A US woman who died at the age of 99 of natural causes lived with a rare congenital condition all her life where her organs were on the wrong side of her body.

Rose Marie Bentley, a pet feed store owner, passed away in October 2017. She donated her body to research at a university in Portland, Oregon. Students in an anatomy class first noticed that many of her organs were not where they should have been.

Despite multiple surgeries, her condition had not been identified. Doctors are astonished at the fact that Mrs Bentley could live such a long and healthy life despite the condition.

She had situs inversus with levocardia - her liver, stomach and other abdominal organs were reversed right to left. Her heart; however, remained in the normal position.

Dr Cam Walker, an assistant professor of anatomy at Oregon Health and Science University, said that the condition is exceedingly unusual.

Dr Walker mentioned that the discovery began when his students were dissecting the cardiovascular cavity and could not locate a major vessel. It was realized that Mrs Bentleys body was unique.

Situs inversus with levocardia is rare. It occurs about once in every 22,000 births. The condition is normally associated with life-threatening heart issues and other abnormalities. This makes Mrs Bentleys long life even more remarkable.

Dr Walker states that it is estimated that only one in 50 million people born with this rare condition live into adulthood. He and his colleagues believe that Mrs Bentley may be the oldest person known to live with this condition. Scientists know about only two other cases where patients reached the age of 70. Dr Walker said that the students will never forget it.

Mrs Bentleys children told the university that she lived a very healthy life, without any chronic conditions except for arthritis. She had undergone three surgeries, but only the doctor who removed her appendix noted its atypical location in her body.