Pope Francis, who has just undergone surgery for an inflamed large colon, is believed to be otherwise in relatively good health, despite having had part of his lung removed when young.
Until now, the 84-year old's biggest affliction appeared to be sciatica, a chronic nerve condition that causes, back, hip and leg pain and has occasionally forced him to cancel official events.
He has dubbed the condition "a troublesome guest".
Francis almost died when he was 21 after developing pleurisy -- an inflammation of the tissues that surround the lung -- according to biographer Austen Ivereigh.
He had part of one of his lungs removed in October 1957.
He recalled the incident in a recent book, "Let Us Dream", saying: "I have some sense of how people with coronavirus feel as they struggle to breathe on ventilators."
The Argentine pontiff also talked about the surgical removal of cysts from the top lobe of his right lung in an interview about his health with renowned Argentinian journalist and doctor, Nelson Castro.
He insisted he had made "a complete recovery... and never felt any limitation since then".
In January, Francis received the coronavirus vaccine alongside his predecessor, ex-pope Benedict XVI.
As archbishop of Buenos Aires, Francis was treated by a Chinese acupuncturist for his back pain, Ivereigh wrote in The Tablet Catholic weekly in May.
He also suffered "an almost fatal gallstone infection" at the end of his time as a Jesuit provincial, and had a "brief" issue with his heart in 2004 after a slight narrowing of an artery, the biographer said.
Problems with a "fatty liver" were overcome through changes to his diet.
- 'Walk like a broody chicken' -
The pope's distinctive limp, which becomes more pronounced when he looks tired, is due to a flat foot, rather than his sciatica, Francis told Castro for his book "The Health of Popes".
"When you see me walking like a broody chicken, it's because of that affliction," the pope said.
Francis, who as Jorge Bergoglio was head of the Jesuit order in the 1970s during Argentina's brutal military dictatorship, has also previously sought mental health support.
He spoke with "a great woman psychologist" once a week for six months during the dictatorship, he told Castro, to help him with anxiety.
Nowadays he deals with it by listening to Bach or sipping "mate", a popular Argentinean herbal drink.
The pontiff is reported to go to bed at 9pm and read for an hour before going to sleep for six hours and waking at 4am every day. Lunch is invariably followed by a 45-minute nap.
Francis's Sunday operation was scheduled and performed under general anaesthetic to address symptomatic diverticular stenosis of the colon.
The condition causes potentially painful inflammation of the diverticulum, a pocket that can form on the colon walls and which tend to multiply with age.
Patients with diverticulitis may experience lower abdominal pain, fever or rectal bleeding.
Francis underwent a left hemicolectomy, in which the descending colon -- the part attached to the rectum -- is removed.
He "is in good general condition, alert and breathing spontaneously", spokesman Matteo Bruni said in a statement, adding "a stay of about seven days is expected, barring complications."
Ivereigh noted "how freely and transparently Francis discusses his various conditions, physical and psychological. Imagine any other head of state laying themselves bare this way: Biden? the Queen?"
"How far we are from the Vatican refusing to confirm the Parkinson's everyone could see in the face of John Paul II," he wrote in The Tablet.