The patient, a man in his 70s, had abdominal pain serious enough to send him to a hospital. Doctors there found the culprit: a gallstone had inflamed his pancreas.

Dr Daniel Hall, a surgeon who met with the patient, explained that pancreatitis can be fairly mild, as in this case, or severe enough to cause death. Recovery usually requires five to seven days, some of them in a hospital, during which the stone passes or a doctor uses a flexible scope to remove the blockage.

But “because it can be life-threatening, after patients recover, we usually take out the gall bladder to prevent its happening again,” Hall said. A cholecystectomy, as that operation is known, isn’t high-risk surgery. When done with a laparoscope, it’s usually an outpatient procedure.

But Hall advocates screening all older patients for frailty, and this patient met the criteria. He had coronary artery disease and liver disease, had lost weight and took multiple medications.

Hall’s research, recently published in JAMA Surgery, has found that frail, older adults are more likely than other patients to die after even supposedly minor procedures — and even when the surgery goes well, without complications. Frail, older patients frequently undergo such operations, which surgeons tend to see as routine, simple fixes — but may not be. “Our data indicate that there are no low-risk procedures among patients who are frail,” Hall and co-authors concluded in the study.

What’s frailty? “It’s an accumulation of problems that leave the patient vulnerable to stressors,” said Dr Ronnie Rosenthal, a surgeon at the Yale School of Medicine, US. “And surgery is a big stress.” Even in healthy patients, surgery “demands a lot of reserve from your body,” she added. But when they become frail, “people already use whatever reserve they have just to maintain their daily lives.” After operations, frail patients find it harder than others to regain strength and mobility, and to return to independent lives.

Doctors and researchers assess frailty in a variety of ways. Geriatricians often measure things such as gait and grip strength, and look for unintended weight loss and exhaustion. That face-to-face approach doesn’t work well for researchers examining large populations, so Hall and his colleagues developed a tool they called the risk analysis index. It allows them to calculate frailty based on illnesses, cognitive decline, ability to perform activities of daily living and other factors derived from medical records. They applied that index to about 4,33,000 patients (average age 61) undergoing common surgeries — categorised as low, moderate or high-stress procedures — from 2010 to 2014. Then the team looked at the patients’ subsequent mortality rates.

In this mostly male sample, 8.5 per cent of patients were deemed frail and another 2 per cent very frail. (A 2012 review found that depending on definitions, frailty affects 14 per cent to 24 per cent of the over-65 population.)

Previous studies have shown that surgery poses higher risks for such patients, but “does frailty only matter for the big operations?” Hall wondered. Results from the new study, limited to noncardiac procedures, appear to answer that question.

Surgeons consider operations high-risk if their 30-day mortality rate exceeds 1 per cent. But for frail patients, even the lowest-risk procedures — including removing a cyst from the hand or wrist, repairing a hernia or removing an appendix — had a 1.5 per cent mortality rate within 30 days. For the very frail, the figure was more than 10 per cent.

A moderate-risk procedure like gall bladder removal or joint replacement involved a risk of death that was higher than 5 per cent within a month for frail patients and a nearly 19 per cent for the very frail.

Those numbers rose over time. After six months, roughly 9 per cent of frail patients who’d had the lowest-risk procedures and 16 per cent of those undergoing moderate-risk surgeries had died. So had 35 to 43 per cent of the very frail.

When Hall discussed such matters with his frail patient, whose pancreatitis might never return, the man decided against gall bladder surgery. Time spent in the hospital, possibly in intensive care, and the potential need for recovery in a nursing home sounded unappealing.

Hall said, “We chose not to do the operation.”