Autonomic nervous system evaluation: diagnosis of rectal and lower gut dysfunction.

The main symptoms of autonomic dysfunction of the lower gut are diarrhoea, constipation and faecal incontinence, but these symptoms are not specific. The main diagnostic procedures in the evaluation of the lower gut are transit studies with radiopaque markers, hydrogen breath tests, tests for the differentiation between osmotic and secretory diarrhoea (fasting test and/or stool analysis for electrolytes and osmolality), anorectal manometry and EMG of the anal sphincters.