The Dutchman is understood to be in a stable condition, but is having tests and x-rays.
This is the latest blow in the Kuipers saga after a deadlock in negotiations with Brighton, who are thought to be asking for too much money.
However, the goalkeeper himself is keen on a move to get first team football: "I know Hull would mean dropping down a division but that does not worry me. When I went earlier in the season, I really enjoyed it.
Kuipers in Car Crash
"The set up is very good. It's not like a Third Division club. They have a good manager, a great stadium and good training facilities."