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Abdominal distension in health and irritable bowel syndrome: The effect of bladder filling



Background & aims: Abdominal distension is a common feature of irritable bowel syndrome (IBS), which is difficult to treat and can have the appearance of late pregnancy. It results from an abnormality of the normal accommodation reflex which keeps abdominal girth constant despite changes in gastrointestinal volume resulting from food ingestion or gas accumulation. We speculated that bladder filling might also trigger this abnormal reflex in IBS and this study tested this hypothesis. Methods: Eight females with IBS (aged 21-43, mean 34) were compared with seven female controls (aged 19-56, mean 31) at the same time in the menstrual cycle. Abdominal girth in response to maximum tolerated bladder filling following ingestion of 1500 mls of water was measured using abdominal inductance plethysmography. Symptoms, girth change after bladder emptying, and urine volumes were also recorded. Key results: Baseline girth of patients and controls was 84.8 and 79.9 cm respectively. After reaching maximum tolerated bladder filling, girth increased by a mean of 6.4 (Standard deviation (SD) 2.1) cm in patients compared with 3.5 (1.1) in controls (P = 0.006), with patients having symptoms of bladder hypersensitivity. After voiding urine, girth reduced by 5.3 (3.1) and 1.9 (1.2) in patients vs controls (P = 0.018), despite passing similar mean urine volumes, 789 (364) mls vs 671(286) (P = 0.50). Conclusions & inferences: Bladder filling contributes to abdominal distension in IBS and is unrelated to urine volume suggesting that bladder stretch or hypersensitivity might trigger this response. Frequent bladder emptying may help control this intrusive problem which is very challenging to manage.
Neurogastroenterology & Motility. 20 18; e1 34 37.    
 1 of 6
Many patients with irritable bowel syndrome (IBS) complain of ab
dominal bloating which is defined as the sensation of an increase in
pressure within their abdomen. In approximately 50% of individu
als who complain of bloating1 this sensation can be accompanied
by an increase in abdominal girth which is referred to as visible
abdominal distension. Many patients with either bloating or vis
ible abdominal distension often rank this problem as their most
intrusive symptom.2,3 Patients are at their most comfortable
in the
morning and become more distended throughout the day, espe
cially in response to eating or drinking. In women with particularly
  Revised:27J une2018 
DOI : 10.1111 /nmo .134 37
Abdominal distension in health and irritable bowel syndrome:
The effect of bladder filling
Basma Issa1| Julie Morris2| Peter J Whorwell1
Thisisanop enaccessa rticleunderthetermsoftheC reativeCommonsAt tribution‐Non Commercial‐NoD erivsLicense,whichpermitsuseandd istrib utionin
any medium, provided the original work is properly cited, the use is non‐commercial and no mo difications or ad aptations are made.
©2018TheAut hors.Neurogastroenterology & MotilityPublishe dbyJohnWiley&Sons,Ltd.
Hospit al of South M anches ter, Manchester,
2Department of Medical
Statistics,Universit yHospit alofSouth
Manche ster,Manchester,UK
Correspondence: ProfessorPeterJ
Whorwell,MD,PhD,Neurogastroenterolog y
Unit,Wythens haweHospital,Man chester,
Funding information
The study was supp orted by a n internal
grantfromtheUHSMGastroenterolo gy
Background & Aims: Abdominal distension is a commonfeature of irritable bowel
syndrome (IBS), which is difficult to treat and can have the appearance of late preg‐
nancy. It results from an abnormality of the normal accommodation reflex which
keeps abdominal girth constant despite changes in gastrointestinal volume resulting
from food ingestion or gasaccumulation.Wespeculated thatbladder filling might
also trigger this abnormal reflex in IBS and this study tested this hypothesis.
Methods: Eight females with IBS (aged 21‐43, mean 34) were compared with seven fe
girth in response to maximum tolerated bladder filling following ingestion of 1500 mls
of water was measured using abdominal inductance plethysmography. Symptoms, girth
change after bladder emptying, and urine volumes were also recorded.
Key Results: Baseline gir th of patients and controls was 84.8 and 79.9 cm respec‐
6.4 (Standard deviation (SD) 2.1) cm in patients compared with 3.5 (1.1) in controls
urine, girth reduced by 5.3 (3.1) and 1.9 (1.2) in patients vs controls (P = 0.018), de
spite passing similar mean urine volumes, 789 (364) mls vs 671(286) (P = 0.50).
