Side stitch

Causes

The precise cause of ETAP is unclear. Proposed mechanisms include diaphragmatic ischemia (insufficient oxygen); stress on the supportive visceral ligaments that attach the abdominal organs to the diaphragm; gastrointestinal ischemia or distension; cramping of the abdominal musculature; ischemic pain resulting from compression of the celiac artery by the median arcuate ligament under the diaphragm; aggravation of the spinal nerves; or, most likely, irritation of the parietal peritoneum (abdominal lining).

Although the diaphragm is mostly innervated by the phrenic nerve, and thus could explain referred pain to the shoulder tip region, the main evidence against diaphragmatic ischemia is that ETAP can be induced by activities of low respiratory demand, such as horse, camel, and motorbike riding, where ischemia of the diaphragm is unlikely. In a study using a fluoroscopic technique, diaphragmatic movements during an ETAP episode have been shown to be full and unrestricted.

Some have proposed that this abdominal pain may be caused by internal organs (like the liver and stomach) pulling downwards on the diaphragm, but this hypothesis is inconsistent with its frequent occurrence during swimming, which involves almost no downward force on these organs.

Frictional irritation of the parietal peritoneum has been suggested as a cause of ETAP. The parietal peritoneum traverses the entire abdominal wall, which could account for the widespread distribution of ETAP; the tension in the parietal peritoneum is increased with torso extension; children have a proportionally larger peritoneal surface compared to adults, which could explain the increased prevalence of ETAP in younger individuals; and pain arising from the parietal peritoneum relieves quickly on removal of the stimulus, In fact, the fluid in the peritoneal cavity is highly responsive to osmotic gradients between it and its vascular supply.

In the absence of a clear cause, any treatment techniques are uncertain. Typical strategies involve deep breathing and/or manual pressure on the affected area.

Occurrence

Side stitches occur in every level of athletes from school-aged children, weekend exercisers, or elite athletes, although they are more common in younger people. Activities that use upper body twists, like running, swimming, and horseback riding, report this affliction more often. Approximately two-thirds of runners will experience at least one episode of a stitch each year.

References

References

1. (February 2000). "Characteristics and etiology of exercise-related transient abdominal pain". Medicine & Science in Sports & Exercise.
2. (January 2015). "Exercise-Related Transient Abdominal Pain (ETAP)". Sports Medicine.
3. (December 2006). "Spirometry Measurements During an Episode of Exercise-Related Transient Abdominal Pain". International Journal of Sports Physiology and Performance.
4. (2009). "On Running on Lessons from 40 Years of Running.". Authorhouse.
5. (May 1996). "Does post-laparoscopy pain relate to residual carbon dioxide?". Anaesthesia.
6. (December 1991). "Intraperitoneal local anaesthetic for shoulder pain after day-case laparoscopy". The Lancet.
7. (April 2004). "Effect of Ingested Fluid Composition on Exercise-Related Transient Abdominal Pain". International Journal of Sport Nutrition and Exercise Metabolism.
8. Wetsman, Nicole. (2017-10-20). "When you get a stitch in your side, what's really going on?". [[Popular Science]].