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Balloon Expulsion Test as a Screen for Outlet Obstruction in Children With Chronic Constipation

Belkind-Gerson, Jaime*; Goldstein, Allan M.; Kuo, Braden

Journal of Pediatric Gastroenterology and Nutrition: January 2013 - Volume 56 - Issue 1 - p 23–26
doi: 10.1097/MPG.0b013e31826a909f
Original Articles: Gastroenterology

Objective: Chronic constipation (CC) is a common problem in pediatrics and is often the result of obstructed defecation. The aim of the present study was to study the feasibility and efficacy of the balloon expulsion test (BET) in the diagnosis and management of children with CC.

Methods: Retrospective study comparing BET and high-resolution anorectal manometry (ARM). The BET was done together with ARM in 29 children, ages 8 to 19 years, with CC. For BET, a 60-mL balloon was used. Passage of balloon in 1 minute or less was considered normal.

Results: Fifteen of the 29 children had a normal BET. Of these, 14 also had an ARM, all of which were normal (except for 2 cases with a hypertonic baseline anal sphincter). Thus 12 of 14 with BET and ARM were normal on both (correlation between the tests 86%). Of the 14 children that failed BET, 10 had distal abnormalities by ARM, contrast studies, EMG, or assessment by a pelvic physical therapist. All of the patients with a nonrelaxing sphincter or outlet obstruction were treated with laxatives, anal sphicter Botox, and/or pelvic physical therapy and biofeedback. In follow-up of at least 3 months, all of the patients with a failed BET were improved.

Conclusions: We found a high correlation between a normal ARM and BET. If the BET is abnormal and the ARM does not identify a cause for the distal obstruction, additional studies may be needed, including contrast enema, defecography, or electromyography. BET appears to be a safe, reliable, and useful test in the evaluation and management of CC in children.

*Pediatric Gastroenterology

Pediatric surgery

Gastrointestinal Unit, Massachusetts General Hospital, Harvard Medical School, Boston, MA.

Address correspondence and reprint requests to Jaime Belkind-Gerson, MD, MSc, Pedatric Gastroenterology, Masachusetts General Hospital, Boston, MA 02114 (e-mail:

Received 14 April, 2012

Accepted 18 July, 2012

The authors report no conflicts of interest.

Chronic constipation (CC) in children is a common problem, accounting for 3% of all of the pediatric visits and 35% of referrals to pediatric gastroenterologists (1,2). The present economic burden for evaluating and treating patients with CC in the United States is estimated at $6.9 billion/year (3), and the number of pediatric patients seeking medical help for CC is increasing (4). CC is associated with significant physical and emotional burden for both children and caregivers (5) and recent studies suggest that it may have deleterious effects on growth, development, and general well-being (6). We recently performed a 10-year retrospective study on 264 children with CC who underwent a diagnostic rectal biopsy and found that >30% of patients experienced persistent symptoms for >2 years and a prominent psychiatric burden despite aggressive laxative therapy (7). The results found in the present study also suggest that earlier treatment confers a better prognosis. This is similar to other reports in which one third of constipated children followed beyond puberty continued to have severe constipation (8,9). These findings suggest better treatments are needed rather than laxatives alone, the present standard of care.

In pediatrics, many cases of constipation are due to pelvic outlet obstruction, the causes of which include functional fecal retention, anismus, and anal sphincter achalasia or hypertension, in addition to slow transit constipation (10). In contrast, adults often have slow transit constipation. A safe, reliable, and easily tolerated screening test for pelvic outlet obstruction would be an important advance and allow early diagnosis and prompt initiation of therapy. The balloon expulsion test (BET) is extensively used in adults with constipation and suspected pelvic outlet obstruction. BET is reported to be 88% sensitive and 89% specific for this diagnosis (11). In combination with other tests, including anorectal manometry (ARM) and defecography, BET is useful in guiding directed therapy (12,13) as well as in following progress and response to treatment. Importantly, BET is a simple screening test that can be easily used in the outpatient setting. In adults, the procedure is performed by inserting a balloon catheter into the rectum and inflating it with 60 mL of air. The patient is asked to sit on the commode and attempt to pass the balloon. If the balloon is passed within 60 seconds, outlet obstruction is excluded (14). We recently started using BET at the time of ARM in chronically constipated children 8 years of age and older. We describe our experience in these patients and demonstrate the feasibility and efficacy of BET in the diagnosis and management of children with CC.