Conclusions & Inferences: Bladder filling contributes to abdominal distension in IBS
and is unrelated to urine volume suggesting that bladder stretch or hypersensitivity
might trigger this response. Frequent bladder emptying may help control this intru‐
sive problem which is very challenging to manage.
bladder, bloating, distension, hypersensitivity, irritable bowel syndrome
2 of 6 
   ISSA et Al.
distension, it is not unusual for people to ask t hem whether
they are pregnant.
Techniques such as the gas infusion technique, abdominal induc
have allowed the pathophysiology to be more clearly understood.
Visible abdominal distension is more associated with constipation,1
delayed gastrointestinal transit,4 weak abdominal musculature,5
probable changes in the gastrointestinal flora,6 and an abnormal
accommodation reflex.7‒12 Bloating is more often associated with
visceral hypersensitivity and a tendency to a loose bowel habit.13
However, it is likely that none of these mechanisms are mutually ex‐
clusive and their relative contribution to the problem in any particu‐
lar individual varies.
Azpiroz a nd colleagu es have been st udying the a ccommoda
tion reflex for many years and have shown that in healthy peo
ple this reflex allows an individual to accommodate an increase in
the volume of their abdominal contents without any appreciable
change in abdominal girth. This is achieved by a degree of dia
phragmatic relaxation in conjunction with an increase in tone of
the anterior abdominal musculature. They have shown that this
reflex may be reversed in patients with IBS accompanied by ab
dominal distension, so that an increase in abdominal volume re
sults in contraction of the diaphragm coupled with relaxation of
the anterior abdominal wall,7‒12 leading to an increase in abdomi
nal girth. Interestingly, they have also shown that this abnormality
can be reversed by biofeedback which suggests that it might be a
conditioned response rather than necessarily an alteration in re
flex pathways. These observations were made using CT scanning
or diaphragmatic electromyography in response to a colonic gas
challenge and, therefore, the fact that the infusion of gas triggers
this abnormal reflex, suggests that an increase in colonic volume
might be one of t he activat ors of this reac tion. A simil ar mech
anism might explain why distension is more common in patients
with constipation and this hypothesis is supported by the observa
tion that relieving constipation can lead to a reduction in abdom
inal distension.6
We have developed a technique called abdominalinduc tance
plethysmography(AIP) which allows the measurementof abdom
inal girth in an ambulatory fashion over a 24‐hour period. The
equipment consists of a soft, expandable belt containing a wire,
the inductance of which changes with the shape of the abdomen
and can be captured by a data logger for 30 seconds every minute
and subsequently, transposed into a measurement accurate down
to one millimetre.14 During studies using abdominal inductance
plethysmography, we have noticed that, in some individuals, disten
sion seems to be exacerbated by a full bladder. This has led us to
speculate that an increase in the volume of any abdominal viscus,
especially the bladder in which large volume changes occur, might
result in distension in a patient in whom the accommodation reflex
is already abnormal, such as in IBS. This study was designed to test
this hypothesis by establishing whether bladder filling has any ef
fect on abdominal distension in patients with IBS compared with
healthy controls.
2.1 | Participants
Eight female patients with ROME III defined IBS15 with constipation
(mean age 34, range 21‐43) were compared with seven healthy con‐
trols without any evidence of bowel problems (mean age 31, range
19‐56). Females were used because of their tendency to suffer from
abdominal distension more than males. Those over the age of 55
were excluded to rule out any chance of confounding of the results
as a consequence of the possibility of abdominal muscles weakening
with age. Following initial screening, suitable potential participants
were sent a patient information sheet and subsequently, attended
the Neurogastroe nterology Unit in the afternoon, in order to go
through the informed consent procedure and symptom checking.
2.2 | Procedure
If found to be suitable, all participants completed a questionnaire de
tailing any urological symptoms and the IBS patients had the severity
of their condition assessed using the IBS symptom severity score
(IBS SSS).16 This instrument consists of five components which are
each scored out of 100 giving a maximum total score of 500, with a
score of less than 175 indicating mild IBS, 175‐30 0 moderate IBS and
greater th an 300 seve re IBS. All pa rticipant s were fit ted with the
abdominal inductance plethysmography device, in order for them to
become familiar with the equipment before starting the study on the
following day. Participants were then asked to refrain from smoking,
alcohol, caffeine, and any strenuous physical activity prior to partici‐
pating in the study and those patients with IBS were also asked to
ied when they were in the middle of their menstrual cycle depending
on the length of their cycle.
The following day, participants were asked to return to the unit
the following morning without having had anything to eat or drink
sincemidnight.Allsub jec tswereaskedtoemptyt heirbl add eronar
rival and then sit in a comfortable chair for the duration of the study.
