Functional Abdominal Pain in Children

Functional abdominal pain (FAP) is the one of the most common pain syndrome in children and can be categorized as a functional gastrointestinal disorder (FGID). For the past few years, "recurrent abdominal pain (RAP)" was accepted in describing children with functional abdominal pain1). In Apley's report, RAP is defined by more than three times of pain within 3 months and interference with normal functions such as school activities, social activities, and sports performances2). These events characterized as cramps, blunt or dull pain, usually localized around periumbilical area, and persists below 1 hour2, 3). RAP may have several causes such as inflammatory bowel disease, peptic ulcer, pancreatitis or functional causes. Functional gastrointestinal disorders are conditions that report clusters of symptoms related to disordered function in the gastrointestinal tract (GI) or in the central processing of information originating from the GI tract4). The understanding of FGIDs has altered our concept of illness and diseases shifted away from the simplistic model of disease5). A more comprehensive, biopsychosocial concept of illness has replaced the approach in which the pediatrician's efforts were always directed to identify underlying etiology to symptoms6, 7). This concept of illness takes into account not only the detection of a biological abnormality, but also the patient's perception of their own wellbeing.

RAP is accepted as a functional disorder that accounts for 25% of referrals to tertiary gastroenterological clinics and often gives a negative effect on children8, 9). According to the reports of the incidence of RAP, disparate results have been reported with prevalence ranged from 10 to 25%10~12). The suggestion of population-based reports showed 10~20% of school-aged and especially about 15% of middle- and high school-aged adolescents experienced RAP13, 14). Furthermore, almost 10~18% of school-aged children in developed countries experienced RAP15). The prevalence of RAP tends to decline in boys, not in girls as they grow older16).

The similar prevalence was reported in Asian epidemiological studies. In Sri Lanka, prevalence of RAP is almost 11%17). It has been shown by Boey et al.18, 19) that RAP among school-age children had a prevalence of almost 10%. Similarly, it has been reported by Rasul and Khan that the prevalence of RAP is approximately 11.5% of Bangladesh school-age children20). Most of the studies documented that girls are more affected than boys2, 17~19, 21).

The etiology of RAP has become increasingly complex after Apley's report. Current concepts are diverse and recognize the factors of biological-psychosocial factors22, 23). In a child with recurrent abdominal pain who has no psychological and social factors, furthermore, well-being is predicted to show a better result than the child with pain and any other problems. Also, the severity of the disorder can be affected to the child's clinical outcome24). The causes of RAP are complex and do not provide a single concept of causations. In the Apley and Naish study2), they supposed that organic cause cannot be qualified in approximately 90% of children with RAP. It has been documented that the portion of children with organic cause of RAP was identified to be increased more than previous reports25~28). During the past, new diagnostic tools have been used for the evaluation of children with RAP, and have a contribution to improved evidences of the pathophysiology of pain22). So, the portion of organic RAP was found to be higher than 80% in some of these reports28). The large majority of reports were performed in secondary or tertiary hospitals where children were selected highly and it was more likely that an organic cause was existed25~28). Most of the organic disorders lead to abdominal pain and the pathophysiology is related to infection, inflammation, distension or obstruction. Table 1 demonstrates common causes for RAP among children29, 30).

Table 1
Common Causes of Recurrent Abdominal Pain

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In generally, the complaint of pain in RAP children is somewhat genuine, and cannot be defined as a social modeling, a copy of care-givers' pain, or tools to avoid an unpleasant experience21). The most common clinical symptoms are periumbilical pain, related to functional and autonomic manifestations like vomiting, nausea, paleness and other conditions such as headache2, 17, 20, 21). In this way, on initial clinical manifestation, RAP may copy any kind of sudden onset abdominal disorders, and may stimulate unnecessary and extensive investigations. It has been found that there were severe family history of FGID2, 15, 17, 19, 20). Furthermore, there were some reports that bowel disorder causing abdominal pain is associated with IBS69). Genetic or environment vulnerability might be a cause of this phenomenon and further researches should be needed to solve a definite genetic predisposition21).

