Where Crohn's disease can affect the body

Inflammation in the small bowel may cause cramping, loose stools, reduced appetite or difficulty maintaining weight. Disease involving the colon can bring urgency, diarrhoea or blood in the stool. Inflammation near the anus may cause pain, drainage or a change in bowel movements. Some people develop symptoms beyond the gut, such as joint pain, eye irritation or skin changes. These patterns are clues rather than a diagnosis; infections, food intolerance and other conditions can produce similar symptoms.

Write down where pain occurs, how often you open your bowels, whether stools contain blood, and whether symptoms wake you at night. Share medicines and any recent travel or infection with your clinician. A [GP Consultation](/treatments/consultations-and-assessment/gp-consultation/) can start the assessment. A [Blood Test](/treatments/diagnostics-and-screening/blood-test/) may look for anaemia or inflammation; further testing may be needed to examine the bowel and establish the affected site. Avoid self-diagnosing from symptoms alone.

Seek medical advice for ongoing [Abdominal Pain](/symptoms/abdominal-pain/), persistent [Diarrhoea](/symptoms/diarrhoea/), blood in stool, unexplained weight loss or continuing fatigue. Urgent help is needed for severe pain, repeated vomiting, a distended abdomen, fainting, confusion, or inability to keep fluids down. New drainage or severe pain around the anus also warrants prompt review. The urgency depends on the red flags and how unwell you feel, not on whether Crohn's disease has already been diagnosed.

Ask which part of the digestive tract may be involved, what each test can show, how results will change treatment, and which symptoms should prompt same-day care. Ask how to maintain hydration and nutrition while waiting for assessment.