Motility

Pediatric Gastrointestinal Motility

Gastrointestinal Motility

Digestive System Diagram

Gastrointestinal (GI) motility is the action enabling the passage of food and waste products through the four main regions of the digestive system: esophagus, stomach, small intestine, and large intestine or colon. At each stage of the digestive process, from chewing and swallowing through absorption and elimination, the nervous system sends signals to muscles and other cells in each GI region to move the contents along in a synchronized process called peristalsis.

The four GI regions are separated by special muscles, or sphincters, which regulate the movement of material from one region to the next. Each region has a special function in the digestive process and each has its own distinct type of motility:

organs_digestive_system01

Peptic Stricture
  • The esophagus propels food from the mouth to the stomach in a process initiated by voluntary swallowing. The lower esophageal sphincter (LES) acts as a valve, relaxing during peristaltic contractions following each swallow, but normally remaining tightly closed to prevent the regurgitation or reflux of stomach contents.

organs_digestive_system01

Pyloric Antrum
  • The stomach temporarily stores ingested food while solids are gradually broken down into particles suitable for entry to the small intestine through the pyloric sphincter. Liquids move along quickly, while fatty foods take the longest. Muscular contractions vary according to the type and amount of food. Most of an average meal will have left the stomach in two hours.

Ileocecal Valve
  • The small intestine is where most nutrient absorption occurs. Muscular contractions continue for several hours as food is mixed and moved through at different rates. For example, high-fiber foods move through more quickly than high-fat foods. After most of the contents have entered the large intestine through the ileocecal valve, a slower series of powerful contractions continues between meals, especially at night, to clear residual material from the small intestine.

Anorectum
  • The large intestine stores the accumulating food residues while water and salts are absorbed, until the stretching of the rectum—by the resulting stool—induces relaxation of the anal sphincter and contents can be voluntarily discharged. Patterns of contractions in the colon are influenced by eating the next meal as a new cycle of digestion begins in the stomach. The bigger the meal, the more pronounced the response. Between food and fluid intake, gallons of fluid are dumped into the large intestine every day, with most water reabsorbed by the body. Most contractions of the colon are unsynchronized or non-peristaltic, and residues can remain in the colon normally for up to 30 hours, which means a lot of bacteria.

Abnormalities in the structure of function of these four GI regions at any stage in the digestive process, or in the systemic reaction to particular foods or invading microbes, can result in a GI motility disorder.

GI Motility Disorders

Disorders of GI motility in infants and children, as well as in adults, are most often associated with the following conditions, syndromes, and diseases. Diagnosis and treatment will vary according to the underlying symptoms, severity, and GI regions affected.

Motility Disorders of the Esophagus

An esophageal motility disorder can involve difficulty in swallowing, heartburn, regurgitation of food, reflux, or painful spasms produced by certain food allergies. Examples include gastroesophageal reflux disease (GERD), hiatal hernia, dysphagia, achalasia, and functional chest pain.

Motility Disorders of the Stomach

There are two general categories of stomach-related or gastric motility disorders: delayed gastric emptying (gastroparesis) and rapid gastric emptying (dumping syndrome), as well as functional dyspepsia.

Motility Disorders of the Small Intestine

Disorders of motility in the small intestine can produce symptoms of obstruction or blockage, such as bloating, pain, nausea, and vomiting. Any of these can result from weak or disorganized contractions caused by a variety of conditions generally categorized under intestinal dysmotility and intestinal pseudo-obstruction. When motility patterns fail to adequately sweep the upper part of the small intestine, small-bowel bacterial overgrowth can produce excess gases, resulting in diarrhea and bloating.

Motility Disorders of the Large Intestine

Disorders of motility in the large intestine produce symptoms of either constipation or diarrhea, incontinence, and dehydration. They may be the result of colitis, Hirschsprung’s disease or, more commonly, any of a spectrum of other conditions collectively described as irritable bowel syndrome (IBS) or the more severe inflammatory bowel disease (IBD).

