From: Rabbi Moshe Sofer
To: Rabbi Moshe Leib
The Chasam Sofer rules that when an adhesion between the beis hakosos and diaphragm is accompanied by a blister alone, internal inspection of the beis hakosos wall can render the animal kosher if no penetration is found; however, when a needle is also found resting in the cavity alongside the blister and adhesion, the combined evidence constitutes proof of perforation and the animal is treif even in cases of significant financial loss.
Source: Shu"t Chasam Sofer YD §33