According to the Guinness Book of World Records, how long did the longest surgery of all time last?

Actually, the longest surgery on record occurred in 2001 and lasted more than four straight days—103 hours to be exact. A team of 20 doctors at Singapore General Hospital worked in shifts to separate Ganga and Jamuna Shrestha, 11-month-old twins conjoined at the head. Not only did the girls share a cranial cavity, their brains were partially fused. Typically such separation procedures might take 30 hours—still an eternity in surgical terms—but once underway, doctors discovered that the girls' brains were even more tightly enmeshed than expected.

"When we were planning the surgery, we did not expect it to last so long," says Dr. Keith Goh, who led the operation. "During the course of the surgery, we found that the two brains were so closely adherent to each other that we had to individually coagulate, separate, and divide the blood vessels that were going between the two brains and all the brain tissue that was adherent." He's talking about hundreds of tiny blood vessels, each of which had to be traced and identified as belonging to one or the other of the girls.