GI Motility Testing

Symptoms alone cannot always be relied upon for accurate diagnosis of a particular patient’s motility disorder. Proper evaluation is important to correctly diagnose and properly treat a specific condition. Tests of motility are used to assess and identify abnormal patterns and physiology, usually with a first look at ruling out structural problems before proceeding to functional problems. For each region of the GI tract, there are different tests that assess different functions and provide different information, but the key categories of information provided by GI motility testing include:

  • Correct diagnosis of motility disorder
  • Guide for proper treatment
  • Patient prognosis

A Closer Look

Digestive system

Organs of the Digestive System

Constipation

As food moves through the colon, or large intestine, water is absorbed and waste products are formed as stool. Constipation occurs when too much water is absorbed by the colon or the colon’s contractions are weaker than normal.

Constipation is typically defined as having a bowel movement less than three times a week and usually involves difficult or painful elimination of hard and dry stools. It is a common problem for children, usually temporary and of minor concern, but severe cases can require treatment and may be signs of a more serious underlying problem. Since constipation may make a bowel movement more painful, a child may try to avoid having one. Constipation itself is a symptom, not a disease.

Symptoms of constipation can include:

  • Straining and flushing of the face while attempting bowel movement
  • Hard and dry bowel movements
  • No bowel movements at all for several days
  • Abdominal cramps and pain
  • Nausea
  • Vomiting
  • Weight loss
  • Traces of stool in the underwear (indicative of a backup in the rectum)

Bristol Stool Chart

Bristol Stool

Common causes of constipation can include:

  • Dehydration
  • Lack of dietary fiber
  • Lack of physical activity
  • Irritable bowel syndrome
  • Certain medications or overuse of laxatives
  • Changes in routine or stress
  • Ignoring or avoiding the urge for a bowel movement
  • Specific diseases or other problems with the colon, rectum, or intestinal function, including neurological disorders, metabolic or endocrine conditions, and other systemic disorders.

Treatment depends on age, severity, and ultimate diagnosis. More dietary fiber (from fruits, vegetables, or whole grains), improved liquid intake, and better exercise will often clear up the condition. Laxatives should only be given to children with a doctor’s approval.

Because constipation can be both a symptom and a cause of more serious conditions, a physician should be consulted if episodes last longer than three weeks, normal activities are impacted, painful tears or hemorrhoids appear, normal pushing is not effective in expelling stool, or liquid/soft stool leaks out of the anus.

Cyclic Vomiting Syndrome

Cyclic vomiting syndrome (CVS) involves bouts or cycles of severe nausea and vomiting that last for hours or even days, alternating with asymptomatic periods. CVS occurs mostly in children and has no known cause.

Some histories suggest that each episode tends to be similar to previous ones, starting at about the same time of day, of similar duration, and with the same symptoms at the same level of intensity. CVS usually starts between the ages of 3 and 7. In adults, episodes tend to occur less often than they do in children, but they last longer.

Because other diseases and disorders also cause cycles of vomiting, many cases of CVS remain undiagnosed or misdiagnosed until other, more common disorders are ruled out.

There are four phases in CVS:

  • Prodome Phase signals that nausea and vomiting are about to begin. Often marked by abdominal pain, this phase can last from a few minutes to several hours. Sometimes, medication can stop an episode in progress. Sometimes there is no warning.
  • Episode Phase includes nausea, vomiting, the inability to eat or drink, paleness, drowsiness, and exhaustion.
  • Recovery Phase begins when the episode stops, with the return of healthy color, appetite, and energy.
  • Symptom-Free Interval is the period without symptoms.

The most common trigger of a CVS episode is an infection, but colds, allergies, sinus problems, and the flu can trigger episodes in some people. Emotional stress or excitement in children can set off an episode. Certain foods, eating too much or too little, hot weather, exhaustion, and motion sickness can also trigger episodes.

The principal symptoms of CVS are severe vomiting, nausea, and retching or gagging. Other symptoms can include pallor, exhaustion, and listlessness. Sensitivity to light, headache, fever, dizziness, diarrhea, and abdominal pain may also accompany an episode. Sometimes, the nausea and vomiting are so severe that a person appears to be almost unconscious.

Recurrent vomiting may cause drooling and excessive thirst, but drinking water usually initiates more vomiting, although dilution of acid in the vomit may make the episode less painful. Continuous vomiting can result in dehydration through the loss of water and salts in the body.

