The simple idea
| Problem | What fails | What the patient notices |
|---|---|---|
| Achalasia | inhibitory nerves at the lower oesophageal sphincter are lost → sphincter won't relax and the oesophagus stops squeezing in waves | difficulty swallowing both solids and liquids, regurgitating undigested food, weight loss |
| Gastroparesis | stomach empties too slowly without any blockage (often diabetes) | early fullness, nausea, vomiting food eaten hours earlier |
| Ileus | the whole bowel stops moving (after surgery, severe illness, low potassium, opioids) | swollen belly, no wind, vomiting, quiet bowel sounds |
| Mechanical obstruction | something physically blocks the bowel (adhesion, hernia, tumour, twist) | colicky pain, vomiting, swollen belly — a surgical problem |
| Hirschsprung disease | nerve cells missing in the end of the bowel from birth | constipation and distension in a newborn |
| Irritable bowel syndrome | sensitive gut and altered gut–brain signalling | pain linked to bowel habit changes, without structural damage |