Rome IV defines FAPDs as episodic or continuous abdominal pain that does not occur solely during physiological events such as eating. Rome IV subclassifies FAPDs into a number of clinically distinct entities, namely irritable bowel syndrome (IBS), functional dyspepsia (FD), abdominal migraine and FAPDs not otherwise specified. See box 1 for the diagnostic criteria.1,4 The Rome IV definition states that a diagnosis of FAPD is likely after appropriate medical evaluations have failed to attribute symptoms to another medical condition.1

Paediatric functional abdominal pain disorders (FAPDs) are commonly seen in clinical practice [Image: Shutterstock].

Presentation of pain

According to the American College of Gastroenterology (ACG), children describe pain around the umbilicus (belly button). The pattern of abdominal pain however is difficult to predict. Location and severity may differ. For example, some children experience a sudden onset of pain, while others describe pain that increases slowly in severity. Some are in constant pain, while in others it comes and goes.3

Furthermore, symptoms may differ. Symptoms can range from upper abdominal pain associated with nausea, vomiting and early satiety, to bloating, indigestion, or experiencing abdominal pain with bowel movements.3   

The ACG cautions that other possible causes of FAPD should be investigated (eg acid reflux, lactose intolerance, parasitic infections of the small and large intestines, Helicobacter pylori infection that may cause ulcers in the first portion of the small bowel, celiac disease, food allergies, hepatitis, gall bladder problems, an inflamed pancreas, an intestinal obstruction, appendicitis, and some rare disorders) before a definitive diagnosis is made.3

Development of functional abdominal pain

McClellan and Ahlawat explain that the development of  FAPDs is likely multifactorial. There appears to be sensitisation to the range of normal physiological sensations, which result in visceral hyperalgesia. For example, sensations such as bloating or indigestion may produce pain beyond what is typically experienced by non-affected individuals.4

An initial sensitising event (eg an infection, allergy, altered gut microbiome, or motility disorder) occurs first and later progresses to hypersensitivity. Psychosocial factors such as stress or comorbid anxiety and depression are also associated with the development of hypersensitivity.4

Risk factors

Age does not seem to play a role in the onset of FAPDs. Known risk factors include:1

·       Sex: Young and adolescent girls are more affected than boys (15.9% versus 11.5%). Notably, this difference was also evident at a pre-pubertal age (10 years) (9.9% girls versus 7.7% boys)

·       Psychosocial factors: Several studies reported that children and adolescents with FAPDs have a poor mental health status and lower quality of life compared to healthy children. Up to 50% of children with FAPD are reported to have clinically relevant anxiety or depression.1

·       Genetic factors: A family history of IBS and other FAPDs has been reported as an epidemiological risk factor. For IBS, a substantial overlap in the incidence of abdominal symptoms between mothers and their children has been described. This overlap might be related to certain genes but might more likely be due to a number of social factors, including attentive parental response to child pain behaviours.1

Management and treatment interventions

According to Romano et al, current treatment strategies include:2

  • Support and empathy for the family with reassurance that no serious disease is present
  • Medical management that includes dietary fibre, peppermint oil and antidepressants. With this approach, about 30%–40% of children have resolution of their symptoms.

Thaphar et al note that the role of gut microbiota in the onset of FAPDs is increasingly being recognised and a number of interventions targeting gut microbiota, including probiotics, the low FODMAP diet, prebiotics, and antibiotics, are increasingly being used for the management of FAPDs.1

How effective are probiotics?

Numerous studies have investigated the efficacy of probiotics in the management of FAPDs.

Romano et al (2014) investigated the effect of daily supplementation with the probiotic Lactobacillus reuteri (Lreuteri) DSM 17938 in children with FAPDs. Children (n=60) aged between six- and 16-years who fulfilled the Rome criteria were included in this double-blind, randomised, placebo-controlled study. They were randomised to receive either L. reuteri or identical placebo for four weeks. Follow-up was four weeks without supplementation. Frequency and intensity of pain was self-recorded by participants. The team found that children in the L. reuteri-supplementation group had significantly lower pain intensity compared with those in the placebo group. The team concluded that supplementation with L. reuteri reduced perceived abdominal pain intensity, which may encourage clinicians to use this probiotic in children with FAPD.2

Weizman et al (2016) also focused on the efficacy of L. reuteri in children (n=101) with FAPD. Children between the ages of six and 15 were randomised to receive either L. reuteri or placebo for four weeks. Follow-up was four weeks and the frequency and intensity of pain was self-reported. The team found that L. reuteri was significantly superior to placebo in relieving frequency (1.9 versus 3.6 episodes/week) and intensity (4.3 versus 7.2 score/week) of abdominal pain following four weeks of supplementation.     L. reuteri was also associated with a lower incidence of perceived abdominal distention and bloating.5

