Friday morning brought the best sign yet from Matthew Ouimet, a 2-year-old Antioch boy recovering from double transplant surgery at UCSF Benioff Children's Hospital in San Francisco:

Two thumbs up. Well, most of the way up.

"We helped neuro(logy) do (an) exam," wrote Kristi Ouimet, Matthew's mother, in a Facebook post, "and I asked Matthew to do thumbs up, and both thumbs moved partway up! That's my boy!"

After waiting 15 months for donor organs, Matthew received a kidney and a section of a liver during a 13-hour surgery that ended Wednesday morning. The transplant was necessary because he was born with the genetic condition primary hyperoxaluria Type 1, a defect in his liver which ultimately compromised his kidneys.

He has experienced some postoperative issues, none of which were unexpected. The transplanted organs have yet to become fully functional, and there has been bleeding around the liver which has caused nosebleeds and vomiting. But Kristi Ouimet reported in a text message Friday morning that her son had experienced a good, if not restful, night. Doctors allowed Matthew, who is still being sedated, to breathe on his own for a short time, she said, which he was able to do. They then put him "back on the machine so he doesn't tire out," she wrote.

Shortly before noon Friday came a milestone -- the first trickle of urine produced by the transplanted kidney.

Facebook photos show Matthew being visited in ICU by, among others, his grandparents Joyce and Jim Wisecarver and Don and Bea Ouimet, uncle Jimmy Wisecarver, and siblings Molly and Patrick, who sang to their little brother his favorite song, "Soft Kitty" from the TV show "The Big Bang Theory." His aunt Casey Wisecarver also posted two videos of Matthew on YouTube, including one of Matthew giving the half thumbs up.

Contact Gary Peterson at 925-952-5053. Follow him on Twitter at twitter.com/garyscribe.