Ultrasonography of the right lower quadrant.

Whereas acute appendicitis is the most common cause of right lower quadrant (RLQ) pain, numerous other conditions may cause signs and symptoms that mimic acute appendicitis. These include other appendiceal diseases, inflammatory bowel diseases, nonbowel gastrointestinal conditions, urinary diseases, and, in females, gynecologic diseases and conditions associated with pregnancy. The important role of ultrasonography in the diagnosis of not only acute appendicitis but also each of the other conditions that cause RLQ pain is described. The ultrasound criteria for the positive, negative, and indeterminate appendix ultrasound examination and the sensitivity, specificity, and positive and negative predictive values of this modality are discussed. The limitations of ultrasound in such diagnoses are also discussed, and an algorithm for the management of patients with RLQ pain is suggested.