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Rectoanal pressures and rectal sensitivity studies in chronic childhood constipation
GASTROENTEROLOGY
77:330-336,1979
Rectoanal Pressures and Rectal Sensitivity Studies in Chronic Childhood Constipation PATRICK MICHEL
MEUNIER, JEAN MARIE JAUBERT DE BEAUJEU
The Manometric Investigations Debrousse, Lyon, France
Laboratory
and the Department
Rectoanal pressures and rectal sensitivity studies were performed in 32 control children and 144 chronically constipated children. The rectoanal inhibitory reflex threshold, the maximal anal resting closure pressure, and the conscious rectal sensitivity threshold were studied in these children. The rectoanal inhibitory reflex threshold was increased in 6.2% of the constipated patients. Anal hypertony (increased maximal anal resting pressure) was found in 46% of the constipated children. Decreased rectal sensitivity (increased conscious sensitivity threshold) was found in 68% of the constipated children. The three parameters were found to be normal in only 13% of the constipated subjects. Thus, it appears that children with chronic constipation who do not have Hirschsprung’s disease do have abnormalities at manometry in most cases.
Chronic constipation is a common condition in childhood, which is often accompanied or followed by acquired megarectum and soiling.lm3 The etiology of this symptom may be well-defined (for instance, absent ganglionic cells, endocrine disorder, anorectal lesion, etc.), but chronic constipation in children is very often of unknown origin. The rich terminology that has evolved to define “primary” constipation in children’,” reveals how much this condition is poorly understood. Nevertheless, by using sigmoid or rectoanal pressure studies, attempts have been made to understand better the pathophysiology of chronic constipation in children, and such motility studies have proved to be helpful in this field.‘,“-” Received April 24,1978. Accepted March 20,1979. Address requests for reprints to: Dr. P. Meunier, d’Exploration Fonctionnelle Manometrique Urinaire HBpital Debrousse, 69322 Lyon Cedex 1, France.
MARECHAL,
Laboratoire et Digestive,
This work was supported in parts by grants from U.E.R. MBditale Lyon Nord and U.E.R. de Biologie Humaine. 0 1979 by the American Gastroenterological Association 00X%5085/79/080330-07$02.00
and
of Pediatric Surgery, HBpital
The aims of this study were to investigate further chronic constipation in children by manometric method and to demonstrate, if possible, rectoanal abnormalities in such patients. Material
and Methods
Subjects were performed on 32. A total of 176 investigations control subjects and 144 chronically constipated children. The control subjects included 19 girls and 13 boys aged from 1 to 15 yr (mean age = 8 f 3.6 yr). The constipated subjects included 50 girls and 94 boys aged from 1 to 15 yr (mean age = 6 f 3.7 yr). Informed consent was obtained from the subjects or their parents. The 34 control subjects were selected among children undergoing a urodynamic investigation for nonneurogenic micturition disorders (refluxing ureters, urethral valves, meatal stenosis, etc.). By means of an examination which included the recordings of bladder and rectal pressure, of anal electromyography, and of urine flow, the normality of the sacral innervation was demonstrated in all these control subjects. Because enuresis is so commonly associated with anorectal disorders, enuretic children were systematically excluded from our control group. For the purpose of this study, normality in bowel habits was arbitrarily defined as the passage of at least a normal consistency stool every z days. In the control group, all children that were selected had such bowel habits and were devoid of any gastrointestinal disease. The 144 constipated children were referred for manometric studies after unsuccessful treatments using multiple and diverse laxatives. The clinical data concerning the children were collected by questioning the parents and/or the children. To this aim, a retrospective standardized questionnaire (including stool frequency and consistency, duration of constipation, and the use of drugs) was used. The common clinical history of these constipated patients described a prolonged period of infrequent and abnormal stools, sometimes beginning at the time of birth, but always lasting more than 8 mo. Without treatment, all these patients passed less than three stools per week. However, in most cases, stool frequency was
CHRONIC
August 1979
mainly requlated by the use of laxatives and/or of enemas. Likewise, the consistency of stool varied (from very hard to liquid) with the nature of the treatment employed. In these patients, constipation secondary to another cause was ruled out; constipation induced by drugs (diuretics, anticonvulsants, hypotensives, and psychotherapeutic agents), neurogenic constipation (Hirschsprung’s disease, paraplegia, myelomeningocele, diabetic neuropathy), constipation secondary to anal lesion (fistula, a.bcess, hemorrhoids), and constipation secondary to endocrine disorder (hypothyroidism, hypercalcemia, hypopituitarism) were excluded from this study. Mental retardatilon (demonstrated by clinical evidence of psychomotor retardation) was, likewise, a cause of exclusion. In 59 patients (41% of the total number), encopresis was associated with constipation.
Methods In both control and constipated patients, three parameters were sucessively studied during a single test period. First, the rectoanal inhibitory reflex, i.e., internal sphincter relaxation in response to a transient rectal distension (Figure l),was studied. To this aim, pressures in the anal canal and the rectum were measured by means of a tandem system of two perfused side-opening catheters (internal diameter = 2.6 mm with one Z-3-mm long side opening). In children over 3 yr of age, the openings of the catheters were approximately placed Z-2.5 cm (in the anal canal) and 5 cm (in the rectum) from the anal margin. In younger patients, the approximate distance of the openings from the anal margin varied from 1 to 2 cm (for the anal canal) and from 3 to 5 cm (for the rectum). By means of a constant infusion pump (type 87012 Braun, Melsungen, Federal Republic of Germany), the catheters were perfused with 0.9% saline (flow rate = 0.24 ml - min-I). Since the major cause of inaccuracy during perfusion manometry is the compliance of the recording system,‘~“’ great care was taken to minimize such compliance as much as possible. All the tubing was minimally elastic, pressure
: cm H20
I
k
CONSTIPATION
331
and the perfusion syringes were lubricated with sterile silicone (silkospray, Riisch, Rommelhausen, Federal Republic of Germany). Each catheter was connected to a pressure transducer (type 1280 C, Hewlett-Packard, Medical Electronics Div., Waltham, Mass.) whose output was amplified and recorded on a thermal tip galvanometer recorder (8805 B amplifier and 7758 A recorder, HewlettPackard). In addition, a tube on which was mounted a latex balloon was glued together with the perfused catheters. The balloon, a simple fingercot having little resistance to distension, lay in the rectum 7-15 cm from the anal margin. The tube with the balloon and the two perfused catheters constituted a probe which was introduced without the help of a rectoscope; this probe was unable to overpass the rectosigmoid junction. The indicated distance of the rectal balloon from the anal margin was, therefore, theoric (measured for a rectilinear probe, without taking account of the actual distance of the balloon from the anal margin). In all instances, the distension was rectal. Distension of the rectal balloon by air (total distension time = 0.5-5 set) induced the rectoanal inhibitory reflex. The rectoanal inhibitory reflex threshold (RAIRT), i.e., the distension volume at which a minimal relaxation of 10 cm H,O occurred (Figure l), was determined by taking the average of five trials for each subject. The percentage of variation in the reflex threshold from one trial to another was found to be less than 20%. Next, in order to determine the tone of the anal canal at rest, a rectoanal pressure profile was performed. This was accomplished by the manual pull through (approximate speed = 20 cm . min-‘) of a perfused catheter. The catheter that was employed had an internal diameter of 2.6 mm and a 2-3-mm long side-opening. It was perfused by the same pump described above at a constant flow rate of 4.4 ml - min-‘. The profile catheter was also connected to the same pressure chain and recorder described above. This measurement allowed the determination of the maximal anal resting closure pressure (MARCP), which was calculated by subtracting the rectal pressure from the maximal anal pressure (Figure 2). Each individual value for the MARCP was determined by taking the average value of at least three measurements. For the MARCP, the percentage of variation between the different trials performed varied from 0 to 7%. Pcm
1--
2lle
ot
CHILDHOOD
: Ill‘”
I
I
10 set
I
130
distention
t25
volume
t20
: ml
t15
tro
t5
Figure 1. Rectoanal inhibitory reflex and its threshold (normal subject). Distension of the rectal wall (arrows) induce an anal canal relaxation, the amplitude of which is related to the distension volume. The reflex threshold (i.e., a minimal relaxation of 10 cm H,O), in this series of distensions, is observed for a distension volume of 10 ml. R indicates the rectal pressure recording, and A indicates the anal canal pressure recording.
