What is the next step in managing a patient with right iliac fossa pain, tenderness, elevated WBC, and an inconclusive ultrasound?

Next Step: CT Scan of Abdomen and Pelvis

In a patient with right iliac fossa pain, elevated WBC (14), and an inconclusive ultrasound, the next step is CT scan of the abdomen and pelvis with contrast. This follows the established step-up diagnostic approach for suspected appendicitis when initial imaging is non-diagnostic 1.

Rationale for CT After Inconclusive Ultrasound

The World Society of Emergency Surgery explicitly recommends a staged algorithm using a step-up approach, where CT is performed after an inconclusive or negative ultrasound in suspected appendicitis and acute diverticulitis 1. This approach is supported by:

• CT has significantly higher sensitivity and specificity than ultrasound for diagnosing acute appendicitis 1
• When ultrasound is inconclusive, CT provides definitive diagnostic information in the majority of cases 1
• The step-up approach balances diagnostic accuracy with radiation concerns 1

Why Not Proceed Directly to Surgery

Open appendectomy or diagnostic laparoscopy should not be performed without definitive imaging when ultrasound is inconclusive 1. Here's why:

• This patient lacks rebound tenderness, which suggests the clinical picture is not definitive for acute appendicitis 1
• WBC of 14 is elevated but not dramatically high, placing this patient in an intermediate-risk category 1
• Proceeding to surgery without cross-sectional imaging risks unnecessary appendectomy or missing alternative diagnoses 1
• Diagnostic laparoscopy is reserved for cases where imaging has been unhelpful, not as the next step after a single inconclusive ultrasound 1

Clinical Algorithm for This Scenario

For intermediate-risk patients with inconclusive ultrasound:

1. Obtain CT abdomen/pelvis with IV contrast - This is the standard next step per WSES guidelines 1
2. Consider low-dose CT protocol if available, particularly in younger patients, to minimize radiation exposure while maintaining diagnostic accuracy 1
3. Use oral/rectal contrast based on institutional preference - not mandatory but may aid visualization 1

Important Clinical Caveats

Watch for these pitfalls:

• Do not delay CT for prolonged observation in a patient with persistent symptoms and inconclusive ultrasound - this increases risk of perforation if appendicitis is present 1
• Suprapubic tenderness suggests possible pelvic pathology - CT will evaluate both appendicitis and gynecologic/urologic causes that ultrasound may have missed 1
• The absence of rebound tenderness does not exclude appendicitis - it may indicate early or uncomplicated disease that still requires diagnosis 1
• If CT is contraindicated or unavailable, MRI is an alternative with 94% sensitivity and 96% specificity for appendicitis, though less readily available in emergency settings 1

Why Diagnostic Laparoscopy Is Premature

Diagnostic laparoscopy has definitive diagnosis rates of 86-100%, but it is an invasive procedure reserved for specific situations 1:

• It should be used when imaging has been unhelpful (meaning after CT, not after ultrasound alone) 1
• It carries surgical risks that are not justified when non-invasive imaging can provide the diagnosis 1
• In this case with only one inconclusive imaging study, CT is the appropriate next step before considering any surgical intervention 1