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After obtaining approval from the institutional review board, we retrospectively reviewed the records of children who underwent ARM and BET. All of the patients were between 8 to 19 years of age and were evaluated at Massachusetts General Hospital beginning in 2010. Subjects met the Rome 3 criteria for CC (Table 1). Patients with known Hirschsprung disease, anorectal malformations, spinal cord abnormalities, or drug-induced constipation were excluded. On the night before the ARM, all of the children received a phosphate enema. High-resolution manometric studies were performed (MSE-3888-Z ManoScan System, Given, Imaging, Yokneam, Israel) with the manoscan program as previously described ( Intra-anal pressure was measured in all of the individuals after giving appropriate time for accommodation. Baseline anal sphincter pressure was considered abnormally high if >120 mmHg (15). The presence of internal anal sphincter (IAS) relaxation or rectoanal inhibitory reflex (RAIR) during manometry testing was measured for each balloon distention. Relaxation of the sphincter was present when there was a consistent reproducible decrease in sphincter pressure of at least 50% from baseline within 15 seconds of balloon distention, and a subsequent return to baseline pressure. Children in whom the RAIR could not be elicited even with maximal balloon insufflation were diagnosed with a nonrelaxing IAS (15). A child-life specialist was present throughout the ARM study to help alleviate the child's fear and anxiety, using videos and games while baseline sphincter measurements were obtained and the RAIR was elicited. After the ARM, an 18F catheter (Mui Scientific Anorectal Balloon Expulsion Catheter) was inserted 5 cm into the rectum with the balloon deflated, using a small amount of water-soluble lubricant. The balloon was then inflated with 60 mL of air, which was locked in the balloon using a 3-way stopcock. The catheter was gently pulled back to confirm proper positioning in the rectum. Patients were asked to pass the balloon into the commode. If successful within 1 minute, the test was considered normal (14).



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Twenty-nine patients (ages 8–19) (12 boys) were evaluated (Table 1). The average maximal resting sphincter pressure was 93 mmHg (range 44–162, SD 28). Fifteen of the 29 patients had a normal BET. Of these, 14 subjects also underwent high-resolution ARM. Twelve of these were normal, and 2 had a hypertonic baseline IAS pressure (maximal resting pressures of 152 and 162 mmHg). Despite the high pressure, both patients were able to pass the balloon on BET. Thus, 12 of 14 patients who underwent both BET and ARM were normal on both tests (correlation 86%).

During testing, it appeared that the 4 patients 10 years old or younger may have lacked the maturity to understand and comply with the BET. These 4 subjects were males, and none were able to pass the balloon into the commode; however, 2 of these younger patients also had high-tone and nonrelaxing pelvic floor by a pelvic physical therapist and 1 had an abnormal RAIR by ARM, thereby identifying abnormalities in 3 of 4 subjects that could explain the failed BET. The other 10 children who did not pass the balloon were 12- to 17-year-old and 9 were girls. Five of these patients did pass the balloon, but took 1 to 2 minutes to do so, rather than 60 seconds or less. Six of the 10 subjects had structural or functional abnormalities diagnosed by ARM, defecography, physical examination, or puborectalis EMG that could explain the failed BET and lead to an impediment to pelvic outflow. Findings included an absent RAIR, rectal spasms of unclear etiology on contrast fluoroscopy, and a nonrelaxing or paradoxically contracted puborectalis muscle by defecography or EMG.

All of the patients with a nonrelaxing sphincter or outlet obstruction were treated with laxatives, intrasphincteric Botox and/or pelvic physical therapy and biofeedback. In follow-up of at least 3 months, all of the patients with a failed BET had improved with therapy (Table 2).



