What Is the Costophrenic Angle?

X-ray of rib cage which shows the costophrenic angle.
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  • Written By: Dulce Corazon
  • Edited By: W. Everett
  • Last Modified Date: 16 April 2014
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The word "costophrenic" is a combination of two words: costo, meaning ribs, and phrenic, meaning diaphragm. An angle is usually seen where the diaphragm and the chest wall meet. This is known as the costophrenic angle and this is often seen in X-rays. Normally, the angle measures about 30° and often has a sharp point. In several disorders, blunting or increase in its size can be observed.

Some of the disorders associated with blunting of the costophrenic angle include pleural effusion, hemothorax, and hyper-expansion of the lungs. Pleural effusion is the accumulation of fluid in the space surrounding the lungs. It is often caused by congestive heart failure, lung cancer, and lung infections, such as tuberculosis and pneumonia. In pleural effusion, fluid often gathers in the lower portion of the infected lung, pushing this lung upwards, which generally results in the blunting of the angle of the affected lung.

When blood accumulates in the space around the lungs, it is called a hemothorax. A hemothorax frequently results from direct trauma to the thorax or chest area. Hyper-expansion of the lungs is commonly seen in patients with asthma and emphysema. When the lung hyper-expands, it pushes the diaphragm downwards, which also leads to the blunting of the costophrenic angle in one or both lungs.


Patients with lung disorders are often managed by pulmonologists, or lung specialists. They often ask patients about their medical history, do physical exams, and request diagnostic tests like blood tests and imaging tests. The X-ray results are usually read by a radiogist, an expert in reading imaging tests. When results from the chest X-ray reveal blunting of the costophrenic angle, the medical professional may perform thoracentesis to evaluate the type of fluid that has gathered in the area.

A thoracentesis is a procedurethat involves the insertion of needle through the skin into the pleural cavity. Several fluid samples are then collected and sent to the laboratory for analysis. Treatment often depends on the results of this analysis.

When readings from the chest X-ray reveal blunting of the angle and the cause is massive build up of fluid or blood in the pleural cavity, it is often considered an emergency situation. Surgeons may need to perform tube thoracostomy. Tube thoracostomy is a procedure in which a chest tube is inserted in the pleural cavity to drain the fluid that continues to accumulate in the affected region.


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Post 2

@ceilingcat - I'm glad to know that x-ray technicians know when to notify the doctor. I'm sure more than few lives are saved that way.

I've had pneumonia before, but luckily I've never experienced pleural effusion. I did have to have a chest x-ray though, and my technician had a very nice bedside manner. I'm sure if my costophrenic angle had been blunted, he wouldn't have given it away to me!

Post 1

My friend is in school to be a radiography technician right now, and she just got done learning about the costophrenic angle. She was telling me about it the other day and I thought it was really interesting.

Apparently there are certain things that are considered an emergency when you see them on an x-ray, and this is one of them. Even though an x-ray technician can't make a diagnosis, when they see certain things they are expected to notify the doctor immediately.

As the article said, blunting of the costophrenic angle can mean a serious condition. My friend said her teachers really made them learn how to spot this on an x-ray so they don't make any dangerous mistakes in the future.

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