Small bowel obstruction (SBO) is a common presentation to the emergency department (ED) and represents 15% of hospital admissions for acute abdominal complaints.

Plain radiography, although traditionally recommended as the initial diagnostic imaging modality of choice, has a sensitivity of only 59% to 77%. When clinical and radiographic assessment is indeterminate, computed tomography (CT) becomes the test of choice due to its superior resolution and increased ability to identify both obstruction and its aetiology Aim: this is a prospective study in a sample of patients presenting to the emergency department (ED) with abdominal pain, vomiting, or other symptoms suggestive of a SBO (history of previous surgeries, constipation, abnormal bowel sounds, and abdominal distention). Patients will be evaluated with US prior to x-ray and CT, with possible diagnostic confirms by endoscopy or surgery.

Primary outcome:

Our objective was to study the accuracy of emergency medicine bedside ultrasonography and in patients with suspected small bowel obstruction (SBO).

Secondary outcome:

assess the usefulness of the history and physical examination in the prediction of diagnosis

US Diagnostic criteria:

• Bowel lumen diameter >2.5cm
• Wall thickness > 4 mm
• Decreased/absent peristalsis
• Back/forth stool movements
• Free fluid

Methods The study is based on the assessment of all consecutive patients (19-75 years) presenting in the emergency department of Policlinico VE of the University of Catania (or to other affiliated Hospitals, such as Cannizzaro and/or Ragusa hospitals), which show clinical clues of small bowel obstruction (SBO). The criterion of enrolment is the casual referral to few previously identified physicians, skilled in TUS procedures and which accepted to take part to this study.

The most similar study on this topic demonstrates an extremely high accuracy of US in the diagnosis of intestinal obstruction, so that no actual power analysis can be done. The rationale of the present prospective study is the definition of prevalence of US detected obstruction in patients referred to an emergency facilities with symptoms potentially suggestive for such diagnosis.

Moreover, which clue, if any, such as anaemia, CRP, NLR, hypotension, could reinforce the need of US intestinal study.

This information is not yet available elsewhere. Moreover, in this context, sensitivity and specificity of ultrasound vs. confirm by CT and other procedures will make more sense and will be consequently assessed.

The secondary reason of this investigation is the attempt to detect which are the prevalence and the feature of under-diagnosis or over-diagnosis by US vs. the actual condition.

IMPLEMENTATION. This is a medium-term pilot study, non-interventional, which can be performed better as a single centre investigation, with few skilled and committed emergency physicians, than as a multicentre study, which would have the possible bias of relying on a mosaic or on scarcely skilled or motivated MDs.

Inclusion Criteria:

• acute abdominal pain
• clinical clues of small bowel obstruction (SBO) according to symptoms and physical examination in the clinic

Exclusion Criteria:

• pregnancy
• post-surgical patients
• Trauma

All patients referred to the emergency facility with the clinical suspicion - before any imaging procedure - of small bowel obstruction