**Question:** Best diagnostic sign in CDH

Core Concept:
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Central Diaphragmatic Hernia (CDH) is a congenital defect where part of the abdominal organs herniate into the thoracic cavity, leading to respiratory distress and hypoxia. The diagnostic process involves identifying the herniated organs and assessing their size and position.

**Why the Correct Answer is Right:**
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The correct answer, **Option C**: **"Diaphragmatic thickness measurement"**, is the best diagnostic sign in CDH. In a normal diaphragm, both the pleural and muscle layers are present. However, in CDH, the muscle layer may be thin, absent, or replaced by fibrous tissue due to hypoplasia. A decreased diaphragmatic thickness indicates the presence of CDH.

**Why Each Wrong Option is Incorrect:**
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Option A ("Ventilatory Support") addresses the clinical manifestations of CDH but not the diagnostic sign itself. Option B ("X-ray") is a method used to diagnose CDH, but it is not the diagnostic sign itself. Option D ("Diaphragmatic movement") focuses on the physiological effect of CDH on diaphragm function, but not the diagnostic sign.

**Clinical Pearl:**
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Diaphragmatic thickness measurement is a simple, non-invasive, and reproducible method to diagnose CDH. It aids in early diagnosis, allowing for timely intervention and improving outcomes for the affected infants.

**Correct Answer:** **Option C: Diaphragmatic thickness measurement** is the best diagnostic sign in CDH as it directly assesses the structural abnormality in the diaphragm and helps confirm the diagnosis.