How can I differentiate between functional constipation and secondary causes in adult patients?

Differentiating functional constipation from secondary causes in adult patients involves a thorough clinical assessment combining history, examination, and targeted investigations.

Start with a detailed history to identify symptoms suggestive of secondary causes, such as unexplained weight loss, rectal bleeding, severe abdominal pain, or systemic symptoms like nausea and vomiting, which may indicate obstruction or malignancy. Also, consider medication history and comorbidities that could contribute to constipation, such as hypothyroidism or neurological disorders ¹,².

Perform a physical examination including abdominal and digital rectal examination to assess for masses, faecal impaction, or anatomical abnormalities. Signs such as abdominal distension, tenderness, or absence of bowel sounds may suggest obstruction or other secondary pathology ¹,².

Blood tests including urea and electrolytes, serum calcium, and thyroid function tests should be arranged to exclude metabolic or endocrine causes ¹,².

Functional constipation is more likely when there are no alarm features, normal examination findings, and no biochemical abnormalities. It often presents with symptoms of infrequent, hard stools, straining, and sensation of incomplete evacuation without systemic signs ¹.

If symptoms persist despite initial management or if defecatory disorders are suspected, consider specialist referral for further evaluation such as anorectal manometry or transit studies, although these are not routinely used in primary care ¹.

Recent literature emphasizes the role of gut microbiota and dietary patterns influencing colonic transit time, which may contribute to functional constipation, highlighting the importance of dietary and lifestyle assessment in differentiation (Wu et al., 2024). Additionally, diagnostic criteria and approaches continue to evolve, but current UK guidelines remain the cornerstone for initial differentiation (Park, 2024).