Alarm Signs for Constipation
When evaluating constipation, immediately refer patients for urgent investigation if they present with age >50 years, rectal bleeding, unintended weight loss, iron deficiency anemia, nocturnal symptoms, acute onset constipation in older patients, family history of colorectal cancer, or palpable abdominal/rectal mass. 1, 2, 3
Critical Alarm Features Requiring Urgent Evaluation
Age-Related Red Flags
- Age >50 years warrants structural evaluation of the colon, particularly if the patient has not undergone previous colorectal cancer screening 1
- Acute onset constipation in older patients is particularly concerning and requires prompt investigation to exclude malignancy 2, 3
Bleeding and Anemia
- Rectal bleeding is a major alarm feature that mandates colonoscopy to exclude colorectal cancer or inflammatory bowel disease 1, 4
- Iron deficiency anemia or microcytic anemia requires immediate investigation including colonoscopy and celiac serology, as this combination suggests gastrointestinal blood loss or malabsorption 5, 2, 3
Constitutional Symptoms
- Unintended weight loss is a critical alarm feature that excludes functional constipation and necessitates urgent evaluation for malignancy or inflammatory bowel disease 1, 2
- Nocturnal symptoms (symptoms that wake the patient from sleep) suggest organic disease rather than functional constipation 1
Physical Examination Findings
- Palpable abdominal or rectal mass requires immediate colonoscopy to exclude colorectal cancer 2, 3
- Rectal prolapse identified on digital rectal examination warrants subspecialist referral 2
Family History
- Family history of colorectal cancer increases pretest probability of malignancy and lowers the threshold for structural evaluation 1, 3
- Family history of inflammatory bowel disease or celiac disease should prompt earlier investigation 1
Additional Warning Signs
Duration and Pattern
- Short history of symptoms (particularly <3 months) is more concerning for organic disease than chronic symptoms present for years 1
- Recent change in bowel habit in patients >50 years requires colonoscopy even without other alarm features 1
Associated Symptoms
- Male sex is considered an alarm feature in the context of IBS-like symptoms, as functional bowel disorders are more common in women 1
- Recent antibiotic use may suggest Clostridioides difficile infection or antibiotic-associated colitis 1
When Alarm Features Are Present
Patients with one or more alarm signs require prompt evaluation and should not be empirically treated as functional constipation. 2, 3
Mandatory Investigations
- Complete blood count to assess for anemia 1, 2
- Colonoscopy with biopsies (not flexible sigmoidoscopy alone) is mandatory when alarm features are present, as approximately 50% of neoplasia may be proximal to the splenic flexure 1, 5, 6, 3
- Tissue transglutaminase IgA antibodies with total IgA level should be checked immediately if microcytic anemia is present 5
- Fecal calprotectin to exclude inflammatory bowel disease 5, 6
Critical Pitfall to Avoid
Do not diagnose irritable bowel syndrome or functional constipation in patients with alarm features, particularly weight loss, as this is an exclusion criterion for functional disorders. 6, 2 The presence of alarm features fundamentally changes the diagnostic approach from reassurance and empiric treatment to urgent investigation for serious organic disease.
Timeline for Evaluation
When alarm features are present, colonoscopy should be scheduled urgently within 2-4 weeks, not delayed based on age alone or symptom duration. 5, 6
Signs That Do NOT Constitute Alarm Features
While these symptoms warrant evaluation, they are not alarm features requiring urgent investigation: