Diagnostic Approach to Recurrent Abdominal Pain and Altered Bowel Habits

Age-Based Decision Algorithm

Patients over 45 years with new-onset symptoms require colonoscopy to exclude colorectal malignancy, as this age threshold represents a critical cutoff for increased cancer risk, according to the DIRECT guidelines 1, 2, 3, 4.
The American Gastroenterological Association recommends that colonoscopy should be complete to the cecum and of high quality for patients ≥45 years 3.
For patients <45 years without alarm features, a trial of dietary fiber is appropriate, with a working diagnosis of IBS made based on typical symptoms, normal physical examination, and absence of sinister features 1, 2.
The European Society for Gastrointestinal Endoscopy suggests that increased dietary fiber (25 g/day) is recommended as first-line therapy for constipation-predominant symptoms 5, 6, 7.

Rectal bleeding/hematochezia requires immediate colonoscopy, with a hazard ratio of 10.66 for colorectal cancer, as stated by the National Comprehensive Cancer Network 3, 4.
Unexplained iron deficiency anemia mandates colonoscopy, with a hazard ratio of 10.81 for colorectal cancer, according to the American College of Gastroenterology 3, 4.
Unintentional weight loss ≥5 kg requires colonoscopy, with an odds ratio of 2.23 for early-onset colorectal cancer, as recommended by the American Society for Gastrointestinal Endoscopy 3, 4.

A patient being female, aged <45 years, with symptom duration >2 years, supports the diagnosis of IBS, as suggested by the Rome Foundation 1, 2.
Pain relieved by defecation is a supportive feature for IBS diagnosis, according to the British Society of Gastroenterology 1, 2.

For patients <45 without alarm features receiving fiber trial, prescribe 25 g/day of dietary fiber and re-evaluate in 3-6 weeks, as recommended by the North American Society for Pediatric Gastroenterology 5, 6, 7.
If symptoms persist or worsen, proceed with colonoscopy and additional testing based on predominant symptom pattern, according to the American Gastroenterological Association 1, 2, 5.