[Paradoxical sphincters in the abdomen]

Nitric oxide molecules serve as neurotransmitters to relax smooth muscle tension in many parts of the body. In humans and other mammals they play an important role for correct smooth muscle function in unusual locations. We previously described this mechanism (Stelzner, Chirurg. doi:10.1007/s00104-014-2777-z, 2014) using the occlusive mechanism of the upper and lower esophageal sphincters as an example. Cells producing nitric oxide can be found in the gastric fundus, the anorectal continence organ, vesicourethraltract and also in the uterine cervix in the final trimester of pregnancy. In all these locations they serve as elements of anatomical sphincter structures that have a paradoxical function. These observations confirm the points made in the introduction of this article on the stretch sphincter mechanism of the lower esophageal sphincter and the treatment of gastroesophageal reflux disease by retensioning of the esophagus in the diaphragmatic hiatus. In particular, high-resolution esophageal manometry of the lower esophageal sphincter can easily detect every functional disturbance caused by gastric plication and such changes were to be expected based on what we described in articles I and II.