Ultrasound Evaluation of the Acute Inflammatory Abdomen

The Acute Abdomen refers to a syndrome characterized by abdominal pain and tenderness, typically requiring emergent surgical intervention. The main surgical etiologies of acute abdomen include hemorrhage, perforation, ischemia, obstruction, and inflammation—the latter being the focus of this chapter. Because many of these conditions require urgent operative management, a rapid and precise physical examination is essential, and clinicians must be familiar not only with the clinical presentation but also with imaging modalities that are often crucial for establishing the diagnosis [1].Pain in acute abdomen may arise from stimulation of visceral or parietal nociceptors, each producing distinct clinical characteristics. Visceral pain generally results from involvement or distension of a hollow viscus, presenting as vague, poorly localized discomfort, typically in the periumbilical or hypogastric regions. In contrast, parietal pain is caused by irritation of nociceptors in the parietal peritoneum, leading to sharp, well-localized pain. Depending on the underlying etiology, visceral pain may evolve into parietal pain, often indicating disease progression and a worse prognosis. A classic example is appendicitis, which begins with vague periumbilical pain and later localizes to the right lower quadrant. Referred pain may also occur, such as Kehr’s sign—left shoulder pain due to phrenic nerve irritation, commonly associated with cholecystitis [1].Although accurate clinical assessment is fundamental, point-of-care ultrasonography (POCUS) serves as a valuable adjunct for clarifying abdominal pain. Ultrasound demonstrates high sensitivity for identifying gallstones and inflammatory biliary disease and is also highly sensitive for detecting appendiceal inflammation—although appendicitis remains primarily a clinical diagnosis and CT offers higher diagnostic accuracy [2].This chapter focuses on the use of ultrasonography as a diagnostic tool in inflammatory acute abdomen, addressing appendicitis, cholecystitis, cholangitis, diverticulitis, and pelvic inflammatory disease.