What is the next best step in managing a 33‑year‑old with 2‑day right lower‑quadrant abdominal pain, positive McBurney/Markles point tenderness, rebound tenderness, one bowel movement, intermittent pain, and an inconclusive abdominal ultrasound?

Next Best Step: CT Abdomen/Pelvis with IV Contrast

For this 33-year-old with 2 days of right lower quadrant pain, positive peritoneal signs (Markle's sign, direct and rebound tenderness), and an inconclusive ultrasound, the next best step is CT abdomen and pelvis with IV contrast. 1

Why CT is Essential After Inconclusive Ultrasound

• CT demonstrates 91% sensitivity and 98% specificity for appendicitis when the preceding ultrasound is nondiagnostic or equivocal, making it the definitive next imaging study 2
• A staged ultrasound-then-CT algorithm achieves 99% sensitivity and 91% specificity for acute appendicitis, providing highly accurate diagnosis while the initial ultrasound attempt was reasonable 2
• CT identifies alternative diagnoses in 23-45% of patients presenting with right lower quadrant pain, fundamentally changing management even when appendicitis is suspected 1, 2

Critical Clinical Context

Your patient has high-risk features that mandate definitive imaging:

• Positive peritoneal signs (rebound tenderness, Markle's sign) indicate peritoneal irritation, a key finding in established appendicitis that cannot be ignored 3, 4
• Two days of persistent symptoms with focal peritoneal findings represents intermediate-to-high clinical risk, not a low-risk presentation suitable for discharge 2
• Intermittent pain does NOT exclude appendicitis—early appendicitis commonly presents with waxing and waning symptoms before progression 3

Why Other Options Are Inappropriate

Do not discharge this patient:

• Clinical assessment alone misdiagnoses appendicitis in 34-68% of cases, with negative appendectomy rates of 25% when imaging is omitted 2
• Discharging patients with positive peritoneal signs risks missing early appendicitis or other serious pathology (perforated cecal diverticulum, right-sided diverticulitis, early perforation) 3, 4
• Fever is absent in approximately 50% of appendicitis cases, so lack of fever does not reduce risk 2

Do not repeat ultrasound:

• When ultrasound is equivocal with inflammatory findings present, proceed immediately to CT rather than repeat ultrasound 1
• Ultrasound has a 20-81% non-visualization rate for the appendix, and repeating it only delays definitive diagnosis 1

Do not rely on observation alone:

• Even with classic peritoneal signs, imaging is essential because classic presentation occurs in only 50% of appendicitis cases 2
• NSAIDs and observation can mask evolving symptoms and delay diagnosis 2

Optimal CT Protocol

Order CT abdomen and pelvis with IV contrast only (no oral contrast):

• IV contrast alone provides rapid acquisition with 85.7-100% sensitivity and 94.8-100% specificity 1, 2
• No oral contrast is needed—it delays imaging without improving diagnostic accuracy 2

Alternative Diagnoses CT Will Detect

Beyond appendicitis, CT will identify:

• Right-sided colonic diverticulitis (8% of cases), which can precisely mimic appendicitis 1
• Gynecologic pathology (21.6% of alternative diagnoses): ovarian torsion, ruptured cyst, tubo-ovarian abscess 2
• Gastrointestinal conditions (46% of alternative diagnoses): Crohn's disease, bowel obstruction, cecal diverticulum perforation 2, 4
• Ureteral stones and other genitourinary pathology 2

Management Algorithm After CT

If CT confirms appendicitis:

• Immediate surgical consultation for appendectomy 2
• If perforated with abscess: percutaneous drainage followed by interval appendectomy 2

If CT shows alternative diagnosis:

• Manage according to specific pathology identified 2

If CT is negative but symptoms persist:

• Serial abdominal examinations every 6-12 hours 2
• Repeat CBC to monitor leukocytosis trend 2
• Consider diagnostic laparoscopy if peritoneal signs persist—accuracy is 86-100% for definitive diagnosis 3

Common Pitfall to Avoid

The single most dangerous error is discharging a patient with positive peritoneal signs based on an inconclusive ultrasound and absence of fever. 2, 4 This patient's physical examination findings (rebound tenderness, Markle's sign) indicate peritoneal irritation that requires definitive imaging to exclude surgical pathology. The case report of perforated cecal diverticulum with normal inflammatory markers and negative CT for appendicitis underscores that focal peritoneal signs mandate surgical evaluation when imaging is equivocal 4.