During this time they were asked to drink one and a half liters of
Key Points
• AbdominaldistensionisamajorprobleminIBS.Itistrig
gered by a variety of fac tors but the effect of bladder
filling has not been assessed.
IBS patients became much more distended than the nor‐
mal people in response to a bladder filled with a similar
amount of urine. This suggests that their bladder might
be over‐sensitive and triggering this response.
• Abdominaldistensionisnotoriouslydifficulttotreatand
advising frequent emptying of the bladder might help
patients to control this symptom.
 3 of 6
ISSA et Al .
water over the course of the first hour and remain in the sitting posi‐
tion and refrain from emptying their bladder for as long as possible,
during which time the abdominal girth was continuously recorded.
When they f elt a strong need to e mpty their bla dder, they were
asked to fill in a further questionnaire recording any symptoms and
allowed to pass urine into a toilet that was equipped to collect their
urine so that the volume could be recorded. The participant was
then instructed to return to their seat and girth was measured for a
further 30 minutes following emptying their bladder after which the
study was terminated.
2.3 | Ethical statement
The stu dy was approved by Natio nal Research Ethic s Committee
North West—Greater Manchester South, REF: 12/NW/0667 and
all participant s gave informed consent. All patient data were a n
onymizedandparticipantsallocated auniquestudynumberforthe
purposes of analysis.
2.4 | Power calculation
Based on previous research in our department, a difference in
change of gir th of 5 centimeters between IBS patients and controls
was regarded as meaningful.
Sample size calculation: Withsevensubjectsineach group the
study would have 80% power to detect a difference of 4.5 cm or
more in the change in distension between a patient and control
group (using a simple t‐test with an estimated common standard de‐
viation of 2.5, derived from a previous study, with the conventional
5% significance level).
2.5 | Statistical analysis
Age,bodymassindex(BMI),andgirthmeasurement swerecom
pared bet ween the t wo groups using the simple two tailed t‐
test. Frequency and severity of symptoms were compared with
Fisher’sExact test and the Mann–WhitneyU‐test, respectively.
The conventional two‐sided 5% significance level was used
All patie nts with IBS m et the ROME III cr iteria. Table 1 compar es
the baseline characteristics of IBS patients and controls in terms of
age, BMI and abdominal girth. In addition, for patient s with IBS, it
documents the score of each component of the IBS symptom sever‐
ity score (SSS) and the total score. The mean IBS symptom severity
score for the IBS group was 255 with two patients being classified
as mild, four as moderate, and two as severe. The IBS patients and
controls had similar BMI values (23.3 and 23.9) and were of similar
age (34.3 and 31.4).
Table 2 compares the baseline urological symptoms in patients
and contro ls. As can b e seen all pat ients with I BS tended to have
more symptoms, with urgency of micturition reaching significance.
Figure 1 is an example of the actual output from the abdomi
nal induc tance plethysmography belt in a patient with IBS during
bladder filling and emptying. For comparison, Figure 2 shows the
output fromthebeltina healthy control.Ascanbe seen, inboth
subjects girth increases with time but the curve is much steeper
with bladder filling and declines more sharply after bladder emp
tying in the IBS patient. Table 3 shows the mean changes in girth
for all the IBS patients and controls following the consumption
of1.5liters ofwater.Whenthebladder was full,themeangirth
measurement in IBS patients increased by 6.4 cm compared with
only 3.5 cm in controls, which is a highly significant dif ference
(P=0.00 6).W hen the bladd er was emptied , girth measu rement
TABLE 1 Baseline characteristics of participants in terms of age,
BMI, and girth and symptom severity scores in irrit able bowel
syndrome (IBS) patients
Mean (SD)
P valueIBS (n = 8) Controls (n = 7)
Age 3 4.3 (7. 8) 31.4 (12.4) 0.60
BMI 23.3 (2.6) 23.9 (3.3) 0.72
Abdominalgirth 8 4. 8 (9.7 ) 7 9.9 (6 .8) 0.29
38.6 (25.9) – –
37. 6 (2 8.9 ) – –
Bloating severity 49.0 (18.0) – –
Satisfaction with
Bowel habit
64.5 (15 .8) – –
How much IBS
affecting life
50.1 (15.3) – –
Total IBS score 255.2 (84.1) – –
TABLE 2 Baseline urological symptoms in irritable bowel
syndrome (IBS) patients and healthy controls
Urological symptoms
Median (range) or % (n)
valueIBS (n = 8) Controls (n = 7)
urinate during day
9 (5.22) 5 (5.9) 0.06
urinate during night
1 (1. 2) 0 (0.2) 0.06
Do you have urgency
associated with
passing water?
