Functional abdominal pain is common in primary school kids, and although it usually passes with time and reassurance, it is very real pain.

“It’s very common for kids, between the start of school and the end of primary school particularly, to have abdominal pain,” says Dr Rupert Dr Hinds, Melbourne-based paediatric gastroenterologist.

Once acute illness is ruled out, we sometimes see just a single episode of pain that resolves without clear cause. In other children, we see recurrent presentations of non-emergent pain that can be quite distressing for the child and the parents (and sometimes the doctor!).

“I say to parents often that constipation is a common thing and commonly implicated,” Dr Hinds says. Ruling out constipation can usually be done on history and examination alone, except in much younger children.

So with constipation ruled out or resolved, how do we approach the child with frequent and regular abdominal pain? “We know that whilst about a fifth of kids will have this sort of problem, less than five percent end up with an underlying organic explanation,” Dr Hinds says.

This presentation has had multiple names over the years: recurrent abdominal pain of childhood, chronic abdominal pain, functional abdominal pain. It is usually associated with clear triggers, such as school attendance.

How does functional abdominal pain present?

What differentiates functional abdominal pain from more serious causes is the lack of red flags. Dr Hinds is very reassured by episodic non-localised pain that does not wake a child at night.

“No one’s disputing that the child is in pain,” he clarifies. “The pain is real, but it doesn’t mean a terrible thing is happening.”

“We know that it’s slightly more common in girls than boys. We also know that there’s a slightly increased rate of these problems in neurodivergence, and children with other neurological or psychiatric issues.”

Dr Hinds likes to manage parental expectations early, explaining that without red flags or localising signs and symptoms, we won’t do much and we won’t find much. “I tell them this is something that we are familiar with, we see a lot of,” he says, “and I think it’s important to say upfront that it’s about excluding things and managing things. It’s not about trying to find things super invasively.”

He explains the concept of brain-gut interaction to parents, and finds many understand straight away. They may have their own experiences with, for example, irritable bowel syndrome, and will be able to identify similarities in their own life.

Red flags that warrant further investigation:

Constant pain

Pain that wakes the child overnight

Fevers

Weight loss/failure to grow as expected

Change to bowel habits (besides simple constipation that is treated)

Jaundice

Clinical signs of anaemia

Localised pain (as opposed to periumbilical)

Acute, non-distractible tenderness

For some children, the brain-gut link will be very obvious. For example, the abdominal pain will only occur on Monday mornings before school, or on exam days. For others it may be subtler, but parents will often notice a different pattern on weekends and holidays.

For many of these children and their parents, reassurance and time will be the only treatments necessary. Children with more severe anxiety or other mental health issues may need treatment for these.

So when do we investigate further?

While there are a number of guidelines for investigating subacute abdominal pain in children, they are quite varied— Dr Hinds describes this as “sort of an evidence free zone.” Some guidelines focus only on targeted investigations for localised pain, whereas there is potentially a role for investigating symptoms that persist for a significant period.

Dr Hinds recommends holding off on investigations in the absence of red flags or obvious examination findings such as clinical anaemia or jaundice. Investigating too much, too early increases parental anxiety, and an expectation of subsequent tests until an answer is found, he says.

He feels three to six months is a reasonable time to investigate if symptoms are persisting. He would also investigate if frequency increases.

“In terms of ultrasound in abdominal pain that’s non-localised, the yield is less than 1%,” Dr Hinds says. He rarely orders ultrasounds in likely functional pain unless it is localised, or perhaps in a slightly older child with a strong family history of gallstones.

There is very little role for abdominal x-rays in school-aged children, especially if they are neurotypical. Most can articulate the frequency and type of their bowel motions and thus constipation can be excluded.

In terms of pathology testing, Dr Hinds recommends midstream urine, coeliac serology, full blood examination and iron studies. He usually includes CRP although it is non-specific. He considers kidney and liver function testing low yield in chronic abdominal pain, but understands most will include this.

He recommends avoiding stool sample testing in these patients. He cites ​a study showing that children with functional abdominal pain have the same levels of blastocystis carriage as children without pain.

Faecal calprotectin may have a role in chronic diarrhoea – with the caveat that paediatric normal ranges are higher, and it can be falsely elevated by anything causing inflammation.

What about allergies and intolerances?

Parents will often ask if their child’s recurrent abdominal pain is a food allergy or intolerance. “At this age, a child almost never develops a new onset food allergy,” Dr Hinds says. He recommends discussing things like lactose and fructose intolerance in terms of thresholds.

He discourages breath tests. These are expensive and often unreliable in children who struggle with the technique. If parents are concerned about lactose intolerance, he recommends trialing lactose-free cow’s milk. “Then I’m not troubled because nothing is nutritionally lost. It’s still a useful source of calcium.”

When to refer?

“In general, if there is refractory pain where sensible strategies haven’t resolved it, we’ll be happy to see these children,” Dr Hinds says. For functional abdominal pain, he says he has little more to offer than parental reassurance. “I have no ability to treat these kids any better than you.”

Take Home Message

Functional abdominal pain is common in primary school aged children, and explaining the role of the brain-gut axis does not invalidate the pain. “The pain feels the same as if her brother punched her in the tummy. Kids are not making this up.”

GPs are perfectly placed to monitor these symptoms over time and provide reassurance.