Figure 2. Typical rectoanal pressure profile (normal subject). This recording makes it possible to calculate the maximal anal closure resting pressure (MARCP) subtracting the rectal pressure (RP) from the maximal anal resting pressure (MARP). In this case, MARCP = 60 cm H,O.
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MEUNIER ET AL.
GASTROENTEROLOGY Vol. 77, No. 2
Finally, except in 2 normal children and 28 constipated children, the conscious rectal sensitivity threshold (CRST) was studied by distending the rectal wall by means of a latex balloon inflated with air. The CRST, i.e., the distension volume for which an initial transient sensation occurred was determined (by questioning the child) by taking the average of five trials. For the CRST, the percentage of variation from one trial to another was found to be less than 25%. Determination of the CRST, which necessitates the cooperation of the child being tested, was neither performed on children under 3 yr of age (2 control subjects and 26 constipated patients) nor on 2 older patients (6 and 13 yr) who did not cooperate. The entire manometric examination was performed without the aid of sedation, the children resting in the supine position. Impacted feces, when present, were evacuated a few days before the examination. An enema (Microlax, or Normacol) was often required 1 or 2 hr before the procedure. Previous studies proved that although an enema considerably alters rectoanal manometric parameters, the effect is always of very short duration. Thirty minutes after the evacuation of the enema, the manometric rectoanal parameters were not significantly different from those recorded before the enema. The results of this study are presented on Table 1. Each child (control or constipated) was examined one time. During this examination, the individual value for each of the three parameters (MARCP, RAIRT, CRST) was determined by taking the mean value of the different trials performed. Results (in centimeters H,O for the MARCP and in milliliters for both the RAIRT and the CRST) are expressed as the mean f 1 SD. Normality for each of the three parameters (MARCP, RAIRT and CRST) was considered to be the mean f 2 SD found for the control subjects.
Results Rectal pressure, which was continuously recorded during the RAIRT and the CRST determinations, was not considered to afford useful data in this study, because at rest as well as during transient distensions no significant difference between the control subjects and the constipated patients was found for this parameter. Table
1.
Value of the Rectoanal
Parameters
Obtained
Table 2.
A W A A =
Parame-
Age (Yr)
MARCP (cm H,OJ
RAIRT W
CRST (ml) _____-
Boys
7 f 3.6
73 f 10.1
19 + 6.2
20 f 8.1
(n = 13) Girls (n = 19)
9 * 3.5
69 * 14.7
16 f 7.6
16 k 7.1
The one-way analysis of variance performed on these means provided a F-value of 0.49 for the MARCP, 0.96 for the RAIRT and 1.11 for the CRST. All these values are statistically insignificant.
Control Subjects In order to test the homogeneity of the results in the control population, a statistical analysis was performed using the one-way analysis of variance upon the mean values for the MARCP, the RAIRT, and the CRST found in control boys and girls and in different age classes. In control subjects, the mean values for the MARCP, the RAIRT, and the CRST were not significantly different in boys and girls (Table 2). According to their age, the control subjects were segregated into four groups (Table 3). The mean MARCP, RAIRT, and CRST values calculated for these four age groups were not significantly different (Table 3). Since the means of the MARCP, the RAIRT, and the CRST were neither significantly different in control boys and girls nor in different age groups of controls, results for these subjects were analyzed as a whole. In control subjects, the mean RAIRT was found to be 17 + 7.2 ml (range of 5-30 ml). Thus normality for the RAIRT (mean + 2 SD) was considered as ranging from 3 to 31 ml. Normal individual values for the RAIRT are presented in Figure 3. In control subjects, the MARCP values ranged from 45 to 95 cm H,O, with a mean of 71 + 13.1 cm H,O. Thus, normality for the MARCP (mean -I 2 SD) was considered as ranging from 45 to 97 cm H,O. Normal individual values for the MARCP are presented in Figure 4.
Before and After the Evacuation Before
Control 1 Control 2 Patient 1 Patient 2 Patient 3
Mean Values f SD for the Rectoanal ters in Control Boys and Control Girls
of an Enema
enema
30 Min after
enema
Age (yr)
MARCP (cm H,O)
RAIRT
CRST
MARCP
RAIRT
CRST
Sex
(m!,
(mI1
(cm H&Y
(ml)
(m!,
F M M M F
15 13 15 12 14
85 50 120 60 150
30 30 20 30 20
65 50 130 65 155
30 30 20 30 20
25 10 20 260 10
Measurements performed with the enema in situ are not shown on this table, rectoanal inhibitory reflex and the rectal sensibility, and since determination encc between the different trials). A is for Microlax, and ??for Normacol.
20 10 20 240 20
since, in these conditions, it was not possible to study the of the MARCP were nonreproducible (over 48% of differ-
August
1979
Table
3.
CHRONIC
Mean Values + SD for the Rectoanal parameters Found in Four Different Age Croups in the Control Children RAIRT
CRST
(Y4
MARCP (cm H,O)
(ml)
(ml1
2 k 0.9
65 f 6.1
21 f 5.4
Age
Group
1
subjects) Group
5 + 0.7
2
71 + 12.5
15 f: 6.8
17 f 7.1
(n = 9)
Group
3
6 + 1.3
71 f 12.6
200 0 m160_
I
E 160 u .,
15 -t 5 (only 2
(n = 4)
15 f 4.5
19 + 7.5
w 140_ !i
120 -
ii
-
w loo-
.:.
