Small Bowel Disease: An Approach to Optimise Imaging Technique and Interpretation

Abstract Small bowel imaging presents a challenge from the variety of clinical presentations and types of disease affecting a long organ. Emergency presentation most often involves suspicion of bowel obstruction, unexplained acute abdominal pain with or without signs of sepsis and overt obscure GI bleeding. Conversely non-emergency referrals relate to non-specific constitutional symptoms including weight loss, abdominal patient, and altered bowel habit suggesting malignancy or inflammatory bowel disease, while iron deficiency anaemia after negative colonoscopy and endoscopy indicates occult obscure GI bleeding. CT is the commonest and best-established method of evaluation, except in the setting of known inflammatory bowel disease where MRI or ultrasound are advantageous because they avoid radiation. The CT protocol must be tailored to the clinical situation. Oral preparation is avoided for acute imaging, with the main focus around prompt contrast enhanced scanning: acute obscure bleeding should include non-contrast, arterial and portal venous phases, while obstruction and acute abdominal pain needs portal venous phase assessment. Pre-contrast imaging allows assessment of intramural haemorrhage where there is prior clinical concern for intestinal ischaemia. Conversely non-urgent assessment allows oral luminal preparation with a neutral contrast such as polyethylene glycol or mannitol and enteric or portal venous phase contrast assessment depending on the indication.