Does anyone know tests/nerve blocks to diagnose abnormalities of the sacral parasympathetic nerves?

Background: Megacolon, like megarectum, is a descriptive term. Megacolon denotes dilatation of the colon that is not caused by mechanical obstruction. While the definition of megacolon has varied in the literature, most use a cecum measurement of greater than 12 cm to define megacolon. Adding to this definition, because the diameter of the large intestine is different in different areas, measurements of greater than 6.5 cm for the rectosigmoid region and greater than 8 cm for the ascending colon also are definitive.

Megacolon can be divided into 3 categories as follows: (1) acute megacolon (pseudoobstruction); (2) chronic megacolon, which includes congenital, acquired, and idiopathic causes; and (3) toxic megacolon. This section of the eMedicine journal contains 3 articles devoted to megacolon, and they are separated based on the 3 aforementioned categories (see Differentials). This article is devoted to the acute development of megacolon.


Pathophysiology: Whether dilatation is a phenomenologic expression of the physiology of the colon remains unresolved. Much basic science work has been performed in this area. With respect to the large bowel reacting to its luminal contents, fatty acids appear to reduce the volume of the proximal large bowel. Opiate narcotics (including diphenoxylate and loperamide) may lead to colonic dilatation when used long-term and may limit the ability of the colon to constrict when dilated. Little doubt exists that sacral nerves may be involved with acute megacolon. Some studies report that excessive nitrergic nerve stimulation within the myenteric plexus is vital to the production and maintenance of megacolon. Sacral parasympathetic nerves control both intrinsic cholinergic nerves and intrinsic nitrergic nerves. Sacral sympathetic nerves can reduce intrinsic cholinergic output and also can directly inhibit colonic smooth muscle.


Frequency:


In the US: No large-scale studies have been performed to determine the prevalence or incidence of acute megacolon; however, once present, the approximate risk of a spontaneous perforation from nontoxic megacolon is 3%.
Mortality/Morbidity: The mortality rate associated with spontaneous perforation of nontoxic megacolon is 50%; however, most patients respond to treatment prior to this complication.

Race: Race has not been documented to play a role in megacolon.

Sex: Sex has not been documented to play a role in acute megacolon.

Age: While it can occur in any age group, the vast majority of patients with acquired megacolon are elderly.


Good Luck :)

what