Imaging for Right Lower Quadrant Abdominal Pain

Initial Imaging Selection Algorithm

The American College of Radiology recommends CT of the abdomen and pelvis with IV contrast as the initial imaging study for patients with right lower quadrant pain and suspected appendicitis due to its high diagnostic accuracy 1, 2
For non-pregnant adults, CT abdomen and pelvis with IV contrast is the first-line imaging modality, rated 8/9 on ACR Appropriateness Criteria, providing high sensitivity (85.7-100%) and specificity (94.8-100%) 3, 4, 5
The use of oral or rectal contrast may not be needed depending on institutional preference 4

Ultrasonography as initial screening is recommended, rated 6/9 on ACR Appropriateness Criteria, and should be followed by CT only if ultrasonography is inconclusive or negative 3, 4, 6, 7
Low-dose CT protocols can reduce radiation exposure to approximately 22% of standard-dose protocols without significant difference in negative appendectomy rates 5, 6

For pregnant patients, MRI abdomen and pelvis without IV contrast OR ultrasound abdomen is the primary modality, which avoids ionizing radiation exposure and has superior appendix visualization rates (80% for MRI, 7% for ultrasound) 2, 8
MRI demonstrates excellent sensitivity (100%) and specificity (98%) for pregnant patients 2

CT has reduced negative appendectomy rates from historical 14.7% to 1.7-7.7% 5
Abdominal CT exposes patients to approximately 10 mSv of radiation, compared to annual background radiation of 3 mSv 6
Balancing diagnostic accuracy with radiation exposure is essential, particularly in younger patients 8
Relying solely on conventional radiography has limited diagnostic value for assessing abdominal pain 9
Delaying diagnosis due to oral contrast protocols may increase the risk of perforation 5

The American College of Radiology recommends CT abdomen and pelvis with IV contrast as the most appropriate next step for a patient with right lower quadrant pain, suprapubic tenderness, mild leukocytosis, and inconclusive ultrasound, with a sensitivity of 95% and specificity of 94% for appendicitis 10
CT abdomen and pelvis with IV contrast is recommended when ultrasound is nondiagnostic or equivocal, as it identifies alternative diagnoses in 23-45% of cases presenting with right lower quadrant pain 10
The American College of Radiology suggests that transvaginal ultrasound should be considered as initial imaging when there is specific clinical concern for acute gynecologic pathology, not after an already inconclusive transabdominal ultrasound 11, 12

Diagnostic laparoscopy is premature without definitive imaging confirmation, and CT must be obtained first to guide surgical decision-making and avoid unnecessary operative intervention 10
The American College of Radiology recommends against open appendectomy without imaging confirmation, as it risks both a negative appendectomy and missing the actual pathology 10

Delaying CT imaging in favor of serial examinations or additional ultrasound modalities is not recommended, as it risks progression to perforation if appendicitis is present 10