(n = 11) Group
CHILDHOOD
4
13 + 1.3
72 + 14.9
17 t 7.1
13 + 4.3
5
Patients
Since the means of all parameters (MARCP, RAIRT, and CRST) in control subjects were found to be neither significantly different in boys and girls nor in different age groups, the constipated patients were studied as a whole without consideration of sex and age. Mean values found for the constipated patients were compared with those found for the control subjects using the Student’s t-test. The rectoanal inhibitory reflex was present in all constipated children. Individual values of the RAIRT are presented and compared with those of
1 1
. . . . . . . . . . . . . . . . . . . . . .
I....
60 -
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
:
The one-way analysis of variance performed on these means provided a F-value of 0.31 for the MARCP, 1.23 for the RAIRT. and 1.36 for the CRST. All these values are statistically insignificant.
Constipated
1
. . . . . . . . . . . . .
..... ..::..
The mean CRST for the only 30 control children (11 boys and 19 girls) in which a sensitivity study was performed was found to be 17 f 7.1 ml (range of 5-30 ml:). Thus, normality for the CRST (mean + 2 SD) was’ considered as ranging from 3 to 31 ml. Normal individual values for the CRST are presented in Figure 5.
.. . ... ..... .. . . .. ....... ..... . . . . . .. .. .. . . . . . ....... . ....... ... ... ..........
I..
60,
(n = 8)
333
CONSTIPATION
.:. .
4Ob
control
Figure
.
.
i
constipated
4. Individual values (mean of at least three ments) of the MARCP in control subjects stipated patients.
measureand con-
the control subjects in Figure 3. For the RAIRT, values ranged from 5 to 60 ml with a mean of 20 f 10.8 ml which was not significantly different from those found for the controls (t = 1.49). A large majority of patients (94% of the total number) exhibited a normal RAIRT, with a range of 5-30 ml and a mean of 18 + 7.2 ml. No significant difference (t = 0.70) was found between this mean and that of the controls. However, in 9 cases (6.2% of the total number), the RAIRT values were abnormally high (over 31 ml). In these cases, the mean RAIRT was found to be 51 + 7.8 ml (range of 40-60 ml). The difference between this mean and that of the control subjects, according to Student’s t-test, was very significant (t = 12.32; P < 0.001). Individual MARCP values are presented and compared with those of the control subjects in Figure 4. For the MARCP, values ranged from 45 to 200 cm
...
j:
20
.
.
.
.
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L.....
.
. . . . . . . .
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,o
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I..... I
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0
control
constipated
.
Figure
3. Individual values (mean of five measurements) of the RAIRT in control subjects and constipated patients.
334
MEIJNIER
ET AL.
H,O with a mean of 99 + 39.4 cm H,O, which was significantly different from those found for the controls (t = 3.97; P < 0.001). However, according to the normal range defined with the controls, a total of 78 constipated patients (54% of the total number) were found to have normal MARCP values. In these normotonic patients, the mean MARCP was found to be 70 + 13.9 cm H,O. The comparison of this mean with that of the control subjects showed no significant difference (t = 0.35). Abnormally high MARCP values (over 97 cm H,O) were found in 66 patients (46% of the total number). In this group of hypertonic patients, the MARCP ranged from 100 to 200 cm HzO, and the mean was found to be 133 -+30.9cm H,O. The difference between the mean MARCP values of the patients and controls according to Student’s ttest, was very significant (t = 10.98; P < 0.001). Anal hypotonia (MARCP under 45 cm H,O) was never observed in the constipated patients. The CRST was determined in only 116 constipated patients (aged 3-15 yr). Individual values, ranging from 5 to 350 ml, are presented and compared with those of the controls in Figure 5. The mean CRST in the constipated patients was found to be 81 + 76.6ml and was significantly different from those of the controls (t = 4.56; P < 0.001). According to the normal range defined with the controls, a normal CRST was found in 37 patients (i.e., in 32% of the patients in which rectal sensitivity was studied). In these patients, CRST values ranged from 5 to 30 ml, with a mean of 19 + 8.4 ml. The difference between this mean and that of the control subjects was not significant (t = 1.04). An increased CRST (i.e., decreased sensitivity) was observed in 79 other constipated patients (68% of the total number of children in which rectal sensitivity was studied). In these cases, CRST values ranged from 40 to 350 ml, with a mean of 111 + 77.0 ml. This mean was very significantly different from that of the controls (Student’s t-test: t = 6.66; P < 0.001). As previously shown,7 a close correlation was found between the presence of encopresis and the increase in the CRST. Encopresis was observed in 24% of the children with a normal CRST, in 39% of the children with a CRST between 40 and 90 ml, and in all children with a CRST of over 100 ml. On the other hand, encopresis was found in 51% of the patients -with a normal MARCP (normotonic patients) and in 29% of the patients with an increased MARCP (hypertonic patients). The chi-square test proved that the incidence of encopresis was significantly greater in normotonic patients than in hypertonic patients (2 = 7.48;P < 0.01). A comparable percentage of encopresis was found in patients with a normal RAIRT (41%)and patients with an abnormal RAIRT (44%). The chi-square proved any signif-
GASTROENTEROLOGY
Vol.
77,
No. 2
..
320
8 260
-
260
_
240
-
220
-
.
... ..
200
-
.. ..
160
-
.....
i
160
-
: $
140
-
120
-
100
-
60
-
60
-
40
-
20
-
*
.. . ..
. . . . ..... ..I..
.
.
.
.
.
::.
I
.
.
.
.
O-
control
Figure
5. Individual values (mean CRST in control subjects
. . .. .. .. . ............... ..... .. .. ..... . .. ... ... .. .. ... .. . .. ... .... .. ............ ... ... . .... .. conatipeted
of five measurements) of the and constipated patients.
icant difference between the incidence of encopresis in patients with a normal RAIRT and patients with an abnormal RAIRT ($ = 0.24). Comparable percentages of patients with an increased CRST were found in normotonic and hypertonic patients (72 and 63%, respectively). The chisquare test was unable to demonstrate any significant difference (2 = 0.51)between the distribution of increased CRST in normotonic and hypertonic patients. Likewise, similar proportion of patients with an abnormal RAIRT were found in children with an increased CRST (6.3%) and children with a normal CRST (11%). As shown by the chi-square test, there was no difference between the distribution of abnormal RAIRT in children with a normal CRST and children with an abnormal CRST (d = 0.72). In both normotonic and hypertonic patients, 6% of the children exhibited an abnormal RAIRT. Therefore, there was no difference between the dis-
August
1979
tribution of abnormal RAIRT in normotonic and hypertonic patients (2 = 0.01). Finally, it is interesting to note that in only 15 constipated children (13% of the total number of patients in which the three parameters were studied), all three manometric parameters of this study (RAIRT, MARCP, and CRST) were normal. In these patients (aged 4-12 yr; mean age = 7.3 yr; 10 boys and 5 girls), 5 were encopretics.
