Over the past three decades, point-of-care ultrasound (POCUS) has become routinely utilized as a diagnostic tool by radiologists, emergency physicians, and surgeons, evaluating intra-abdominal pathology, particularly hepatobiliary, vascular, urologic, and gynecologic disorders. With advances in the resolution of scanning devices, POCUS has become increasingly useful for the evaluation of abnormalities of the gastrointestinal (GI) tract as well, particularly in the case of an acute abdomen.
Disorders of the GI tract, such as perforation, bowel infarction, bowel obstruction, or appendicitis, require urgent surgical intervention, so rapid evaluation and diagnosis are imperative. In most cases, particularly involving the bowel, computed tomography (CT) is the best modality for making an accurate diagnosis; however, CT utilization should be carefully considered because it comes at the cost of time, expense, exposure to ionizing radiation, and potential nephrotoxicity. While CT, angiography, magnetic resonance imaging (MRI), and endoscopy may not be immediately available in many settings, rapid POCUS can be used to help narrow the differential diagnosis and determine the urgency of further workup and management. POCUS may guide the timing and application of further diagnostic testing as well as the decision to use oral or rectal contrast material. In rural settings, POCUS may prompt immediate referral to a higher level of care. For appendicitis, ultrasound confirmation can obviate the need for CT, which is particularly important for pregnant patients and children.
Clinical indications for performing POCUS of the GI tract include the following:
Acute abdominal pain and peritonitis
Intractable nausea and vomiting
Abdominal distention or mass
Unexplained shock or sepsis
Begin a focused evaluation with adequate pain control for the patient in order to facilitate the workup. In the case of an acute or “surgical” abdomen, rapidly inspect for free intraperitoneal fluid and free air utilizing a low-frequency convex transducer (3–5 MHz). Begin with a brief examination of the upper and lower quadrants using the same technique as the focused assessment with sonography for trauma (FAST) (see Chapter 9, “Trauma”) to identify free fluid in the abdomen or free air under the diaphragm or abutting the abdominal wall. Free air is frequently found at the ventral surface of the liver from the right intercostal window. Free fluid is frequently found in the right paracolic gutter, suprapubic region, or adjacent to loops of bowel and may contain gas echoes.
After the initial survey, continue the exam with the low frequency transducer to localize anatomical landmarks and GI structures of interest. If intraluminal gas echoes obscure the exam, try repositioning the patient into semilateral, lateral, or semierect positions. If body habitus allows, a higher frequency probe (>7 MHz) provides a more detailed exam of the laminar structures of the GI tract and abdominal wall; however, the higher frequency transducer may not be useful in patients with ...