There was indeed a scientific investigation after the (widely reported) fire that ignited during a patient’s cervical conization procedure at the University of Tokyo Hospital, causing “a wide range of burns [to the] thighs [and] rear” to the patient. That scientific report is lavishly illustrated with photographs.
To determine whether the accident could have been caused by an ill-timed fart from the patient combined with a high power laser — rather than negligence by the doctors or equipment failure — researchers conducted tests, then issued a report.
After reviewing the surgery video and testimony of the surgeon, it was clear that the fire did not start on any coverings or drapes the patient had on, nor on any alcohol based antiseptic. This left but one option for the researchers: recreate the conditions using a “test doll”, laser, and bucket of lean beef with intestinal gasses.
A potential problem with the fart lighting hypothesis was figuring out how the fart could have gotten to the vaginal area, since intestinal gases are released by the butt, located on the opposite side of the surgical field. The scientists set up the test doll in a position to replicate the event, and used a test gas to track the direction the fart may have flowed in. By following smoke fumes fed through a tube, as seen in the pictures here starting from the top going down, it could be shown that gasses emitted from the rear could get sucked up towards the vagina. It is thought that this trapped intestinal gas (the patient’s fart) could begin the combustion process once the energy from the laser interacted with the flesh and gas.
To add even more fiber to the experiment, the researchers took lean beef, placed the lean beef in a bucket, and filled that bucket with intestinal gasses of various concentrations. By firing a laser at the lean beef, a very small explosion could ignite the experimental farts, as shown below.
The researches conclude that: (1) farts can be lit on fire by using a laser, and that (2) those farts could possibly be lit on fire if those farts are sucked into a vagina while a laser is aimed at that vagina.
BONUS: A music video that perhaps expresses the doctors’ reaction when the incident occurred:
“We Didn’t Start The Fire”, by Billy Joel:
BONUS (distantly related topic): Someone’s video explanation of a different way to light a fart (using a lighter):
BONUS (extension of that distantly related topic): Fart lighting compilation: