What is the initial screening and treatment approach for a patient presenting with symptoms suggestive of inflammatory bowel disease (IBD)?

Initial Screening for Inflammatory Bowel Disease

For patients aged 16-40 presenting with chronic lower gastrointestinal symptoms lasting >4 weeks, measure faecal calprotectin alongside basic laboratory tests, and refer urgently to gastroenterology for ileocolonoscopy if calprotectin is >250 μg/g. 1, 2

Primary Care Assessment

Essential History Components

• Stool characteristics: frequency, consistency, presence of blood or mucus, urgency, nocturnal symptoms 1, 2
• Systemic symptoms: fever, weight loss, malaise, fatigue 1, 2, 3
• Red flag features: rectal bleeding with abdominal pain, change in bowel habit, iron deficiency anemia, abdominal/rectal/anal mass, unexplained anal ulceration 1, 2
• Medication history: recent NSAID use (affects calprotectin interpretation), antibiotics, recent travel 1, 2
• Smoking status and family history of IBD 1, 2
• Extraintestinal manifestations: joint pain, skin changes, eye symptoms 1, 2

Physical Examination Findings

• Vital signs: pulse rate (tachycardia suggests severe disease), blood pressure (hypotension indicates volume depletion), temperature (fever suggests complications), weight (compare to baseline) 1, 2
• General appearance: assess for anemia, fluid depletion 1, 2
• Abdominal examination: tenderness, distension, palpable masses 1, 2
• Rectal examination: inspect for perianal disease, anal ulceration, masses 1, 2

Mandatory Initial Laboratory Testing

All patients must have the following tests in primary care: 1, 2

• Complete blood count (assess for anemia, leukocytosis) 1, 2
• Urea and electrolytes 1, 2
• C-reactive protein (CRP) 1, 2
• Coeliac serology 1, 2
• Stool culture including Clostridium difficile toxin 1, 2

Faecal Calprotectin Interpretation and Action

Do not perform calprotectin testing if NSAID use within the past 6 weeks. 1

Calprotectin <100 μg/g

• IBS is likely; treat as IBS in primary care 1
• Consider other diagnoses if symptoms persist: bile acid malabsorption, microscopic colitis, medication effects 1
• If IBD remains strongly suspected based on clinical features or family history, refer to gastroenterology despite low calprotectin 1, 2

Calprotectin 100-250 μg/g

• Consider repeat testing or routine referral to gastroenterology 1
• If strong clinical suspicion exists (red flag features, family history), proceed with urgent referral regardless of intermediate values 1, 2
• This intermediate range is challenging to interpret as mild elevation may reflect non-specific low-grade inflammation 1

Calprotectin >250 μg/g

• Refer urgently to gastroenterology for ileocolonoscopy 1, 2
• Exclude infectious causes before referral 1

Critical Pitfalls to Avoid

• Do not rely on CRP alone: approximately 15-20% of patients with active IBD have normal CRP levels 1, 2
• Do not defer colonoscopy based on intermediate calprotectin if clinical suspicion is high: calprotectin should be interpreted in light of pre-test probability 1, 2
• Do not delay assessment if systemically unwell: patients with suspected acute severe colitis require urgent inpatient assessment regardless of test results 1
• Do not ignore red flag features: rectal bleeding with abdominal pain, unexplained weight loss, or palpable masses warrant immediate cancer pathway referral per NICE guidelines 1

Calprotectin Sampling Technique

Use the first stool passed in the morning and store for no more than 3 days at room temperature before analysis to minimize variation in calprotectin levels. 1

Secondary Care Diagnostic Workup

Once referred to gastroenterology:

Endoscopic Evaluation

• Ileocolonoscopy with terminal ileal intubation is the reference standard 1, 2
• Multiple biopsies from affected and normal-appearing areas, including terminal ileum 1, 2
• For suspected Crohn's disease: document focal, asymmetric inflammation and skip lesions 1, 2
• For ulcerative colitis: assess disease extent, look for loss of vascular pattern, granularity, friability, ulceration 1, 2

Cross-Sectional Imaging

• MR enterography is essential at diagnosis to assess small bowel involvement and detect complications in Crohn's disease 2

Avoid Colonoscopy in Severe Colitis

• In moderate to severe disease, flexible sigmoidoscopy is safer than colonoscopy due to higher perforation risk 1, 2
• Colonoscopy in severe colitis should only be performed by experienced endoscopists with minimal air insufflation 1