My gut feeling is that visceral manipulation is yet another sCAM practice based on falsehoods, an economy of truth, and, basically, lies. Science-based medicine gives us the low down:
“I think we can reasonably assume that any abdominal manipulation sufficient to disrupt adhesions would risk tissue damage and internal bleeding, but [visceral manipulation] is not likely to do that. As practiced, VM amounts to relaxation, suggestion, and gentle massage; so it is not likely to cause physical harm unless it replaces other, effective treatments. It’s more likely to cause harm to the wallet and to critical thinking.
From Science Based Medicine on VM