Abdominal radiograph showing a high-resolution solid-state colonic motility catheter placed with its tip at the hepatic flexure. The arrow points to the endoclip used to secure the catheter in place
Endoscopic image of colonic motility catheters , (a) water-perfused catheter in the process of being clipped to a fold in the cecum and (b) a solid-state catheter in the colonic lumen with the pressure sensors in silver
There is variability in study protocols with no prospective data indicating superiority of any specific one. Studies of relatively short duration, approximately 4–8 h, are usually adequate to evaluate response to stimuli and form a plan of intervention. However, studies lasting 24 h performed in ambulating subjects provide more physiologic data. Provocation tests are used to assess response to stimuli such as food and medications. Food is the most powerful physiologic stimulus of colonic motility, and its ingestion induces an increase in phasic and tonic motor activity, also known as the gastrocolonic response . The early response is most intense in the distal colon and may result in an urge to defecate. A second peak in motility is seen after 50–110 min lasting up to 3 h. Increased motor activity following a meal may be regarded as an indication of the integrity of the neurohumoral control of colonic motility. The postprandial observation period is typically followed by administration of a stimulant laxative directly into the colon. The expected response to such a provocative intervention in individuals with normal motility is the occurrence of HAPC [12, 13]. Absent response has been interpreted as being diagnostic of colonic inertia and myenteric plexus damage in adults and children [14, 15]. Stimulation with other drugs, such as neostigmine, and use of a barostat to measure tonic changes are not routinely done in children.
Pediatric studies are initiated after the effect of the sedation or the anesthesia used for placement of the catheter has resolved. Some have suggested the study can be performed as early as 4 h after recovering from anesthesia , but others have recently reported an important effect of anesthesia on the study interpretation when study is performed the same day of anesthesia . The study can be safely performed the same day when colonoscopy is performed with intravenous sedation (benzodiazepines). Typical protocols in pediatrics start with fasting period when baseline colonic motility without stimulation is monitored for 1–2 h. The child is then offered and asked to eat a large, age-appropriate meal. The postprandial motility is recorded for at least one more hour starting at the end of meal. Pharmacologic provocation is then usually performed with 0.2 mg/kg of bisacodyl (max 10 mg), which is infused through the motility catheter into the most proximal portion of the colon or via an ostomy opening if present (Fig. 9.3). Symptoms experienced by the child are noted during the entire study. It is particularly informative to observe the child’s reaction to the onset of the urge to defecate associated with the administration of bisacodyl. Thus, it is imperative that a nurse or a physician is in the room with the child undergoing the test at all times. The patient is most likely to report abdominal cramping and have a bowel movement as a result of the HAPC. It is not unusual for the child’s withholding behavior to be finally recognized as such by the parents once it is pointed out by the medical provider observing the study. Some children wrongly identify the cramping that is due to colonic contractions with pain or deny any sensation and elect to lay in bed instead of heading to the commode. The feedback from the medical provider as this is taking place has the potential to be very educational to both the patient and the parents .
A 6-h-long colonic manometry study with fasting, postprandial, and post-stimulant motility tracing
Identifiable Motility Patterns
High-amplitude propagating contractions (Fig. 9.4) are defined as contractions with an amplitude of greater than 80 mmHg, a duration of greater than 10 s, and propagation of 30 cm or more. They are expected to stop at the junction between sigmoid colon and rectum. They typically occur following meals, upon awakening, and can be induced by bisacodyl, glycerin, and other colonic irritants. They are more common in younger children  and in patients who have had a distal colonic resection, such as in patients after surgery for Hirschsprung’s disease . Recent studies have also shown that propagated contractions of varied amplitude can also be induced by saline infusion and distention of the right colon [21, 22]. Low-amplitude propagating contractions (LAPC ), in contrast to HAPC, are defined as having amplitude of less than 50 mmHg. They occur 45–120 times per 24 h and are typically 5–40 mmHg in amplitude. They occur significantly more often during the day than at night and, much like HAPC, increase in frequency following meals and upon waking [23, 24]. The function of LAPC is poorly understood. They are likely to be associated with lesser propulsive movement of intraluminal contents and have been reported to be involved with the transport of less viscous colonic contents, such as fluid or gas .
