this refers to perforation of the gastro-intestinal tract
free perforation occurs when GIT contents spill freely into the abdominal cavity, causing diffuse peritonitis
contained perforation occurs when a full-thickness hole is created but free spillage is prevented because contiguous organs wall off the area (eg. a penetrating DU walled off by the pancreas)
the patient with a perforated abdominal viscus generally becomes rapidly unwell and presents with severe pain and a rigid abdomen.
this is a surgical emergency requiring immediate fluid resuscitation and transfer to theatre ASAP once diagnosis is made
diagnosis in free perforations is usually supported by the finding of free gas under the diaphragm on an erect CXR
not to be confused with normal gastric or hiatus hernia air bubble, nor with lucencies from adipose tissue, nor the normal post-laparotomy/laparoscopy free gas
a perforated peptic ulcer cannot be predicted in advance - it only becomes clinically evident after it has occurred
blood tests and radiology are generally normal prior to perforation