Hiatus Hernia
Widening of the diaphragmatic oesophageal hiatus lets part of the stomach migrate into the thorax, and whether it drags the gastro-oesophageal junction upward with it (sliding, disrupting the reflux barrier) or herniates alongside a normally sited junction (rolling, risking obstruction and strangulation) determines both the symptoms and the urgency.
First principles
Why the hiatus normally holds the stomach below the diaphragm
The oesophagus passes through the diaphragm at the oesophageal hiatus, a muscular ring formed mainly by the right crus and reinforced by the phrenico-oesophageal ligament, which keeps the gastro-oesophageal junction (GOJ) firmly intra-abdominal. Anything that stretches this ligament or widens the hiatus (ageing, obesity, pregnancy, or chronically raised intra-abdominal pressure from straining or coughing) allows part of the stomach to migrate upward into the thorax.
Educational content pending clinical review. Not medical advice.