Key points

Chronic abdominal pain continues to be one of the most common problems seen by pediatricians and pediatric gastroenterologists. Globally, irritable bowel syndrome (IBS) seems to affect 11% of the population, with 30% of these individuals presenting for medical care. In a community-based study from 1996, 13% of middle school students and 17% of high school students experienced pain on a weekly basis. A more recent study used online questionnaires and the ROME III criteria. In this study, parents of children living in the United States between the ages of 4 years and 18 years were asked to report on gastrointestinal symptoms ; 23.1% of children qualified for at least 1 FGID. FGIDs account for approximately 50% of pediatric gastroenterology consultations.

Abdominal pain continues to be a frustrating presenting symptom, putting strain on the current fast-paced health care environment. Diagnosis and treatment of a child with abdominal pain take time—time for listening, counseling, and education; time that is difficult to find in current practice settings. A vast majority of patients who present for evaluation of abdominal pain do not have organic disease in the classic sense and fall into a functional category.

Many providers still believe that children with chronic abdominal pain are anxious or stressed. According a survey by the American Academy of Pediatrics and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition, 16% of the 300 pediatricians surveyed thought that functional abdominal pain was a wastebasket diagnosis. Only 11% of these pediatricians thought that functional abdominal pain was a specific diagnosis based on clear criteria. Any of these preconceptions has an impact on the physician-patient relationship and potentially affects future therapeutic interaction.

FGIDs have a significant impact on those effected. FGIDs lead to significant difficulties with long-term comorbidities, including depression anxiety, lifetime psychiatric disorders, social phobia, and somatic complaints. The distinction between organic disease and nonorganic disease (FGIDs) is a spurious one. Research continues to support the understanding that these disorders are related to alterations in the enteric nervous system (ENS) and in the modulation between the ENS and the CNS, alterations that have an organic etiology through the modulation of neurotransmitters, receptors, and cellular processing pathways involved in the nervous system.

Abdominal pain is best understood within the framework of the biopsychosocial model of disease. The biopsychosocial model emphasizes the multifactorial nature of abdominal pain, including genetic, environmental, social, and psychological components. Treatment plans need to develop and adapt over time and be extremely individualized. As understanding of the pathophysiology of FGIDs increases, there will be a larger repertoire of therapies from which to select. This article reviews current understanding of pain-related FGIDS and the etiology, pathophysiology, and treatment modalities available.

Etiology

The possible causes of abdominal pain in children are numerous, ranging from benign disorders to life-threatening surgical emergencies. Abdominal pain may arise from disorders in multiple organ systems, including the pulmonary, gastrointestinal, urologic, and gynecologic systems. Infectious, neoplastic, metabolic, and anatomic mechanisms may all lead to the presenting symptom of abdominal pain ( Table 1 ) Patients and families are left anxious. Providers are concerned that they may be missing a diagnosis. These concerns often lead to numerous referrals and ongoing potentially invasive testing. Fortunately, there are a several alarm symptoms that help practitioners differentiate those children with organic disease, who requiring further investigation from those with FGIDs ( Box 1 ). Without these symptoms, extensive testing is unlikely to uncover other disorders.

Etiology

The possible causes of abdominal pain in children are numerous, ranging from benign disorders to life-threatening surgical emergencies. Abdominal pain may arise from disorders in multiple organ systems, including the pulmonary, gastrointestinal, urologic, and gynecologic systems. Infectious, neoplastic, metabolic, and anatomic mechanisms may all lead to the presenting symptom of abdominal pain ( Table 1 ) Patients and families are left anxious. Providers are concerned that they may be missing a diagnosis. These concerns often lead to numerous referrals and ongoing potentially invasive testing. Fortunately, there are a several alarm symptoms that help practitioners differentiate those children with organic disease, who requiring further investigation from those with FGIDs ( Box 1 ). Without these symptoms, extensive testing is unlikely to uncover other disorders.

Evaluation

The evaluation of a patient with abdominal pain begins with a detailed history and physical examination. Patients often describe their symptoms using “diagnoses,” such as “I have been having problems with reflux.” Providers must focus specifically on each symptom. How long has the pain been occurring? Has the pain gotten better or worse or remained stable? What is the pain’s location? Is the pain associated with meals or sleep? Are there any specific triggers that worsen or alleviate the pain? History and physical examination should always include review of alarm symptoms, which may guide a provider to more specific testing (see Box 1 ). Clinical judgment should be used, however, in this evaluation and these alarm symptoms should be seen in the context of the entire history. Finally, evaluation of the patient’s functioning, although it often does not indicate the ultimate diagnosis, provides clues as to child and parent coping strategies.

At minimum, basic laboratory studies should include a complete blood cell count and urinalysis. Depending on the history, a complete metabolic panel, amylase, lipase, erythrocyte sedimentation rate, C-reactive protein, or thyroid function testing may be indicated.

In the appropriate clinical setting, the practitioner needs to evaluate for Infectious causes, such as Giardia and other parasitic, bacterial, and viral diseases.

Many patients with IBS present with diarrhea. In children, this may raise concerns for inflammatory bowel disease. Fecal calprotectin has become a more common screening test for mucosal inflammation with values of less than 50 mg/g stool, suggesting that inflammation is unlikely.

