• Chronic Constipation
• Colonic Manometry
• Colonic Transit Studies

Background & aim: Functional constipation (FC) is a common condition encountered in paediatric population that severely impacts patients’ quality of life. Patients refractory to medical treatments are eligible for further investigations, including colonic manometry (CM) and transit studies (CTS). Colonic transit assessment can be performed with either colonic scintigraphy (CS) or with radiopaque marker (ROM) test and based on their results, constipation can be classified into slow transit constipation (STC) and obstructed defecation. Scientific literature about the concordance between manometric features and colonic transit is currently sparse and a recent study reports good correlation between CS and CM in constipated children. The aim of this study was to evaluate the agreement between CM and CTSs and the presence of specific manometric patterns suggestive of STC or outlet obstruction, respectively.

Methods: Consecutive FC patients that had been referred at our centre from 2012 to 2017 were retrospectively evaluated. All patients underwent CM and at least one of the CTSs (either CS or ROM test) as part of their diagnostic work-up. CM was performed as per standardised protocol including at least 1 hour of basal recording, standardised test-meal and administration of two different dose of bisacodyl (0.2 and 0.4 mg/kg). ROM test was performed by administering three different sets of markers in three subsequent days, followed by abdominal radiograph on day 4. CS protocol consisted in administering 111I radiolabelled water along with standard meal. Images were taken at 24 and 48 hours and geometric centres were calculated. All patients underwent bowel clear-out prior to the studies. Based on previously published papers, results from CM were categorised into normal, abnormal distal motor activity and colonic inertia; whereas results of CTSs were classified into normal transit, recto-sigmoid hold-up and slow transit. Cohen keppa, Fisher`s exact and Anova test were used for the statistical analysis.

Results: Twenty-nine children (11 males and 18 females, mean age 10.1 years, SD 3.16) were included. As part of their workup, 24.1% (n=7) of the patients had only CS, 62.1 % (n=18) had only ROM test and 13.8% had both tests (n=4). CTSs showed normal values in 3.4% (n=1), outlet obstruction in 24.1% (n=7) and a slow transit in 72.4% (n=21) of patients, respectively. Conversely, CM showed a normal pattern in 65.5% (n=19) of the patients, abnormal distal contraction in 27.6% (n=8) and colonic inertia in 6.9% (n=2). The concordance between the two colonic transit tests was high 100% (Cohen K = 1); whereas, CTSs and CM showed no agreement (Cohen K = 0.079). When comparing different CM patterns in STC and outlet obstruction patients, the presence of partially propagating high-amplitude propagating contractions (HAPCs) was significantly associated with outlet obstruction (p=0.020). Conversely, changes in the motility index from baseline, HAPCs waveform, presence of common cavity features or retro-propagating contractions and colorectal reflex were not predictive of the prevalent colonic transit pattern. Also, the number of HAPCs and low-amplitude propagating contractions (LAPCs) was not significantly associated with CTSs results (p=0.057 and 0.873 in STC and outlet obstruction, respectively).

Conclusions: Constipated patients may require CM or CTSs as part of their diagnostic workup. CS and ROM test have a high agreement in classifying the type of constipation. In contrast, we found no agreement between CM and CTSs results. The presence of partially propagating contractions into the distal colon appears to be significantly correlated with outlet obstruction as assessed with CTS, whereas, none of the other colonic manometric patterns was significantly associated with outlet obstruction or STC. All these functional tests have a clinical utility in assessing the pathophysiological mechanisms underlying constipation and may guide clinicians’ therapeutic choices. Given the high agreement between CS and ROM studies, both these radiological techniques can be used to assess the type of constipation, based on centre expertise. On the contrary, CM may be useful in assessing the contractile response following different provocative tests and demonstrating the integrity of colonic neuro-muscular function. Although further larger studies are needed to replicate our data, our results show that manometry and transit studies, by exploring different pathophysiology aspects underlying chronic constipation, have both clinical utility in the diagnostic workup of FC patients.