The 19-year-old will stay with Neale Cooper's side for a month and is expected to go straight into the squad for Saturday's game at Crewe.
"I've never hidden the fact I'd love Ryan to come back," Cooper told Pools' official website. "He came in last year and did really well for us and fitted in straight away.
"I've been chasing it up, but he's been in and about the first-team plans at Sunderland this year.
"I'm delighted we've managed to do the deal now and I have to say Sunderland have been really helpful with us, they want him to get games and I think he will really thrive playing off big Steve Howard."