Thank you for the query.
It is possible that such trauma could cause severe abdominal pain
. In some cases back trauma causes extraperitoneal heamatoma which can stay there for a very long time if not infected. Usually it appears around the kidneys. Usually it gives abdominal pain and back pain
or burning when urinating can be present as well.
Such significant weight lost should be also explained with cancer. It can be stomach cancer
cancer. To have it diagnosed upper GI should be performed and abdominal CT with oral contrast. Such CT will also answer if there is any heamatoma caused by mentioned trauma.
Hope this will help.