How can I differentiate between functional constipation and constipation due to an underlying medical condition in children?

To differentiate between functional (idiopathic) constipation and constipation caused by an underlying medical condition in children, a working diagnosis of idiopathic constipation is made by excluding 'red flags' during history-taking and physical examination ¹,². If any 'red flag' symptoms are present, the child should not be treated for constipation in primary care and should be referred urgently to a healthcare professional with experience in the specific area of concern ².

Key 'Red Flag' Findings from History-Taking:

• Timing of onset: Constipation reported from birth or the first few weeks of life, especially in a child younger than 1 year, is a red flag ².
• Passage of meconium: Failure to pass meconium or a delay of more than 48 hours after birth in a term baby is a red flag ².
• Stool patterns: 'Ribbon stools' are a red flag, particularly in a child younger than 1 year ².
• Growth and general wellbeing: Faltering growth is a red flag ².
• Symptoms in legs/locomotor development: Previously unknown or undiagnosed weakness in legs or locomotor delay are red flags ².
• Abdomen: Abdominal distension accompanied by vomiting is a red flag ².

Key 'Red Flag' Findings from Physical Examination:

• Perianal area: Abnormal appearance, position, or patency of the anus, such as fistulae, bruising, multiple fissures, a tight or patulous anus, an anteriorly placed anus, or an absent anal wink, are red flags ².
• Abdominal examination: Gross abdominal distension is a red flag ².
• Spine/lumbosacral region/gluteal examination: Abnormalities like asymmetry or flattening of the gluteal muscles, evidence of sacral agenesis, discoloured skin, naevi, a sinus, a hairy patch, a lipoma, a central pit (dimple where the bottom cannot be seen), or scoliosis are red flags ².
• Lower limb neuromuscular examination: Deformity in lower limbs (e.g., talipes), abnormal neuromuscular signs unexplained by an existing condition (e.g., cerebral palsy), or abnormal reflexes (if performed) are red flags ².

If 'amber flag' symptoms or signs are present, or if ongoing constipation has not responded to optimal laxative treatment in primary care, specialist referral is needed to consider further tests for underlying conditions such as coeliac disease and hypothyroidism ¹. If red flags have been excluded, and a diagnosis of idiopathic constipation is made, reassure the child and parents/carers that underlying causes have been excluded and that idiopathic constipation is treatable with laxatives, though it may take several months ¹,².