Sputum examination
Last reviewed: 23.04.2024
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Sputum is a pathological secret of the respiratory tract that is secreted during coughing and is caused by damage to the mucous membrane of the trachea, bronchi and lung tissue by infectious, physical or chemical agents.
Sputum analysis in patients with pneumonia in many cases (although not always) allows:
- determine the nature of the pathological process;
- to clarify the etiology of inflammation of the respiratory tract and lung tissue, in particular to isolate the pathogen of inflammation;
- determine the main properties of the pathogen, including its sensitivity to antibiotics;
- evaluate the effectiveness of treatment.
Sputum analysis includes:
- Macroscopic examination (determination of sputum character, its quantity, color, transparency, odor, consistency, presence of impurities and various inclusions).
- Microscopic examination (determination of cellular and other sputum elements, as well as the study of microbial flora in native and stained smears).
- Microbiological study (identification and study of the properties of the alleged causative agent of the disease).
The chemical study of sputum has not yet found wide application in clinical practice, although it also has some diagnostic significance.
[Sputum for research
Sputum for examination is collected in the morning on an empty stomach after preliminary thorough rinsing of the mouth and throat with boiled water. Sometimes it is recommended that you rinse your mouth with a 1% solution of aluminum alum.
The patient coughs up sputum directly into clean, dry glassware with a tight-fitting lid. If microbiological examination of the sputum is expected, it is cleared into a sterile Petri dish or other sterile container. It is important to warn the patient that when sputum is collected, the ingestion of saliva into samples sent to the laboratory can significantly change the results of the study. Only freshly sputum is sent to the laboratory, since prolonged standing, especially at room temperature, leads to autolysis of cell elements and reproduction of microflora. If necessary, short-term storage of phlegm in the refrigerator is allowed.
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General properties of sputum
Number of sputum
The amount of sputum usually ranges from 10 to 100 ml per day. Few sputum is separated in acute bronchitis, pneumonia, congestion in the lungs, at the onset of an attack of bronchial asthma. At the end of an attack of bronchial asthma, the amount of sputum is increased. A large amount of sputum (sometimes up to 0.5 liters) can be released during pulmonary edema, as well as during suppuration in the lungs, if the cavity with the bronchus is reported (abscess, bronchiectasis, gangrene of the lung, tuberculosis in the lung, accompanied by tissue decay) . It should be borne in mind that a decrease in the amount of sputum released during suppuration in the lungs may be due to the abatement of the inflammatory process, as well as the result of impaired drainage of the purulent cavity, which is often accompanied by worsening of the patient's condition. The increase in the amount of sputum may be regarded as a sign of worsening of the patient's condition, if it depends on exacerbation, for example, of a suppuration process; in other cases, when an increase in the amount of sputum is associated with an improvement in the drainage of the cavity, it is regarded as a positive symptom.
Sputum color
Most sputum is colorless, the attachment of a purulent component gives it a greenish tinge that is observed with an abscess of the lung, gangrene of the lung, bronchiectasis, actinomycosis of the lung. When sputum appears in fresh sputum, sputum is colored in various shades of red (sputum during hemoptysis in patients with tuberculosis, actinomycosis, lung cancer, lung abscess, with lung infarction, cardiac asthma and pulmonary edema).
Sputum smear (with croupous, focal and influenza pneumonia, with pulmonary tuberculosis with curdled decay, stagnation in the lungs, pulmonary edema, with pulmonary form of anthrax) or sputum of brown color (with lung infarction) indicates the content in it is not fresh blood, but the products of its decay (hematin).
Dirty-green or yellow-green color can have sputum, which separates with various pathological processes in the lungs, combined with the presence of jaundice in patients .
Yellow-canary color of sputum is sometimes observed with eosinophilic pneumonia. The ophthalmic sputum discharge is possible with lung siderosis.
Blackish or grayish sputum occurs with coal dust and smokers.
Sputum may be stained with some medications, for example, rifampicin stains the discharge into red.
Smell of phlegm
Sputum is usually odorless. The appearance of odor contributes to a violation of outflow of sputum. Putrid odor it acquires in the abscess, gangrene of the lung, with putrefactive bronchitis as a result of joining putrefactive infection, bronchoectatic disease, lung cancer, complicated by necrosis. For the revealed echinococcal cyst is characterized by a peculiar fruity smell of phlegm.
Sputum of sputum
Purulent sputum on standing is usually divided into 2 layers, putrefactive - on 3 layers (upper frothy, medium serous, lower purulent). Especially characteristic is the appearance of a three-layer sputum for gangrene of the lung, while the appearance of double-layered sputum is usually observed in the abscess of lung and bronchiectasis.
Sputum reaction
Sputum usually has an alkaline or neutral reaction. The decomposed sputum gets an acid reaction.
Nature of sputum
- Mucous sputum is excreted in acute and chronic bronchitis, asthmatic bronchitis, tracheitis.
- Muco-purulent sputum is characteristic for abscess and gangrene of the lung, silicosis, purulent bronchitis, exacerbation of chronic bronchitis, staphylococcal pneumonia.
- Purulent-mucous sputum is characteristic for bronchopneumonia.
- Purulent sputum is possible with bronchiectasis, staphylococcal pneumonia, abscess, gangrene, actinomycosis of the lungs.
- Serous sputum is separated with pulmonary edema.
- Serous-purulent sputum is possible with an abscess of the lung.
- Bloody sputum is excreted in case of lung infarction, neoplasms, pneumonia (sometimes), trauma of the lung, actinomycosis and syphilis.
It should be noted that hemoptysis and impurity of blood to sputum are not observed in all cases of lung infarcts (in 12-52%). Therefore, the absence of hemoptysis does not give grounds for refusing the diagnosis of a lung infarct. It should also be remembered that it is not always possible to analyze sputum with the appearance of a large amount of blood in the lungs due to pulmonary pathology. To simulate pulmonary bleeding can, for example, gastric or nasal bleeding.