75% (6) 43% (3) 0.32
How often do you have urgency?
Occasionally 17% (1) 100% (3)
Usually/often 83% (5) 0% (0) 0.05
How severe is your
56 (31.75) 37 (35.42) 0.38
4 of 6 
   ISSA et Al.
subsided by 5.3 cm in IBS patients compared to only 1.9 cm in con
trols (P = 0.018). However, there was no significant difference in
the mean volume of urine passed by IBS patients and controls on
emptying their bladders (mean (SD) volume: 789 (364) mls, range:
190‐1250 vs 671 (286) mls, range: 225‐1000, (P = 0.50). Figure 3
is a graphical representation of the mean change in girth measure
ment from baseline in all patients and controls.
Table 4 compares the symptoms induced by a full bladder and
their severity in IBS patients and controls and again shows that IBS
patients tended to be more symptomatic.
The results of this study show that in patients with IBS and healthy
controls, filling of the bladder with similar volumes of urine leads
to a substantial increase in abdominal girth in patients with IBS but
not in healthy controls. Furthermore, the fact that a relatively small
number of patients were required to detect a significant effect in‐
dicates that the differences were clear‐cut and unequivocal. This
observation supports the hypothesis that, on the assumption that
the accommodation reflex is disordered in some individuals with IBS,
an increase in the volume of any abdominal viscus might result in a
similar reaction.
Obviously, the bladder is the intra‐abdominal organ which un‐
dergoes the widest range of volume changes and it is, therefore,
likely to have the greatest effect. There is already evidence that the
colon is involved in this reflex and our dat a would support the notion
that similarly, changes in the volume of the small bowel and stom‐
ach might also be impor tant. Indeed, a response to an increase in
volume of the stomach in a patient with IBS could explain why so
many patients with this condition complain of an almost instanta‐
neous increase of girth within minutes of starting a meal or even just
FIGURE 1 Abdominalinductanceplethysmographytracefrom
an irritable bowel syndrome patient showing a steady increase in
girth af ter drinking 1500 cc of water followed by a sharp decline
after bladder emptying (arrow)
09:21 09:51 10:21 10:5111:21 11:51
Girth (cm)
Bladder emptying
FIGURE 2 Abdominalinductanceplethysmographytracefrom
a healthy control showing a slight increase in girth after drinking
1500 cc of water followed by a small decline after bladder emptying
09:37 10:07 10:47 11:1811.51 12:27
Girth (cm)
Bladder emptying
TABLE 3 Changes in abdominal girth in irritable bowel
syndrome (IBS) patients and healthy controls after maximum
bladder filling and following bladder emptying
Mean change in girth (SD) in
P valueIBS (n = 8) Controls (n = 7)
Change from baseline
to full bladder
6.4 (2.1) 3.5 (1.1) 0.006
Change from full to
empty bladder
5.3 (3.1) 1.9 (1.2) 0.018
FIGURE 3 Comparison of the mean change in girth from
baseline and 95% confidence intervals resulting from bladder filling
in irritable bowel syndrome patients and healthy controls
Baseline 30
Change in girth (cm)
of test
 5 of 6
ISSA et Al .
drinkinga glass ofwater.Whether more subtle changesin volume,
especially in the presence of visceral hypersensitivity, can initiate
this response in these patients is less clear, but it would be of inter‐
time of menstruation might partly explain the exacerbation of IBS
symptoms, including bloating and distension, with menses that many
women with this condition report.17,1 8
It would be useful to understand what leads to a disturbance of
the accommodation reflex in the first place and whether it is a con‐
ditioned response or an alteration of reflex pathways. Furthermore,
once initiated how do changes in intra‐abdominal volume mediate
this effect? The most likely explanations are either as a result of
pressure changes within the viscus or in response to stretching of
the mucosa or serosa. Visceral hypersensitivity is one of the most
common physiological abnormalities described in patients with IBS
and it is temp ting to attribute a role to this phe nomenon in the patho‐
genesis of distension. However, this abnormality seems to be more
common in patients with bloating in the absence of distension,13 al
though this is not a clear‐cut difference and there is some overlap.
Whatever mechanismsare involved,aclearer understandingwould
be useful because bloating and distension are notoriously difficult
symptoms to treat and better management strategies are needed.