Discussion From the above results, it appears that patients with chronic childhood constipation who do not have Hirschsprung’s disease do have abnormalities at m.anometry in most cases. The relationships between the rectoanal parameters herein described and constipation should be considered. Although demonstration of the rectoanal inhibitory reflex is not accurate in the neonatal period, the accuracy increases with age”; after 1 yr of age, the finding of anal relaxation after rectal distension rules out the possibility of Hirschsprung’s disease. Most authors agree that the study of the rectoanal (and sufficient) in inhibitory reflex is required chronic constipation to demonstrate the presence of ganglionic cells in the rectal wall.“-” Furthermore, it has been shown17 that only rectosphincteric manometry achieved 100% diagnosis accuracy between constipated patients with and without colonic aganglionosis. This is the reason why the study of the rectoanal inhibitory reflex is the more useful examination in chronic constipation. However, the significance of an increased RAIRT, as it was observed in 6.2% of our constipated patients, is unclear. An increased RAIRT might be due simply to the balloon not stretching the rectal walls, or it is possible that this abnormal reflex threshold was an artefact due to an incompletely evacuated ampula, which prevented correct distension of the rectum. In about 50% of the constipated patients, an increased MARCP was found. Such hypertony might be related to outlet obstruction which has been recently defined by Martelli et al.” Anal hypertonia is compatible with sphincteric relaxation, since the rectoanal inhibitory reflex was present in all hypertonic patients. It is highly probable, however, that an hypertonic sphincter plays a part in constipation by creating difficulties in feces elimination, leading to fecal retention. The improvement of some constipated children”,‘” or adults” after anal sphincterotomy becomes clear from the results of our study, since anal hypertonia was so frequently demonstrated in constipated patients. Thus, it is logical to
CHRONIC
CHILDHOOD
CONSTIPATION
335
assume that the indication for anal sphincterotomy remain on the finding of an increased MARCP. The basis of the increase of the conscious rectal sensitivity threshold, observed in a majority of constipated patients, is worthy of discussion. First, the hypothesis that the distending balloon did not stretch the rectal wall could be proposed, since chronic constipation in children is commonly associated with an enlarged rectum.‘-’ Therefore, in our study, stools were evacuated before the examination, and such an hypothesis supposes that the rectum behaves like a plastic reservoir keeping its shape and properties even when feces are removed. Since the rectum has viscoelastic properties,” this hypothesis seems improbable, at least for the large distending volumes. The increase of the CRST probably remains abnormal because of the rectal mechanoreceptors. When fecal retention occurs, the rectal wall is distended. This distension induces an increased response threshold for the rectal mechanoreceptors. In the normal individual, the rectoanal inhibitory reflex is controlled by the cerebral cortex, because this reflex has a threshold close to that of conscious rectal sensitivity, while, in children with an increased CRST, sphincteric relaxation occurs before rectal sensation arises, a situation clearly conducive to soiling.” This is the reason for which a close correlation was found between the incidence of encopresis and the increase in the sensitivity threshold. A decrease in conscious rectal sensitivity has previously been observed in children with megarectum.‘~7~2’ In this study, abnormal conscious rectal sensitivity was demonstrated in most of the chronically constipated children; an increased CRST was found in 68% of the patients. Although subjective, and sometimes difficult, specially in children, rectal sensitivity studies, introduced by Goligher and Hughes,‘” are very useful in the management of such patients. Finally, it should be noted that we were unable to demonstrate differences in rectal pressure between the control group and the constipated patients. This finding appears rather surprising since most of the patients exhibited rectoanal abnormalities. The explanation of this fact might remain in the methodology chosen (rectal pressure measurements at rest and during transient rectal distensions); a study of the viscoelastic properties of the rectal wall, according to Arhan et al.,z0.23would probably offer a better assessment of rectal abnormalities.
References 1. Callaghan RP, Nixon HH: Megarectum: vations. Arch Dis Child 39:153-157,1964 2. Oppe TH: Megacolon and megarectum
physiological in older
children.
ohserProc
336
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R Sot Med 66:863-865,1967 3. Bentley JFR: Constipation in infants and children. Gut 12:65961971 4. Ehrenpreis T: Megacolon and megarectum in older children and young adults. Classification and terminology. Proc R Sot Med 6679%601,1967 5. Nixon HH: Megarectum in the older child. Proc R Sot Med 66:861-863,1967 6. Davidson M, Bauer CH: Studies of distal colonic motility in children. IV. Achalasia of the distal rectal segment despite presence of ganglia in the myenteric plexuses of this area. Pediatrics 21:746-766, 1958 7. Meunier P, Mollard P, Marechal JM: Physiopathology of megarectum: the association of megarectum with encopresis. Gut 17:X4-227.1976 8. Scobie WG. Kirwan WO, Smith AN: Colonic motility in children with constipation. Dis Co1 Rect 20:672-676,1977 9. Zabinsky MP, Spiro HM, Biancani I? Influence of perfusion rate and compliance on esophageal manometry. J Appl Physiol38:177-1861975 10. Dodds WJ, Stef JJ, Hogan WJ: Factors determining pressure measurement accuracy by intraluminal esophageal manometry. Gastroenterology 70:117-123.1976 11. Meunier P, Mar&ha1 JM, Mollard P: Accuracy of the manometric diagnosis of Hirschsprung’s disease. J Pediatr Surg 13:411-415,1978 12. Lawson JON, Nixon HH: Anal canal pressures in the diagnosis of Hirschsprung’s disease. J Pediatr Surg 2544-552.1967
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13. Schnaufer L, Talbert JL, Hailer JA. et al: Differential sphincteric studies in the diagnosis of anorectal disorders of childhood. J Pediatr Surg 2:538-543,1967 14. Arhan P, Faverdin C, Thouvenot J: Anorectal motility in sick children. Stand J Gastroenterol7:369-314.1972 15. Meunier P, Mollard P: Control of the internal anal sphincter study with human subjects). Pfliigers Arch (Manometric 370:233-239,1977 16. Holschneider AM: Manometrie des Anorektums. Z Gastroenterol15:215-221,1977 17. Tobon F, Schuster MM: Megacolon: special diagnostic and therapeutic features. Johns Hopkins Med J 135:91-165,1974 18. Martelli H, Devroede G, Arhan P, et al: Mechanisms of idiopathic constipation: outlet obstruction. Gastroenterology 75:623-631,1978 19. Schandling B, Desjardins JG: Anal myomectomy for constipation. J Pediatr Surg 4:115-118,1969 20. Arhan P, Faverdin C, Persoz B, et al: Relationship between viscoelastic properties of the rectum and anal pressure in man. J Appl Physiol41:677-682.1976 21. Porter NH: Megacolon: a physiological study. Proc R Sot Med 54:X343-1647,196l 22. Goligher JC, Hughes ESR: Sensibility of the rectum and colon. Its role in the mechanism of anal continence. Lancet 1:543548,195l 23. Arhan P, Devroede G. Danis K, et al: Viscoelastic properties of the rectal wall in Hirschsprung’s disease. J Clin Invest 62:82-87.1978
77:330-336,1979
Rectoanal Pressures and Rectal Sensitivity Studies in Chronic Childhood Constipation PATRICK MICHEL
MEUNIER, JEAN MARIE JAUBERT DE BEAUJEU
The Manometric Investigations Debrousse, Lyon, France
Laboratory
and the Department
Rectoanal pressures and rectal sensitivity studies were performed in 32 control children and 144 chronically constipated children. The rectoanal inhibitory reflex threshold, the maximal anal resting closure pressure, and the conscious rectal sensitivity threshold were studied in these children. The rectoanal inhibitory reflex threshold was increased in 6.2% of the constipated patients. Anal hypertony (increased maximal anal resting pressure) was found in 46% of the constipated children. Decreased rectal sensitivity (increased conscious sensitivity threshold) was found in 68% of the constipated children. The three parameters were found to be normal in only 13% of the constipated subjects. Thus, it appears that children with chronic constipation who do not have Hirschsprung’s disease do have abnormalities at manometry in most cases.