Clinician should not perform many investigations to rule out organic etiology of pain in children with RAP. Too much evaluation may increase parental concern and make the child unnecessarily stressfull21). On the other hand, indefiniteness of the diagnosis and basis of the symptoms have a tendency to damage the trust between pediatrician and parent. Hence, it is important from parent-child's purpose and the pediatrician's purpose to approach an equitable diagnosis at initial visit21). There were no reports that showed the basis, severity, duration or focus of the abdominal pain to rule out organic causes. In spite of insufficient studies to document differentiations between functional and organic disorders, it had been demonstrated that children with RAP tend to have headache, nausea, vomiting, anorexia, altered bowel movement than children without RAP70). Besides, there were no reports that have validated the physical signs and symptoms to identify organic causes in RAP patients. 'Red flag signs' in Table 2 have been applied by many pediatricians to confirm organic causes in children29, 30).

Table 2
Red Flag Sings in History and Physical Examination

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1. Pediatric Rome III criteria

In 1984, the XII International Congress of Gastroenterology was held in Lisbon, and adults investigators who had an interest in FGID were requested to develop diagnostic criteria of IBS71, 72). Four years after the initial committee73), the recommendations of International Congress of Gastroenterology was presented and named 'Rome criteria'. There were a few published reports to reference to validate the recommendations of criteria. Finally they reviewed several researches and discussed to reach a consensus73). From this effort, production of complete classification system could be formed with criteria for 24 FGIDs as Rome I criteria72). The Rome I criteria was revised with addition of more information about clinical, pathophysiological, diagnostic features and management methods for each FGIDs74). Psychological and social aspects of FGIDs and guideline for managements was also provided by this committees74). From this publication and application of the Rome criteria, a better understanding of childhood FGIDs could be obtained and patient care improved associated with this development4). This recent effort induces the development of the Rome III criteria in April 200675, 76). From the introduction of Rome II criteria in 199977), over 200 Medline quotations were developed, but from the introduction of Rome III criteria, over 600 quotations were developed. The neonate/toddler and the child/adolescent committees published the Rome III criteria, separately. In Table 3, pediatric FGIDs were presented from the Rome III criteria75, 76, 78). Most important changes of the Rome III pediatric criteria were the decline in the duration of symptoms from 3 to 2 months except for cyclic vomiting syndrome and abdominal migrain4).

Table 3
Rome III Diagnostic Criteria for Pediatric Functional Gastrointestinal Disorders

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Reassurance, careful advices, pharmacological therapies, behavioral and psychosocial modulations should be included in conventional management for RAP79). Especially, reassurance including information of no serious organic causes and general advices should be consisted in the care of child with RAP because it is helpful to control or overcome painful conditions. The pediatrician should recognize that the pain is real and not harmful80). Based on the necessity of medication and psychological intervention, the association between the level of management and improvement is so much important in RAP children's function81). It is helpful to give symptomassociated pharmacologic treatment in typical cases. For example, desipramine hydrochloride and amitriptyline (tricyclic antidepressants) could be used to manage the pain of visceral origin. Dicyclomine and hyoscyamine (anticholinergics) could be also applied to control antispasmodic properties. Laxatives and stool softeners in childhood constipation might be helpful to decrease symptoms and signs. It is recommended that pediatricians should have an effort to decrease prescription of medicines to children who have the higher level of symptoms not responding to initial therapy82). They also demonstrated that when applying therapeutic use of drugs, clinicians should notice that RAP is a fluctuating situation. Multiple recent literatures on behavioral and psychological treatments of children with RAP have been resumed83~85). Recent study showed three different therapeutic approaches such as voluntary procedures86, 87), dietary fiber88~90), and behavioral-cognitive managements 82, 91~94). According the guidelines of recent research24), cognitive and behavioral therapies arise as a promising and efficacious management for RAP. Dietary fiber therapy for children with constipation comes out as a probable management. Voluntary procedures do not satisfy the most alleviated concept of empirical or supportive therapies one and only, and there were no therapeutic approach to meet the criteria for a well-known management24).

Importantly, we approach so much closely in the understanding of childhood FGIDs because of the developing study into this area expedited by publications with the Rome criteria. Childhood FGIDs could be caused by the complex interaction among gut sensitivity, motility, environmental factors, early life events, and psychosocial factors. The comprehensive investigation, consideration of various treatment options is important for children with RAP, along) with consideration of the efficacy and safety of other management tools. It is necessary to perform further research to improve in knowledge of the factors concerned with the pathogenesis and to provide evidence for helpful therapies.