Patients with IBS frequently complain of bladder symptoms sug‐
gestive of an irritable bladder and are certainly over‐represented
in urology clinics.19 In addition, urodynamic studies in IBS patients
have shown that approximately 50% have a demonstrable abnormal‐
it y.20 In the current study we have again confirmed that IBS patients
have a propensity to have symptoms suggestive of an irritable blad‐
der (Table 2). Furthermore, when their bladders were full, IBS pa
tients also complained of more symptoms (Table 4). However, we did
not obser ve any differences in the volume of urine passed between
patients and healthy controls, which suggests that the observed dif‐
ferences in the change in abdominal girth with bladder filling were
not related to the amount of urine in the bladder. To investigate this
further, it would have been interesting to establish whether there
was a relationship between any urodynamic abnormality and the
observed distension response. However, it was felt that the incor‐
poration of urodynamic investigation was not ethically justified in
this study, when it was not even known whether there would be a
distension response to bladder filling.
disordered accommodation reflex, it is possible that, as with anis
mus, biofeedback might have therapeutic potential and this has
been confirmed by the Barcelona group.21 In addition, some life
style approaches may be worthy of consideration. For instance,
patients with constipation should be encouraged to keep their
bowel as empt y as possible and this may even be worth consider
ing when the constipation is relatively mild. Furthermore, as gas
insufflation studies have been shown to have an effect, dietary
manipulation aimed at reducing fermentation should also be ad
tric filling, it would be of interest to know whether slowing the
speed of fluid or food int ake might have an ameliorating effec t.
Lastl y,in t he light of our find ings, it would se em reasonable t o
recommend that patients with abdominal distension should be ad
vised to keep their bladders as empty as possible, especially as it
appears that distension starts to be triggered by even mild blad
der filling (Figures 1 and 3). Consequently, we now recommend
that patients with troublesome distension try to pass urine on a
reasonably regular basis. In addition, in the design and conduct of
any future clinical studies or trials on abdominal distension, the
possible confounding effect s of bladder filling need to be taken
into consideration.
In conclusion, the mechanisms leading to the enigmatic symptom
of abdominal distension are gradually being unraveled, but we still
do not have all the answers.
Symptoms IBS Controls P value
Do you have pain in your bladder? %
answering yes
88% 43% 0.12
Howsevereist hepain(0−100sclae)?
Median (range)
59 (33.94) 30 (8.38) *
Do you have a tight feeling in your
tummy? % answering yes
100% 71% 0.20
How severe is t his feeling? Median
74 (4 5.9 2) 57 (36.93) *
Do you have a bloated feeling? %
answering yes
88% 43% 0.12
How severe is t his feeling? Median
69 (50.92) 28 (25.46) *
Do you feel distended? % answering yes 88% 43% 0.12
How severe is t his feeling? Median
73 (52.93) 28 (25.46) *
*P‐values relating to severity comparisons not included because numbers with each particular sy mp‐
tom in the control group are too small.
TABLE 4 Comparison of symptoms
induced by a full bladder in irritable bowel
syndrome (IBS) patients and healthy
controls and their severity
6 of 6 
   ISSA et Al.
acted as a consultant for, or received research grant support from,
the following companies: Almirall Pharma, Chr. Hansen, Danone
Research, Ironwood Pharmaceuticals, Sucampo Pharmaceuticals,
BIandPJWconceivedtheideaandBIcondu ctedthes tudy;JMcon
ducted the statistical analysis; PJW and BI reviewed the literature
and drafted the manuscript and all authors approved the final ver‐
sion of the paper.
Peter J Whorwell‐0002‐5220‐8474
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Aim . Current clinical recommendations accentuate current methods for the diagnosis and treatment of irritable bowel syndrome (IBS). Key points. IBS is a functional bowel disorder manifested with recurrent, at least weekly, abdominal pain with the following attributes (any two leastwise): link to defecation, its frequency or stool shape. The symptoms are expected to persist for at minimum three months in a total six-month follow-up. Similar to other functional gastrointestinal (GI) disorders, IBS can be diagnosed basing on the patient symptoms compliance with Rome IV criteria, provided the absence of potentially symptom-causative organic GI diseases. Due to challenging differential diagnosis, IBS can be appropriately established per exclusionem, with pre-examination as follows: general and biochemical blood tests; tissue transglutaminase IgA/IgG antibody tests; thyroid hormones test; faecal occult blood test; hydrogen glucose/ lactulose breath test for bacterial overgrowth; stool test for enteric bacterial pathogens and Clostridium difficile A/B toxins; stool calprotectin test; abdominal ultrasound; OGDS, with biopsy as appropriate; colonoscopy with biopsy. The IBS sequence is typically wavelike, with alternating remissions and exacerbations often triggered by psychoemotional stress. Treatment of IBS patients includes dietary and lifestyle adjustments, various-class drug agents prescription and psychotherapeutic measures. Conclusion . Adherence to clinical recommendations can facilitate timely diagnosis and improve medical aid quality in patients with different clinical IBS variants.
