Understanding Functional Abdominal Pain Disorders in Children and Adolescents

By Beate Beinvogl, MD, MPH1, Samuel Nurko, MD, MPH1, Neil Schechter, MD2
1Division of Pediatric Gastroenterology
Center for Motility and Functional Gastrointestinal Disorders
2Department of Anesthesiology, Critical Care and Pain Medicine,
Boston Children’s Hospital
Boston, Massachusetts

Introduction
Acute abdominal pain, like any other type of acute pain, typically has the purpose to alert our body to danger and protect it from harmful consequences.1 However, there also exists a form of pain which is chronic and non-protective, where an abnormal pain response and pain perception itself becomes the disease. It is the equivalent of a malfunctioning fire alarm that continues to go off in the absence of an actual fire.

Functional gastrointestinal disorders (FGIDs) constitute a group of chronic conditions resulting from disorders of gastrointestinal function and/or abnormal central processing of information originating from the gastrointestinal tract. Per definition, in patients with FGIDs, there is no discovered pathology that explains the abdominal pain and associated symptoms. Chronic abdominal pain is a common symptom associated with FGIDs.

FGIDs are common in children and adolescents, with a prevalence of 0.3 - 25% in Western countries and a pooled prevalence of 13.5% (95% CI 6.2 – 11.9) worldwide.2-5 FGID related symptoms are common reasons for consultation with primary care and dominate pediatric gastroenterology subspecialty practice.6 Patients with FGIDs describe a decreased quality of life comparable to patients with organic disease such as inflammatory bowel disease.7 Some patients go on to develop severe disability, frequent school absenteeism and social isolation.8

Studies over the last decades have improved significantly our understanding of pain-predominant FGIDs to be the result of a complex interplay between environmental, biological and psychosocial factors superimposed on a genetic predisposition and early life events.9 These factors are thought to come together as the ‘perfect storm’ resulting in visceral hypersensitivity, an arousal state and changes in central pain processing, allowing minimal gastrointestinal triggers to result in the experience of disabling symptoms of chronic abdominal pain and other gastrointestinal symptoms such as nausea, vomiting, constipation or diarrhea.10 Sometimes patients are able to report an event or trigger at the onset of symptoms, such as an infection, concussion, injury, traumatizing event. Other times there is no obvious trigger. Understanding of FGIDs necessitates a paradigm shift away from the traditional medical model where every symptom has a cause, to a framework that integrates all aspect of an individual (genetics, sensitizing medical events, environmental and psychosocial factors, comorbidities) and recognizes that these all play a role in the experience of symptoms related to FGIDs. This framework is known as the bio-psycho-social model of disease.

Diagnostic approach
FGIDs are diagnosed based on the Rome IV criteria, which provide a positive symptom-based guideline to the diagnosis.10  FGIDs associated with abdominal pain are termed functional abdominal pain disorders (FAP disorders) and can be further subdivided into four groups based on the associated gastrointestinal symptoms: functional dyspepsia, irritable bowel syndrome, abdominal migraine and functional abdominal pain not otherwise specified, though a significant degree of overlap between these conditions exists. (Table 1)10

Table 1. Rome IV Criteria for Functional abdominal pain disorders10

Functional dyspepsia
Must include one or more of the following bothersome symptoms at least four days per month for at least two months:

  1. Postprandial fullness
  2. Early satiety
  3. Epigastric pain or burning not associated with defecation
  4. After appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

Subtypes:

  1. Postprandial distress syndrome: bothersome postprandial fullness or early satiation that prevents finishing a regular meal. Supportive features include upper abdominal bloating, postprandial nausea, or excessive belching
  2. Epigastric pain syndrome: includes bothersome (severe enough to interfere with normal activities) pain or burning localized to the epigastrium. The pain is not generalized or localized to other abdominal or chest regions and is not relieved by defecation or passage of flatus. Supportive criteria can include burning quality of the pain but without a retrosternal component and the pain commonly induced or relieved by ingestion of a meal but may occur while fasting.

