Review for 10.1186/s12876-024-03309-5 (2024)

Title: Influence of the Examination Position and Distension Medium on the Rectal Sensory Test
in Patients with Functional Constipation
Version: 1 Date: 08 Apr 2024
Reviewer's report:
Rectal hyposensitivity is an important pathophysiology of intractable constipation and is
commonly measured by balloon-based rectal sensory test (RST). This study provides important
data for standardizing the method of RST. I should be grateful if you could answer my comments
shown below.
Major points
1. Limitations of the study are not stated at all in the Discussion.
In line 112, you state that there was no correlation between BMI, age and rectal sensory function.
With only 39 cases, it would be impossible to analyze the correlation between age and rectal
sensory threshold. Thus, the small number of cases is one of the limitations of this study.
The international anorectal physiology working group (IAPWG) recommends that when
performing balloon expulsion test (BET), the balloon should be introduced with the subject lying
in the left lateral position, followed by transferring the subject to the sitting position for the
evacuation. On the contrary, the IAPWG recommends that the rectal sensory test (RST) should
be performed in the left lateral position with the hips and knees flexed. This difference in body
position during the BET and RST can be assumed to be due to the fact that the threshold value
tends to change with balloon position in the RST. You state in line 81: distance between the
bottom of the balloon and the anal margin: 5 cm. Nevertheless, one of the limitations of this
study is that the balloon position may change in the sitting or squatting position.
2. This paper does not fully explain the details of the RST methodology.
When RST was performed in a sitting or squatting position, please explain in the Method whether
the balloon catheter was inserted into the rectum in the left lateral position or in a sitting or
squatting position.
You state in line 81: distance between the bottom of the balloon and the anal margin: 5 cm. The
average length of the subject's anal canal was 2.15 cm, so there was about 3 cm from the upper
edge of the anal canal to the lower edge of the balloon. Therefore, the balloon might fall down to
the anal canal when the subject was in a sitting or squatting position. Therefore, please explain
in the Method how the balloon was fixed so that its position does not change.
This is because if the balloon slips down without being secured, it will come into contact
with the mucosa of the anal canal, which is more sensitive than the rectum. According to the
following reference, the middle and upper part of the anal canal seems to have a lower sensory
threshold than the rectum. References: Abe T, et al. Effects of age and sex on the anorectal
sensory threshold to electrical stimulation: a single-center observational study. J Anus Rectum
Colon 2023 Apr 25;7(2):74-81. Therefore, fixation of the balloon position is the most important
requirement in this study.
In addition, you discuss anorectal angle in line 216; therefore, the position of the upper body
in the sitting position should also be explained in the Method, since the anterior tilt angle of
the upper body in the seated position affects the anorectal angle. If possible, photographs of the
patient in the left lateral, sitting, and squatting positions in this study would be helpful for the
reader's understanding.
3. The Introduction is only 17 lines long, but there are 93 lines of the Discussion.
Most of this redundant discussion consists of what should be written in the Introduction and a
repetition of the Results.
4. The conclusions of this paper are difficult to understand.
You state in line 228 that it is necessary to use the commonly used defecation posture of patients
for rectal sensation testing rather than collecting data from the left lateral position alone. Does
this mean that measurements need to be taken in two positions, the usual defecation position
and the left lateral position? Which do you think is the most superior posture? The IAPWG
recommends the use of air as distension medium, but based on the results of this study, would
you recommend the use of air or water? Please indicate the recommended posture and medium
in RST based on the results of this study.
Minor points
1. Lines 27-29 are not clear. It is not clear whether frequency of bowel movements is the
number of bowel movements itself or the value of frequency of bowel movements in the CSS.
According to my calculations from the raw Excel data, the latter seems to be the correct.
In contrast, the painful evacuation score has a “score”, indicating that it is the CSS score.
However, the correct term is painful evacuation “effort”. Based on the above, the following text
is recommended. Among the items of the Constipation Scoring System, the score of frequency
of bowel movements showed a negative correlation with the first constant sensation volume
(r = -0.323, P = 0.045). Conversely, the score of painful evacuation effort showed a positive
correlation with the desire to defecate volume (r = 0.343, P = 0.033).
2. The SOP in line 38 is not a well-known abbreviation that can be abbreviated on first
appearance.
3. Similar to the above, lines 112-115 should be modified as follows. Among the items of the
CSS, the score of frequency of bowel movements showed a negative correlation with FCSV (r
= -0.323, P = 0.045). This means that patients who have fewer bowel movements have lower
FCSV (Is this correct?). In contrast, the score of painful evacuation effort showed a positive
correlation with DDV (r = 0.343, P = 0.033) (Fig. 1).
4. Since you are comparing sensory thresholds with each item of CSS, you should indicate not
only the total score of CSS in Table 1, but also the mean value of all 8 items. In this way,
the readers will understand that the included patients were mainly constipated patients with
defecation difficulty rather than those with decreased frequency of bowel movement.