Chapter 10: Sonographic Approach to Acute Abdominal Pain

INTRODUCTION

The purpose of this chapter is to provide an overview of the ultrasound approach for the acute abdomen. The discussion is organized by generalized pain versus localized pain and outlines conditions where point-of-care ultrasound (POCUS) may be helpful. The reader is referred to specific chapters of the book for more detailed discussion of these findings.

CLINICAL CONSIDERATIONS

Abdominal pain is a common presenting complaint in the acute care setting, comprising 5–10% of adult visits.^1–5 Patients presenting with acute, nontraumatic abdominal pain can pose a diagnostic challenge to clinicians, as many causes are serious or immediately life threatening (Table 10-1). The most frequent diagnoses for patients presenting to the emergency department (ED) with abdominal pain vary widely by country but consistently show high rates of nonspecific abdominal pain, renal and biliary colic, appendicitis, bowel obstruction, and diverticulitis.^4,6,7 Older patients account for a higher percentage of visits and have a higher mortality than younger patients.^8–10 One study showed that 50–65% of adults over the age of 65 years presenting with abdominal pain required hospitalization and nearly 20% required surgery.¹¹

Evaluation of acute, nontraumatic abdominal pain has evolved over the last 30 years.¹² Before the ubiquity of advanced imaging and rapid turnaround for laboratory tests, many patients were admitted to the hospital for observation and serial examinations. In modern practice, there is a greater impetus to determine a diagnosis and to obtain a definitive disposition.

The workup of abdominal pain typically begins with a careful history and physical examination, which guides the clinician in choosing further lab tests or diagnostic imaging. Historically, clinicians have used conventional radiography as an initial imaging modality; however, plain radiographs have limited utility apart from revealing free air under the diaphragm or bowel gas patterns suggestive of bowel obstruction. With the rare exception of revealing undisclosed radio-opaque foreign bodies, radiographs rarely provide insight into etiology and may not add much value to clinical assessment.

In the last the last 30 years, sonography and computed tomography (CT) have become much more readily available. CT is an excellent imaging modality to diagnose not only intraperitoneal pathology, but also findings in the retroperitoneum. However, CT is relatively contraindicated in pregnant patients, children, and younger adults due to ionizing radiation exposure. Other disadvantages include time, expense, and use of nephrotoxic dye. Magnetic resonance imaging (MRI) is an alternative, but has limited availability and is expensive, time intensive, and requires the patient to remain completely still for a prolonged period of time.

In contrast, ...