A new study shows that those who donated part of their liver experience both physical and psychological complications years later.

The liver is the largest organ in the body, and it performs many different roles, including filtering poisons from the body, creating bile that aids digestion and converting food into energy. When a person donates a portion of their liver for transplant, the remaining liver in the donor’s body regrows to full size within a couple months.

But according to the study, nearly half of the 83 donors surveyed suffered from pain, digestive problems and/or depression three or more years after the surgery. About 31 percent said they had diarrhea or an intolerance to fatty foods and about 10 percent said they had gastroesophageal reflux.

“There is a risk for some long-term complaints, which may be potentially controllable by workup modifications, improvements in surgical techniques, and a thorough follow-up of donors at the transplant centers,” said Georgios Sotiropoulos, lead researcher and professor of surgery and transplantation at University Hospital Essen in Germany.

About 4,500 people have donated a portion of their liver for transplant in the U.S., according to the national transplant database. The first such surgery was performed in 1989.