A stitch is a sharp, stabbing pain just under the ribcage. It strikes when exercising, and is twice as likely to occur on the right side of the body as the left. Remedies for stitches are mentioned as far back as Pliny the Elder, but so far the exact cause has only been narrowed down to three main possibilities: a) strained diaphragm ligaments, b) restricted blood flow, and c) irritation of the membrane surrounding the abdominal organs.
1. Diaphragm (theory a)
Running on a full stomach may jolt the ligaments supporting the abdominal organs, which strains the diaphragm. But stitches are also common in swimmers, where there’s no jolting.
2. Spleen (theory b)
Increased heart rate during exercise forces extra blood cells into the spleen. This causes it to swell, restricting blood flow to the limbs and diaphragm muscle – another possible source of stitch pain.
3. Liver (theory b)
Likewise, the liver also blocks blood flow as it swells. The liver sits on the right, which may explain why stitches are mostly on that side of the body.
4. Peritoneum (theory c)
This membrane surrounds your abdominal organs and may become irritated as it rubs against your side. Sugary drinks seem to exacerbate this.
5. Right shoulder blade
Stitches often cause a phantom or ‘referred’ pain in the shoulder, because the phrenic nerve from the diaphragm also connects the shoulder.
The quickest way to ease a stitch is to press firmly upwards, underneath your ribs. It isn’t clear why this helps though.