Diagnosis is difficult because there are no specific tests to identify CVS, and it can take time to identify a pattern or cycle to the vomiting. A doctor will diagnose CVS by analyzing symptoms and medical history, and by excluding more common diseases or disorders with similar symptoms.

There is no cure for CVS, but there are various modes of treatment. Sometimes, it is possible to stop an episode from starting by taking ibuprofen to relieve abdominal pain, or using ranitidine or omeprazole to reduce stomach acid. Once an episode begins, treatment is mainly supportive, ranging from bed rest to hospitalization and intravenous rehydration, and even sedation. Symptom-free intervals are a good time to eliminate or treat known triggers. Because symptoms and triggers of CVS are similar to migraine headaches, medications for migraines such as propranol, cyproheptadine, or amitriptyline can sometimes help.

Complications of severe vomiting can include dehydration, electrolyte imbalance, peptic esophagitis, hematemesis, esophageal tearing, stomach bruising, and tooth decay.

Gastroesophageal Reflux Disease

When the lower esophageal sphincter (LES) fails to prevent gastroesophageal reflux (GER) or backing up of stomach acids and other contents into the esophagus, the lining of the esophagus can become irritated and even seriously damaged over time. The most common symptom is heartburn, which in infants may appear as difficult or painful swallowing, inconsolable crying, spitting up, and a refusal to eat. Up to one-third of babies have GER at some time, but almost all outgrow it within a year.

Gastroesophageal reflux disease (GERD) is a more serious form of GER caused by chronic weakening or improper functioning of the LES.

Gastroparesis

Also known as delayed gastric emptying, gastroparesis is the slowing or stopping of the movement of food through the digestive tract. In normal digestion, the stomach contracts to move food into the small intestine in a process controlled by the vagus nerve. If the nerve is damaged or the muscles of the stomach and intestines do not work properly, gastroparesis occurs.

Symptoms of gastroparesis can include:

  • Heartburn or gastroesophageal reflux
  • Nausea and vomiting
  • Fullness after a few bites of food
  • Weight loss and lack of appetite
  • Bloating
  • Abnormal blood glucose levels
  • Stomach spasms

Causes of gastroparesis can include:

  • Diabetes
  • Gastroesophageal reflux disease
  • Stomach surgery
  • Viral infection
  • Medications such as narcotics and anticholinergics
  • Smooth muscle disorders such as scleroderma and amyloidosis
  • Nervous systems disorders such as abdominal migraine and Parkinson’s
  • Metabolic disorders such as hypothyroidism

Reglan (metoclopramide) stimulates motility of the upper gastrointestinal tract without stimulating gastric, biliary, or pancreatic secretions. While its mode of action is unclear, it seems to sensitize tissues to the action of acetylcholine. The effect of metoclopramide on motility is not dependent on intact vagal innervation, but it can be abolished by anticholinergic drugs.

Gastroenteritis

Gastroenteritis is a general term referring to inflammation or infection of the GI tract, primarily the stomach and intestines. It is usually of acute onset, lasting less than 10 days, and tends to be self-limiting. If inflammation is limited to the stomach, it is called gastritis. If limited to the small intestine, it is called enteritis.

Symptoms of gastroenteritis can include:

  • Loss of appetite
  • Lethargy
  • Fever
  • Diarrhea
  • Loose or watery stool
  • Stomach cramps
  • Dehydration
  • Sleeplessness
  • Low fever and headache
  • Mucous or blood in the stool
  • Vomiting

Causes of gastroenteritis can include:

  • Viral infection
  • Bacterial infection
  • Parasitic infection
  • Poor feeding in infants

Viruses are responsible for the majority of cases of gastroenteritis in children, with rotavirus being the most common of all. Viruses are easily transmitted from person to person by close contact and inadequate hygiene.

Gastroenteritis can also occur in the form of food poisoning, with vomiting more likely than diarrhea, or other GI infections with diarrhea more common than vomiting. Common bacteria responsible for gastroenteritis include salmonella, shigella, staphylococcus, campylobacter, and cryptosporidium. E. coli in contaminated water or improperly handled raw meat is another common bacterial agent.

