How should a 36-year-old woman with acute right lower quadrant abdominal pain, normal vital signs, negative urine pregnancy test, no fever, vomiting, dysuria, or vaginal discharge, and physical exam showing right lower quadrant tenderness with guarding on muscle contraction (positive McBurney's sign) but no rebound or peritoneal signs and a pelvic exam without cervical motion tenderness or mass be evaluated and managed?

Evaluation and Management

This patient should undergo CT abdomen and pelvis with IV contrast as the initial imaging study to definitively diagnose or exclude appendicitis and identify alternative causes of her right lower quadrant pain. 1

Clinical Context and Differential Diagnosis

This 36-year-old woman presents with acute right lower quadrant pain following physical activity (yard work), which is a critical clinical clue. The pain that worsens with abdominal wall muscle contraction suggests abdominal wall strain or musculoskeletal injury rather than intra-abdominal pathology. However, the absence of fever, peritoneal signs, and negative pelvic exam findings creates diagnostic uncertainty that requires imaging to exclude serious pathology.

Key Clinical Features to Consider:

• Pain with muscle contraction (positive Carnett's sign) typically indicates abdominal wall pathology
• Absence of peritoneal signs (no rebound, no guarding with palpation) makes complicated appendicitis less likely
• Normal vital signs and no fever argue against acute infection
• Negative pregnancy test excludes ectopic pregnancy
• Normal pelvic exam makes adnexal torsion, ovarian cyst rupture, and pelvic inflammatory disease less likely 2

Recommended Imaging Approach

CT Abdomen and Pelvis with IV Contrast

This is the single most appropriate initial imaging study for this clinical scenario. 1

Rationale:

• Sensitivity of 95% and specificity of 94% for appendicitis diagnosis 1
• Identifies alternative diagnoses in 94.3% of non-appendicitis cases, including gynecologic pathologies (ovarian cysts, adnexal masses), gastrointestinal conditions (colitis, inflammatory bowel disease), and musculoskeletal causes 1
• Contrast-enhanced CT without oral contrast performs equivalently to protocols with enteral contrast (sensitivity 90-100%, specificity 94.8-100%) and avoids treatment delays 1
• In patients with non-appendiceal diagnoses on CT, 41% required hospitalization and 22% needed surgical or image-guided intervention, demonstrating the clinical impact of accurate diagnosis 1

Alternative: Ultrasound

Ultrasound could be considered as an initial study but has significant limitations:

• Appendix not visualized in 45% of patients 1
• When the appendix is not seen, indirect signs have highly variable performance (sensitivity 31.8-83.9%, specificity 56.7-96.7%) 1
• More operator-dependent and less comprehensive for alternative diagnoses 3

Ultrasound is most appropriate when there is high suspicion for gynecologic pathology specifically, but this patient's normal pelvic exam makes this less likely 3

Clinical Decision-Making Algorithm

1. Given the clinical presentation (pain with muscle contraction, no peritoneal signs, post-exertion onset):

   • Primary differential: Abdominal wall strain/hematoma vs. appendicitis vs. gynecologic pathology

2. Order CT abdomen/pelvis with IV contrast (no oral contrast needed) 1

3. If CT shows:

   • Appendicitis: Proceed to surgical consultation for appendectomy 4
   • Abdominal wall hematoma/strain: Conservative management with NSAIDs, rest
   • Gynecologic pathology: Appropriate gynecologic consultation
   • No acute pathology: Reassurance, outpatient follow-up, consider musculoskeletal treatment

Important Caveats

Common Pitfalls to Avoid:

• Do not rely on clinical examination alone: Even with atypical features, the negative appendectomy rate without imaging is unacceptably high at 25% 1
• Do not delay imaging for oral contrast administration: This increases time to diagnosis without improving accuracy 1
• Do not dismiss gynecologic causes in reproductive-age women: Ovarian cyst rupture, corpus hemorrhagicum, and adnexal torsion can mimic appendicitis and account for 12.8% of cases presenting as suspected appendicitis 2
• Consider abdominal wall pathology: Pain worsening with muscle contraction (Carnett's sign) is a key distinguishing feature often overlooked

Special Considerations:

The 2025 WSES Jerusalem Guidelines emphasize that clinical risk scores and imaging improve diagnostic accuracy and reduce negative appendectomy rates 4. While this patient's presentation is somewhat atypical for appendicitis, imaging remains essential because:

• Appendicitis presents "classically" in only 50% of cases 1
• Women of reproductive age have multiple potential etiologies requiring different management strategies 2, 3
• Delayed or missed diagnosis of appendicitis increases perforation risk and associated morbidity 1

Laboratory Studies

While awaiting imaging, obtain:

• Complete blood count (leukocytosis supports but does not confirm appendicitis) 2
• C-reactive protein (elevated in appendicitis but nonspecific) 3
• Urinalysis (to exclude urinary tract infection/urolithiasis) 3

The diagnosis cannot be confirmed or excluded clinically and requires imaging for definitive management. 3, 4