Example of a cluster of high-amplitude propagating contractions (HAPC ) recorded with an 8-recording-site water-perfused catheter
An increase in colonic motility, often measured as the “motility index” (a parameter which takes into account both frequency and amplitude of contractions), is expected after ingestion of a meal. The increase in motility involves both tonic and phasic contractions and may be difficult to quantify especially when the postprandial period is associated with motion artifacts. Evaluation of postprandial changes in colonic tone using the electronic barostat is not commonly done in children . Visual interpretation of the gastrocolonic response produces the maximum variability in interindividual interpretation of the test. On the other hand, there seems to be great concordance among different investigators in the recognition of HAPC . The median agreement regarding the overall interpretation of the colonic manometry in children being either normal or abnormal is 87 % .
Indications for the Study
To assess patients with constipation unresponsive to adequate medical therapy
To guide surgical interventions including placement of diverting stoma, segmental colonic resection, or formation of a conduit for administration of antegrade enemas
To evaluate the function of a disconnected colon before possible closure of a diverting ostomy
Chronic intestinal pseudo-obstruction
To determine if the colon is involved in the disease
To help plan which organs to transplant before a small bowel transplant
Hirschsprung’s disease and repaired imperforate anus
To clarify the pathophysiology of persistent symptoms after removal of the aganglionic segment or repair of anorectal malformations when there is no anatomical abnormality likely to explain the symptoms
Most children with constipation have functional constipation , a condition related to a maladaptive response to an uncomfortable defecation. A small proportion of children with constipation have symptoms unresponsive to aggressive medical and behavioral therapy which are severe enough to dramatically affect quality of life. In constipated children, especially in the presence of fecal incontinence, the chronicity of the symptoms can be very frustrating and may lead to distrust of the medical team and loss of self-esteem for the child. Colonic manometry is indicated for the evaluation of such children in order to discriminate normal from abnormal colonic motor function [28, 29] which may be associated with an underlying colonic neuromuscular disease (Fig. 9.5). This information can then be used to guide management . Resection of colonic segments found to have abnormal motor function leads to improvement in symptoms [31, 32]. Interestingly, there seems to be little or no correlation between manometric findings and histopathologic abnormalities, suggesting that our current ability to study the morphology and function of the enteric neuromusculature is limited .
Post-stimulant tracing of normal high-amplitude propagating contractions in the descending colon and abnormal non-propagating low-amplitude pressurization in the sigmoid colon
A study by Villareal et al. used HAPC as a marker for intact neuromuscular colonic function . The colonic manometry pattern, namely, the failure to demonstrate colonic HAPC, directed the providers to the formation of a diverting ostomy (ileostomy or colostomy). In patients who had evidence of a dilated colon with abnormal motility patterns, repeat manometry testing after a period of decompression (5–30 months) led to an improved motor function. Aspirot et al. evaluated the effect of chronic use of antegrade enemas on colonic motility in children and adolescents with severe constipation . All children with abnormal manometry prior to cecostomy placement showed improvement in colonic motility after using antegrade enemas for at least 1 year. Colonic manometry may also be used to predict clinical response to antegrade enemas. Retrospective studies have indicated that patients with HAPC and an intact gastrocolonic response are more likely to have a satisfactory outcome when receiving antegrade enemas [36, 37]. The propagated contractions seem to be essential to propel colonic contents during antegrade irrigation. However, the motor response is still not a guarantee for success, as even some patients with intact HAPC have had a poor outcome, indicating that motility pattern is important, but there are additional factors, such as compliance with the antegrade enema schedule and anorectal and pelvic floor function, possibly playing a role.
Chronic Intestinal Pseudo-obstruction
Chronic intestinal pseudo-obstruction (CIPO ) is a heterogeneous group of disorders that vary in cause, severity, course, and response to treatment. Di Lorenzo et al. studied patients with CIPO and found a subgroup of patients with chronic constipation as part of their CIPO symptomatology who had abnormal HAPC, absent gastrocolonic response, or complete lack of identifiable colonic motor activity . A thorough manometric evaluation including colonic manometry needs to be performed during the evaluation for possible isolated small bowel or multivisceral transplantation in children with CIPO, in order to assess which organs need to be transplanted and if a permanent diverting ileostomy will be needed .
