What is the significance of the knee to chest position in diagnosing appendicitis (inflammation of the appendix)?

From the Guidelines

The knee to chest sign is a useful clinical maneuver in diagnosing appendicitis, particularly when the appendix is retrocecal, but it should be used in conjunction with other diagnostic tools like CT scans, which have a high diagnostic yield with sensitivities ranging from 85.7% to 100% and specificities ranging from 94.8% to 100% 1.

Diagnostic Approach

When evaluating a patient for suspected appendicitis, a comprehensive approach is necessary. This includes:

• Clinical history and physical examination, including the knee to chest sign
• Laboratory tests, such as white blood cell count
• Imaging studies, with CT scans being the primary diagnostic modality due to their high sensitivity and specificity

CT Scan Findings

CT scans can provide valuable information in diagnosing appendicitis, including:

• Maximal outer diameter of the appendix, with a cutoff value of 8.2 mm yielding a sensitivity of 88.8%, specificity of 93.4%, and accuracy of 91.7% 1
• Presence of fat stranding, absence of intraluminal gas, and other signs that can indicate appendicitis

Limitations of the Knee to Chest Sign

While the knee to chest sign can be a useful diagnostic tool, it has its limitations. It is not definitive on its own and should be considered alongside other clinical findings. Additionally, the sign may not be positive in all cases of appendicitis, particularly if the appendix is not retrocecal.

Conclusion is not allowed, so the answer will continue without one.

The knee to chest sign, also known as the psoas sign or iliopsoas test, is performed by having the patient lie on their back and actively bring their knee to their chest, or the examiner passively flexes the patient's hip while they're lying on their back. The test is positive when this movement causes pain in the right lower quadrant of the abdomen, suggesting irritation of the iliopsoas muscle by an inflamed appendix 1. In the context of appendicitis diagnosis, CT scans are the preferred imaging modality due to their high diagnostic accuracy, with the most recent study indicating a summary sensitivity of 0.95 and a summary specificity of 0.94 for CT in the diagnosis of appendicitis 1.

From the Research

Knee to Chest Appendicitis Sign

• The knee to chest appendicitis sign, also known as the psoas sign, is a clinical test used to diagnose appendicitis 2.
• This sign is positive when a patient experiences pain in the right lower quadrant of the abdomen when they bring their right knee towards their chest, indicating irritation of the psoas muscle by an inflamed appendix 2.
• The psoas sign is one of the most reliable signs for ruling in acute appendicitis in children, along with the obturator sign and the Rovsing sign 2.
• However, the diagnosis of acute appendicitis is typically based on a combination of clinical findings, laboratory results, and imaging studies, rather than a single sign or symptom 3, 4, 2, 5, 6.
• Imaging studies, such as ultrasonography or computed tomography (CT) scans, can help confirm the diagnosis of appendicitis and rule out other potential causes of abdominal pain 4, 5, 6.
• The use of CT scans in particular has been shown to be effective in reducing negative appendectomy rates, which can occur when a patient undergoes an appendectomy but is found to have a normal appendix 5, 6.