Oh?
The Klingons made his insides look exactly like an Earth Human complete with Tyler's own DNA.
That plus the fact that he was a prisoner of war in a society that relishes extremely torturing their enemies to get information, would be the foremost factor in any medical exam given upon his return.
Thus any damage and/or scarring internal or otherwise, would be expected and most likely ignored beyond the medical aspects of it.
The staff doing that exam, would only be checking for the subject's viability to remain functional as a Star Fleet Officer and his continued health beyond.
Unless otherwise instructed by higher-ups, they would not be doing the type of exams that might possibly indicate something else was amiss.
Also, remember that the commanding officer who was vouching for Tyler was someone also hiding his "differences" from people, so there'd be no reason for Lorca to insist on more probing exams.