Chronic constipation is a common condition in childhood, which is often accompanied or followed by acquired megarectum and soiling.lm3 The etiology of this symptom may be well-defined (for instance, absent ganglionic cells, endocrine disorder, anorectal lesion, etc.), but chronic constipation in children is very often of unknown origin. The rich terminology that has evolved to define “primary” constipation in children’,” reveals how much this condition is poorly understood. Nevertheless, by using sigmoid or rectoanal pressure studies, attempts have been made to understand better the pathophysiology of chronic constipation in children, and such motility studies have proved to be helpful in this field.‘,“-” Received April 24,1978. Accepted March 20,1979. Address requests for reprints to: Dr. P. Meunier, d’Exploration Fonctionnelle Manometrique Urinaire HBpital Debrousse, 69322 Lyon Cedex 1, France.
MARECHAL,
Laboratoire et Digestive,
This work was supported in parts by grants from U.E.R. MBditale Lyon Nord and U.E.R. de Biologie Humaine. 0 1979 by the American Gastroenterological Association 00X%5085/79/080330-07$02.00
and
of Pediatric Surgery, HBpital
The aims of this study were to investigate further chronic constipation in children by manometric method and to demonstrate, if possible, rectoanal abnormalities in such patients. Material
and Methods
Subjects were performed on 32. A total of 176 investigations control subjects and 144 chronically constipated children. The control subjects included 19 girls and 13 boys aged from 1 to 15 yr (mean age = 8 f 3.6 yr). The constipated subjects included 50 girls and 94 boys aged from 1 to 15 yr (mean age = 6 f 3.7 yr). Informed consent was obtained from the subjects or their parents. The 34 control subjects were selected among children undergoing a urodynamic investigation for nonneurogenic micturition disorders (refluxing ureters, urethral valves, meatal stenosis, etc.). By means of an examination which included the recordings of bladder and rectal pressure, of anal electromyography, and of urine flow, the normality of the sacral innervation was demonstrated in all these control subjects. Because enuresis is so commonly associated with anorectal disorders, enuretic children were systematically excluded from our control group. For the purpose of this study, normality in bowel habits was arbitrarily defined as the passage of at least a normal consistency stool every z days. In the control group, all children that were selected had such bowel habits and were devoid of any gastrointestinal disease. The 144 constipated children were referred for manometric studies after unsuccessful treatments using multiple and diverse laxatives. The clinical data concerning the children were collected by questioning the parents and/or the children. To this aim, a retrospective standardized questionnaire (including stool frequency and consistency, duration of constipation, and the use of drugs) was used. The common clinical history of these constipated patients described a prolonged period of infrequent and abnormal stools, sometimes beginning at the time of birth, but always lasting more than 8 mo. Without treatment, all these patients passed less than three stools per week. However, in most cases, stool frequency was
CHRONIC
August 1979
mainly requlated by the use of laxatives and/or of enemas. Likewise, the consistency of stool varied (from very hard to liquid) with the nature of the treatment employed. In these patients, constipation secondary to another cause was ruled out; constipation induced by drugs (diuretics, anticonvulsants, hypotensives, and psychotherapeutic agents), neurogenic constipation (Hirschsprung’s disease, paraplegia, myelomeningocele, diabetic neuropathy), constipation secondary to anal lesion (fistula, a.bcess, hemorrhoids), and constipation secondary to endocrine disorder (hypothyroidism, hypercalcemia, hypopituitarism) were excluded from this study. Mental retardatilon (demonstrated by clinical evidence of psychomotor retardation) was, likewise, a cause of exclusion. In 59 patients (41% of the total number), encopresis was associated with constipation.
Methods In both control and constipated patients, three parameters were sucessively studied during a single test period. First, the rectoanal inhibitory reflex, i.e., internal sphincter relaxation in response to a transient rectal distension (Figure l),was studied. To this aim, pressures in the anal canal and the rectum were measured by means of a tandem system of two perfused side-opening catheters (internal diameter = 2.6 mm with one Z-3-mm long side opening). In children over 3 yr of age, the openings of the catheters were approximately placed Z-2.5 cm (in the anal canal) and 5 cm (in the rectum) from the anal margin. In younger patients, the approximate distance of the openings from the anal margin varied from 1 to 2 cm (for the anal canal) and from 3 to 5 cm (for the rectum). By means of a constant infusion pump (type 87012 Braun, Melsungen, Federal Republic of Germany), the catheters were perfused with 0.9% saline (flow rate = 0.24 ml - min-I). Since the major cause of inaccuracy during perfusion manometry is the compliance of the recording system,‘~“’ great care was taken to minimize such compliance as much as possible. All the tubing was minimally elastic, pressure
: cm H20
I
k
CONSTIPATION
331
and the perfusion syringes were lubricated with sterile silicone (silkospray, Riisch, Rommelhausen, Federal Republic of Germany). Each catheter was connected to a pressure transducer (type 1280 C, Hewlett-Packard, Medical Electronics Div., Waltham, Mass.) whose output was amplified and recorded on a thermal tip galvanometer recorder (8805 B amplifier and 7758 A recorder, HewlettPackard). In addition, a tube on which was mounted a latex balloon was glued together with the perfused catheters. The balloon, a simple fingercot having little resistance to distension, lay in the rectum 7-15 cm from the anal margin. The tube with the balloon and the two perfused catheters constituted a probe which was introduced without the help of a rectoscope; this probe was unable to overpass the rectosigmoid junction. The indicated distance of the rectal balloon from the anal margin was, therefore, theoric (measured for a rectilinear probe, without taking account of the actual distance of the balloon from the anal margin). In all instances, the distension was rectal. Distension of the rectal balloon by air (total distension time = 0.5-5 set) induced the rectoanal inhibitory reflex. The rectoanal inhibitory reflex threshold (RAIRT), i.e., the distension volume at which a minimal relaxation of 10 cm H,O occurred (Figure l), was determined by taking the average of five trials for each subject. The percentage of variation in the reflex threshold from one trial to another was found to be less than 20%. Next, in order to determine the tone of the anal canal at rest, a rectoanal pressure profile was performed. This was accomplished by the manual pull through (approximate speed = 20 cm . min-‘) of a perfused catheter. The catheter that was employed had an internal diameter of 2.6 mm and a 2-3-mm long side-opening. It was perfused by the same pump described above at a constant flow rate of 4.4 ml - min-‘. The profile catheter was also connected to the same pressure chain and recorder described above. This measurement allowed the determination of the maximal anal resting closure pressure (MARCP), which was calculated by subtracting the rectal pressure from the maximal anal pressure (Figure 2). Each individual value for the MARCP was determined by taking the average value of at least three measurements. For the MARCP, the percentage of variation between the different trials performed varied from 0 to 7%. Pcm
1--
2lle
ot
CHILDHOOD
: Ill‘”
I
I
10 set
I
130
distention
t25
volume
t20
: ml
t15
tro
t5
Figure 1. Rectoanal inhibitory reflex and its threshold (normal subject). Distension of the rectal wall (arrows) induce an anal canal relaxation, the amplitude of which is related to the distension volume. The reflex threshold (i.e., a minimal relaxation of 10 cm H,O), in this series of distensions, is observed for a distension volume of 10 ml. R indicates the rectal pressure recording, and A indicates the anal canal pressure recording.
