Chapter 75: Acute Abdominal Pain

INTRODUCTION

Acute abdominal pain, particularly when severe, requires an expeditious evaluation because a missed or delayed diagnosis may lead to significant morbidity and mortality. The first step is to determine whether the patient has a life-threatening cause of acute abdominal pain. After the patient has been stabilized, the emergency physician or hospitalist must then determine whether the patient needs emergent surgery. The decision to obtain an emergency surgical consultation depends on the history and physical examination (with ancillary radiographic examinations of secondary importance), and when signs of an acute abdomen are present, a surgical consult should be requested, with concurrent diagnostic testing as appropriate. In other instances, a thorough history and physical examination is required with close observation and repeat examinations are often needed. Elderly patients and very young patients may present with atypical or nonspecific signs and symptoms that otherwise might be dismissed as insignificant.

Appendicitis, cholecystitis and choledocholithiasis, intestinal obstruction, pancreatitis, mesenteric ischemia, bowel perforation, and diverticulitis account for two-thirds of hospital admissions for acute abdominal pain and are associated with significant morbidity and mortality. In addition, physicians must be mindful of complications following procedures.

PATHOPHYSIOLOGY

Patients may experience visceral pain, parietal pain, and/or referred abdominal pain.

Visceral pain is typically dull or crampy in character. It is caused by stretching, torsion, distention, or contraction of organs. The visceral innervation of the gut and accessory organs comes via the anchoring mesentery, so pain does not always localize to the quadrant in which the pathology resides, and is often midline. Pain innervation corresponds to dermatomes that match the innervations of the injured organ. Epigastric visceral pain corresponds with organs proximal to the ligament of Treitz, including the hepatobiliary system and the spleen. Periumbilical visceral pain corresponds with injury to organs distal to the ligament of Treitz and the hepatic flexure of the colon. Lower abdominal visceral pain corresponds to injury to organs distal to the hepatic flexure.

Parietal pain is sharp in character and localized to the site of peritoneal inflammation or capsular. This pain is similar to skin and muscle pain and lateralization occurs due to unilateral parietal innervations.

Referred pain is typically well localized. It occurs because visceral afferent nerves carrying stimuli from an inflamed organ enter the spinal cord at the same level as somatic afferent nerves from remote locations.