It is a little more involved than some other contry's medicals,
Jobear.
The best thing is do NOT tell them about it - and I understand that if there were any medical procedures, they are only interested in those from the past 5 years.
Here's a link to
JCAB Medical, tips and hints that will help explain a few things.
JapJok is a disillusioned pilot, who enjoys putting crap on the Japanese for EVERYTHING, so I'll leave it up to you to determine how much credence you give his comments.
Again - do NOT tell them about it. If it is "discovered" during your check, you can always say, something like, "Oh that! Yes I'd forgotten completely about it, it has never given me any problems since."
Don't volunteer ANYTHING that might remotely sink you.
If YOU mention it, they will take it to be something of a VERY serious nature.