Pink sputum, rust-colored sputum, pus-smelling sputum...what's going on?

Author: Shi Huanzhong, Chief Physician, Beijing Chaoyang Hospital, Capital Medical University

Reviewer: Wang Qian, Chief Physician, Third Medical Center, PLA General Hospital

Sputum is a liquid secreted by the respiratory tract when it is irritated. Its main components are mucus, foreign matter, desquamated mucosal epithelial cells, pathogenic microorganisms, etc.

Under normal circumstances, the respiratory mucosa secretes mucus every day, which protects the respiratory tract and adheres to foreign matter inhaled into the respiratory tract, such as dust, polluted particles in the air, etc. The mucus will wrap these substances and irritate the bronchi, and be expelled from the body through coughing.

Therefore, healthy people may also have sputum in their respiratory tract, which is generally colorless or grayish white, and the frequency of coughing and sputum is not high.

If you have frequent coughing and sputum production, and the color of the sputum changes, or are accompanied by other uncomfortable symptoms, you should be alert to related respiratory diseases.

1. Coughing up rusty sputum and having a fever, what is going on?

This situation is covered in a very important chapter in the textbook, namely acute bacterial pneumonia, and the pathogen can basically be directly identified, which is Streptococcus pneumoniae.

Figure 1 Original copyright image, no permission to reprint

If it is viral pneumonia, it may be a simple cough without sputum, or it may be coughing up white mucus sputum, generally without purulent sputum, while bacterial pneumonia will have purulent sputum.

Why does pneumonia caused by Streptococcus pneumoniae produce rust-colored sputum? Because in the pathological process of pneumonia caused by Streptococcus pneumoniae, small blood vessels in the lower respiratory tract will rupture and bleed. This blood can settle in the alveoli. Over time, red blood cells are destroyed and hemosiderin is released, which appears rust-colored when coughed up.

For example, pneumonia caused by Klebsiella pneumoniae has brown jelly-like sputum; for example, infection with Pseudomonas aeruginosa has yellow-green sputum; if there is a foul smell on the basis of purulent sputum, it may be an anaerobic infection. Therefore, based on the characteristics of sputum, we can preliminarily judge what pathogen is infected.

Of course, such typical severe pneumonia cases are rarely seen in outpatient clinics nowadays, because most patients are treated before their condition becomes serious. After treatment, patients usually recover quickly.

2. What causes coughing up pink foamy sputum?

When coughing up pink foamy sputum, the first thing we think of is heart problems.

For example, if a patient has rheumatic heart disease or other heart diseases, heart failure, especially left heart failure, can cause pulmonary edema. Pulmonary edema can cause some small blood vessels to rupture, so some blood will be mixed in the sputum, and some foam will form pink foamy sputum.

Therefore, pink foamy sputum is generally used to describe the symptoms of acute pulmonary edema caused by left heart failure. In addition, patients with left heart failure will also have difficulty breathing. Those with severe conditions may not even be able to lie flat and can only sit upright to relieve breathing difficulties.

Figure 2 Original copyright image, no permission to reprint

Why do we need to sit? Because when sitting, the blood in the body is concentrated in the lower limbs, which can reduce the burden on the heart and make the patient feel more comfortable.

Of course, left heart failure also has manifestations of the heart itself. Since left heart failure has occurred, it means that the heart disease has existed for some time. If you ask carefully, most patients will have some symptoms of heart discomfort.

3. Coughing up a lot of pus-smelling sputum accompanied by a fever of 39 degrees, what is going on?

The most common acute infections usually occur in young and middle-aged people, while the elderly may not have such a dramatic reaction, and even if similar inflammation is present, its manifestations may not be typical.

When patients have a large amount of purulent sputum, especially purulent and smelly sputum accompanied by high fever, there are usually two situations: one is a large-scale acute pneumonia; the other is acute lung abscess caused by anaerobic bacterial infection.

For example, when young and middle-aged people have reduced resistance due to rain, cold or fatigue, bacteria that are not easy to cause acute infection (such as bacteria in the mouth) may enter the lungs through inhalation or blood circulation, leading to acute pneumonia or acute lung abscess.

Through chest X-ray examination, if simple flake-like infiltration shadows are found, it indicates the imaging features of acute pneumonia; if in addition to the flake-like shadows there are cavities, and there are fluid-air levels in the cavities, it indicates the imaging changes of acute lung abscess.

Combined with other examinations, routine blood tests revealed that the blood count was elevated, higher than the normal value. A normal white blood cell count is generally 9×109/L, 9.5×109/L. If it is as high as 20×109/L or even 30×109/L, it can basically support the clinical diagnosis, but a true diagnosis still requires finding the pathogen.

Sputum can be used, or other specimens, such as bronchoalveolar lavage fluid, or even blood specimens, etc. For example, a sputum smear examination can be done to see bacteria under a microscope. After a certain period of culture, the pathogens can be cultured and the diagnosis can be confirmed.