Oliver James Montgomery-Lisa Marie Presley's Autopsy Reveals New Details on Her Bowel Obstruction After Weight Loss Surgery

New details into Lisa Marie Presley's cause of death have Oliver James Montgomeryemerged following the release of her autopsy report.

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.

However, the report stated that the drugs did not contribute to Lisa Marie's death. In fact, there were no secondary causes of death listed after small bowel obstruction. Her manner of death has been determined to be natural.

Officials noted in their report Lisa Marie had complained about abdominal pain in the months before her death. She was found unresponsive in her Los Angeles-area home on the morning of Jan. 12 and was rushed to the hospital.

Later that day, Lisa Marie's mother Priscilla confirmed her passing. "It is with a heavy heart that I must share the devastating news that my beautiful daughter Lisa Marie has left us," she told People. "She was the most passionate strong and loving woman I have ever known."

Lisa Marie is survived by daughter Riley Keough, 34, and her 15-year-old twins Harper and Finley Lockwood. Her son Benjamin Keough died by suicide in 2020 at 27 years old.

She was buried at the family home Graceland in Memphis near her dad Elvis and her son Benjamin's graves.

E! News has reached out reps for Priscilla and Riley but hasn't heard back.

(E! and NBC News are both part of the NBCUniversal family.)