**Question:** Dysphagia lusoria is diagnosed by

A. Barium swallow study
B. Esophagogastroduodenoscopy
C. Chest X-ray
D. High-resolution manometry

**Core Concept:**

Dysphagia lusoria is a rare condition characterized by difficulty swallowing (dysphagia) caused by compression of the esophagus by the right subclavian artery. This condition typically presents in adults, often after the age of 40, and is believed to be caused by a developmental anomaly of the right subclavian artery during fetal development.

**Why the Correct Answer is Right:**

A. Barium swallow study (radiography) is the most appropriate method for diagnosing dysphagia lusoria due to its ability to visualize the esophagus and surrounding structures. Barium contrast helps to identify the abnormal course of the right subclavian artery that compresses the esophagus during swallowing, leading to the characteristic "Cow's Paw" appearance on X-ray.

**Why Each Wrong Option is Incorrect:**

B. Esophagogastroduodenoscopy (EGD) is a diagnostic procedure used to evaluate the esophagus, stomach, and duodenum. It is mainly used for evaluating gastrointestinal symptoms like pain, bleeding, or inflammation but not for diagnosing vascular causes of dysphagia such as dysphagia lusoria.

C. Chest X-ray is essential for diagnosing conditions related to the chest and lungs, not specifically for evaluating swallowing issues or vascular anomalies like dysphagia lusoria.

D. High-resolution manometry is a diagnostic tool for evaluating the esophageal motility disorders, such as achalasia, but not for diagnosing vascular compression of the esophagus, like in dysphagia lusoria.

**Clinical Pearl:**

Dysphagia lusoria is a rare condition with an estimated prevalence of 0.3% to 0.8% in the general population. The diagnosis of this condition relies on identifying the "Cow's Paw" sign on a lateral chest radiograph, which demonstrates the right subclavian artery crossing behind the trachea, instead of its usual anterior position. This anomaly can be associated with other congenital anomalies, including aortic coarctation, interrupted aortic arch, and persistent left subclavian artery. In addition to radiography, the clinical history of dysphagia and the "Cow's Paw" sign on radiography are essential for the diagnosis of dysphagia lusoria.