Functional diarrhea

Gastrointestinal dysfunction appearing as chronic or recurrent diarrhea that is not attributable to diseases associated with structural or biochemical abnormalities is defined as functional diarrhea.

Epidemiology

Different study designs and definitions of functional diarrhea or chronic diarrhea in different studies have provided researchers with different prevalence rates, making international comparisons difficult. A study of adults in Sweden found that the prevalence of self-reported diarrhea was 9.8%. [1] A study compared the prevalence of community diarrhea in Australia, Canada, Ireland, and the United States and found prevalence rates of 6.4%, 7.6%, 3.4%, and 7.6%, with diarrhea defined as liquid stools more than three times. Or defecation within any 24 hours in the four weeks prior to the interview. [2] A population-based study in Canada using Rome II criteria found the prevalence was 8.5%. [3] A survey of healthy volunteers in Mexico City using Rome II criteria found the prevalence of functional diarrhea was 3.4%. [4]

Causes of the functional diarrhea

Thus, the causes of functional diarrhea are not organic disorders - diseases of the digestive system organs, but disorders of the gastrointestinal tract, which arise from pathological changes in the interaction between the intestine and the brain: the enteric (intestinal) nervous system (ENS), which controls the motor function of the colon and the entire GI tract, with the central nervous system (CNS).

In the group of GI disorders of a functional nature, experts include:

• abnormal motility (peristalsis) of the intestine in the form of an increase in its propulsive (propulsive) activity;
• changes in the function of the intestinal mucosa (whose epithelium forms a barrier that separates antigens from the contents of the intestinal lumen);
• Gut microbiota imbalance (microbial dysbiosis) - gut dysbiosis - with changes in the composition of symbiotic bacteria present in the gut that participate in the formation of intestinal immune homeostasis;
• visceral hypersensitivity or hypertrophic reaction of internal organs to severe or repeated exposure to physical/emotional stress - in the absence of damage to the structure of visceral organs;
• CNS changes in the form of central sensitization syndrome - pathologically increased excitability of neurons in response to normal stimuli.

Although functional diarrhea is characterized by the absence of abdominal pain, it is often considered a subtype of irritable bowel syndrome with diarrhea predominance (IBS-D), contrary to its definition as agreed upon and endorsed by the international community of experts in gastroenterology. This definition is based on the presence of liquid stools, their chronic nature and the absence of concomitant irritable bowel syndrome (which may be caused by a previous infectious gastroenteritis).

Risk factors

Increase the risk of functional diarrhea:

• hereditary factors;
• excessive bacterial growth in the small intestine;
• congenital disorders of the structure of the mucous membrane of the GI tract;
• peripheral autonomic failure;
• nervous overload, stress, anxiety, depression;
• stomach or gallbladder surgery.

Pathogenesis

The mechanism of development of functional diarrhea is poorly understood, but to date its pathogenesis is associated with impaired motility and increased rate of intestinal emptying - the passage of consumed food through the gastrointestinal tract in the lower intestine, defined by experts as rapid intestinal transit.

Neuropeptides (somatostatin, neurotensins, motilin, acetylcholine, serotonin and CRH - corticotropin-releasing hormone affecting the response to stress and depression) are involved in the maintenance of motor activity colon, which occurs as widespread high-amplitude contractions of smooth muscle cells of its walls. They modulate gastric and intestinal peristalsis by activating receptors on internal afferent neurons of the autonomic nerves of the ENS and afferent vagus nerves connecting the enteric (intestinal) nervous system to the CNS.

Thus, when the regulation of intestine-brain interaction is impaired, the mechanisms coordinating the rate of emptying of the large intestine, the increase of which leads to rapid defecation and watery consistency of the stool - due to functional insufficiency of the large intestine to absorb water and electrolytes in its lumen stop working.

Symptoms of the functional diarrhea

According to the international community of experts-gastroenterologists, the diagnostic criteria for functional diarrhea are considered to be frequent defecation of liquid consistency, which is not accompanied by abdominal pain or bloating.

Diarrhea must occur in at least two-thirds of defecations within the last three months of symptom onset and at least six months prior to diagnosis, with no identifiable cause (structural or biochemical) and no physical or laboratory abnormalities that could explain the GI symptoms.

Symptoms of functional diarrhea also include intestinal cramps, mucus in the stools, a feeling of incomplete emptying of the bowel, and tenesma (false urges to defecate).

Complications and consequences

One of the most serious consequences of diarrhea of a functional nature is dehydration of the body - isotonic dehydration, leading to complications that can manifest themselves in renal failure; metabolic, cardiac and brain function disorders; weakening of the immune system; nutrient deficiencies - with iron deficiency (and the development of anemia), as well as other vital macro and microelements.

Diagnostics of the functional diarrhea

Functional diarrhea is predominantly a diagnosis of exclusion. This means that the differential diagnosis - according to the diagnostic criteria for this condition - should exclude possible causes of diarrhea such as: irritable bowel syndrome with predominant diarrhea; bacterial, parasitic or viral intestinal infections; drug side effects and food allergies; celiac disease, lactose intolerance and glucose or fructose malabsorption; gallbladder problems; etc.

And this requires blood tests: general; for the level of C-reactive protein and immunoglobulin IgA; for antibodies to tissue transglutaminase. Also taken a general stool analysis, fecal bacterial examination and determination of the level of calprotectin, lactoferrin and bile acids.

If the tests do not reveal any cause of chronic diarrhea, instrumental diagnosis is performed using barium intestinal radiography; colonoscopy; ultrasound, CT or MRI of the abdomen, and if necessary - functional imaging (scintigraphy).

Treatment of the functional diarrhea

In most cases, treatment of functional diarrhea targets symptoms and suspected or identified physiologic changes.

In drug therapy can be used drugs of various pharmacological groups, primarily antidiarrheal drug Imodium or Loperamide, [5] as well as other tablets for diarrhea.

Antispasmodics that can reduce the intensity of intestinal peristalsis include the drug Enterospasmyl (Meteoxan) containing floroglucinol dihydrate. Also significantly reduce stool frequency and improve its consistency are the myotropic antispasmodics Mebeverine, Meverine, Alverina citrate or Duspatalin for functional diarrhea. [6], [7]

Clinicians have found a similar effect in the absorbent Diosmectite (Smecta), which consists of natural alumina and magnesium silicate clay.

If indicated, means that promote the restoration of normal intestinal microbiota are used - Lactovit forte, Hilak forte and other probiotics. [8], [9]

Antidepressants may be prescribed to slow gastrointestinal motility in functional diarrhea. The contraction/laxation and release of enzymes in the digestive system is influenced by neurotransmitters (acetylcholine, dopamine, etc.), and tricyclic antidepressants are used to modify their action on the GI tract. In addition, antidepressants of the serotonin and norepinephrine reuptake inhibitor (SSRI) group are sometimes used to treat functional diarrhea (as well as irritable bowel syndrome): Duloxetine (Intriv), Venlafaxine (Venlaxor, Velafax and other trade names).

Additionally it is possible to use folk remedies for diarrhea.

An important role in the therapy of functional diarrhea is played by nutrition and dietary modification with a decrease in foods with fermentable oligo-, di-, monosaccharides and an increase in fiber intake. For more information see:

• Diarrhea diet
• Diet for dysbacteriosis

Prevention

There are currently no special measures that can prevent conditions that lead to functional diarrhea. But gastroenterologists advise avoiding stress and not neglecting the state of the intestinal microbiota.

Forecast

In each individual case, the prognosis depends on the nature of the functional disorder of the gastrointestinal tract, but such a condition, of course, negatively affects the general state of health, quality of life and performance.