Deborah Bethards, M.D.
Most gastroenterologists have encountered patients who complain of chronic constipation. Colonoscopy shows no anatomical abnormalities. Nonetheless, conservative treatment with laxatives and bulking agents brings only temporary, minor relief. After several failed treatment attempts, the patient is distressed, uncomfortable and anxious; the gastroenterologist is frustrated. Deborah Bethards, M.D., a gastroenterologist at Penn State Hershey Medical Center’s Neurogastroenterology and Motility Clinic explains, “Failure of conservative treatment to resolve constipation should be a red flag. With no other detectable abnormality, the possibility of a chronic pelvic floor disorder that primarily affects women—known as dyssynergic defecation—should be considered.”
With this disorder, the rectosigmoid area does not function properly so that during attempted defecation, paradoxical anal contraction occurs, and pelvic floor muscles fail to relax. The result is that stool is retained in the rectum. If left untreated, complications such as fecal impaction, rectocele, megacolon, and fecal incontinence may occur. Continue reading
Functional gastrointestinal (GI) motility disorders, including functional dyspepsia, are very common, often chronic, and disabling conditions that account for a large proportion of consultations with primary care and specialist physicians. Despite the absence of anatomical GI abnormalities, patients with functional GI disorders suffer with varying bouts of unexplained pain, cramping, diarrhea, vomiting, and constipation.
R. Alberto Travagli, Ph.D.
The research laboratories of R. Alberto Travagli, Ph.D., and Kirsteen Browning, Ph.D., of Penn State Hershey Neural and Behavioral Sciences, focus on describing the pathophysiology of these disorders. Travagli and Browning have recently conducted a series of in vitro and in vivo experiments (in collaboration with Gregory Holmes, Ph.D.) designed to better describe the role of stress in causing the gastroparesis that often occurs in such disorders. Evidence from these experiments,
Kirsteen Browning, Ph.D.
as well as from other laboratories, points toward stress related re-organization of the vagal sensory-motor loop connecting the gut to the central nervous system (CNS). The efferent limb of this reflex loop involves preganglionic parasympathetic neurons in the dorsal motor nucleus of the vagus (DMV), which provide the vagal output back to the GI tract. DMV neurons innervate postganglionic neurons located within the GI tract which belong to one of two distinct pathways; one is an excitatory pathway that increases gastric tone, motility and secretion via activation of muscarinic cholinergic receptors. The other is an inhibitory pathway that inhibits gastric functions mainly by releasing nitric oxide or vasoactive intestinal polypeptide. Continue reading