Irritable bowel syndrome (IBS) is a disorder of the gut-brain interaction that affects between 25-45 million people in the United States, and 10-15% of the world’s population. Typical irritable bowel syndrome symptoms are recurrent abdominal pain and altered bowel habits, but can also include bloating, abdominal distension, bowel urgency, constipation, and gas. Studies suggest these symptoms are more severe in irritable bowel syndrome patients with added visceral sensitivity.
Visceral pain is a hallmark of irritable bowel syndrome, and it behooves gastrointestinal healthcare providers and patients to familiarize themselves with this condition. In this article, we’ll define visceral hypersensitivity, explore potential causes, and discuss helpful management options.
What is visceral hypersensitivity?
To understand visceral hypersensitivity, think about it this way…
Visceral refers to the internal organs, especially those in the abdomen. In irritable bowel syndrome, visceral hypersensitivity, or visceral hypersensitivity, the terms used to describe an increased sensation or perception of sensation in the gut (an organ) in response to different stimuli, such as gas, stool, or normal functioning of the gastrointestinal tract (e.g. peristalsis).
There are two types of visceral sensitivity: 1) hyperalgesia, and 2) allodynia. You shouldn’t need to remember these terms, but here’s what you should know:
- Hyperalgesia refers to a reduced pain threshold or intensified pain sensation to normally uncomfortable stimuli. For example, imagine you and ten of your closest friends devoured a large platter of beans each. All of you would eventually produce gas (i.e. stimuli) and appreciate some time and space away from one another. Those without added visceral sensitivity might feel minor discomfort, but those with visceral hypersensitivity would feel visceral pain despite producing roughly the same amount of gas.
- Allodynia refers to an increased or painful response to normal stimuli, such as peristalsis. Here, the body interprets otherwise normal sensations as uncomfortable or painful.
In irritable bowel syndrome, these heightened pain sensations usually present as bloating and/or abdominal pain. Studies have shown that irritable bowel syndrome patients with visceral pain display more severe symptoms than those without. So, we know that this extreme sensitivity contributes to gastrointestinal symptoms and severity.
How is hypersensitivity diagnosed?
In research models, a rectal barostat is used to measure visceral pain. Basically, a balloon is inserted and inflated in the rectum at varying levels of pressure and volume. Participants register what they feel throughout the procedure. Those with visceral pain report heightened awareness of smaller balloons.
Don’t worry. If you expect you have visceral pain, it’s unlikely you’ll undergo a rectal barostat. Most clinicians diagnose visceral hypersensitivity based on clinical experience, patient presentation, and exclusion of other diagnoses.
By the way, visceral pain isn’t limited to the rectum. Irritable bowel syndrome patients may experience greater sensations and lower pain thresholds throughout the entire gastrointestinal tract, notably in the small and large intestines.
What causes hypersensitivity?
Anywhere from one-third to 90% of irritable bowel syndrome patients show signs of visceral pain, but it’s more common in females (thanks hormones!), people with IBS-D (vs. IBS-C, which is constipation-predominant), and those with a history of stress, anxiety, depression, and/or early life stressors. Also, some research suggests a higher risk among young people compared to older individuals. With aging comes wisdom and a decreased number of sensory neurons in the gut.
As with the pathogenesis of irritable bowel syndrome, the exact cause of visceral pain is unknown. A wide range of factors is at play within the peripheral and central nervous systems, including microbial infections, intestinal hyperpermeability, the gut microbiota, inflammation, and immune dysregulation, diet, genetics, brain-gut interaction, central pain perception, and psychological components.
Many of these factors play off one another to contribute to visceral pain. For example, someone might develop a microbial infection (e.g. food poisoning), leading to post-infectious IBS with ongoing low-grade inflammation and increased gut permeability. In the setting of inflammation, the intestinal hyperpermeability might allow for the passage of pro-inflammatory agents through the gut wall, which would excite the GI nervous system, and finally the spinal cord leading to central sensitization —
a condition where the nervous system is in a high state of reactivity. Because of the microbial infection, this person might also have an increased number of mast cells and mast cell activation. Mast cells control a variety of processes, including gut permeability, pain sensation, and immunity.
Let’s not forget about dysbiosis within the gut microbiota. As a GI dietitian, I spend much of my time counseling patients on how their gut microbiome influences overall health. An imbalance in this “forgotten organ” can induce hypersensitivity throughout the GI tract.
The potential causes of visceral pain extend well beyond what we’ve talked about, but this should give you a gist of how it depends on a variety of factors.
You have visceral hypersensitivity, so now what?
Here’s some good news… because there are many proposed risk factors and mechanisms that contribute to visceral pain, there’s a wide range of potential treatments.
A variety of pharmaceuticals have the potential to address visceral pain, including tricyclic antidepressants, low-dose selective serotonin reuptake inhibitors (SSRIs), anti-inflammatory agents, and GABA analogs.
You can speak with your doctor about what, if any, medication might work best for you.
While there’s no specific diet for visceral pain, patients can work with dietitians to personalize dietary recommendations to reduce gas production, promote normal bowel movements, strengthen the gut barrier, reduce the risk of food poisoning and promote a diverse gut microbiota.
A note on the low FODMAP diet for visceral hypersensitivity… Patients with hyperalgesia (a reduced pain threshold or intensified pain to uncomfortable stimuli), might benefit from a low FODMAP diet to reduce gas production within the GI tract. Many randomized, controlled trials have shown the effectiveness of a low FODMAP diet in improving IBS symptoms, including visceral pain. FODMAPs are certain types of poorly absorbed carbohydrates (sugars and fibers) that are highly fermentable in the presence of bacteria. They can lead to uncomfortable gas, bloating, diarrhea, and other GI symptoms in people with irritable bowel syndrome.
Super important! Everyone, with or without visceral pain, can benefit from chewing their food well and eating slowly. These are two of the most important things we can do to optimize digestion and reduce abdominal pain.
You might come across the following supplements as potential non-pharmaceutical approaches for managing visceral pain. Most of the research has been conducted on animals, not humans. We have much to learn about their application in humans, including efficacy and dosing, but keep them on your radar:
- Enteric-coated peppermint oil
A note on probiotics… There’s tremendous interest in the potential for probiotics to address visceral pain, especially in those with IBS. I’ve worked with many irritable bowel syndrome patients who were taking probiotics at the recommendation of a practitioner. However, in my professional opinion, we don’t have enough evidence to recommend probiotics for irritable bowel syndrome patients with visceral pain at this time.
A note on peppermint oil… Peppermint is an effective and safe remedy for abdominal pain and universal IBS symptoms. I frequently recommend peppermint oil to soothe abdominal pain and bloating. Enteric-coated peppermint oil is less apt to cause heartburn in at-risk patients.
Lifestyle & Psychological Approaches
Lifestyle and psychological approaches address physiological and psychological stressors, which is key to managing visceral pain. Here’s a list of therapies to consider:
- Cognitive-behavioral therapy
Visceral pain is a distinctive feature of irritable bowel syndrome affecting anywhere from one-third to 90% of irritable bowel syndrome patients. Fortunately, patients need not suffer in silence. Research continues to shed light on potential causes of this uncomfortable condition. As we unravel the underlying mechanisms, we will continue to make advancements in developing and recommending effective treatments.
If you suspect visceral pain is worsening your IBS symptoms, I strongly recommend you find a medical team that is well-versed in sensitivity and pelvic pain. One of the best ways to do this is to ask your GI doctor about it and see how they respond. Are they receptive to talking about it? Do they have a team of specialists (e.g. therapist, dietitian) whom they work with or refer to? Together, you will create a plan that works best for you.
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