CT Abdomen and Pelvis with IV Contrast is the Most Appropriate Next Step
For a patient with right lower quadrant pain for 12 hours, mildly elevated WBC (12.5-14), and inconclusive ultrasound, proceed directly to CT abdomen and pelvis with IV contrast. This is the definitive imaging modality that will either confirm appendicitis or identify alternative pathology requiring intervention.
Why CT is the Clear Choice
CT abdomen and pelvis achieves 95% sensitivity and 94% specificity for appendicitis, and critically, identifies non-appendiceal causes of RLQ pain in the majority of cases. 1 The American College of Radiology rates CT with contrast as 8/9 ("usually appropriate") for suspected appendicitis, compared to transvaginal ultrasound at only 5/9 ("may be appropriate"). 1
Key Clinical Context
Normal or mildly elevated WBC does not exclude appendicitis. The "classic" presentation occurs in only 50% of patients, and you cannot rely on WBC alone to exclude surgical pathology. 2
After inconclusive ultrasound, CT changes management in 43% of patients initially suspected to have appendicitis. 2 Among patients with non-appendiceal CT diagnoses, 41% require hospitalization and 22% need surgical or image-guided intervention. 1
The absence of rebound tenderness does not exclude appendicitis or other surgical emergencies. This patient has had symptoms for 12 hours with persistent tenderness—time is critical. 1
Why NOT the Other Options
B) Transvaginal Ultrasound - Inappropriate
- Transvaginal US is rated only 5/9 by ACR and is specifically indicated when pelvic/gynecologic pathology is the PRIMARY concern, not appendicitis. 1
- This patient's presentation (suprapubic AND lower quadrant tenderness, elevated WBC) suggests appendicitis or gastrointestinal pathology as the leading diagnosis, not gynecologic disease. 1
- Ultrasound after negative/inconclusive initial US has only 51.8% sensitivity for appendicitis compared to CT's 95%. 2
C) Diagnostic Laparoscopy - Premature
- Going directly to surgery without definitive imaging risks unnecessary negative appendectomy and misses alternative diagnoses. 1
- CT identifies alternative causes (ovarian pathology, diverticulitis, colitis, inflammatory bowel disease, urologic causes) that would change surgical planning entirely. 1, 2
- The negative appendectomy rate with preoperative CT is only 1.7-7.7%, demonstrating the value of imaging before surgery. 1
D) Open Appendectomy - Inappropriate
- Open appendectomy without imaging confirmation is outdated practice and carries unacceptable risk of negative appendectomy. 1
- Even if appendicitis is present, CT determines perforation status, abscess formation, and whether the patient is a candidate for interval appendectomy versus immediate surgery. 1
The Diagnostic Algorithm
Obtain CT abdomen and pelvis with IV contrast immediately. 1, 2
If CT confirms appendicitis: Proceed to surgical consultation. Look for signs of perforation (extraluminal gas, abscess, phlegmon) which may alter surgical timing. 1
If CT shows alternative pathology: 41% of non-appendiceal diagnoses require hospitalization or intervention—CT will guide appropriate specialty consultation. 1
If CT is negative: The patient can be safely discharged with close outpatient follow-up, as negative CT has extremely high negative predictive value. 2
Critical Pitfalls to Avoid
Do not obtain repeat ultrasound after inconclusive initial US. While repeat US can make a diagnosis in 55% of equivocal cases in children, this is still inferior to CT's diagnostic accuracy, and this patient is likely an adult given the clinical presentation. 1
Do not delay CT for prolonged clinical observation. With 12 hours of symptoms and persistent tenderness, the risk of perforation increases with time. CT changes management in the majority of cases. 1, 2
Do not order plain radiographs. They have extremely limited sensitivity for appendicitis and significantly delay definitive diagnosis. 1
Answer: A) CT