Most Appropriate Next Step: Transvaginal Ultrasound (TVUS)
For a 28-year-old woman with right lower quadrant pain, mild leukocytosis (WBC 12.5), and an inconclusive transabdominal ultrasound, the most appropriate next step is transvaginal ultrasound (TVUS) before proceeding to CT. 1
Rationale for TVUS as the Next Step
The American College of Radiology specifically recommends pelvic ultrasound (transvaginal) as the preferred imaging modality in women of childbearing age with lower quadrant pain, rating it as "appropriate" (rating 5/9) for this clinical scenario. 2
TVUS provides superior diagnostic information in 62% of pelvic pathology cases compared to transabdominal ultrasound alone, with additional diagnostic information obtained in 55% of these cases. 3, 4
In reproductive-age women with an inconclusive transabdominal ultrasound, TVUS can reveal alternative gynecologic causes of pelvic pain or directly visualize a pelvic appendix that may not have been adequately seen on the initial study. 5
Combined transabdominal and transvaginal ultrasound achieves 97.3% sensitivity and 91% specificity for diagnosing pelvic pathology in adult women when performed by experienced operators. 6
Why Not CT Immediately?
Performing CT as the initial study in young women exposes them to unnecessary ionizing radiation (approximately 10 mSv), and the ACR specifically recommends completing the ultrasound evaluation first to avoid this risk while still allowing accurate assessment of both gynecologic emergencies and appendicitis. 1
The staged ultrasound-then-CT algorithm (transabdominal followed by transvaginal, then CT only if needed) achieves approximately 99% sensitivity and 91% specificity for acute appendicitis in adult women, providing a highly accurate, radiation-sparing approach. 5
Critical Differential Diagnoses in This Patient
The differential diagnosis in a 28-year-old woman with RLQ pain includes:
Appendicitis – remains possible despite inconclusive initial ultrasound, as fever is absent in approximately 50% of appendicitis cases and mild leukocytosis (WBC 12.5) is common in early disease. 5
Gynecologic pathology – including ovarian torsion, ruptured ovarian cyst, ectopic pregnancy, or pelvic inflammatory disease, which account for approximately 21.6% of alternative diagnoses in patients presenting with RLQ pain. 5
Right-sided colonic diverticulitis – can present with normal inflammatory markers and mimic appendicitis. 5
When to Proceed to CT
If TVUS is nondiagnostic or equivocal, proceed directly to CT abdomen and pelvis with IV contrast (no oral contrast needed) as the definitive next step. 1
CT with IV contrast demonstrates approximately 91% sensitivity and 98% specificity for appendicitis when the preceding ultrasound is nondiagnostic or equivocal. 5
CT identifies alternative diagnoses in 23-45% of cases presenting with right lower quadrant pain, fundamentally changing management. 5, 1
Why Not Diagnostic Laparoscopy or Open Appendectomy?
Diagnostic laparoscopy is premature without definitive imaging confirmation, as CT must be obtained first to guide surgical decision-making and avoid unnecessary operative intervention. 1
Open appendectomy without imaging confirmation risks both a negative appendectomy (historically 14.7-25% without imaging) and missing the actual pathology, which could be gynecologic or other non-surgical conditions. 5, 1
Clinical assessment alone misdiagnoses acute appendicitis in 34-68% of cases, demonstrating poor diagnostic accuracy without imaging confirmation. 5
Common Pitfalls to Avoid
Do not assume that absence of fever excludes appendicitis – fever is absent in approximately 50% of appendicitis cases. 5
Do not skip TVUS and proceed directly to CT in reproductive-age women – this exposes patients to unnecessary radiation when TVUS may provide the diagnosis. 1
Do not delay imaging if symptoms worsen during observation – progression to perforation increases morbidity and, in reproductive-age individuals, elevates the risk of complications. 5
Ensure a quantitative β-hCG test is obtained immediately to exclude ectopic pregnancy before any further imaging in reproductive-age women with RLQ pain. 5