Wilkinson's club, Newcastle, have not ruled him out of Saturday's pre-season friendly against Glasgow at Kingston Park.
England star Wilkinson travelled with Newcastle on their 10-day tour of Japan, but he complained of sickness and was admitted to a Tokyo hospital last week, where tests revealed an appendix problem.
Wilkinson has not had the appendix removed, and his condition will continue to be monitored, although he definitely misses Tuesday's game against Toyota Verblitz, near Nagoya.
He had hoped to play a part on the Falcons' pre-season trip, having recovered from another 'stinger' injury to his neck and shoulder sustained during the British & Irish Lions' second Test defeat against New Zealand in Wellington two months ago.
Falcons, meanwhile, launch their Premiership campaign away to Sale Sharks on September 2.