Figure 2. Typical rectoanal pressure profile (normal subject). This recording makes it possible to calculate the maximal anal closure resting pressure (MARCP) subtracting the rectal pressure (RP) from the maximal anal resting pressure (MARP). In this case, MARCP = 60 cm H,O.
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GASTROENTEROLOGY Vol. 77, No. 2
Finally, except in 2 normal children and 28 constipated children, the conscious rectal sensitivity threshold (CRST) was studied by distending the rectal wall by means of a latex balloon inflated with air. The CRST, i.e., the distension volume for which an initial transient sensation occurred was determined (by questioning the child) by taking the average of five trials. For the CRST, the percentage of variation from one trial to another was found to be less than 25%. Determination of the CRST, which necessitates the cooperation of the child being tested, was neither performed on children under 3 yr of age (2 control subjects and 26 constipated patients) nor on 2 older patients (6 and 13 yr) who did not cooperate. The entire manometric examination was performed without the aid of sedation, the children resting in the supine position. Impacted feces, when present, were evacuated a few days before the examination. An enema (Microlax, or Normacol) was often required 1 or 2 hr before the procedure. Previous studies proved that although an enema considerably alters rectoanal manometric parameters, the effect is always of very short duration. Thirty minutes after the evacuation of the enema, the manometric rectoanal parameters were not significantly different from those recorded before the enema. The results of this study are presented on Table 1. Each child (control or constipated) was examined one time. During this examination, the individual value for each of the three parameters (MARCP, RAIRT, CRST) was determined by taking the mean value of the different trials performed. Results (in centimeters H,O for the MARCP and in milliliters for both the RAIRT and the CRST) are expressed as the mean f 1 SD. Normality for each of the three parameters (MARCP, RAIRT and CRST) was considered to be the mean f 2 SD found for the control subjects.
Results Rectal pressure, which was continuously recorded during the RAIRT and the CRST determinations, was not considered to afford useful data in this study, because at rest as well as during transient distensions no significant difference between the control subjects and the constipated patients was found for this parameter. Table
1.
Value of the Rectoanal
Parameters
Obtained
Table 2.
A W A A =
Parame-
Age (Yr)
MARCP (cm H,OJ
RAIRT W
CRST (ml) _____-
Boys
7 f 3.6
73 f 10.1
19 + 6.2
20 f 8.1
(n = 13) Girls (n = 19)
9 * 3.5
69 * 14.7
16 f 7.6
16 k 7.1
The one-way analysis of variance performed on these means provided a F-value of 0.49 for the MARCP, 0.96 for the RAIRT and 1.11 for the CRST. All these values are statistically insignificant.
Control Subjects In order to test the homogeneity of the results in the control population, a statistical analysis was performed using the one-way analysis of variance upon the mean values for the MARCP, the RAIRT, and the CRST found in control boys and girls and in different age classes. In control subjects, the mean values for the MARCP, the RAIRT, and the CRST were not significantly different in boys and girls (Table 2). According to their age, the control subjects were segregated into four groups (Table 3). The mean MARCP, RAIRT, and CRST values calculated for these four age groups were not significantly different (Table 3). Since the means of the MARCP, the RAIRT, and the CRST were neither significantly different in control boys and girls nor in different age groups of controls, results for these subjects were analyzed as a whole. In control subjects, the mean RAIRT was found to be 17 + 7.2 ml (range of 5-30 ml). Thus normality for the RAIRT (mean + 2 SD) was considered as ranging from 3 to 31 ml. Normal individual values for the RAIRT are presented in Figure 3. In control subjects, the MARCP values ranged from 45 to 95 cm H,O, with a mean of 71 + 13.1 cm H,O. Thus, normality for the MARCP (mean -I 2 SD) was considered as ranging from 45 to 97 cm H,O. Normal individual values for the MARCP are presented in Figure 4.
Before and After the Evacuation Before
Control 1 Control 2 Patient 1 Patient 2 Patient 3
Mean Values f SD for the Rectoanal ters in Control Boys and Control Girls
of an Enema
enema
30 Min after
enema
Age (yr)
MARCP (cm H,O)
RAIRT
CRST
MARCP
RAIRT
CRST
Sex
(m!,
(mI1
(cm H&Y
(ml)
(m!,
F M M M F
15 13 15 12 14
85 50 120 60 150
30 30 20 30 20
65 50 130 65 155
30 30 20 30 20
25 10 20 260 10
Measurements performed with the enema in situ are not shown on this table, rectoanal inhibitory reflex and the rectal sensibility, and since determination encc between the different trials). A is for Microlax, and ??for Normacol.
20 10 20 240 20
since, in these conditions, it was not possible to study the of the MARCP were nonreproducible (over 48% of differ-
August
1979
Table
3.
CHRONIC
Mean Values + SD for the Rectoanal parameters Found in Four Different Age Croups in the Control Children RAIRT
CRST
(Y4
MARCP (cm H,O)
(ml)
(ml1
2 k 0.9
65 f 6.1
21 f 5.4
Age
Group
1
subjects) Group
5 + 0.7
2
71 + 12.5
15 f: 6.8
17 f 7.1
(n = 9)
Group
3
6 + 1.3
71 f 12.6
200 0 m160_
I
E 160 u .,
15 -t 5 (only 2
(n = 4)
15 f 4.5
19 + 7.5
w 140_ !i
120 -
ii
-
w loo-
.:.
