Irritable Bowel Syndrome.
Dr.Barin Bose MS,FACRSI, FAIS.
Consultant Surgeon and Coloproctologist.
Jabalpur Hospital and Research Centre.
The irritable bowel syndrome (IBS) is the most common of all the digestive disorders, affecting nearly everyone at one time or the another and accounting for up to 50% of patients referred to a gastroenterologic practice. Although chacterized as a disorder of bowel moility, in many patients it is an exaggeration of normal physiologic response. IBS is one of the most common functional gastrointestinal disorder characterized by chronic abdominal pain or disorder, which is associated with change in stool frequency and /or form.
Numerius terms have been used to describe the syndrome, they are -
But of all these Irritable bowel syndrome seems to be he most appropriate term. Tearms that include the word colon or colitis are inaccurate because the condition is not limited to the colon and inflammation is not a feature. Further more use of the term colitis leads to confusion with ulcerative colitis.
Pathogenesis - The cause and pathogenesis of IBS remain obscure. Never the less, clinical and laboratory evidence indicate that it is most likely a disorder of bowel motility. Constipation and abdominal cramps are prominent complaints of many patients with IBS. These symptoms could be explained on the basis of hypertonic segments of the bowel which slows down the transit by increasing the resistance to passage of feces. On the other hand it is possible that patients with diarrhea have a hypototile bowel, which would decrease resistance to passage of feces or that they simply have an increase in peristaltic contractions. Both number of mast cells and their mediators have been shown to be increased in the intestinal mucosa of patients with IBS. This increased mast cells in the intestinal mucosa could be due to hypersensitivity to foods . It is a gastrointestinal disorder in which a disturbed brain gut axis has been thought to have a role.
Clinical Presentation Patients with IBS typically complaints of crampy abdominal pain and constipation.In some patients chronic constipation is punctuated by brief episodes of diarrhea. A minority of patients have only diarrhea. Symptoms usually have been present for months to years, and it is common for patients with IBS to have consulted several physicians about their complaints and to have undergone one or more gastrointestinal evaluation, but without any releaf . Patients correlate symptoms with emotional stress.Stools are mixed with excessive mucous discharge but blood is never present unless the IBS is associated with haemorrhoids.
Abdominal cramps are a feature but they are releaved temporarily by defecation. Bowel movements are clustered during the morning or may occur through out the day but rarely the patient is awakened at night .
Rome III has subdivided IBS into
These subtype are based on the stool consistency which can be determined by Bristol Stool Scale Form.
Two dimensional display of the 4 possible IBS subtypes according to bowel form at a particular point in time. IBS C IBS with constipation ;
IBS D IBS with diarrhea ; IBS - M mixed IBS ; IBS U unsubtyped IBS.
The Bristol Stool Form Scale
Features suggestive of Irritable Bowel Syndrome
Physical Examination Patients generally appears healthy, although they may be somewhat tense or anxious. If abdominal pain is a prominent symptoms, voluntary guarding may be present, sometimes a tender sigmoid colon is palpable. A digital rectal examination is important to rule out non IBS disorders.
Diagnostic Studies : Because of the diagnosis of IBS is largely one of exclusions, a number of clinical and laboratory studies should be performed to rule out other treatable disorders.
Routine tests such as a complete blood count , an ESR and stool test for occult blood are done in all patients. If the patient complaints of diarrhea, the stool should be examined for leucocytes, ova, parasites and bacterial pathogens. A flexiable sigmoidoscopic examination and a double contrast barium enema should be performed in all patients.
Additional diagnostic studies such as ultrasound abdomen for gall stones. Barium meal and follow through to rule out Crohns disease. Serum amylase is to be dont to rule out pancreatitis. A lactose tolerance test may be necessary to confirm lactose deficiency in some patients.
Tegaserod ( Tagibs / Zelnorm) : Irritable bowel syndrome with constipation and chronic idiopathic constipation are both lower gastrointestinal dysmotility disorders. Clinical investigations have shown that both motor and sensory functions of the gut appears to be altered in patients suffering from irritable bowel syndrome. While in patients with chronic odiopathic constipation, reduced intestinal motility is the predominant cause of the condition. Both the enteric nervous system and 5-hyderoxytryptamine are thought to represent key elements in the etiology of both IBS and idiopathic constipation. Approximately 95% of serotonin is found through the gastrointestinal tract, primarily stored in entrochromaffin cells but also in enteric nerves acting as a neurotransmitter. Serotonin has been shown to be involved in regulating motility, visceral sensitivity and intestinal secretion. Investigations suggest an important role of serotonin Type-4 (5-HT 4) receptors in the maintenance of gastrointestinal function in human. 5-HT 4 receptors has been found through the human gastrointestinal tract. Tegaserod is a 5-HT 4 receptor agonist that binds with high affinity at human 5-HT 4 receptors. Tegaserod , by acting as an agonist at neuronal 5-Ht 4 receptors, triggers the release of further neurotransmitters such as calcitonin gene-related peptide from sensory neurons. The action of 5HT 4 receptors in the gastrointestinal tract stimulates the peristaltic reflex and intestinal secretions, as well as inhibits visceral sensitivity. In short Tegaserod imitates the action of the neurotransmitter serotonin and helps to coordinate the nerves and muscles in the intestine.
Alosetron : This drug is a nerve receptor antagonist that is supposed to relax the colon and slow the movement of waste through the lower bowel. But the drug was removed from the market just nine months after its approval when it was linked to at least four deaths and severe side effects in 197 people. In June 2002, when the Food and Drug Administration (FDA) decided to allow alosteron to be sold again but with restrictions . The drug can be prescribed only by doctors enrolled in a special program and is intended for severe cases of
diarrhea - predominant IBS in women who havent responded to other treatments.