Impairment of motor function of the colon is commonly considered the basic symptom of irritable bowel syndrome. Generally, it is associated with derangement of stool pattern. Constipation-predominant stool pattern is the most common one – half of all the patients suffering from irritable bowel disorder has it. Diarrhea-predominant and alternating stool patterns are almost equally prevalent.
The second basic symptom of irritable bowel syndrome is abdominal pains. Most often pains are spastic and are localized in the abdominal area, but and their intensity and localization may be different depending on the patient. Painful sensations may occur not in the area of the colon and have extra-abdominal localization. Usually pains are aggravated right before defecation and are relieved after it.
At present several diagnostic criteria of irritable bowel syndrome are developed. The most popular are the so called Rome criteria, based on the symptomatologic approach to the classification of functional disorders of the gastrointestinal tract. Irritable bowel syndrome can be diagnosed based on at least 12 weeks, which need not be consecutive, if there was abdominal discomfort or pain:
– relieved with defecation; and/or
– onset associated with a change in frequency of stool; and/or
– onset associated with a change in form (appearance) of stool.
The symptoms that cumulatively support the diagnosis of irritable bowel syndrome are:
– abnormal stool frequency (“abnormal” may be defined as greater than 3 bowel movements per day and less than 3 bowel movements per week);
– abnormal stool form (lumpy/hard or loose/watery stool);
– abnormal stool passage (straining, urgency, or feeling of incomplete evacuation);
passage of mucus;
– bloating or feeling of abdominal distention.
It is necessary to note, that in recent years the look on the essence of irritable bowel syndrome has considerably changed due to expansion of knowledge in etiology, pathogenesis and clinical features of IBS. First of all, the connection of gastrointestinal tract disorders with pathological processes in the central nervous system is emphasized. Thus, irritable bowel syndrome is considered to be the clinical manifestation of neurotransmitter system disbalance, and the notion of functional disorder is being reconsidered.
Modern etiopathogenetic concepts of irritable bowel syndrome are based on the interaction of genetic and psychogenic (i.e. connected with psychotraumatic influences) pathophisiological, psychopathological and personal disorders.