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Background & aims: In patients with functional gut disorders, abdominal distension has been associated with descent of the diaphragm and protrusion of the anterior abdominal wall. We investigated mechanisms of abdominal distension in these patients. Methods: We performed a prospective study of 45 patients (42 women, 24-71 years old) with functional intestinal disorders (27 with irritable bowel syndrome with constipation, 15 with functional bloating, and 3 with irritable bowel syndrome with alternating bowel habits) and discrete episodes of visible abdominal distension. Subjects were assessed by abdominothoracic computed tomography (n = 39) and electromyography (EMG) of the abdominothoracic wall (n = 32) during basal conditions (without abdominal distension) and during episodes of severe abdominal distension. Fifteen patients received a median of 2 sessions (range, 1-3 sessions) of EMG-guided, respiratory-targeted biofeedback treatment; 11 received 1 control session before treatment. Results: Episodes of abdominal distension were associated with diaphragm contraction (19% ± 3% increase in EMG score and 12 ± 2 mm descent; P < .001 vs basal values) and intercostal contraction (14% ± 3% increase in EMG scores and 6 ± 1 mm increase in thoracic antero-posterior diameter; P < .001 vs basal values). They were also associated with increases in lung volume (501 ± 93 mL; P < .001 vs basal value) and anterior abdominal wall protrusion (32 ± 3 mm increase in girth; P < .001 vs basal). Biofeedback treatment, but not control sessions, reduced the activity of the intercostal muscles (by 19% ± 2%) and the diaphragm (by 18% ± 4%), activated the internal oblique muscles (by 52% ± 13%), and reduced girth (by 25 ± 3 mm) (P ≤ .009 vs pretreatment for all). Conclusions: In patients with functional gut disorders, abdominal distension is a behavioral response that involves activity of the abdominothoracic wall. This distension can be reduced with EMG-guided, respiratory-targeted biofeedback therapy.
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Objective: Patients with irritable bowel syndrome and abdominal bloating exhibit abnormal responses of the abdominal wall to colonic gas loads. We hypothesised that in patients with postprandial bloating, ingestion of a meal triggers comparable abdominal wall dyssynergia. Our aim was to characterise abdominal accommodation to a meal in patients with postprandial bloating. Design: A test meal (0.8 kcal/ml nutrients plus 27 g/litre polyethylenglycol 4000) was administered at 50 ml/min as long as tolerated in 10 patients with postprandial bloating (fulfilling Rome III criteria for postprandial distress syndrome) and 12 healthy subjects, while electromyographic (EMG) responses of the anterior wall (upper and lower rectus, external and internal oblique via bipolar surface electrodes) and the diaphragm (via six ring electrodes over an oesophageal tube in the hiatus) were measured. Means +/- SD were calculated. Results: Healthy subjects tolerated a meal volume of 913±308 ml; normal abdominal wall accommodation to the meal consisted of diaphragmatic relaxation (EMG activity decreased by 15±6%) and a compensatory contraction (25±9% increase) of the upper abdominal wall muscles (upper rectus and external oblique), with no changes in the lower anterior muscles (lower rectus and internal oblique). Patients tolerated lower volume loads (604±310 ml; p=0.030 vs healthy subjects) and developed a paradoxical response, that is, diaphragmatic contraction (14±3% EMG increment; p<0.01 vs healthy subjects) and upper anterior wall relaxation (9±4% inhibition; p<0.01 vs healthy subjects). Conclusions: In functional dyspepsia, postprandial abdominal distension is produced by an abnormal viscerosomatic response to meal ingestion that alters normal abdominal accommodation.
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The abdomen normally accommodates intra-abdominal volume increments. Patients complaining of abdominal distension exhibit abnormal accommodation of colonic gas loads (defective contraction and excessive protrusion of the anterior wall). However, abdominal imaging demonstrated diaphragmatic descent during spontaneous episodes of bloating in patients with functional gut disorders. We aimed to establish the role of the diaphragm in abdominal distension. In 20 patients complaining of abdominal bloating and 15 healthy subjects, we increased the volume of the abdominal cavity with a colonic gas load, while measuring abdominal girth and electromyographic activity of the anterior abdominal muscles and of the diaphragm. In healthy subjects, the colonic gas load increased girth, relaxed the diaphragm, and increased anterior wall tone. With the same gas load, patients developed significantly more abdominal distension; this was associated with paradoxical contraction of the diaphragm and relaxation of the internal oblique muscle. In this experimental provocation model, abnormal accommodation of the diaphragm is involved in abdominal distension.