(n = 11) Group
CHILDHOOD
4
13 + 1.3
72 + 14.9
17 t 7.1
13 + 4.3
5
Patients
Since the means of all parameters (MARCP, RAIRT, and CRST) in control subjects were found to be neither significantly different in boys and girls nor in different age groups, the constipated patients were studied as a whole without consideration of sex and age. Mean values found for the constipated patients were compared with those found for the control subjects using the Student’s t-test. The rectoanal inhibitory reflex was present in all constipated children. Individual values of the RAIRT are presented and compared with those of
1 1
. . . . . . . . . . . . . . . . . . . . . .
I....
60 -
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
:
The one-way analysis of variance performed on these means provided a F-value of 0.31 for the MARCP, 1.23 for the RAIRT. and 1.36 for the CRST. All these values are statistically insignificant.
Constipated
1
. . . . . . . . . . . . .
..... ..::..
The mean CRST for the only 30 control children (11 boys and 19 girls) in which a sensitivity study was performed was found to be 17 f 7.1 ml (range of 5-30 ml:). Thus, normality for the CRST (mean + 2 SD) was’ considered as ranging from 3 to 31 ml. Normal individual values for the CRST are presented in Figure 5.
.. . ... ..... .. . . .. ....... ..... . . . . . .. .. .. . . . . . ....... . ....... ... ... ..........
I..
60,
(n = 8)
333
CONSTIPATION
.:. .
4Ob
control
Figure
.
.
i
constipated
4. Individual values (mean of at least three ments) of the MARCP in control subjects stipated patients.
measureand con-
the control subjects in Figure 3. For the RAIRT, values ranged from 5 to 60 ml with a mean of 20 f 10.8 ml which was not significantly different from those found for the controls (t = 1.49). A large majority of patients (94% of the total number) exhibited a normal RAIRT, with a range of 5-30 ml and a mean of 18 + 7.2 ml. No significant difference (t = 0.70) was found between this mean and that of the controls. However, in 9 cases (6.2% of the total number), the RAIRT values were abnormally high (over 31 ml). In these cases, the mean RAIRT was found to be 51 + 7.8 ml (range of 40-60 ml). The difference between this mean and that of the control subjects, according to Student’s t-test, was very significant (t = 12.32; P < 0.001). Individual MARCP values are presented and compared with those of the control subjects in Figure 4. For the MARCP, values ranged from 45 to 200 cm
...
j:
20
.
.
.
.
. .
L.....
.
. . . . . . . .
..I
,o
. ..*
I..... I
--I .
.
.
.
.
.
0
control
constipated
.
Figure
3. Individual values (mean of five measurements) of the RAIRT in control subjects and constipated patients.
334
MEIJNIER
ET AL.
H,O with a mean of 99 + 39.4 cm H,O, which was significantly different from those found for the controls (t = 3.97; P < 0.001). However, according to the normal range defined with the controls, a total of 78 constipated patients (54% of the total number) were found to have normal MARCP values. In these normotonic patients, the mean MARCP was found to be 70 + 13.9 cm H,O. The comparison of this mean with that of the control subjects showed no significant difference (t = 0.35). Abnormally high MARCP values (over 97 cm H,O) were found in 66 patients (46% of the total number). In this group of hypertonic patients, the MARCP ranged from 100 to 200 cm HzO, and the mean was found to be 133 -+30.9cm H,O. The difference between the mean MARCP values of the patients and controls according to Student’s ttest, was very significant (t = 10.98; P < 0.001). Anal hypotonia (MARCP under 45 cm H,O) was never observed in the constipated patients. The CRST was determined in only 116 constipated patients (aged 3-15 yr). Individual values, ranging from 5 to 350 ml, are presented and compared with those of the controls in Figure 5. The mean CRST in the constipated patients was found to be 81 + 76.6ml and was significantly different from those of the controls (t = 4.56; P < 0.001). According to the normal range defined with the controls, a normal CRST was found in 37 patients (i.e., in 32% of the patients in which rectal sensitivity was studied). In these patients, CRST values ranged from 5 to 30 ml, with a mean of 19 + 8.4 ml. The difference between this mean and that of the control subjects was not significant (t = 1.04). An increased CRST (i.e., decreased sensitivity) was observed in 79 other constipated patients (68% of the total number of children in which rectal sensitivity was studied). In these cases, CRST values ranged from 40 to 350 ml, with a mean of 111 + 77.0 ml. This mean was very significantly different from that of the controls (Student’s t-test: t = 6.66; P < 0.001). As previously shown,7 a close correlation was found between the presence of encopresis and the increase in the CRST. Encopresis was observed in 24% of the children with a normal CRST, in 39% of the children with a CRST between 40 and 90 ml, and in all children with a CRST of over 100 ml. On the other hand, encopresis was found in 51% of the patients -with a normal MARCP (normotonic patients) and in 29% of the patients with an increased MARCP (hypertonic patients). The chi-square test proved that the incidence of encopresis was significantly greater in normotonic patients than in hypertonic patients (2 = 7.48;P < 0.01). A comparable percentage of encopresis was found in patients with a normal RAIRT (41%)and patients with an abnormal RAIRT (44%). The chi-square proved any signif-
GASTROENTEROLOGY
Vol.
77,
No. 2
..
320
8 260
-
260
_
240
-
220
-
.
... ..
200
-
.. ..
160
-
.....
i
160
-
: $
140
-
120
-
100
-
60
-
60
-
40
-
20
-
*
.. . ..
. . . . ..... ..I..
.
.
.
.
.
::.
I
.
.
.
.
O-
control
Figure
5. Individual values (mean CRST in control subjects
. . .. .. .. . ............... ..... .. .. ..... . .. ... ... .. .. ... .. . .. ... .... .. ............ ... ... . .... .. conatipeted
of five measurements) of the and constipated patients.
icant difference between the incidence of encopresis in patients with a normal RAIRT and patients with an abnormal RAIRT ($ = 0.24). Comparable percentages of patients with an increased CRST were found in normotonic and hypertonic patients (72 and 63%, respectively). The chisquare test was unable to demonstrate any significant difference (2 = 0.51)between the distribution of increased CRST in normotonic and hypertonic patients. Likewise, similar proportion of patients with an abnormal RAIRT were found in children with an increased CRST (6.3%) and children with a normal CRST (11%). As shown by the chi-square test, there was no difference between the distribution of abnormal RAIRT in children with a normal CRST and children with an abnormal CRST (d = 0.72). In both normotonic and hypertonic patients, 6% of the children exhibited an abnormal RAIRT. Therefore, there was no difference between the dis-
August
1979
tribution of abnormal RAIRT in normotonic and hypertonic patients (2 = 0.01). Finally, it is interesting to note that in only 15 constipated children (13% of the total number of patients in which the three parameters were studied), all three manometric parameters of this study (RAIRT, MARCP, and CRST) were normal. In these patients (aged 4-12 yr; mean age = 7.3 yr; 10 boys and 5 girls), 5 were encopretics.
