Ultrasound of Small Bowel Obstruction: A Pictorial Review

Abstract

Small bowel obstruction (SBO) is a common condition requiring urgent attention that may involve surgical treatment. Imaging is essential for the diagnosis and characterization of SBO because the clinical presentation and results of laboratory tests may be nonspecific. Ultrasound is an excellent initial imaging modality for assisting physicians in the rapid and accurate diagnosis of a variety of pathologies to expedite management. In the case of SBO diagnosis, ultrasound has an overall sensitivity of 92% (95% CI: 89–95%) and specificity of 93% (95% CI: 85–97%); the aim of this review is to examine the criteria for the diagnosis of SBO by ultrasound, which can be divided into diagnostic and staging criteria. The diagnostic criteria include the presence of dilated loops and abnormal peristalsis, while the staging criteria are represented by parietal and valvulae conniventes alterations and by the presence of free extraluminal fluid. Ultrasound has reasonably high accuracy compared to computed tomography (CT) scanning and may substantially decrease the time to diagnosis; moreover, ultrasound is also widely used in the monitoring and follow-up of patients undergoing conservative treatment, allowing the assessment of loop distension and the resumption of peristalsis.

Overview of point-of-care ultrasound in diagnosing intestinal obstruction

“…[30] The roles of POCUS in clinical practice and its accuracy in the evaluation of IO have been well described in the literature. [13,22,31] In this paper, we summarized the diagnostic criteria of ultrasound for SBO and CO, pertaining to the morphological and functional characteristics of bowels. Having clear criteria would help further in making systematic and accurate clinical judgments.…”

The “Black Pattern”, a Simplified Ultrasound Approach to Non-Traumatic Abdominal Emergencies

“…Fluids, especially if poor in cells, appear as black, hypoechoic to anechoic in US, because most of the US’ beam goes through them and only a small part of the waves is reflected and returns to the transducer. The search for black fluid and its possible shades of gray is the basic principle of our POCUS protocol [ 3 , 4 , 7 ]. This US approach is versatile and a valuable tool for physicians involved in emergency settings and also suitable for physicians without extensive training or background in clinical sonography [ 8 ].…”

“…US diagnostic criteria include the presence of dilated loops and abnormal peristalsis. Small bowel dilatation is defined as bowel diameter ≥ 2.5 cm measured from outer wall to outer wall [ 3 , 50 , 51 ] ( Figure 5 ).…”

“…Ultrasound (US) is rightly regarded as the initial imaging tool for the evaluation of patients with abdominal pain. It is crucial in the management of both trauma [ 1 , 2 ] and non-traumatic emergencies [ 3 , 4 ].…”

“…This approach has many advantages over traditional imaging modalities: it is rapid, portable, non-invasive, repeatable, less expensive, and does not entail ionizing radiation exposure. POCUS has several applications, including diagnostic, screening, and procedural, as already recognized by leading scientific societies [ 1 , 3 , 5 ]. Scanning is limited to the areas of interest and focused targets, based on pre-test probability.…”