General Surgery

Luminal obstruction of the appendix triggers a closed-loop build-up of pressure that progresses predictably from visceral pain to localised peritonism, ischaemia and, if untreated, perforation.

A mechanical block or a paralysed bowel both stop luminal contents moving forward, so gas and fluid accumulate proximally, and the cardinal features (distension, vomiting, absolute constipation) follow directly from where along the gut that stoppage sits.

Abdominal contents push through the narrow, rigid femoral canal below and lateral to the pubic tubercle, and because that canal is tighter and less compliant than the inguinal canal, femoral hernias carry a much higher risk of strangulation and are treated as surgical emergencies until proven otherwise.

A weakness in the abdominal wall at the inguinal canal lets peritoneal contents bulge through above and medial to the pubic tubercle, and the entire clinical picture (reducibility, cough impulse, and the danger of strangulation) follows from that defect being a tube the bowel can slide in and out of, or get trapped within.

Sudden abdominal pain reflects one of two mechanisms: a hollow viscus obstructing and distending (colic) or the peritoneum being inflamed and irritated (peritonism), and telling them apart, not naming a diagnosis, decides whether a patient needs the theatre now.