Boas' sign

Boas' sign is a clinical sign indicative of visceral pain in the epigastric region, often associated with diseases of the gallbladder. It is named after the German-American physician Isidor Clinton Boas, who first described this sign. Boas' sign is characterized by the presence of hyperesthesia (increased sensitivity) or tenderness upon palpation in the right subscapular area of the back. This sign is particularly relevant in the diagnosis of acute cholecystitis, a condition marked by inflammation of the gallbladder, but it may also be present in other conditions affecting the gallbladder and surrounding structures.

Clinical Presentation

Patients presenting with Boas' sign may report a history of pain in the upper right quadrant of the abdomen, which may radiate to the back. This pain is typically acute in onset, sharp, and may be exacerbated by movements that involve the torso. The presence of Boas' sign is an important diagnostic clue, especially in cases where abdominal pain is the primary symptom with an unclear cause.

Pathophysiology

The pathophysiological basis of Boas' sign lies in the irritation of the phrenic nerve, which innervates the diaphragm but also has sensory fibers extending to the subscapular area. In conditions like acute cholecystitis, the inflamed gallbladder can irritate the phrenic nerve, leading to referred pain and hyperesthesia in the areas supplied by the nerve, particularly the right subscapular region.

Diagnostic Importance

Boas' sign is of significant diagnostic importance in the evaluation of patients with suspected gallbladder disease. It is one of several physical examination findings that can help differentiate gallbladder-related pain from other causes of abdominal pain. However, the absence of Boas' sign does not rule out gallbladder disease, and further diagnostic testing, such as ultrasound or computed tomography (CT) scan, may be necessary to confirm the diagnosis.

Differential Diagnosis

While Boas' sign is most commonly associated with gallbladder disease, it is important to consider other potential causes of right subscapular pain and hyperesthesia. These may include:

• Pleurisy
• Subphrenic abscess
• Hepatic abscess
• Renal colic

A thorough history and physical examination, along with appropriate diagnostic testing, are essential to differentiate these conditions.

Management

The management of conditions associated with Boas' sign depends on the underlying cause. In the case of acute cholecystitis, treatment may involve antibiotics, pain management, and potentially cholecystectomy (surgical removal of the gallbladder). The approach to other conditions presenting with Boas' sign will vary based on the specific diagnosis.

Conclusion

Boas' sign is a valuable clinical sign in the diagnosis of gallbladder disease, particularly acute cholecystitis. Its presence should prompt further investigation to confirm the diagnosis and determine the appropriate course of treatment. However, clinicians should also be aware of other potential causes of right subscapular pain and hyperesthesia to ensure accurate diagnosis and management.

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