Case #01 Discussion:

RLQ pain is a common complaint in the ED, especially in the age group of this patient. The differential diagnosis for RLQ pain and tenderness is quite long, and includes such things as appendicitis, ruptured ovarian cysts, ectopic pregnancy, ovarian torsion, diverticulitis, RLL pneumonia, etc. Imaging is an important diagnostic tool to use in conjunction with a careful history and physical exam. Three modalities are commonly used: plain film, ultrasound, and CT.

On plain film radiographs of the abdomen/pelvis, fecaliths, mass effect, and free air from a perforated viscus are most commonly looked for. Fecaliths (seen in 5% of appendicitis cases) are radiodense, mass effect is seen when air-filled bowel loops are displaced, and free air (rare in appendicitis) is best seen against the abdominal wall on left lateral decubitus films. Localized displacement of bowel loops (mass effect) indicate a mass in the bowel wall, a mesenteric mass, or intraperitoneal mass such as appendicitis or diverticulitis. On ultrasound, an inflamed appendix is dilated (>6mm is considered diagnostic), thick-walled, and is not compressible. CT is also helpful in assessing the size and wall-thickness of the appendix, and for evaluating abscess formation.