Discussion From the above results, it appears that patients with chronic childhood constipation who do not have Hirschsprung’s disease do have abnormalities at m.anometry in most cases. The relationships between the rectoanal parameters herein described and constipation should be considered. Although demonstration of the rectoanal inhibitory reflex is not accurate in the neonatal period, the accuracy increases with age”; after 1 yr of age, the finding of anal relaxation after rectal distension rules out the possibility of Hirschsprung’s disease. Most authors agree that the study of the rectoanal (and sufficient) in inhibitory reflex is required chronic constipation to demonstrate the presence of ganglionic cells in the rectal wall.“-” Furthermore, it has been shown17 that only rectosphincteric manometry achieved 100% diagnosis accuracy between constipated patients with and without colonic aganglionosis. This is the reason why the study of the rectoanal inhibitory reflex is the more useful examination in chronic constipation. However, the significance of an increased RAIRT, as it was observed in 6.2% of our constipated patients, is unclear. An increased RAIRT might be due simply to the balloon not stretching the rectal walls, or it is possible that this abnormal reflex threshold was an artefact due to an incompletely evacuated ampula, which prevented correct distension of the rectum. In about 50% of the constipated patients, an increased MARCP was found. Such hypertony might be related to outlet obstruction which has been recently defined by Martelli et al.” Anal hypertonia is compatible with sphincteric relaxation, since the rectoanal inhibitory reflex was present in all hypertonic patients. It is highly probable, however, that an hypertonic sphincter plays a part in constipation by creating difficulties in feces elimination, leading to fecal retention. The improvement of some constipated children”,‘” or adults” after anal sphincterotomy becomes clear from the results of our study, since anal hypertonia was so frequently demonstrated in constipated patients. Thus, it is logical to
CHRONIC
CHILDHOOD
CONSTIPATION
335
assume that the indication for anal sphincterotomy remain on the finding of an increased MARCP. The basis of the increase of the conscious rectal sensitivity threshold, observed in a majority of constipated patients, is worthy of discussion. First, the hypothesis that the distending balloon did not stretch the rectal wall could be proposed, since chronic constipation in children is commonly associated with an enlarged rectum.‘-’ Therefore, in our study, stools were evacuated before the examination, and such an hypothesis supposes that the rectum behaves like a plastic reservoir keeping its shape and properties even when feces are removed. Since the rectum has viscoelastic properties,” this hypothesis seems improbable, at least for the large distending volumes. The increase of the CRST probably remains abnormal because of the rectal mechanoreceptors. When fecal retention occurs, the rectal wall is distended. This distension induces an increased response threshold for the rectal mechanoreceptors. In the normal individual, the rectoanal inhibitory reflex is controlled by the cerebral cortex, because this reflex has a threshold close to that of conscious rectal sensitivity, while, in children with an increased CRST, sphincteric relaxation occurs before rectal sensation arises, a situation clearly conducive to soiling.” This is the reason for which a close correlation was found between the incidence of encopresis and the increase in the sensitivity threshold. A decrease in conscious rectal sensitivity has previously been observed in children with megarectum.‘~7~2’ In this study, abnormal conscious rectal sensitivity was demonstrated in most of the chronically constipated children; an increased CRST was found in 68% of the patients. Although subjective, and sometimes difficult, specially in children, rectal sensitivity studies, introduced by Goligher and Hughes,‘” are very useful in the management of such patients. Finally, it should be noted that we were unable to demonstrate differences in rectal pressure between the control group and the constipated patients. This finding appears rather surprising since most of the patients exhibited rectoanal abnormalities. The explanation of this fact might remain in the methodology chosen (rectal pressure measurements at rest and during transient rectal distensions); a study of the viscoelastic properties of the rectal wall, according to Arhan et al.,z0.23would probably offer a better assessment of rectal abnormalities.
References 1. Callaghan RP, Nixon HH: Megarectum: vations. Arch Dis Child 39:153-157,1964 2. Oppe TH: Megacolon and megarectum
physiological in older
children.
ohserProc
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R Sot Med 66:863-865,1967 3. Bentley JFR: Constipation in infants and children. Gut 12:65961971 4. Ehrenpreis T: Megacolon and megarectum in older children and young adults. Classification and terminology. Proc R Sot Med 6679%601,1967 5. Nixon HH: Megarectum in the older child. Proc R Sot Med 66:861-863,1967 6. Davidson M, Bauer CH: Studies of distal colonic motility in children. IV. Achalasia of the distal rectal segment despite presence of ganglia in the myenteric plexuses of this area. Pediatrics 21:746-766, 1958 7. Meunier P, Mollard P, Marechal JM: Physiopathology of megarectum: the association of megarectum with encopresis. Gut 17:X4-227.1976 8. Scobie WG. Kirwan WO, Smith AN: Colonic motility in children with constipation. Dis Co1 Rect 20:672-676,1977 9. Zabinsky MP, Spiro HM, Biancani I? Influence of perfusion rate and compliance on esophageal manometry. J Appl Physiol38:177-1861975 10. Dodds WJ, Stef JJ, Hogan WJ: Factors determining pressure measurement accuracy by intraluminal esophageal manometry. Gastroenterology 70:117-123.1976 11. Meunier P, Mar&ha1 JM, Mollard P: Accuracy of the manometric diagnosis of Hirschsprung’s disease. J Pediatr Surg 13:411-415,1978 12. Lawson JON, Nixon HH: Anal canal pressures in the diagnosis of Hirschsprung’s disease. J Pediatr Surg 2544-552.1967
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13. Schnaufer L, Talbert JL, Hailer JA. et al: Differential sphincteric studies in the diagnosis of anorectal disorders of childhood. J Pediatr Surg 2:538-543,1967 14. Arhan P, Faverdin C, Thouvenot J: Anorectal motility in sick children. Stand J Gastroenterol7:369-314.1972 15. Meunier P, Mollard P: Control of the internal anal sphincter study with human subjects). Pfliigers Arch (Manometric 370:233-239,1977 16. Holschneider AM: Manometrie des Anorektums. Z Gastroenterol15:215-221,1977 17. Tobon F, Schuster MM: Megacolon: special diagnostic and therapeutic features. Johns Hopkins Med J 135:91-165,1974 18. Martelli H, Devroede G, Arhan P, et al: Mechanisms of idiopathic constipation: outlet obstruction. Gastroenterology 75:623-631,1978 19. Schandling B, Desjardins JG: Anal myomectomy for constipation. J Pediatr Surg 4:115-118,1969 20. Arhan P, Faverdin C, Persoz B, et al: Relationship between viscoelastic properties of the rectum and anal pressure in man. J Appl Physiol41:677-682.1976 21. Porter NH: Megacolon: a physiological study. Proc R Sot Med 54:X343-1647,196l 22. Goligher JC, Hughes ESR: Sensibility of the rectum and colon. Its role in the mechanism of anal continence. Lancet 1:543548,195l 23. Arhan P, Devroede G. Danis K, et al: Viscoelastic properties of the rectal wall in Hirschsprung’s disease. J Clin Invest 62:82-87.1978