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Visceral pain is pain that results from the activation of nociceptors of the thoracic, pelvic, or abdominal viscera (organs). Visceral structures are highly sensitive to distension (stretch), ischemia and inflammation, but relatively insensitive to other stimuli that normally evoke pain such as cutting or burning. Visceral pain is diffuse, difficult to localize and often referred to a distant, usually superficial, structure. It may be accompanied by symptoms such as nausea, vomiting, changes in vital signs as well as emotional manifestations. The pain may be described as sickening, deep, squeezing, and dull. Distinct structural lesions or biochemical abnormalities explain this type of pain in only a proportion of patients. These diseases are grouped under gastrointestinal neuromuscular diseases (GINMD). Others can experience visceral pains, often very intense in nature, without any evidence of structural, biochemical or histolopathologic reason for such symptoms. These diseases are grouped under functional gastrointestinal disorders (FGID) and the pathophysiology and treatment can vary greatly from GINMD. The two major single entities among functional disorders of the gut are functional dyspepsia and irritable bowel syndrome.
Visceral hypersensitivity is a term used to describe hypersensitive visceral pain perception, which is commonly experience by individuals with functional gastrointestinal disorders.
In the past viscera were considered insensitive to pain but now it is clear that pain from internal organs is widespread and that its social burden may surpass that of pain from superficial (somatic) sources. Myocardial ischemia, the most frequent cause of cardiac pain, is the most common cause of death in the United States. Urinary colic produced from ureteral stones has been categorized as one of the most intense forms of pain that a human being can experience. The prevalence of such stones has continuously increased, reaching values of over 20% in developed countries. Surveys have shown prevalence rates among adults of 25% for intermittent abdominal pain and 20% for chest pain; 24% of women suffer from pelvic pain at any point in time. For over two-thirds of sufferers, pain is accepted as part of daily life and symptoms are self-managed; a small proportion defer to specialists for help. Visceral pain conditions are associated with diminished quality of life, and exert a huge cost burden through medical expenses and lost productivity in the workplace.