Irritable bowel syndrome
Must include all of the following:

  1. Abdominal pain at least four days per month associated over at least two months with one or more of the following:
    a. Related to defecation
    b. A change in frequency of stool
    c. A change in form (appearance) of stool
  2. In children with constipation, the pain does not resolve with resolution of the constipation
  3. After appropriate evaluation, the symptoms cannot be fully explained by another medical condition

Abdominal migraine
Must include all of the following occurring at least twice for at least six months before diagnosis:

  1. Paroxysmal episodes of intense, acute periumbilical, midline or diffuse abdominal pain lasting one hour or more
  2. Episodes are separated by weeks to months.
  3. The pain is incapacitating and interferes with normal activities
  4. Stereotypical pattern and symptoms in the individual patient
  5. The pain is associated with 2 or more of the following:
    a. Anorexia
    b. Nausea
    c. Vomiting
    d. Headache
    e. Photophobia
    f. Pallor
  6. After appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

Functional abdominal pain not otherwise specified
Must be fulfilled at least four times per month for at least two months and include all of the following:

  1. Episodic or continuous abdominal pain that does not occur solely during physiologic events (eg, eating, menses)
  2. Insufficient criteria for irritable bowel syndrome, functional dyspepsia, or abdominal migraine
  3. After appropriate evaluation, the abdominal pain cannot be fully explained by another medical condition

Patients meeting criteria for a specific FAP disorder in the absence of another medical condition that may explain the symptoms after appropriate medical evaluation, can be diagnosed as such.10 Historically FAP disorders were thought to be a diagnosis of exclusion, leading to excessive testing. It is only in the most recent revision of the Rome criteria (Rome IV), which recommends appropriate evaluation, thereby allowing for selective or no testing and in the absence of alarm symptoms, allows for the diagnosis to be made as early as at the first visit.10 However, clinical experience shows that both medical providers and affected patients often have difficulty making and accepting the diagnosis of a FAP disorder, probably at least in part due to the lack of a biomarker or confirmatory test. Patients still frequently undergo extensive and costly testing in search for the ‘cause’ of their symptoms prior to being given the diagnosis, despite studies showing that extensive testing in the absence of warning signs does not change the diagnosis or outcome.8,11,12

In patients with suspected FAP disorders, an individualized understanding of each patient, including biological and psychosocial aspects of their illness is important. This includes taking a detailed history is essential to understand the pain characteristics and associated gastrointestinal symptoms. Per definition, chronic abdominal pain and/or gastrointestinal symptoms must occur at least four days per week over the course of at least two months.10 Patient often complain of constant or recurrent episodic pain and/or can identify triggers of pain such as eating, defecation, movement, stress, as well as relieving factors. A detailed review of systems is important, as patients frequently have comorbidities such as chronic headaches, fibromyalgia, chronic fatigue, postural orthostatic tachycardia syndrome, dysmenorrhea, anxiety or depression. A thorough psychosocial history helps understand other potential exacerbating factors of pain such as anxiety, school avoidance, learning difficulties, depression. Patient with functional gastrointestinal disorders may appear sad and report severe pain and discomfort, but are typically non-toxic with normal vital signs. It is important, however, to acknowledge the pain as ‘real’ and never doubt the pain severity in order to maintain a good therapeutic relationship, which is key in treatment success.

A careful physical exam should be performed, aimed at identifying any triggers of pain and ruling out differential diagnoses. Alarm symptoms such as unintentional weight loss, significant or bilious vomiting, chronic severe diarrhea, gastrointestinal bleeding, fevers, right upper or right lower quadrant abdominal pain, hepatosplenomegaly, fullness or palpable masses, costovertebral tenderness, delayed puberty, poor growth, night time symptoms awaking patients from sleep, other abnormal physical findings and a family history of inflammatory bowel disease should prompt further work up as patient with these features have a higher prevalence of organic disease.13 Any further testing or empiric treatment should be focused to rule out specific differential diagnoses or potential triggers of pain such as celiac disease or non-celiac gluten sensitivity, disaccharidase deficiencies, abdominal wall pain, gastritis, peptic ulcer disease, esophagitis, eosinophilic gastroenteritis, giardiasis. It should be noted, however, that FAP disorders can coexist with other medical diagnoses including other gastrointestinal disorders such as inflammatory bowel disease, or nonspecific findings on testing.14,15

