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Irritable bowel syndrome and spasmolytics 21
Table VII. Rectal motility parameters in IBS patients
Motility Parameters
Motor Activity
(as a % of total time)
(normal: 75.6±4.7)
Motor Quiescence
(as a % of total time)
(normal: 24.46±4.7)
Intraluminal pressure
(cm H 2
O)
(normal: 25-30)
Motility index
(normal: 8,5)
Type of IBS Before After Before After Before After Before After
IBS with predominant constipation (n= 36) 75.3±6.2 75.4±8.2 24.7±4.3 26.4±4.8 58.4±0.57 47.3±5.6 5.7±3.1 5.9±2.8
IBS with predominant diarrhea (n= 21) 70.5±6.8 70.2±4.3 24.4±5.8 24.5±4.3 56.4±0.44 48.4±5.9 5.9±2.2 6.8±2.2
IBS with predominant pain and bloating (n= 39) 75.4±5.2 72.6±2.3 26.8±4.4 22.±4.0 52.8±0.55 48.6±4.6 5.2±2.4 5.8±2.6
Table VIII. Sigmoid motility parameters in IBS patients
Motility parameters Time of activity (%)
normal: (85.8±2.2)
Time of rest (%)
(normal: 14.2±2.2)
Intraluminal pressure
(cm H 2
O)
(normal: 30-40)
Activity index
normal: 12,5)
Type of IBS Before After Before After Before After Before After
IBS with predominant constipation (n= 36) 67.3±4.2 69.6±5.2 35.2±4.2 32.4±4.4 47.4±4.8 42.2±6.2 7.2±1.6 7.5±2.2
IBS with predominant diarrhea (n= 21) 65.5±6.8 68.4±4.2 33.4±6.6 30.2±4.2 45.4±4.6 40.3±5.2 7.5±2.2 7.4±1.8
IBS with predominant pain and bloating (n= 39) 64.4±4.6 68.3±4.2 36.6±6.4 32.3±6.8 48.2±4.6 40.8±5.6 7.5±1.8 7.4±2.8
Visceral hypersensitivity testing, in contrast, proved more
useful; increases in the threshold for pain coinciding with a
decrease in the patients’ experience of pain as a symptom.
Furthermore, it is worth noting that the lower the level
of the pain threshold at baseline, the more pronounced the
effect, which might explain the low effectiveness of the
various preparations among IBS patients with predominant
constipation. Indeed, the pathogenesis of VHS in different
types of IBS may vary to some extent as may the impact of
various pharmacological agents.
Values for visceral sensitivity are considerably influenced
by the method employed. It appears that not only the
material employed in the manufacture of the balloon, but
also the technique of inflation can significantly influence
the study outcome. Slow constant inflation results in
accommodation of the rectum, while stepwise inflation does
not and hypersensitivity has been observed far more often in
studies employing step-wise inflation methods. Accordingly,
the threshold for pain sensitivity with the more traditional
method of slow continuous balloon inflation was significantly
lower than with the use of the tracked step technique [21,
22]. Indeed, Lembo et al could not differentiate between
IBS subjects and controls when using the constant inflation
technique [7]. Apart from methodological issues, it is also
evident that variations in perception by individual patients,
prior conditioning [23] and psychological factors will also
influence the outcome of such tests and present considerable
challenges in developing the ideal test for VHS as well
as in understanding the pathogenesis of pain in IBS [12].
Pending the development of the ideal technique, balloon
inflation employing the step-wise technique remains the
most accessible method for assessing VHS in clinical
practice. However, it is noteworthy that the threshold for
discomfort/sensation documented in this study is remarkably
similar to that of Bouin et al, who reported, in their large
series of IBS and control subjects that a cut off threshold of
40 mmHg was highly sensitive (90.7%) and specific (71.8%)
in differentiating IBS patients from healthy controls [6].
We acknowledge the limitations of the study. It was
not formally randomized; however, the demographics of
the various groups illustrate that each was representative
of the overall population and of IBS in the community.
Furthermore, the investigators were blinded to the treatments
and as results of objective tests from the bulk of the recorded
data, this should have minimized the effects of a failure to
randomize. It is also possible that drug effects could have
unblinded the patients; we feel that this is unlikely as the one
drug that had an effect on symptoms, buscopan, is poorly
bio-available when taken orally with associated plasma
levels being below levels of detection [24].
In conclusion, in this study, while we observed the
presence of visceral hypersensitivity in all IBS patients
studied, the lowest threshold for pain sensitivity was
noted among those with predominant diarrhea. Among the
therapeutic agents studied, the most pronounced effect on the
pain sensitivity threshold was reached with buscopan when
given orally, and had its greatest impact among those with
predominant diarrhea. In contrast, none of the therapies had
a major effect on any of the parameters of colorectal motility
studied. We propose, therefore, that visceral hypersensitivity
and not motor dysfunction may be a more appropriate
target for assessing the impact of proposed antispasmodics/
spasmolytics in IBS.
Conflicts of interest
Nothing to declare.
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