Crohn's disease: where it most often affects the gut

The location of inflammation helps explain symptoms, but it does not by itself establish a diagnosis. Disease near the end of the small intestine may cause cramping around the lower abdomen, loose stools, or difficulty absorbing nutrients. Large-intestine involvement can bring diarrhoea, urgency, or blood and mucus in the stool. Some people have inflammation in more than one area, with healthy-looking sections between affected areas.

Symptoms can change when inflammation becomes more active or settles. A scan, stool assessment, endoscopy, and blood tests may be used together to map the affected areas and look for inflammation.

Keep a short record of pain location, bowel changes, appetite, weight change, fever, and any mouth or joint symptoms. Bring the record and your medicines to a GP consultation. A clinician may arrange a blood test and other assessments, then discuss treatment aimed at controlling inflammation and protecting nutrition.

Arrange medical advice for ongoing abdominal pain, repeated diarrhoea, unexplained weight loss, tiredness, or blood in the stool. Seek urgent help for severe or rapidly worsening pain, a swollen abdomen with vomiting, inability to keep fluids down, faintness, or heavy rectal bleeding.

Ask which part of the digestive tract may be involved, which tests can clarify the location, whether nutrition needs attention, and which symptoms should prompt same-day help.