Jadrešin et al (2017) looked at the effect of three months supplementation of L. reuteri in children (n=55) with FAPDs. Follow-up was 30-days without supplementation. Children between four- and 18-years were randomised to receive L. reuteri daily, or placebo. Symptoms were evaluated using the Wong-Baker FACES rating scale and the Bristol scale for stool shape and consistency. They found that children in the L. reuteri group had significantly more days without pain (median 89.5 versus 51 days). Abdominal pain was less severe in children taking probiotics during the second month and fourth month. Both groups experienced significant reduction in the severity of abdominal pain from first to fourth month, with the reduction more prominent in the intervention group.6

Maragkoudaki et al’s (2017) study randomised children (n=54) with a confirmed diagnosis of FAPD to either L. reuteri or placebo for four weeks. They found that both Lreuteri and the placebo significantly reduced the frequency and intensity of abdominal pain episodes at four and eight weeks compared to baseline. However, L. reuteri decreased the use of pain-relieving drugs at four weeks and school absences at four and eight weeks, unlike placebo. They concluded that while both L. reuteri and the placebo were effective in alleviating pain in children with FAPD, only L. reuteri improved the child’s and family’s normal activities.7

Trivić et al (2021) reviewed evidence for the use of strain-specific probiotic in children with FAPDs. The review included nine randomised controlled trials (a total of 702 children, 506 with functional abdominal pain, four- to 18-years).

Lactobacillus rhamnosus GG and Lactobacillus reuteri DSM 17938 were the only two probiotic strains investigated. Significant reduction in pain intensity and increase in number of days without pain were found in children taking L. reuteri. They concluded that L. reuteri was proven to decrease the pain intensity in children with FAPDs.8

Rome IV diagnostic criteria for FAPDs


The criteria must be fulfilled for at least two months and include all of the following:

  • Abdominal pain at least four days per month associated with defaecation and/or a change in the frequency of stool and/or a change in the appearance of stool
  • Abdominal pain does not resolve with resolution of the constipation (children in whom the pain resolves have functional constipation, not IBS)
  • After appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

The criteria must be fulfilled for at least two months before diagnosis and must include one or more of the following bothersome symptoms at least four days per month:

  • Postprandial fullness
  • Early satiation
  • Epigastric pain or burning not associated with defaecation
  • After appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

Abdominal migraine

The criteria must be fulfilled for at least six months before diagnosis and include all of the following occurring at least twice:

  • Paroxysmal episodes of intense, acute periumbilical, midline or diffuse abdominal pain lasting one hour or more (should be the most severe and distressing symptom)
  • Episodes are separated by weeks to months. The pain is incapacitating and interferes with normal activities, stereotypical pattern, and symptoms in the individual patient
  • The pain is associated with two or more of the following: anorexia, nausea, vomiting, headache, photophobia, or pallor
  • After appropriate evaluation, the symptoms cannot be fully explained by another medical condition.

FAPD not otherwise specified

The criterial must be fulfilled for at least two months before diagnosis and at least four times per month and include all of the following.

  • Episodic or continuous abdominal pain that does not occur solely during physiological events (for example, eating and menses)
  • Insufficient criteria for IBS, FD, or abdominal migraine
  • After appropriate evaluation, the abdominal pain cannot be fully explained by another medical condition.


FAPDs negatively impact children’s quality of life. The onset of FAPDs is multifactorial. Girls are at higher risk of developing FAPDs. Other risk factors include psychosocial factors and a genetic predisposition. The role of gut microbiota in the onset of FAPDs is increasingly being recognised. Numerous studies have found that probiotics decrease frequency and intensity of pain in children with FAPDs.

  • Thapar N, Benninga MA, Crowell MD et al. Paediatric functional abdominal pain disorders. Nature Reviews Disease Primers, 2020.
  • Romano C, Ferrau V, Cavataio F et al. Lactobacillus reuteri in children with functional abdominal pain (FAP). J Paediatr Child Health, 2014.
  • American College of Gastroenterology. Functional abdominal pain in children
  • McClellan N and Ahlwat R. Functional Abdominal Pain In Children. StratPearls (Internet), 2020.
  • Weizman Z, Abu-Abed J, Binsztok M et al. Lactobacillus reuteri DSM 17938 for the Management of Functional Abdominal Pain in Childhood: A Randomized, Double-Blind, Placebo-Controlled Trial. J Pediatr, 2016.
  • Jadrešin O, Hojsak I, Mišak Z et al. Lactobacillus reuteri DSM 17938 in the Treatment of Functional Abdominal Pain in Children: RCT Study. JPGN, 2017.
  • Maragkoudaki M, Chouliaras G, Orel R et al. Lactobacillus reuteri DSM 17938and a placebo both significantly reduced symptoms in children with functional abdominal pain. Acta Paediatrica, 2017.
  • Trivić I, Niseteo T, Jadrešin O et al. Use of probiotics in the treatment of functional abdominal pain in children-systematic review and meta-analysis. Eur J Pediatr,