Mom's Missing Superior Vena Cava

Hi. I would like to start by saying that thanks to my mother, I have been doing Medical research for about 5 yrs now, just as a hobby. Well, the doctors finally came up with something that stumped me. Appearently, my mother has been missing her Superior Vena Cava since birth. Over the years, she has dealt with several issues, such as shortness of breathe, and light headedness, along with loss of balance. In 2005 she was diagnosed with MS. Recently, she has been having issues with her digestive system, mainly bowel movements. For some reason, she hasn't had  one in almost a month now. I think it may have something to do with the body trying to compensate for the missing blood passage and overloading smaller veins in the rest of the body to circulate it back to the heart. My theory is that it has caused a vein somewhere around her intestine to swell or become enlarged, causing a blockage in her intestine. Is this a possibility? We are picking up a  copy of the medical report today from her doctors, but I'm not sure it will tell me what I'm looking for.

Thanks a Bunch!
Pandalytle