Not a tributary of Azygos Vein among the following is
**Core Concept**
The Azygos vein is a significant venous structure that plays a crucial role in the drainage of blood from the posterior walls of the thorax and abdomen. It originates from the junction of the right ascending lumbar and right subcostal veins, forming a plexus-like structure known as the Azygos system.
**Why the Correct Answer is Right**
The Intercostolumbar azygos vein is not considered a tributary of the Azygos vein. Instead, it is part of the Azygos system and contributes to the formation of the Azygos vein itself. The Azygos vein receives blood from the ascending lumbar veins, subcostal veins, hemiazygos, and accessory hemiazygos veins, but not directly from the intercostolumbar azygos vein. This distinction is essential in understanding the venous drainage of the thoracic and abdominal regions.
**Why Each Wrong Option is Incorrect**
**Option A:** The Lumbar Ascending vein is indeed a tributary of the Azygos vein, draining blood from the posterior abdominal wall.
**Option B:** The Subcostal Vein is also a tributary of the Azygos vein, draining blood from the posterior thoracic wall.
**Option D:** The Right Bronchial Vein is not a tributary of the Azygos vein; it drains directly into the Superior Vena Cava.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the Azygos system is a complex network of veins that drain blood from the posterior walls of the thorax and abdomen. The correct identification of tributaries and branches of the Azygos vein can be critical in understanding various clinical conditions, such as thoracic outlet syndrome or abdominal trauma.
**✓ Correct Answer: C. Intercostolumbar azygos vein**