Abdominal pain is one of the most common symptoms in children and adolescents and is estimated to account for approximately 5% of unscheduled office visits.[1] Acute abdominal pain may require medical or surgical intervention to prevent disability or even death. The precise number of children who experience acute abdominal pain is unknown, but each year, 4 in 1000 children undergo surgery for suspected appendicitis. More commonly, abdominal pain is a recurrent symptom not associated with physical disability or mortality.[2] Recurrent abdominal pain (RAP) as a recognizable entity in childhood was first characterized by Apley and Naish as pain that occurs at least three times over a period of 3 or more months severely enough to affect daily activities in children older than 3 years.[3] The prevalence of RAP is estimated to be between 0.3% and 19%, although in large studies the prevalence is far lower, 0.3% to 8%.[4] One reason for the broad range may be the lack of uniformity of criteria for making the diagnosis of RAP; definitions may be too broad and may include other functional gastrointestinal disorders, such as functional dyspepsia.[4]

Although a multidimensional measurement of RAP has been created,[5] no consensus exists on an exact definition of RAP. Some trends have been noted, such as a higher prevalence of RAP in girls. The highest prevalence occurs in children between 4 and 6 years of age and in early adolescence. Studies have also demonstrated associations between RAP and the child's family dynamics (eg, children living in a single-parent household are more likely to experience RAP[6]), psychological comorbidity such as anxiety,[7] and socioeconomic environment in which children living in low-income, low-educated–worker families were more likely to experience pain.[8]

Criteria have been established in adults to categorize abdominal pain: the Rome I criteria, later updated as Rome II to improve the definition of functional gastrointestinal disorders. Although this classification system can help categorize patients so appropriate treatment options can be considered, not all children can be clearly placed in these categories. Some authorities have argued against using the classification in children,[9] with one major reason being that the most common location of RAP is periumbilical pain, and this is not considered in the Rome II criteria. Twenty-seven percent of children with abdominal pain do not meet Rome II criteria.[10]

Pediatric gastroenterologists have identified and developed similar criteria for childhood functional disorders, including RAP.[11] These criteria—the Rome III Criteria for Functional Bowel Disorders Associated With Abdominal Pain or Discomfort in Children—are based on symptom classification. Four classes were identified, including (1) functional dyspepsia, (2) irritable bowel syndrome, (3) childhood functional abdominal pain (with a subgroup of children having childhood functional abdominal pain syndrome), and (4) abdominal migraine. The usefulness of the Rome III criteria has yet to be established.

Along with the difficulty in characterizing different types of functional abdominal pain, assessing the effectiveness of various treatments is also difficult. For example, a well-known fact is that significant inconsistencies exist in the methodologic approaches currently used to assess pain.[12] The influence of age and developmental maturation, individual differences (eg, temperament, coping patterns), family interactions, and community and cultural contexts may influence the expression of RAP. To address some of these issues, a multidimensional analytic approach has been developed to assess the primary outcome in clinical trials.[5]

In light of suboptimal classification and assessment tools, a symptom-based differential diagnosis with an emphasis on identifying the warning signals for organic disease is currently the most useful approach to patient care. However, primary care physicians must recognize that functional abdominal pain can lead to significant dysfunction and disability, with school absences, repeated visits to health care professionals, and secondary psychological problems if assessment and initiation of treatment are either ignored or delayed.[13] BOX 159-1 lists the causes of RAP by symptom subtype.