Irritable Bowel Syndrome-Diarrhea Dominance

The digestive system is one of the important systems of the body. Digestion of food, absorption of nutrients, and metabolism of the food are maintained by this system. That is why the maintenance of gut health is an essential indicator of healthy life. Around 20 percent of the world's population suffers from chronic gastrointestinal disorders. These conditions are responsible for several gut problems, like abdominal pain, altered stool consistency, and indigestion. Irritable bowel syndrome is one of the common gut disorders that causes severe abdominal complications.

What Is IBS?

IBS, or irritable bowel syndrome, belongs to a group of disorders known as functional gastrointestinal disorders. This is one of the common chronic conditions responsible for frequent medical attention. Abdominal pain, cramps, constipation, and altered stool consistency are the usual symptoms of this condition. Around 9 to 23 percent of the world's population suffers from this condition. This is the most prevalent gastrointestinal pathology in the United States.

Pathophysiology:

Gastrointestinal motor disturbance and visceral hypersensitivity are regarded as the primary cause of irritable bowel syndrome. These factors are responsible for altered intestinal transit. Over the years, researchers have identified several causative factors for this condition. These are:

• Infection and Immune Activation in IBS: Bacterial overgrowth is considered one of the primary causes of irritable bowel syndrome. Overgrowth of gram-positive aerobic and facultative anaerobic bacteria like Staphylococcus, Streptococcus, Lactobacillus, Prevotella disiens, and Prevotella divia in the small intestine is associated with this condition. Even in some cases, the growth of anaerobic stains like Bacteroides fragilis can be noted in the small intestine. Such bacterial overgrowth can be seen in the upper gastrointestinal tract apart from the lower portion of the gastrointestinal tract. Several factors, like Helicobacter pylori-induced gastritis, improper intestinal clearance, and metabolic and neoplastic diseases, are considered risk factors.

• Chronic inflammation of the gut plays a vital role as the causative factor for irritable bowel syndrome. Conditions like celiac disease (a chronic immune disorder of the small intestine), inflammatory bowel disease (a chronic inflammation of the digestive tract), and gastroenteritis (inflammation of the lining of the stomach and intestine) are associated with irritable bowel syndrome. Chronic inflammation and infection are responsible for the change in the permeability of the intestinal tract. This causes the infiltration of inflammatory cells and the formation of edema due to the release of cytokines. This causes altered peristalsis and neuromuscular activity. Also, the activation of natural and adaptive immune systems.

• Stress and Depression: Anxiety and depression are often correlated to irritable bowel syndrome. It is often seen in 75 percent of cases. Dysregulation of the gut-brain axis is considered the main factor involved in this case. Also, in these patients, pain modulation and emotional arousal are highly activated. These factors cause inhibitory feedback mechanisms for emotional arousal and higher activity of visceral stimuli. The release of neurotransmitters like norepinephrine and a lower level of GABA (gamma-aminobutyric acid) due to stress is associated with irritable bowel syndrome.

• Serotonin Dysregulation: Serotonin or 5-HT3 is associated with gut motility, sensations, and secretion. The altered concentration of serotonin is responsible for abnormal gut movement and secretions.

• Gut-Brain Axis: The gut-brain axis is controlled by the central nervous system, hypothalamic-pituitary axis (HPA), and the autonomic nervous system. Any trigger in the vagus, the spinal, and the enteric nerves causes alteration in this axis. Among these nerves, the vagus nerve plays a pivotal role in communicating with the brain. Also, neurotransmitters like serotonin, corticotropin-releasing hormone, cholecystokinin, and somatostatin play a vital role in maintaining the gut-brain axis.

Clinical Types:

Based on different symptoms, different clinical conditions of IBS are:

• IBS-C (Constipation Dominance) - More than 25 percent of the stool is hard and lumpy stool.

• IBS-D (Diarrhea Dominance) - More than 25 percent of stool is watery in consistency.