Hirschsprung’s Disease and Anorectal Malformations
After resection of the abnormally innervated bowel in Hirschsprung’s disease, a large percentage of patients continue to struggle with abnormal defecatory function . Our approach to these patients, in collaboration with the surgical team, is to first evaluate for anatomical abnormalities, presence of a residual aganglionic zone, absence of dentate lines due to iatrogenic damage, and quality of anal sphincter function. A contrast enema is used to assess the anatomy and rule out obstructive Soave cuff, bowel stricture, or colonic twist. That is followed by an anorectal manometry , an examination of the anorectal area under general anesthesia, and a repeat full thickness biopsy to assess anal sphincter basal pressure, integrity of the anal canal, and presence and quality of ganglion cells, respectively. If necessary, colonic manometry is then performed for further evaluation. The findings on colonic manometry testing may be classified into four groups, each associated with different physiology . Each category directs different therapy: (1) The first group of patients has HAPC which progress through the neorectum all the way to the anal verge. The amplitude of the HAPC exceeds that of the voluntary contraction of the external anal sphincter. The result is incontinence or rectal pain as the patient attempts to retain the stool. (2) The second group has normal colonic motility with fear of defecation and stool withholding. The negative experience related to attempted defecation before surgical removal of the aganglionic segment or in the postoperative period may result in fecal retention. Identification of normal colonic manometry pattern in these children provides reassurance in the diagnosis and more confidence in the behavioral and medical treatment plan. (3) Abnormal colonic manometry with lack of HAPC, poorly propagating HAPCs, or simultaneous increases in pressure in the distal colon (Fig. 9.5) may be due to a neuropathic motility disorders proximal to the aganglionic segment, possibly associated with intestinal neuronal dysplasia  or with a common cavity phenomenon. (4) Finally, a small number of patients with defecation disorders postsurgery for Hirschsprung’s disease have normal colonic motility and a hypertensive anal sphincter. Successful treatment options for this subset of patients have included myectomy, which leads to irreversible destruction of the internal anal sphincter and potential risk of incontinence, and botulinum toxin injection into the hypertensive anal sphincter without the risk of permanent sphincter damage but with the need for repeated injections [43–45]. Similar findings have been described in children with continence disorders after anorectal malformations repair. Heikenen et al. have reported that propagation of excessive numbers of HAPCs into the neorectum as well as internal anal sphincter dysfunction can contribute to fecal incontinence in these children .
Additional Types of Studies
Ambulatory 24-h Colonic Manometry
A limitation of traditional colonic manometry studies is the duration of the study. There is a well-established circadian variation in colonic motility which is missed during short studies [24, 47–49]. Twenty-four-hour colonic manometry has been proposed as a more informative test which evaluates a time period felt to be more representative of the normal patient’s environment and eating and sleeping patterns. It has been performed in children using water-perfused probes , but it is best done using solid-state catheters which do not confine the patient to a restricted environment. Solid-state probes have been placed via colonoscopy with clips adhering to multiple sites of the colonic wall. The patient is allowed to ambulate, eat, and defecate in a hospital setting for 24 h with continuous manometric measurement. It is unclear how much the additional information collected during a 24-h study changes clinical management compared to a shorter study with meal ingestion and pharmacological stimulation.
Wireless Motility Capsule
This tool has been approved by the US Food and Drug Administration (FDA) for measurement of gastric emptying and whole gut transit time. Once swallowed, this fairly sizable capsule (diameter and length similar to a video capsule) is capable of measuring intraluminal pH, pressure, and temperature throughout the entire gastrointestinal tract. Data is transmitted to a data receiver and downloads to a computer for analysis. Gastric emptying is measured by timing the point from ingestion to the point where the pH rises above pH6, indicating that the capsule has left the acid environment of the stomach and has entered the more neutral pH of the duodenum . Because it has a single pressure measurement, propagation of motor activity cannot be defined. Wireless pH motility capsule has been found to be useful in evaluating colonic transit and has been validated in adults as an alternative to radiopaque markers as a tool to assess colonic transit . The exact role of the wireless pressure capsule in the evaluation of children with possible colonic dysmotility is still under investigation.