The singer, who is the only child of Elvis Presley and Priscilla Presley, died of complications stemming from small bowel obstruction on Jan. 12 at the age of 54.
The obstruction was “in the form of a strangulated small bowel caused by adhesions that developed after bariatric surgery years ago,” according to an autopsy report obtained by NBC News July 13. Officials noted in their findings that the issue is a known long-term complication of the procedure.
Bariatric surgery—commonly known as gastric bypass surgery—is a medical weight-loss procedure that modifies the digestive system, typically creating a smaller pouch from the stomach and connecting it directly to the small intestine, according to the Mayo Clinic.
In addition, therapeutic levels of Oxycodone and Buprenorphine—a medication used to treat pain as well as opioid overuse—were found in Lisa Marie’s system at her time of death, per a toxicology report. Traces of Quetiapine—an antipsychotic drug often used as treatment for schizophrenia, bipolar disorder and depression—were also present.