Clinical presentation and diagnostic criteria
The pathophysiological essence of the syndrome lies in the development of a persistent complex of symptoms affecting the lower parts of the digestive tract. As already noted, the process is localized predominantly in the colon, where basic physiological processes of feces formation and elimination are disrupted.
To diagnose IBS, a clear time criterion is required: functional disorders must continue for at least 12 weeks over the course of one calendar year.
In addition, pain syndrome and abdominal discomfort must necessarily be combined with at least two persistent signs of bowel dysfunction from the following list:
- Changes in stool frequency (the patient may suffer from either increased or decreased bowel movements).
- Disorders of the act of defecation itself (difficulty with evacuation, feeling of incomplete evacuation).
- Disruption of normal stool consistency.
- Discharge of visible mucus along with feces.
- Pronounced meteorism (excessive gas accumulation causing bloating).
The role of neurohumoral regulation and psychosomatics
In the pathogenesis of irritable bowel syndrome, regulatory mechanisms at the level of the central nervous system and the local balance of biologically active substances (BAS) play a colossal role.
Firstly, a specific patient personality type is distinguished, which is a serious risk factor. Patients with IBS are highly characterized by:
- Hysterical and aggressive behavioral reactions.
- Presence of depressive episodes and obsessive states.
- Hypochondriacal manifestations and cancerophobia (pathological fear of developing a malignant tumor).
Secondly, at the local level, a dysbalance of biologically active substances occurs. Disruption of adequate regulation of bowel functions is directly related to changes in the concentration and activity of a whole cascade of mediators and hormones. This process involves:
- Biogenic amines: serotonin and histamine.
- Peptides: bradykinin, cholecystokinin, and neurotensin.
- Vasoactive intestinal peptide (VIP).
- Endogenous opiates: enkephalins and endorphins.
Alimentary risk factor
In addition to psychological and neurohumoral aspects, the most important trigger for the development of irritable bowel syndrome is the alimentary factor (the patient's dietary features).
The development of the pathology is promoted by two main dietary habits:
- Irregular meals: chaotic eating habits disrupt the natural rhythms of the digestive system.
- Predominance of refined foods: lack of rough dietary fiber and an excess of processed foods in the diet.
The logical consequences of such dietary behavior are profound functional alterations. The patient experiences changes in the motor and evacuation function of the digestive tract. Following the motility disorder, a change in the normal ratio of intestinal microflora occurs (dysbiosis develops), which together closes the vicious circle of IBS pathogenesis, increasing flatulence, pain, and stool disorders.
Briefly: answers to topical questions
What clinical subtypes of IBS are distinguished based on the predominant stool consistency according to the Bristol Stool Scale?
Depending on the predominant stool consistency, four main clinical subtypes of irritable bowel syndrome are distinguished.
- IBS with constipation (IBS-C) — characterized by predominant constipation.
- IBS with diarrhea (IBS-D) — characterized by predominant diarrhea.
- Mixed IBS (IBS-M) — characterized by alternating constipation and diarrhea.
- Unclassified IBS — a non-specific variant of the disease course.
With which organic gastrointestinal diseases is it necessary to perform differential diagnosis of IBS?
Differential diagnosis of irritable bowel syndrome must be performed with a number of organic diseases that can mimic this pathology.
- Chronic inflammatory bowel diseases (IBD)
- Celiac disease
- Lactose and fructose intolerance
- Microscopic colitis
- Colon tumors
What is the pathophysiological mechanism of visceral hypersensitivity in irritable bowel syndrome?
The basis of IBS pathogenesis is a disruption of neuroendocrine regulation along the brain–gut axis. The key mechanism is the development of visceral hypersensitivity, which leads to impaired intestinal motor function.
Triggers of visceral hypersensitivity can include previous intestinal infections, local inflammatory processes, intestinal trauma, and food allergies.
Patients with IBS also show an increase in GI barrier permeability; normalization of the mucosal-epithelial barrier permeability is indicated as the goal of rebamipide administration.
Which groups of pharmacological drugs are used for pathogenetic therapy of various IBS subtypes?
For the pharmacotherapy of IBS, the sources indicate the following groups and drugs:
- Antispasmodics — baseline therapy regardless of the IBS type; for pain syndrome, antispasmodics of various pharmacological groups are used, including trimebutine, mebeverine, hyoscine butylbromide, pinaverium bromide.
- Trimebutine — a synthetic anticholinergic agent; used in patients with IBS to reduce pain and normalize stool frequency and consistency. Its effects include normalization of intestinal motility and an increase in the pain sensitivity threshold.
- In IBS with predominant diarrhea: loperamide, diosmectite, rifaximin, probiotics; also antidiarrheal drugs and enterosorbents.
- In IBS with predominant constipation: laxatives, including psyllium preparations, macrogol, lactulose; and/or prucalopride.
- For microflora correction: prebiotics and probiotics.
- Amitriptyline — prescribed to adults to reduce abdominal pain when antispasmodics are ineffective; contraindicated in children under 18 years of age.
Remember the "2–12" rule for diagnosing IBS: it is necessary to find at least 2 persistent symptoms of bowel dysfunction that have bothered the patient for a total of at least 12 weeks in a year.
Class and exam questions
How many signs of intestinal dysfunction are required to establish a diagnosis?
The syndrome must be combined with at least two persistent signs (e.g., mucus discharge, flatulence, changes in stool frequency or consistency).
Which part of the gastrointestinal tract is predominantly affected in IBS?
The pathological process in irritable bowel syndrome is localized primarily in the colon.
Which biologically active substances (BAS) are involved in regulatory dysfunction in IBS?
The imbalance involves serotonin, histamine, bradykinin, cholecystokinin, neurotensin, VIP ( vasoactive intestinal peptide ), as well as enkephalins and endorphins.
How do refined foods contribute to the development of the pathology?
The predominance of refined foods in the diet and irregular meals lead to altered motor-evacuation function and disrupt the intestinal microflora balance.
What else to study on this topic
- Mechanisms of serotonin and histamine effects on colonic motility
- The association of hypochondria and cancerophobia with somatic gastrointestinal manifestations
- The role of vasoactive intestinal peptide (VIP) in intestinal secretion
- Pathogenesis of intestinal microflora alterations associated with irregular nutrition
- The effect of endorphins and enkephalins on pain sensitivity in IBS
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