Although controversial, screening for celiac disease is recommended in the current Rome IV. In a prospective cohort study, the prevalence of celiac disease was 4 times higher in patients with IBS compared with the general population.

Carbohydrate malabsorption may lead to abdominal pain, bloating, and diarrhea, symptoms that mimic IBS. The most common disaccharidase deficiency is primary lactase deficiency. Before more formal testing, a brief period of a lactose elimination diet should be considered in patients with compatible symptoms. Endoscopic biopsies may be sent for measured disaccharidase activity. Breath testing is a more functional test and is helpful in determining malabsorption of the tested disaccharide. Patients may be enzyme deficient or malabsorb carbohydrate; however, these abnormalities do not necessarily correlate with intolerance and symptoms.

Routine radiographic studies have minimal yield in patients with abdominal pain and no alarm symptoms. Abdominal radiographs may help define a pneumonia, demonstrate free air, and help evaluate intestinal air or access stool burden. Studies have indicated that without alarm symptoms, ultrasound has little utility in differentiating a patient with organic disease from functional causes. One study demonstrated that abdominal/pelvic ultrasound in patients with abdominal pain and no alarm symptoms only detected abnormalities in 1%. Recent studies on cancer risks in children receiving CT have led to a move to limit its use as an investigational tool for abdominal pain.

More invasive testing, such as endoscopy, remains controversial. Endoscopy in patients with chronic abdominal pain may find abnormalities 25% to 56% of the time; however, the presence of inflammation may not predict successful resolution of the problem. There is little evidence that a normal endoscopy in patients without alarm symptoms provides benefit in the management of children with abdominal pain. A recent study demonstrated that a negative endoscopy did not affect the persistence, frequency, or intensity of abdominal pain. A negative endoscopy did not lead to improvement in school absenteeism or disruption of daily functioning.

Fortunately, classification systems, such as ROME IV, exist to help physicians make a diagnosis of FGIDs in a proactive manner and not by exclusion.

Rome IV

Approximately 25 years ago, an international group of clinical practitioners and researchers met to establish a classification system for FGIDs, which would help in the diagnosis, the standardization of research, and dissemination of information on these common but poorly understood disorders. The symptoms-based classification was selected because it was thought the most relevant to clinical practice and less tied to a single pathophysiologic mechanism (ie, motility). The process of consensus was used to revise these criteria in 1999, 2006, and most recently 2016 with the publication of Rome IV . Rome IV now divides pediatric FGIDs into 3 forms :

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  Nausea and vomiting disorders

  
  
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  Abdominal pain disorders

  
  
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  Defecation disorders

Functional abdominal pain disorders (FAPDs) in children and adolescents

In Rome IV, the committee reevaluated the terminology used in describing pain-based FGIDs.

The term, functional abdominal pain , was not specific enough a descriptor for either clinical or research purposes. The terminology has been changed to FAPDs, which is inclusive of FD, IBS, functional abdominal pain–not otherwise specified (FAP-NOS), and abdominal migraine. Each of these disorders has been carefully defined by the committee. The last phrase of each definition was altered to ensure that FAPD did not become a diagnosis of exclusion and mandates an appropriate, selective evaluation.

FD is defined as

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  Bothersome symptoms at least 4 times a month for at least 2 months, which include

  
  
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  Postprandial fullness

  
  
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  Early satiation

  
  
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  Epigastric pain or burning not associated with stooling

  
  
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  After appropriate evaluation, symptoms that cannot be fully explained by another medical condition

IBS is defined as

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  Abdominal pain at least 4 days per month over at least 2 months associated with 1 or more of the following:

  
  
  
  
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    Related to defecation

    
    
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    A change in stool frequency

    
    
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    A change in stool form

  
  

In children with abdominal pain and constipation, the pain does not resolve with resolution of the constipation and, after appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

IBS has been divided into 4 subtypes based on the Bristol Stool Form Scale :

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  IBS-C — constipation predominate

  
  
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  IBS-D — diarrhea predominate

  
  
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  IBS-M — mixed stool types

  
  
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  IBS-U — unsubtyped

Subtyping of IBS has been important in directing therapy. Many current therapies are being targeted to treat and approved for use with specific subtypes.

FAP-NOS is defined as abdominal pain occurring at least 4 times a month and all of the following:

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  Episodic or continuous abdominal pain that does not occur solely during physiologic events

  
  
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  Insufficient criteria for IBS, functional dyspepsia, or abdominal migraine—after appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

Pathophysiology

FGIDs are the result of a complex interplay of factors that affect the individual and combine to produce disease. This paradigm is the biopsychosocial conceptual model. This model defines FGIDs as gastrointestinal symptoms resulting from a combination of

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  Early life events, which may include

  
  
  
  
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    Genetics

    
    
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    Environmental factors (trauma, infections, parental behaviors)

  
  
  
  
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  Psychosocial factors

  
  
  
  
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    Life stress

    
    
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    Personality traits

    
    
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    Psychological state

    
    
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    Coping

    
    
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    Social support

  
  
  
  
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  Physiologic factors

  
  
  
  
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    Motility disturbance

    
    
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    Visceral hypersensitivity

    
    
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    Altered CNS processing

    
    
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    Altered mucosal and immune function

    
    
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    Altered gut microbiota