• IBS-M (Mixture of Constipation and Diarrhea) - In this condition, both hard-lumpy and watery stools can be seen.

• IBS-U (Unsubtype) - The alteration of stool is insufficient to be classified into any category.

What Is IBS-D?

Irritable bowel syndrome with diarrhea dominance is one of the most common subtypes of irritable bowel syndrome. Around 40 percent of patients with IBS suffer from this condition. The diagnostic criteria for this condition are:

1. Persistent pain in the abdomen for more than three months and a history of at least three episodes of pain in a month.

2. Abdominal pain and cramps. Patients often say the reduction of the discomfort after defecation.

3. Altered frequency of the stool with frequent changes in its shape and consistency.

4. Frequent abdominal bloating with the urgency of passing the stool. Patients often complain of waking up from sleep due to diarrhea.

5. The amount of loose and watery stool is more than 25 percent. On the other hand, the amount of hard stool is less than 25 percent.

The pathophysiology of diarrhea-dominant irritable bowel syndrome is the same as other conditions. But researchers have identified numerous risk factors for this condition. These are:

1. Gastrointestinal dysbiosis, or irregularity of the gut microbiota, is one of the main causes of this condition. Blastocystis hominis is one of the predominant protozoa associated with this condition. On the other hand, a reduction in the number of Bifidobacterium faecis can be seen. The amount of Actinobacteria in these patients is elevated. Also, an increased number of Lactobacillaceae species, Streptococci species, and Clostridia species can be seen in such patients.

2. Overproduction of bile acids and malabsorption of bile acids are often related to diarrhea-dominance irritable bile syndrome. Defective ileal uptake is one of the prime causes of this type of pathology.

3. Visceral hypersensitivity is also an important cause of diarrhea-dominance irritable bowel syndrome. Abdominal pain and motility caused by visceral hypersensitivity are responsible symptoms associated with this type of IBS. The release of inflammatory mediators causes the secretion of chemicals like the substance P. Such chemicals stimulate the nerve endings are caused visceral hypersensitivity. Also, the sensitization of NMDA receptors by protein kinase C is associated with visceral hypersensitivity.

What Are the Treatment Options for IBS-D?

The treatment options for irritable bowel syndrome with diarrhea dominance are:

1. Dietary modification is the first step toward the management of this condition. Low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) in the diet are advised to the patient. Wheat, milk, and dairy products should be avoided. Red meat should be avoided, and moderate consumption of fresh fruits is advised. Meals should not be skipped. Intake of food containing insoluble fibers should be reduced. Alcohol or consumption of fizzy drinks should be reduced.

2. Loperamide, an opioid receptor agonist, can be prescribed to reduce intestinal motility. This drug can also be helpful in the reduction of loss of water and electrolyte.

3. Prebiotics: These are the non-digestible oligosaccharides. Gut microorganisms ferment these substances and produce small-chain fatty acids. These, in turn, help in the improvement of gut health. Berberine, curcumin, quercetin, and resveratrol are examples of prebiotics.

4. Probiotics: The administration of microorganisms can be proven to be helpful in the improvement of gut health. Microorganisms like Lactobacillus casei, Lactobacillus planatarum, Lactobacillus bulgaricus, Lactobacillus acidophilus, and Bifidobacterium longum are administered as probiotics.

5. Drugs like antidepressants and selective serotonin reuptake inhibitors can be prescribed to some patients to reduce abdominal symptoms like cramps and pain. Though, these drugs are associated with several adverse symptoms.

Conclusions:

Irritable bowel syndrome is a very common gut disorder. Several factors, like changes in gut microbiota, stress, and chemical dysregulation, are responsible for this condition. Diarrhea dominance is one of the main clinical subtypes of this condition. Patients complain of watery stool, abdominal pain, and cramps in this condition. Proper diet, administration of probiotics, and medication can be helpful in curing such problems.