Hi, TradeDayDan . . . first of all my best thoughts to you and your mother.
I have a pocket medical dictionary and looked up what I could about what it is that your mother has.
I will try to help you translate it.
Contiguous (connected to) intra (within) peritoneal (abdominal wall lining) infarcted (blood flow to area has been stopped) omentum (part of the abdominal wall lining where it folds to the stomach, colon or other abdominal organs). Due to the cut off of blood flow, this is what is causing the gangrene which is simply that tissue cells are dying off.
During this surgery, they will likely determine if it is dry or wet gangrene. Dry gangrene can be taken care of by returning the blood flow to normal but if wet gangrene, the area affected will need to be removed.
Again, my thoughts are with you both.
Hope this has helped.