Background: We have previously shown that the menstrual cycle has no effect on rectal sensitivity of normal healthy women, despite them having looser stools at the time of menses. Patients with irritable bowel syndrome (IBS) often report significant exacerbation of their IBS symptoms with menses, raising the possibility that IBS patients may respond differently to the menstrual cycle. Aim and methods: Rectal responses to balloon distension during days 1–4 (menses), 8–10 (follicular phase), 18–20 (luteal phase), and 24–28 (premenstrual phase) of the menstrual cycle were assessed in 29 female IBS patients (aged 21–44 years), diagnosed by the Rome I criteria. During the course of the study patients completed symptom diaries to assess abdominal pain and bloating (visual analogue scale), and frequency and consistency of bowel habits. In addition, levels of anxiety and depression were assessed using the hospital anxiety and depression questionnaire. Results: Menses was associated with a worsening of abdominal pain and bloating compared with most other phases of the menstrual cycle (p<0.05). Bowel habits also became more frequent (p<0.05) and patients tended to have a lower general well being. Rectal sensitivity increased at menses compared with all other phases of the cycle (p<0.05). There was no associated change in rectal compliance, wall tension, or motility index. Neither was there any difference in resting anal pressure or the distension volumes required to relax the internal anal sphincter during the menstrual cycle. Conclusion: These data (1) confirm that IBS symptomatology is exacerbated at menses and (2) show for the first time that in contrast with healthy women, rectal sensitivity changes with the menstrual cycle. These cyclical changes in sensitivity suggest that women with IBS respond differently to fluctuations in their sex hormonal environment or its consequences compared with healthy females.
Background: Using an experimental model of colonic gas infusion, we previously showed that the abdominal walls adapt to its content by an active phenomenon of abdominal accommodation. We now hypothesized that abdominal accommodation is a physiological phenomenon, and aimed to confirm that it can be induced by ingestion of a meal; a secondary aim was to determine whether the response to gut filling is region-specific. Methods: In healthy subjects (n = 24) a nutrient test meal was administered until tolerated at a rate of 50 mL min(-1). Electromyographic (EMG) activity of the anterior wall (upper and lower rectus, external and internal oblique) was measured via four pairs of surface electrodes, and EMG activity of the diaphragm via intraluminal electrodes on an esophageal tube. To address the secondary aim, the response to gastric filling was compared with that induced by colonic filling (1440 mL 30 min(-1) anal gas infusion; n = 8). Key results: Participants tolerated 927 ± 66 mL of meal (450-1500 mL). Meal ingestion induced progressive diaphragmatic relaxation (EMG reduction by 16 ± 2%; P < 0.01) and selective contraction of the upper abdominal wall (24 ± 2% increase in activity of the upper rectus and external oblique; P < 0.01 for both), with no significant changes in the lower rectus (4 ± 2%) or internal oblique (5 ± 3%). Colonic gas infusion induced a similar response, but with an overall contraction of the anterior wall. Conclusions & inferences: Meal ingestion induces a metered and region-specific response of the abdominal walls to accommodate the volume load. Abnormal abdominal accommodation could be involved in postprandial bloating.
  We previously showed that changes in intra-abdominal content induce a volume-dependent muscular response of the anterior abdominal wall and the diaphragm. We aimed to determine the contribution of the thorax to abdominal accommodation and the influence of the intra-abdominal expansion rate.   Gas (1440 mL total load) was infused into the colon of nine healthy subjects, while abdomino-thoracic perimeters (by tape measure), electromyography (EMG) activity of the diaphragm (via six ring electrodes over an esophageal tube in the hiatus), intercostals and anterior abdominal wall (via five pairs of surface electrodes) and the position of the diaphragm by ultrasonography were measured. Infusion rates of 24, 48, and 96 mL min(-1) were tested on separate days.   Gas infusion induced anterior abdominal wall contraction (18 ± 1% EMG increment; P < 0.001) with relatively modest girth increment (4.9 ± 0.9 mm; P = 0.001), diaphragmatic relaxation (by 15 ± 1%; P < 0.001) with cephalad displacement (by 23 ± 6 mm; P = 0.005), and intercostal contraction (by 19 ± 2%; P < 0.001) with increased thoracic perimeter (by 2.0 ± 0.5 mm; P = 0.009). Responses were similar with the three infusion rates.   Accommodation of intra-abdominal loads involves a volume-related integrated abdomino-thoracic response regardless of the expansion rate.
