I don't think many of us know much about medical astrology. I'd look at aspects to the Sun (life force), ascendant (an extension of you and your over all health) and 6th house ruler first. If you have planets in the 6th, they may come into play also. Saturn usually brings long-term illnesses vs. planets like Mars where they are more sudden and hit you hard. Neptune illnesses are more difficult to diagnose. The 12th house is also associated with hospital stays, so, if you have any transits there, that might explain it.