Lynch traveled to Philadelphia on Monday to see a specialist about the injury.
He suffered the injury in practice before the Seahawks' Week 10 game against the Arizona Cardinals. He started and played 79 percent of the team's snaps. But coach Pete Carroll said the injury started to bother him late in the 39-32 loss.
Lynch was listed as questionable before Sunday's game against the San Francisco 49ers, but he didn't feel right during pregame warm-ups, Carroll said. The Seahawks went on to win 29-13 without Lynch.
From 2010 to 2014, Lynch missed just one game due to injury. He has missed three of 10 games this season while dealing with hamstring, calf and neck issues, in addition to the abdominal injury. From 2011 to 2014, he piled up 1,181 carries, the most of any running back in the NFL.
The Seahawks are 5-5 and fighting for an NFC wild-card berth. Quarterback Russell Wilson was asked Monday about possibly going forward with Lynch sidelined.
"We'll hopefully have Marshawn back," Wilson said. "To have one of the best running backs in the game makes my job a little bit easier, to have him out there making plays. Just praying that he's healthy, for his own sake, then also for our team's sake. He's a difference-maker for sure."
Lynch has carried 111 times for 417 yards on the season. His 3.76 yards per carry ranks 37th in the league.
Replacing Lynch in the backfield is undrafted rookie free agent Thomas Rawls, who carried 30 times for 209 yards in the win over the 49ers. On the season, Rawls is averaging 5.98 yards per carry, the best mark in the NFL. He has 604 yards on 101 carries this season.
ESPN Seahawks reporter Sheil Kapadia contributed to this report.