Therapeutic approach
As the basis for treatment, it is essential to establish a good therapeutic alliance. It is important to acknowledge that the patient’s pain experience is real, not imagined or “in their head”, and to provide an explanation for the symptoms, as well as providing reassurance. Education is essential to change the framework away from the medical model, where pain is interpreted as an alarm sign of impending harm, towards the understanding that pain itself is the illness in the form of abnormal or dysfunctional pain signaling and perception. It is important to understand and explain to patients that this type of chronic abdominal pain is a non-protective, hurtful but not harmful pain. In this model of chronic abdominal pain, diagnostic evaluations are a means to identify triggers of the abnormal pain signaling as opposed to the search for the cause of pain.

Because FAP disorders result from a complex interplay of brain, gut, genetics and environment, a multimodal and ideally multidisciplinary treatment approach should be taken.8,9,16,17 Treatment is aimed at eliminating triggers of pain to minimize the arousal state, reduce visceral hypersensitivity and modulate pain with the help of both pharmacologic and non-pharmacologic strategies.18-20 Learning coping strategies to manage the discomforts related to FAP disorders is essential to minimize symptom-related disability. In patients with healthy coping skills, signals from the frontal lobes in the brain may reduce pain transmission to the sensory cortex. On the other hand, however, patients with poor coping skills, academic or social stress, coexisting mental health conditions are therefore at higher risk of functional disability from abdominal pain.21

Psychological Interventions
Cognitive behavioral therapy specifically has been shown to be one of the most effective psychological interventions for the treatment of chronic pain, including pain associated with a pediatric FGID.22-24 Internet-based therapy sessions may be of value in the treatment of IBS.25 Hypnotherapy has also been shown efficatious.26

Other Non-pharmacologic Interventions
There is some evidence to support the efficacy of dietary changes such as restricting poorly absorbable carbohydrates (low-FODMAP diet in IBS) and supplementing certain strains of probiotics.19,27 Non-invasive neurostimulation appears to be a promising technique for the treatment of FAP disorders in children.28 Physical activity is important for conditioning and can be prescribed in the form of a graduated exercise program. A transcutaneous electrical nerve stimulation device (TENS unit) can be used.

Pharmacologic Interventions
Evidence showing efficacy of pharmacologic interventions for FAP disorders in children and adolescents is limited. A high placebo response rate of about 40% in pediatric patients with FAP disorders should be kept in mind when interpreting study results.18,29  Commonly used pharmacologic interventions include the use of laxatives or anti-diarrheals to regulate defecation, antibiotics and probiotics for bacterial overgrowth/dysbiosis, proton pump inhibitors or histamine-2 receptor blockers to treat gastritis or esophagitis, cyproheptadine to increase gastric accommodation, anti-emetics for chronic nausea, and/or promotility agents for gastroparesis. Antispasmodics and peppermint oil may be helpful to reduce abdominal cramping. Central pain modulators such as gabapentin/pregabalin or antidepressants (tricyclic antidepressants, selective serotonin reuptake inhibitors) may be helpful in reducing pain signaling.18,20

Treatment of psychiatric and other chronic pain comorbidities is essential. Headaches, chronic musculoskeletal pain, fibromyalgia, anterior cutaneous nerve entrapment are frequently seen in patients with FAP disorders and it is essential to treat these adequately to reduce the overall arousal state. Anxiety or depression often negatively affect pain perception and pain modulation.
Once the concept of chronic pain as a ‘false alarm’ is understood and accepted as a real and hurtful but not harmful pain, it becomes clear that the pain should not be a hindrance to activity and should in fact be encouraged. Systematic school reintegration for those who are missing school is essential. While most patients do well over time with outpatient treatment, there is a subgroup of patients that go on to be severely disabled and may require a more intensified rehabilitative approach in specialized ambulatory or inpatient programs.8

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