What is Visceral Hypersensitivity?
Visceral hypersensitivity, also known as visceral hyperalgesia, is a condition where there is pain within the viscera, which are the inner organs, and this pain is more acute than normal. Visceral hypersensitivity is a term used to describe an increase in pain sensation, which is more than the normal within the internal organs.
Patients suffering from visceral hypersensitivity will react sharply to an internal stimulus which he/she would normally not perceive as pain. For example non-sufferers would feel the stimulus as mild discomfort, whereas people suffering from visceral hypersensitivity will experience severe pain.
Patients suffering from visceral hypersensitivity tend to have lowered threshold for abdominal discomfort and pain in response to pressure, distension or stimulation of the abdomen.
What are the Causes of Visceral Hypersensitivity?
The causes of visceral hypersensitivity could be psychological and the causes of visceral hypersensitivity could be local problems in the nerves of the gut or problems between the connection of the brain and gut.
Researchers are using visceral hypersensitivity to better understand the irritable bowel syndrome. There are many theories regarding visceral hypersensitivity in IBS and some of the potential causes are:
- Changes in the micro RNA molecules of the cells which line the intestine.
- Pain originating from the nerves of the cells, which line the large intestine.
- Changes in neurotransmitters and other receptors of these cells.
- Increase in the permeability of the intestine (leaky gut).
- Change in the interactions between the peripheral nervous system and the central nervous system.
In Which Conditions are Visceral Hypersensitivity Seen?
Visceral hypersensitivity is a characteristic feature of irritable bowel syndrome (IBS). Other than this, visceral hypersensitivity can also be seen in people who have: functional dyspepsia, non-cardiac chest pain and functional abdominal pain.
The Relationship Between Visceral Hypersensitivity and Irritable Bowel Syndrome (IBS)
Although visceral hypersensitivity is known to be a characteristic feature of IBS, however, only about 30 to 40 % of patients suffering from IBS are known to have visceral hypersensitivity, which is an exaggerated pain or sensitivity to colon distension. There also need not be a direct relation between visceral hypersensitivity and the severity of the patient’s symptoms of IBS.
So, it is thought that visceral hypersensitivity experienced by patient with IBS occurs due to changes in the function of the nervous system at the level of intestines as well as the brain.
There is sensitization of the nerve pathways in the GI tract to stimulation which leads to over-reactivity and pain amplification. Patients who are not suffering from IBS will have response from the parts of the brain upon rectal distension, which are associated with controlling pain. In patients suffering from IBS, the areas of the brain which respond to rectal stimulation are also associated with anxiety and vigilance and which are also the parts of the brain that increase the pain sensation.
Balloon Distension Test for Measuring Visceral Hypersensitivity
Visceral hypersensitivity is being studied for better understanding of the cause of IBS. A balloon distension test is used to measure visceral hypersensitivity for better research purposes. This test helps in assessing the patient’s response to pressure within the rectum.
In balloon distension test, a balloon is placed within the patient’s rectum and is gradually filled with air. People who experience pain at lower levels of pressure are characterized as having visceral hypersensitivity when compared to people who are able to withstand significant air inflation without feeling any pain or discomfort. According to studies, patients suffering from IBS tend to experience lower pain threshold in balloon distension test.
How is Visceral Hypersensitivity Treated?
First line of treatment for visceral hypersensitivity in patients suffering from IBS is prescribing medicines which affect the nerve function in the gut. The aim of the medicines is decreasing the irritability of these nerves. Medicines prescribed for these belong to the same category, which is used in brain nerve disorders like depression. However, the dosage needed to treat gut problems or visceral hypersensitivity is usually very low.
Medicines used for treating visceral hypersensitivity are:
- Selective serotonin reuptake inhibitors (SSRI) such as citalopram.
- Tricyclic antidepressants such as trimipramine and amitriptyline.
- Selective norepinephrine and serotonin inhibitors (SNRI) such as duloxetine.
All these medicines are prescribed at a very low dose in visceral hypersensitivity when compared to depression; however, they are still able to block the pain signals which are transmitted from the bowel to the brain and reduce the increased pain response, which the patient feels in visceral hypersensitivity.
Complementary Treatment for Visceral Hypersensitivity
Complementary therapies can also be used for treating visceral hypersensitivity and these include cognitive behavioral therapy, hypnotherapy both of which help in relieving anxiety and stress which are the main triggers of symptoms of irritable bowel syndrome including visceral hypersensitivity. Acupuncture also can help in relieving pain from visceral hypersensitivity.