that hospitals provide the safest possible care for patients," he said.
"Hospitals should follow this guidance and monitor the quality of care they are giving to their patients and ensure that they are providing appropriate levels of services and staffing."