What You Need to Know About Functional Constipation and Fecal Incontinence

Chronic constipation in young children that does not have an identifiable cause is called functional constipation (sometimes referred to as idiopathic constipation). This occurs when a child has difficulty passing stool when there are no apparent signs of physical or anatomical problems. Children with functional constipation may be experiencing emotional and neurological problems, but otherwise are physically healthy and anatomically normal.

In some cases, chronic constipation (with or without fecal soiling), can be a sign of more serious underlying disorders, including anorectal malformations, Hirschsprung disease, spinal cord problems and colonic dysmotility. In a typical child’s anatomy, the muscles that control fecal continence function normally when a child has an intact anal sensory mechanism that triggers when they need to go to the bathroom. This sensation is called the rectoanal inhibitory reflex (RAIR). When the RAIR is absent, the sphincter fails to relax in response to a full rectum. Instead, the sphincter tightens up, holding in the stool. For children with anorectal malformations, Hirschsprung disease or spinal cord abnormalities, this sensation often does not work appropriately or is absent. 

To determine the right treatment plan, it’s important to distinguish whether fecal incontinence is related to these more serious conditions or if it’s happening due to chronic constipation alone.

Yes, functional constipation can occur at any age in childhood. However, different criteria for a diagnosis exists for children who are less than four years of age and for those over four years old.

For infants and toddlers up to four years old, two of the following symptoms must be present for at least one month to receive a diagnosis of functional constipation:

• A maximum of two stools per week
• A history of excessive stool retention
• Difficult and painful bowel movements (which promotes withholding behavior and stool accumulation that can perpetuate the cycle of constipation)
• Large diameter stools or a large fecal mass in the rectum

For children four years old and older, two or more of the following symptoms must be present each week for at least one month to receive a diagnosis: 

• A maximum of two stools per week
• An episode of incontinence
• Difficult and painful bowel movements (which promotes withholding behavior and stool accumulation that can perpetuate the cycle of constipation)
• Large diameter stools or a large fecal mass in the rectum
• Volitional stool retention

Achieving fecal continence depends on three main factors: 

• The function of the anal sphincter muscles (internal and external)
• Anal canal sensation (RAIR)
• Reliable colonic motility (intestinal contractions)

When functioning normally, the internal sphincter muscle maintains a closed anus most of the time. When stool is present in the rectum, the stool is detected, and the internal sphincter relaxes.  It is at this time that the voluntary muscles take over the role of closing the anus, holding in the stool until the appropriate time (when these muscles are allowed to relax).  If the internal sphincter muscle is not functioning well, this “uncoordinated relaxation” can lead to constipation. 

To achieve normal fecal continence, a treatment plan may include non-surgical and/or surgical treatments, depending on the severity of the child’s condition.

Non-surgical treatments will include a bowel management program that may involve:

• Administering medications (such as laxatives) when needed to soften stool and enemas to relax rectal muscles.
• Customized nutrition plans developed by dietitians that are high in fiber and offer helpful tips for parents. The chosen diet may need to either promote or slow down stooling.
• Education for families on how continence works and why some children experience soiling as well as connecting parents with support groups.
• Establishing a bathroom schedule and routine (based around the gastrocolic reflux, which is the connection of eating a meal and then coordinating with the colon getting ready to empty) to train your child to recognize their body cues and to avoid soiling and accidents.
• Setting up a reward system to help encourage your child to go to the bathroom.
• Access to social workers who provide assistance in making travel arrangements and accommodations for those attending a bowel management program from out of state or out of the country.

If these non-surgical treatments and interventions fail to work, surgery may be performed. Surgery is more common for children with more serious underlying conditions such as anorectal malformations, Hirschsprung disease or spinal cord abnormalities, but may be needed for those patients with functional constipation as well.

Distinguishing anatomic fecal incontinence from chronic constipation that causes overflow soiling is key to a successful treatment plan. 

Children with true anatomic fecal incontinence experience soiling because of a physiological or anatomic abnormality (including patients with anorectal malformations, Hirschsprung disease, and spinal cord problems). These children will likely need surgery to help restore bowel function and set them up to be able to be clean for stool. 

Children with functional constipation do not have any anatomical or physical abnormalities present. They experience soiling because of severe constipation combined with rectal impaction. However, these children have the potential for bowel control on their own through a bowel management treatment program that usually does not involve surgical intervention. Sometimes treatment to relax the sphincters using botulinum toxin (Botox) or surgery – which  can provide a route for a flush of the colon through the appendix – are very valuable additions to the medical treatment.

