Constipation is a symptom characterized by excretion of hard, small, or voluminous stools, with a reduced frequency of evacuation (1,3). In most instances, no clear cause is identified, and patients are considered to have idiopathic or functional constipation(3). It is accepted that 95% of normal people evacuate from 3 to 21 times a week (4). None of these criteria proved satisfactory in defining constipation in children and adults(5-7). The subjective aspect of the concept of constipation makes it necessary to establish an objective criterion to describe it. The total and segmental colonic transit time, traced by radio-opaque markers, allows the identification of the colon segment that has a motility alteration that causes constipation, and helps in determining an effective treatment, depending on segmental transit times (9-19). Therefore, we measured total and segmental colonic transit time in constipated adolescents and compared the results with those in nonconstipated adolescents. This is the first study measuring total and segmental colonic transit time in constipated patients in Brazil.
PATIENTS AND METHODS
The population studied consisted of 13 adolescents, aged 12 to 18, with constipation, and 13 without constipation. Patients were seen at the Hospital de Clínicas de Porto Alegre and Hospital Materno Infantil Presidente Vargas, in Porto Alegre, Rio Grande do Sul, Brazil from November 1993 to November 1994. The constipated adolescents had hard stools, difficulty in evacuating, less than three bowel movements a week, no evidence of palpable rectal mass, and a history of constipation of at least 1 year's duration. Adolescents with neurologic and metabolic diseases. Hirschsprung's disease, spinal and anal anomalies, surgery of the colon, mental retardation, and a history of drug abuse were excluded. The group of nonconstipated adolescents had no digestive complaints and had more than three bowel movements per week. All of the adolescents and their parents gave their informed written consent after the initial interview. The protocol was approved by the Ethics Board of the Hospital de Clínicas de Porto Alegre.
The radio-opaque markers were introduced through polyethylene catheters produced by the Biomedical Engineering Department at Hospital de Clínicas de Porto Alegre (not available for commercial use in Brazil). The physical characteristics of the markers were: specific weight between 1.20 and 1.35, mass between 20 and 40 mg, and length between 3 and 6 mm. Twenty markers were placed in each gelatin capsule. The technique used to measure total and segmental colonic transit time has been described by Metcalf et al. (1) The adolescents swallowed one capsule a day for 3 days, and on the fourth day, a plain abdominal radiograph was taken. Abdominal radiographic films were obtained by a high-kilovoltage fast-film technique, to reduce radiation exposure (estimated surface exposure, 0.08 mrad per film). The numbers of markers present in this radiograph was counted, and previously determined bony landmarks were used to locate each colonic segment. The markers to the right of the line extending from the fifth lumbar vertebra to the right iliac crest were considered to be in the right colon. The markers located to the left of the line extending to the left anterior-superior iliac crest were considered to be in the left colon. The markers below the lines were considered to be in the rectosigmoid and rectum. The calculations of total and segmental colonic transit times were based on the count of markers per segment and were multiplied by 1.2, a constant that represented the ratio between the period in which the exam was performed (72 hours) and the number of markers ingested (60) and expressed in hours. On the days the measurements were performed, the adolescents were advised not to alter their diets and not to ingest foods that might alter bowel motility. The fiber intake was standardized at 15 g a day. Because of poor compliance in adolescents regarding nourishment, the test was performed on outpatients taking their normal diet. Any treatment with laxatives was discontinued at least 7 days before the test. All adolescents were seen by one of the authors (CZ), and all radiographs were interpreted by the same radiologist, who did not know whether the patient was constipated. For this research a cross-sectional study was designed. The condition to be studied was constipation, and the outcome was the total and segmental colonic transit times with measured radio-opaque markers. The Wilcoxon-Mann-Whitney test was used for statistical analysis of independent samples. The cutoff point for statistical significance was p < 0.05. The transit times are described as means ± standard deviations and medians. The patient with constipation was considered to have slow colonic transit when there was delay in transit through the right colon, the left colon, or both. They were considered to have distal obstruction when the delay occurred in the rectosigmoid. The normal values for total and segmental transit times were taken from the 95th percentile of adolescents without constipation.