Also known as giardi for the culprit protozoa passed via the fecal-oral route through personal contact and contaminated food and water, giardiasis is an increasingly common cause of gastroenteritis, infecting hundreds of millions of people worldwide. Day-care environments, rural settlements, and wilderness areas are typical reservoirs, but only about a third of infected people exhibit symptoms.

The principal treatment for gastroenteritis is rehydration and elimination of sources of infection. Symptoms may continue for up to a week, with bowel movements returning to normal a week after that. When symptoms remain severe, a doctor may prescribe antimicrobial therapy. Sometimes, combining an antimicrobial drug and an antimotility drug seems to be effective more rapidly, but antimotility agents risk the delay of flushing of toxins for the intestines. Oral rehydration and a clean environment remain the preferred treatment for children.

Hirschsprung’s Disease

hirschsprung's diseaseHirschsprung’s disease (HD), also called aganglionic megacolon, is a disorder of the large intestine and always develops before birth. The principal symptom is constipation, but some children with HD cannot have bowel movements at all, as the stool creates a blockage. If not treated, stool blockage can lead to more serious problems of infection and even bursting of the colon.

In a normal intestine, muscles push the stool to the anus and elimination from the body. Dedicated nerves cells, or ganglion cells, signal the muscles to push. A person with HD is born without these nerve cells in the lower part of the intestine. There is no known cause for the cells to have ceased growing during fetal development, but there are genetic implications, even if neither parent has HD.

Symptoms of HD may show up in early infancy, when newborns fail to start normal bowel movements. If the length of the colon affected is short, serious symptoms may not appear until later in life, but children and teenagers with HD will always have had problems with constipation.

Tests for HD can include barium enema, manometry, or biopsy. Treatment is surgical, in which the diseased portion of the colon is removed and the remaining healthy part is attached to the anus by a pull-through operation. Whether a ileostomy (removal of the entire colon) or colostomy (removal of part of the colon) is performed, temporary use of a stoma and bag is sometimes required until the intestine is healthy enough for reattachment to the anus.

Nine out of 10 children with HD pass stool normally after a pull-through and lead normal lives. Complications, particularly with long-segment HD, can include continued constipation or diarrhea, and recurring infection of the large intestine (entercolitis).

Inflammatory Bowel Disease

ulcerative colitisInflammatory bowel disease (IBD) is a group of inflammatory conditions of the large intestine, and in some cases, the small intestine. It should not be confused with the less severe inflammatory bowel syndrome (IBS). About one-third of all persons with IBD have onset before adulthood, with the peak age between 10–30 years. It does tend to run in families.

Symptoms of IBD include pain, diarrhea, vomiting, and weight loss. Diagnosis is generally by colonoscopy with biopsy. Complications include toxic megacolon and bowel perforation, as well as an increased risk of colorectal cancer. Flare-ups of some forms of IBD can occur even after symptoms are successfully controlled by immunosuppression and steroids.

The number of cases of IBD has increased as the number of parasitic infections has fallen, and IBD is rare where parasitic infections are common, so it has been hypothesized that some forms of IBD may be an autoimmune response caused by an overactive immune system lacking traditional parasitic targets.

Irritable Bowel Syndrome

information of colonAlso known as spastic colon, irritable bowel syndrome (IBS) is a functional bowel disorder involving abdominal pain and irregular bowel habits—not obviously related to well-recognized causes or routinely testable abnormalities, and not to be confused with the more serious IBD.

Medications include stool softeners and laxatives for IBS constipation, or antispasmodics for IBS diarrhea or cramps.

Some drugs affecting serotonin in the intestines can help reduce symptoms of IBS by stimulating intestinal motility. Agonists may help relieve IBS constipation and antagonists may help relieve IBS diarrhea, but both classes of drug are problematic for risks and effectiveness, especially in cases of IBS misdiagnosis.

Phases and Agents of Intestinal Digestion Affecting Motility

Delivery of Gastric Chyme to Duodenum

Several key hormones and other agents influence gastric emptying from the stomach to the duodenum of the small intestine.

