Irritable bowel syndrome

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. With irritable bowel syndrome, irritable means easily provoked.
Bowel refers to the intestines, and syndrome means a collection of signs and symptoms that occur together. So in irritable bowel syndrome, or IBS for short, individuals experience recurrent abdominal pain and changes in bowel habits, even though everything looks normal on standard testing.
To understand IBS we first need to understand how the intestines normally work. The main job of the intestines is to absorb nutrients and water from the food we eat.
For that to happen properly, food has to move through at the right speed. That movement is controlled by peristalsis, a coordinated pattern of muscle contractions called motility.
These contractions are guided by the enteric nervous system, sometimes described as the gut's own brain because it can work automatically.
But motility isn't the whole story. The intestines also need to sense what's happening inside them.
As the bowel fills, sensory nerves detect stretch and send signals to the brain. The brain interprets those signals and sends messages back to adjust motility and sensation.
This back and forth communication is called the brain-gut axis. Serotonin and the gut microbiome help fine tune the system.
When everything is balanced, the gut moves smoothly and normal stretching doesn't cause pain. In healthy individuals, all of these systems work together to maintain a normal threshold for discomfort.
The intestines can stretch and contract, causing no pain because sensory nerves only activate when stimulation becomes strong enough to cross that threshold.
You can picture this like a line drawn across a graph. Below that line, signals are considered normal.
Everyday motility, small amounts of gas, and routine contraction stay below the line, so no pain is felt. Now imagine that line suddenly drops.
When this balanced system becomes disregulated, the threshold lowers. The same normal stretch that used to stay below the line now crosses it.
A small amount of gas or a routine contraction is suddenly interpreted as pain. That shift explains why everyday intestinal activity becomes uncomfortable.
Importantly, the structure of the intestines remains normal. In other words, the problem is not structural, it's functional and sensory.
This lower threshold is what we call visceral hypersensitivity and represents one of the central features of IBS. But visceral hypersensitivity does not come alone.
Several other processes can reinforce and sustain it. First, changes in the intestinal microbiome.
Some people with IBS have a different mix of bacteria in their gut. These microbes can produce more gas than usual and interact differently with the immune system.
More gas means more stretch inside the intestine. And when the pain threshold is already lower, that extra stretch is much more likely to feel uncomfortable.
Second, mast cell activation. IBS is not an inflammatory condition like Crohn's disease, but the immune system can still be slightly more active than normal.
In some people with IBS there are more mast cells sitting close to sensory nerves in the intestinal wall. When these mast cells release chemicals like histamine, they irritate the nearby nerves.
Those nerves become more sensitive, which lowers the pain threshold even further. Third, stress-related brain gut signaling.
When someone feels stressed, the brain sends stronger signals down to the intestines. In people with IBS, this response is amplified.
The gut may start moving more irregularly, and normal sensations can suddenly feel stronger or uncomfortable. Finally, people with IBS often have altered gut motility because serotonin signaling is often disrupted.
The intestines may contract too quickly or too slowly. If motility is too fast, there is not enough time to absorb water, leading to looser stools.
If motility is too slow, too much water is absorbed, making stools harder and more difficult to pass. Now you can use the mnemonic IBS makes my stomach very mad to remember the main pathophysiologic features, including microbiome changes, mast cell activation, stress, visceral hypersensitivity, and motility alterations.
We do not always know what sets IBS off. In many cases, there is no clear starting event.
What we do know is that IBS tends to run in families, which tells us that genetics plays a role, but there's no single IBS gene.
Instead, some people may simply be wired in a way that makes their nerves more sensitive, their gut more reactive, or their stress response stronger.
In other cases, IBS begins after something specific, like a gastrointestinal infection. Even after the infection goes away, the gut can stay unusually sensitive.
This is called post-infectious IBS. The main symptom of IBS is recurring abdominal pain.
It's usually crampy and often feels better after a bowel movement. That pain almost always comes along with changes in bowel habits, and those changes define the different types of IBS.
In IBS with diarrhea, or IBSD for short, the bowels move too quickly. Stools become loose or watery, and there might be a strong sense of urgency.
On the flip side, in IBS with constipation or IBSC, the bowels move too slowly. Stools become hard, difficult to pass, and may require straining.
Next, there's mixed IBS or IBSM where individuals switch back and forth between these patterns and don't fit neatly into either category.
The last type is called IBS with unclassified bowel habits or IBSU where individuals do not fit neatly into any of these categories.
Regardless of the pattern, many people with IBS also experience bloating and a feeling of abdominal fullness. Some notice mucus in the stool.
Symptoms often flare up after eating certain foods, especially those that are easily fermented in the gut or during periods of stress.
But IBS does not only affect the intestines. Many individuals also experience anxiety, depression, or conditions like fibromyalgia.
Because IBS is a functional condition, there is no structural abnormality seen on imaging or colonoscopy. Diagnosis is based on the pattern of symptoms.
Individuals experience recurrent abdominal pain associated with changes in bowel habits such as diarrhea, constipation, or both.
However, before confirming the diagnosis, order additional tests to rule out other conditions that can cause similar symptoms like inflammatory bowel disease.
Unlike inflammatory bowel disease, IBS does not cause mucosal inflammation, ulceration, bleeding, or elevated inflammatory markers.
Other conditions that might mimic IBS include celiac disease, thyroid dysfunction, infection, and even colon cancer. Treatment for IBS focuses on reducing symptoms and is tailored to what bothers the individual most.
Diet changes are often the first step, especially limiting high FODMAP foods. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.
These are carbohydrates that gut bacteria easily ferment, which can increase gas and bloating. Medications can help regulate bowel motility, either easing constipation or slowing diarrhea.
Because stress affects the brain-gut connection, therapies like cognitive behavioral therapy can also significantly improve symptoms.
All right, as a quick recap, IBS is a functional bowel condition where the intestines look normal but function abnormally.
IBS presents with recurrent abdominal pain linked to changes in bowel habits such as diarrhea, constipation, or both. The core issue is brain gut access dysfunction, which lowers the pain threshold and results in visceral hypersensitivity.
Other factors that can amplify and sustain symptoms include altered intestinal motility. Microbiome shifts, immune activation,