Groups of adolescents studied were similar in gender distribution, 9 boys and 4 girls in each group. There was no statistically significant difference in age, weight and height between the two groups (p > 0.05). The interval between stools was 5.8 ± 2.3 days in the constipated group; those in the nonconstipated group had daily stools (p< 0.01). The distribution of clinical features, bulky or small stools, encopresis, rectal mass, intense use of laxatives, bowel movements per week was the same in both groups. The mean daily intake of fibers in the constipated group was 11.5 ± 4.8 g, and in those without constipation 13 ± 6.1 g (p > 0.05). Table 1 shows the mean ± standard deviation and the lower and upper limits of the total and segmental colonic transit time in the constipated and nonconstipated groups. There was a statistically significant difference in right colon(p < 0.03), left colon (p < 0.001) and in total colonic transit time (p < 0.001). No statistically significant difference was found in the rectosigmoid (p = 0.8). Regarding the medians of the measurements of total and segmental colonic transit time, the values for the constipated and non constipated groups, respectively, were: right colon, 13.2 and 7.2 hours (p < 0.001); left colon, 25.2 and 7.2 hours (p < 0.001); rectosigmoid colon, 16.6 and 12 hours(p = 0.8); total 68.4 and 27.6 hours (p < 0.001). The upper limit of total transit time was 50.4 hours, with segmental times of 12 hours in the right colon, 28.8 hours in the left, and 36 hours in the rectosigmoid. Nine of the 13 constipated adolescents had slow colonic transit, 2 had distal obstruction, and 2 had normal transit times. The plain abdominal radiograph of a constipated adolescent with slow colonic transit (all markers in the right and left colon) is shown in Figure 1. The plain abdominal radiograph of a constipated adolescent with distal obstruction (the markers are retained in the rectosigmoid) is shown inFigure 2.
The interval between stools or their frequency are objective data that were used in epidemiologic surveys to define constipation (21-25). Approximately 95% of normal adults have 3 to 21 stools a week. In this study the group of constipated adolescents had an interval of 5.8 ± 2.3 days between stools, and the nonconstipated group had daily stools (p < 0.01).
No statistically significant difference was found in daily fiber intake between constipated and nonconstipated adolescents. Despite the small number of subjects studied, our results show that constipated patients took in an amount of fiber similar to normal persons (18,26,27). In patients with severe constipation, those with slow colonic transit times, increasing intake of fibers did not appear to alleviate the constipation, probably because of the reduced contractile activity of the smooth muscle of the bowel (28).
Using radio-opaque markers to measure the total and segmental colonic transit times is a simple method and allowed us to divide patients with constipation into three subgroups (1,29-35): slow colonic transit time(Fig. 1), distal obstruction (Fig. 2), and normal colonic transit time. In this study, a simplified method was used, with a single radiograph taken on the fourth day, after 3 consecutive days of marker intake. According to Metcalf et al., this single-radiograph technique provides an optimum correlation with that of daily radiographs(1). A significant prolongation of total and segmental transit times was recorded in the constipated group compared with that in the nonconstipated group: right colon transit time (p < 0.05); left colon transit time (p < 0.01); and total colon transit time(p < 0.01). The difference between the two groups in the measure of transit time in the rectosigmoid was not significant (Table 1). Eleven (84.6%) of the 13 constipated adolescents had some change in colonic transit time. Nine (69.2%) had slow colonic transit, and 2 (15.4%) had distal obstruction. No specific data for adolescent were found in the literature concerning this distribution of results. In children with functional constipation, distal obstruction is described as the most frequently seen alteration (36,37). In adults the data are variable. Chaussade et al. (30,31), Walker et al. (38), and Kuijpers (39) recorded predominantly slow colonic transit times. Turnbull et al.(34), Kolster et al. (14), and Pemberton et al. (40) recorded predominantly distal obstruction in adults. Our data for total and segmental colonic transit times in nonconstipated adolescents are similar to those described in the literature (Table 2).
Measuring total and segmental colonic transit times with radio-opaque markers allows the identification of two types of disordered colonic motility in functional constipation, slow colonic transit and distal obstruction, and therefore allows treatment according to the location of the delay. In those patients with slow transit constipation the options are limited. Usually, their condition does not respond to large doses of laxatives. Recently, it has been shown that cisapride (41) and misoprostol(42) may be beneficial. In adults with intractable slow transit constipation, surgery has been recommended (40,43). In those patients with distal obstruction, with pelvic-floor expulsion problems, biofeedback may be a good option(9,13,39,43). The simplified technique of Metcalf et al. (1)-that of obtaining a single radiograph-proved useful. It reduces the exposure to radiation and is indicated in constipated children and adolescents who have been refractory to the usual treatments. Metcalf's technique is more practical than is colonic scintigraphy (44,45). Orocecal transit time can be measured, using the hydrogen breath test (46). In conclusion, total and segmental colonic transit times measured with radio-opaque markers provide the most useful information at the lowest cost and least inconvenience to the constipated patient. This method should help establish whether a constipated adolescent requires a different therapeutic regimen for slow transit constipation or for outlet obstruction.
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