Hi Raymond, you didn't mention if your wife had a C-section or not which might be TMI. However, it may be relevant. As Grog mentioned below, castor oil packs stimulates the lymphatic system. So what does this have to do with the type of birth your wife had. C-sections can disrupt the lymph system causing edema. It is likely the castor oil pack stimulated Peyerís Patches and restored Lymphocytes in her gut.
I only know because I've had abdominal surgery and the result has been the same (swollen belly) except mine is a bit more difficult to resolve due to abdominal adhesions. My stomach is board flat in actually except when the lymph flow is stagnant.