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Our results show that BET appears to be a feasible and effective test in children with CC. Although the test was easily performed in children older than 10 years, it can also be successful in mature 8- to 10-year-olds. The diameter of a 60-mL balloon is approximately 5 cm. While interviewing our patients about average stool diameter, we found that diameters exceeding 5 cm were common; thus, we opted to use the same volume of insufflation as for adults. We found that most patients had no problem passing the balloon in the allotted time and the results correlated highly with the results of ARM.

The BET helped guide therapy in all of the patients studied (with the possible exception of the 4 younger children who may not have been able to comply with the study), steering the diagnosis toward slow-transit constipation or other causes (behavioral, and so on) when the balloon was successfully passed. In cases in which the balloon was unable to be passed and abnormalities of the sphincter puborectalis muscle or pelvic floor were identifed, patients were treated with botulinum toxin instillation into the sphincter and/or with pelvic physical therapy/biofeedback. Thus, BET results helped guide therapy in these cases.

We found that there was some anxiety and fear surrounding the tests, which is not uncommon in chronically constipated children who may have had previous traumatic experiences with enemas, suppositories, and other anorectal therapies. By explaining the purpose of the tests to parents, they often helped soothe and prepare the children, and were invited to be in the room during the testing. A child life specialist was involved with distracting and helping patients to relax before and during the study. Often movies, video games, and other aids were used while the testing was done to decrease anxiety. Using these techniques, we believe this test may be feasible even in the initial outpatient visit as a useful screen for pelvic outlet dysfunction. The BET can also be valuable as a follow-up measure once treatment is under way.

We typically perform ARM before BET. Anorectal stimulation and asking the patient to do voluntary external anal sphincter squeeze may result in sphincter training immediately before the BET, which may influence the results. This is a potential limitation in the present study and may be addressed in future studies by alternating the order of BET and ARM.

Normative values for anal sphincter maximal resting pressure in children are unknown. The normal range is 40 to 70 mmHg in adults. The average measurement for resting pressure in our cohort was 93.4 mmHg (range 46–162), suggesting a higher pressure in pediatrics; however, this is a cohort of constipated children, which may account for the higher values. Because the majority of patients were able to expel the balloon, it may be that younger patients have a relatively hypertonic sphincter, but these results should be interpreted cautiously and verified with a healthy, nonconstipated pediatric population. The high resting sphincter pressure was not found by Raghunath et al in their study of constipated and encopretic children using water-perfusion ARM, where the average sphincter tone was 43 ± 14 in patients with constipation alone and 51 ± 17 in children with constipation and encopresis (16). In a study using water perfusion ARM in constipated children, Chumpitazi et al (15) use normal values of 60 to 120 mmHg, which is why we chose to use 120 mmHg as the upper limit of normal. Future studies in healthy pediatric volunteers using high-resolution ARM are needed to establish normal values. These same authors use a minumum of 5% of relaxation to diagnose a normal RAIR (15). In our series, we found that in all of the patients in whom we could elicit the RAIR, the relaxation was at least 50% of baseline pressure.

In the present study, excluding the younger patients, 9 of 10 that could not pass the balloon, were girls. The association of dyssynergic defecation and female sex in the pediatric population is not known. Although the finding may be partly due to the predominance of girls in our sample, it warrants further investigation.

One of the most important findings of the present study is the high correlation between a normal ARM and BET. If the BET is abnormal and the ARM does not identify a cause for the distal obstruction, our results suggest that additional studies may be needed, including contrast enema, defecography, or EMG to look for a paradoxic puborectalis contraction or abnormalities of pelvic relaxation. In conclusion, BET appears to be a safe and useful test in the evaluation and management of chronically constipated children. Additional studies are needed to define age-specific variables, including optimal balloon volume, expulsion time, and patient position in the pediatric population.

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anorectal manometry; balloon expulsion; children; constipation; defecation disorders

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