Abdominal bloating is a frequent symptom in various categories of patients; however, its origin is unclear. Our aim was to establish the mechanisms of abdominal bloating. The study evaluated 56 patients whose predominant symptom was abdominal bloating. Of these, 47 (44 female and 3 male; aged 19-74 years) were diagnosed with functional intestinal disorder by Rome II criteria and 9 (7 female and 2 male; aged 18-64 years) were diagnosed with intestinal dysmotility by gastrointestinal manometry. Computed tomographic scans were obtained before (basal level) and during a severe bloating episode. Control scans were also obtained from 12 healthy subjects (11 female and 1 male; aged 19-62 years). Morpho-volumetric differences between basal and severe bloating scans were measured using an original computer analysis program. During severe bloating, patients with dysmotility exhibited anterior wall protrusion (23 +/- 4 mm; P < .001 vs basal) associated with a marked increase in total abdominal volume (1.4 +/- 0.3 L; P = .002 vs basal) and with cephalic displacement of the diaphragm. By contrast, in patients with functional intestinal disorder, total abdominal volume barely increased (0.3 +/- 0.1 L; P < .001 vs dysmotility); in these patients, abdominal distention (14 +/- 2 mm anterior wall protrusion; P < .001 vs basal) was related to diaphragmatic descent (-12 +/- 3 mm; R = -0.62; P < .001). Abdominal distention might be caused by an increase in intra-abdominal volume or abdomino-phrenic displacement and ventro-caudal redistribution of contents.
Bloating symptoms are common in patients with irritable bowel syndrome (IBS) seen in primary care and gastrointestinal clinics. However, the underlying mechanisms of IBS are poorly understood, and there are few data available about the epidemiology of this syndrome or the impact of its symptoms. We investigated the prevalence, characteristics, and impact of bloating symptoms in patients with IBS. IBS patients were identified by Rome II criteria in a U.S. population representative web-based survey. Patients were asked about the quality, frequency, and severity of their gastrointestinal symptoms. The impact of these symptoms was investigated by assessing patients' health-related quality of life, utilization of health care, and use of medications. Of the 337 IBS patients in this study, 82.5% (n = 278) reported bloating symptoms, the second most bothersome symptom after abdominal cramping. The symptoms were more prevalent in female patients, 87.4% (n = 209), than in male patients, 70.4% (n = 69) (P < .0001), and in patients with constipation, 88.7% (n = 47), and mixed symptoms, 88.8% (n = 135), than in patients with diarrhea, 72.3% (n = 96), (P = .02 and P < .01, respectively). Bloating symptoms were the third (of 14) most important reason to seek medical care, and more than half of the patients reported regular use of anti-gas medications. Bloating symptoms were associated with decreased energy levels (P = .04), food intake (P < .01), and physical functioning (P = .06). Bloating symptoms are common in patients with IBS, and their prevalence and relative severity differ on the basis of sex and IBS subtype. Bloating symptoms are associated with a decrease in the quality of life and increases in health care utilization and use of medications.
A sensation of abdominal swelling (bloating) and actual increase in girth (distension) are troublesome features of irritable bowel syndrome (IBS), which is more common in patients with constipation, especially those with delayed transit. To establish whether a fermented dairy product containing Bifidobacterium lactis DN-173 010 reduces distension in association with acceleration of gastrointestinal transit and improvement of symptoms in IBS with constipation. A single centre, randomized, double-blind, controlled, parallel group study in which patients consumed the test product or control product for 4 weeks. Distension, orocaecal and colonic transit and IBS symptoms were assessed on an intention-to-treat population of 34 patients. Compared with control product, the test product resulted in a significant reduction in the percentage change in maximal distension [median difference - 39%, 95% CI (-78, -5); P = 0.02] and a trend towards reduced mean distension during the day [-1.52 cm (-3.33, 0.39); P = 0.096]. An acceleration of orocaecal [-1.2 h (-2.3,0); P = 0.049] as well as colonic [-12.2 h (-22.8, -1.6); P = 0.026] transit was observed and overall symptom severity [-0.5 (-1.0, -0.05); P = 0.032] also improved. This probiotic resulted in improvements in objectively measured abdominal girth and gastrointestinal transit, as well as reduced symptomatology. These data support the concept that accelerating transit is a useful strategy for treating distension.