What is the clinical significance of a positive Mcburney sign in a patient with abdominal pain?

McBurney Sign in Abdominal Pain

McBurney sign—direct tenderness at McBurney's point (located one-third the distance from the anterior superior iliac spine to the umbilicus)—is a useful but insufficient clinical finding for diagnosing appendicitis that must be confirmed with imaging, specifically CT abdomen/pelvis with IV contrast, which has 85.7-100% sensitivity and 94.8-100% specificity. 1, 2

Clinical Significance and Limitations

What McBurney Sign Indicates

• McBurney's point represents the typical anatomical location of the appendix, and tenderness at this site suggests peritoneal irritation from an inflamed appendix 1
• The sign was described by Charles McBurney in 1891 as the point of maximal tenderness in acute appendicitis, located "between an inch and a half and two inches from the anterior spinous process of the ilium on a straight line drawn from that process to the umbilicus" 3, 4
• A positive McBurney sign remains a key finding on abdominal examination when evaluating patients with right lower quadrant pain 4

Critical Limitations You Must Understand

• Only 35% of appendix bases actually lie within 5 cm of McBurney's point, and 15% are more than 10 cm distant from this landmark 5
• Less than half of all patients with confirmed appendicitis have tenderness maximal over McBurney's point 5
• The classic presentation (including McBurney point tenderness, fever, and leukocytosis) is present in only approximately 50% of appendicitis cases 6, 1
• McBurney's point tenderness is over-emphasized as the key to diagnosis, leading to missed cases when clinicians rely too heavily on this single finding 7

Diagnostic Algorithm When McBurney Sign is Present

Immediate Assessment Required

• Do not proceed to surgery based on clinical findings alone—negative appendectomy rates reach 14.7-25% without preoperative imaging 6
• Assess for complete clinical picture: periumbilical pain migrating to right lower quadrant, anorexia/nausea/vomiting, fever (though absent in ~50% of cases), and leukocytosis 1, 6
• Examine for additional peritoneal signs: guarding, rigidity, rebound tenderness, or positive Rovsing sign (left lower quadrant palpation causing right lower quadrant pain) 1

Mandatory Imaging Confirmation

• Order CT abdomen and pelvis with IV contrast without enteral contrast as the definitive next step for adolescents and adults with positive McBurney sign 6, 2, 1
• CT achieves 90-100% sensitivity and 94.8-100% specificity, and reduces negative appendectomy rates to 1.7-7.7% 6, 2
• CT identifies alternative diagnoses in 23-45% of patients presenting with right lower quadrant pain and classic symptoms, fundamentally changing management 6, 2

Alternative Imaging Approaches

• In children, start with ultrasound to avoid radiation exposure, then proceed to CT if ultrasound is nondiagnostic or equivocal 6
• Staged ultrasound followed by CT achieves 99% sensitivity and 91% specificity 6
• In pregnant patients, use MRI which demonstrates 96% sensitivity and specificity 2, 1

Common Pitfalls to Avoid

Do Not Rely on Clinical Examination Alone

• Clinical determination of appendicitis is notoriously poor—even experienced clinicians miss the diagnosis when relying solely on physical examination 6
• The absence of fever does not exclude appendicitis, as fever is absent in approximately 50% of confirmed cases 6
• Normal WBC count significantly reduces probability but does not exclude appendicitis (negative likelihood ratio 0.25) 6

Recognize Atypical Presentations

• Atypical presentations occur in approximately 50% of patients, requiring a lower threshold for imaging 1
• Female patients of childbearing age have more atypical presentations and lower diagnostic accuracy on ultrasound (false-positive rate 35.5% vs 6.2% in men) 1
• Elderly patients frequently lack the classic triad and present with signs of peritonitis including abdominal distension, generalized tenderness, and palpable mass 1
• Obesity significantly reduces ultrasound accuracy, with false diagnosis rates of 34.4% in obese men versus 6.2% in non-obese men 1

Do Not Delay Imaging

• NSAIDs and pain medications can mask evolving symptoms and delay diagnosis 6
• If symptoms persist or worsen during observation, proceed immediately to CT imaging 6
• Delayed presentation increases perforation risk, particularly in elderly patients who typically present later 1

Alternative Examination Techniques

• The "pinch-an-inch" test can be used as a less uncomfortable alternative to rebound tenderness: grasp and elevate a fold of abdominal skin over McBurney's point, then allow it to recoil briskly—pain when the skin strikes the peritoneum indicates peritonitis 8
• Obturator sign (pain with internal rotation of the flexed hip) suggests pelvic appendix location 1

When to Discharge vs. Admit

Low-Risk Patients Without Classic Findings

• Discharge with mandatory 24-hour follow-up if patient has low clinical suspicion (mild symptoms, no peritoneal signs, normal vital signs) 6, 1
• Provide clear return precautions for worsening pain, fever, vomiting, or development of peritoneal signs 6
• If symptoms persist or worsen at follow-up, proceed to imaging (ultrasound first-line in pediatrics, CT in adults) 6

High-Risk or Positive Imaging

• Surgical consultation and antimicrobial therapy if appendicitis is confirmed on imaging 6
• Immediate assessment in emergency department for severe pain, persistent vomiting, fever, or worsening symptoms 6