The ability to achieve fecal continence depends on the individual case of each child. Generally, children who have had surgery for anorectal malformations or Hirschsprung disease will have some level of deficiency or difficulty in their ability to achieve fecal continence. Hirschsprung patients may also need to “learn” how to overcome the inability to relax their sphincter muscles so they can achieve bowel control. Botulinum toxin (Botox) or an enema program may help with this sphincter dysfunction. For patients with an anorectal malformation, the status of their spine is a key determinant as to whether their colorectal anatomy functions well.

Most newborns pass their first stool (meconium) within 24 hours of birth. 98 percent of infants will pass their first meconium stool within 48 hours. However, premature infants may have a delayed passage of meconium without any underlying problem. 

A newborn who fails to pass stool within the first two days of life should be closely monitored and evaluated. This may involve a physical examination to rule out anorectal malformations or any other underlying problems. Several diagnostic techniques may be performed including a biopsy or water-soluble contrast enema to evaluate for conditions such as small left colon syndrome, meconium ileus (when stool is blocking the small intestine), meconium plug syndrome or Hirschsprung disease. 

If no anatomical issues are present, the cause of functional constipation in infants is typically around the time of transition from breast milk to formula or to the introduction of solid foods. An infant may have hard stools that are difficult and painful to pass. This traumatic experience may result in voluntary withholding of stool. This behavior is characterized by grunting, arching of the back, stiffening of the legs and the body.  

Infants with functional constipation may respond to the addition of fruit juices to their diet, such as prune juice. Changing formula (especially if the current formula contains iron) may be helpful. Some solid foods that are introduced to the infant’s diet such as rice cereal, bananas, or applesauce, may also be constipating and should be avoided. 

If dietary changes are unsuccessful, then a stool softener or a stimulant laxative should be added to the regimen. For infants with mild constipation, a trial of polyethylene glycol, milk of magnesia, lactulose or sorbitol should be considered. More effective treatment can usually be achieved by a stimulant laxative such as those containing senna with the goal of producing a soft and easy-to-pass daily bowel movement.

For infants with severe functional constipation, a history of anorectal malformation repair, or those who have had prior surgery for Hirschsprung disease, a stimulant laxative by itself or in addition to a stool softener should be used. Adding a water-soluble fiber also helps, as it makes the laxative more effective by providing a little bulk to the stool, so a more formed, yet soft, bowel movement can be passed.

It is important to be aware of a small group of infants who are exclusively breastfed who may not have a daily bowel movement. These patients may have a bowel movement once every two to 14 days (around an average of five days). They do not exhibit any discomfort and their stools range from soft to loose in consistency, and no intervention is required.

The onset of constipation in toddlers is often related to toilet training. If a toddler’s history, physical exam, and other diagnostic tests including a contrast enema do not reveal an anatomical reason for the constipation – and medical therapy is not effective – then anal sphincter and colonic motility studies may be conducted.

Anal sphincter and colonic motility studies will evaluate for several issues, including: 

• The function of the anal sphincters and whether they relax and tighten at the appropriate time
• For assessment of the colonic motility there are three main scenarios:
  
  • Normal or slow but with movement throughout the colon
  • Segmentally abnormal – one specific part of the colon does not work well, but the rest does
  • Diffusely abnormal – the entire colon moves too slowly

If a child is having incontinence for both urine and stool, or is having lower extremity neuromuscular symptoms, then imaging of the spinal cord with an MRI may be performed.

Treatment in this age group generally includes dietary modifications, teaching good toileting habits and use of stool softeners with or without stimulant laxatives. Toddlers with anorectal malformations usually require a more aggressive bowel management program, often with the use of rectal enemas. If these treatments do not work, the more definitive interventions are needed to either improve the function of the sphincters, or of the colon, or both.5

New onset of constipation in school age children is uncommon. Gastrointestinal specialists will need to determine whether it is truly a new issue or a chronic problem that has never been diagnosed or treated effectively. 

School age children that do experience functional constipation may have several physical, behavioral or psychosocial issues that are affecting them, including:

• Experiencing physical and/or sexual abuse
• Irritable bowel syndrome (IBS)
• Starting a new school 
• Tethered spinal cord or occult spina bifida