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Treatment of irritable bowel syndrome in primary care

BMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a2213 (Published 13 November 2008) Cite this as: BMJ 2008;337:a2213

Pathogenesis of Irritable bowel syndrome (IBS),a common syndrome seen by General Physicians In West Bengal

Irritable bowel syndrome (IBS) is one of most common syndrome seen by
General Physicians and referral to Gastroenterologists of Kolkata
metropolis from suburban of West Bengal. In India, actually more men than
women present for symptoms of IBS, but this does not mean that men suffer
more than women from IBS in India 1. Worldwide prevalence of this disease
is 10-15% 2 .IBS is one of several functional disorders, in absence of any
detectable organic causes and diagnostic criteria of ROME-2 of NICE guide
line of the disease 3. IBS patients’ shows siginificantly larger cortical
fMRI activity volume in equal subluminal pressure than age matched normal
individuals’ control.

Other functional disorders those are to be
considered in differential diagnosis of IBS are fibromalagia, chronic
pelvic pain, interstitial cystitis and celiac sprue[CS]3 in case of IBS
with diarrhea. On the basis of bowel habit, IBS has been categorized into
three subgroups like IBS with diarrhea (more commonly seen in men), IBS
with constipation (more commonly seen in women) and IBS with mixed bowel
habits3.

In kolkata, west Bengal, patients with IBS often (10-15%) shows
also wheat intolerance, sugar malabsorptions, lactose intolerance&
hence to be also differentiated from CS. Celiac Sprue[CS] patients
presents almost like IBS. including recurrent abdominal pain, abdominal
discomfort, bloating, flatus, diarrhea in absence of alarming symptoms
&sign. Majority of Patients with IBS complain of abdominal bloating which
varies in severity, increases during course of days tends to get worse
after a meal and subside overnight. This symptoms trouble some often very
much then abdominal pain.

Bloating accompanied by distension appears to
be more commonly associated with IBS with constipation then with IBS with
diarrhea. Factors responsible for this bloating are stress, abdominal
motility, abdominal muscle weakness and exaggerated abdominal
accommodation reflex, due to excessive gas in small gut rather then in
colon. Distension of abdomen can occur in both IBS with diarrhea and IBS
with constipation more with IBS with constipation and must have a
mechanical factor for fecal material within the bowel. IBS like symptoms
develop also in 10% of adult populations after bacterial, viral or enteric
infections which are known as post infection IBS and develop when there is
a long duration of gastritis, or colitis and presence of psychosocial
factors. IBS may be in association with Crohn’s disease. IBS is often thus
described as brain gut disorder.

Although patho-physiology of IBS remains
yet unknown, alteration of GI motility, balance of absorption and
secretion in the intestine is the underlying cause of irregularities of
bowel habits and these abnormalities is mediated part by dys-regulation
of gut mediated serotonin signaling system. Abnormally peripheral visceral
receptors, visceral alternants, spinal cord synaptic alterations,
descending pain modulatory responses and cortical hyper vigilance and or
combination of all these are today known factors that can contribute to
hypersensitivity of gut in diarrhea prone IBS. Normal large gut is
chronically in a state of inflammation which occurs because of the balance
between commensal enteric organism and host immune system. Inflammatory
cells including mast cells, activated T lymphocytes are increased above
normal in the mucosa in a subset of patients with IBS, suggestive of low
grade IBD particularly Crohn’s. Further more lymphocytes infiltration of
myenteric plexus is associated with neuron degeneration has been observed
in severe IBS and have increased mast cells in muscularis mucosa from 7-
30% patients who have recovered from a proved episode of bacterial
enteritis may develop IBS. Colonic inflammations are associated with
production of numbers of important mediators including 5HT, prostaglandin,
bradykinin, & other growth factors. These abnormal releases of 5HT
have central role in manifestation of IBS. More than 95% of 5HT is present
in enterochromaffin cells(EC) of intestine. 5HT is released from these
cells following striking or increased luminal pressure for example after a
meal, leading to abdominal cramp-a characteristic of IBS. 5HT then acts on
primary intrinsic afferent neurons to initiate the peristaltic reflex by
activation of ascending excitation and descending inhibition. 5HT then is
primarily retaken up by specific serotonin transporter (SERT) expressed in
entrocytes. Serotonin, 5HT plays a critical role in the regulation of
gastrointestinal motility, secretion and sensation.

Therefore alteration
in 5HT biosynthesis content, release, contributes to disordered GI
function. The role of 5HT in pathophysiology of IBS remain yet unclear.
Studies with number of EC cells and mucosal content 5HT suggest that 5HT
availability is altered in IBS. Probably defects in 5HT signaling- are
associated with IBS. It has been seen that mucosal 5HT tryptophan
Hydroxilase-1 messenger RNA, serotonin transporter messenger RNA[SERT] and
serotonin transpoter imuno reactivity are all reduced in IBC-C, IBS-D and
also in Ulcerative colitis(UC)4 Celiac sprue may be co-mixed with IBS-D.

When a patient comes to a gastroenterologist they suggest serum bio
chemistry panel like complete Blood count, Stool examinations for ovas and
parasite, fecal occult blood test[3 samples], ESR and albumin level in
case of suspected IBS to exclude organic lesions besides double balloon
colonoscopy. But these are insufficient evidences to support any of these
diagnostic tests in diagnosis of IBS. Rather serologic testing for
identifying celiac sprue is worthy one. Non invasive serologic tests are
available for diagnosis of celiac sprue in kolkata with high degree
specificity and sensitivity. For example IgA anti endomysial antibody and
IGA anti tissue transglutaminase antibody are 98% sensitive and 100%
specific for Celiac sprue but very costly

References

1.Tally NG, O. keele E.A, Zinsmeister A.R, Meton LV “ Prevalence of G .I
symptoms in elderly- a population based study” Gastroenterology
102;895;1992

2.Drossman D.A, Camilleri M, Mayer EA, Whitehead AGA “ Technical review on
Irritable bowel syndrome “ Gastroenterology 123; 2108-31;2002

3.Emeran .A. Mayer” irritable bowel syndrome” N eng. J. Med 358:16; April
17;1692-99;2008.

4.Mathew. D coates, Christine R Mahoney, David R linden “ Molecular
defects in mucosal Serotonin content and decreased serotonin re-uptake
Transporter in Ulcerative colitis and Irritable bowel Syndrome”
Gastroenterology 126;1657-64;2004

Competing interests:
None declared

Competing interests: No competing interests

11 December 2008
Professor Pranab Kumr Bhattacharya
Professor, Dept. of pathology, In charge of histopathology Unit, in charge of Cytogenetics, Ex-In c
Bhattacharya Rupak,BSc(cal)Msc(JU) ,BhattacharyaUpasana ,GhoshUdayMD(med)CalNRSMCH,DsguptaJayantaMD(cal)DM(cal)Gastro,Asso.Prof.Gastro ;Ghosh SukumarDM(cal),DipCard(cal) Asst.Prof,Chakraborty .A, Sarkar DMS(cal )FRCS(UK) IPGME&R ,Kol-20, W. B, India
Institute of Post Graduate Medical Education& Research (IPGME&R)