Hormones

  • Gastrin is released by the stomach in response to proteins, and acts to increase gastric motility and emptying. Low levels of stomach acid inhibit gastrin release.
  • Epinephrine (adrenalin) is released from the adrenal medulla during stress, and acts to decrease gastric motility and emptying.
  • Secretin is released from the duodenum and acts to decrease gastric motility and emptying.
  • Gastric inhibitory peptide (GIP) is released from the duodenum and acts to decrease gastric motility and emptying.

Neurotransmitters

  • Acetylcholine is released via the parasympathetic nervous system and acts to increase gastric motility and emptying.
  • Norepinephrine is released via the sympathetic nervous system and acts to decrease gastric motility and emptying.

Other Substances

  • Fats emptied into the duodenum act to decrease gastric motility and emptying by causing release of GIP.
  • Acids emptied into the duodenum act to decrease gastric motility and emptying.

Duodenal Phase of Digestion (First Intestinal Phase)

The pancreas and liver release a variety of hormones and other agents into the duodenum of the small intestine, entering through the common bile duct. Imbalances or disturbances in the absolute or relative levels of these agents, or dysfunction of their secreting organs, can affect motility through the small intestine.

Duodenal Release of Hormones

  • Secretin is a peptide hormone triggered in response to acidic chyme from the stomach, and acts to neutralize acid levels and counteract blood glucose spikes. It also has an optimizing effect on CCK.
  • Cholesystokinin (CCK) is a peptide hormone that affects the digestion of fat, protein, and carbohydrates, and also acts as a hunger suppressant. It stimulates the release of pancreatic enzymes, liver bile, the contraction of the gallbladder, and relaxation of the Oddi’s sphincter.

Bile duct

Bile Duct

Bile Secretion and Release

  • Bile is continuously produced and secreted by the liver. Stored and concentrated in the gallbladder between meals, it is released through Oddi’s sphincter into the duodenum when chyme enters from the stomach. Bile helps emulsify fats, and is important in the absorption of fat-soluble vitamins. It further neutralizes excess stomach acid before it enters the final section of the small intestine (ileum). Bile salts are also bactericidal to invading microbes. In the absence of bile, fats become indigestible and are excreted in the feces, which can cause problems of motility and degrade further absorption of nutrients.

Bile duct

Bile Duct

Digestion and Absorption (Second Intestinal Phase)

The jejunum is central of the divisions of the small intestine, lying between the duodenum and the ileum. This is where the majority of nutrients are digested and absorbed through the action of numerous enzymes acting on proteins, fats, and carbohydrates. Imbalances here can cause disorders of motility as well as inadequate nutrition.

Small Intestinal Motility

The small intestine acts to ensure absorption of nutrient and aboral (away from the mouth) movement of content.

Types of small intestine movements include:

  • Segmentation, which produces movements of villi in digestion and absorption.
  • Peristalsis, or contractile waves, move chyme aborally to the large intestine, sweeping the small intestine clean in 8–10 hours.

Large Intestine and Water Reabsorption

Water and salts are reabsorbed by the walls of the large intestine, while bacteria (intestinal flora) break down remaining undigested nutrients. The large intestine houses over 700 species of bacteria that perform a variety of functions. A mucous layer protects the large intestine from foreign bacteria. The immune system produces antibodies, which may work against normal “friendly” flora, but can also be effective against related pathogens. Imbalances here can also result in infection-related problems with motility.

Two major types of intestinal flora include:

  • Fermentative bacteria, which break down undigested carbohydrates.
  • Putrefactive bacteria, which break down undigested proteins, releasing hydrogen sulfide and methane gas.

A balanced diet, effective digestion, and normal motility promote fermentative and putrefactive equilibrium.

Large Intestine Motility

The large intestine acts to ensure the absorption of fluids and salts as matter is condensed and stored in the rectum for normal elimination.

Types of large intestine movements include:

  • Segmentation, which produces movements of villi in propulsion and absorption.
  • Peristaltic, which rushes further compact matter aborally 2–3 times a day.

Links to Key Motility Sites

Citations

  1. Rome III Journal Articles on Gastroenterology

Selected IFFGD Publications

  1. Whitehead, W.E. Gastrointestinal Motility Disorders of the Esophagus and Stomach. IFFGD Brochure 510: 2001.
  2. Jaffin B.W. Esophageal Motility Disorders. IFFGD Fact Sheet 518; 1998.