What Causes Abdominal Cramps After Consuming Prune Juice?

HI, My husband most likely has the same GI virus that I have and was diagnosed with yesterday. One of the many annoying symptoms is that it is hard to keep food down, and any drink too. While I was at the doc s office yesterday he drank a glass of prune juiice and has very bad cramps and been i n the bathroom a lot. He also has an appt with a kidney doc on Monday due to his histoy of illnesses and the pain meds he has taken for several years. We are worried abot how his kidneys might be effected. Lots of pain has been the norm for a long time but now he just want s to crawl up in a ball most of the time. His upper and lower GI test were good - all ok! Why so much pain after the prune juice? Seemes silly to ask this but he is really hurting!