Sputum

In everyday language, sputum refers to any material expelled from the mouth. Medically, it typically refers to content coughed up from deeper parts of the respiratory system, such as the airways and lungs. In many respiratory diseases, daily sputum production can exceed one liter. Depending on the condition, sputum may be mucous, mucopurulent, purulent, bloody, or frothy, with colors ranging from red, black, brown, to green. Coughed-up material may be pure blood or clear liquid resembling spring water.

Many people occasionally examine their sputum, especially during respiratory illness. Historically, doctors diagnosed lung diseases based solely on sputum appearance. Even today, despite advanced diagnostics, sputum examination remains invaluable, sometimes allowing diagnosis through visual inspection alone.

Purulent sputum always indicates a pus-filled focus in the respiratory system, often from cavities where pus enters airways and is expelled by coughing. Various bacteria cause this, entering the lungs via inhalation, blood, or nearby infected organs. Localized purulent foci may develop after pneumonia or inhaled foreign bodies. Pus gradually seeps into airways and is coughed out. A common cause of purulent sputum is dilated bronchi (bronchiectasis).

Seeing blood in sputum often causes unnecessary panic. Spat blood isn’t always coughed up from the lungs. Blood mixed with saliva usually originates from the mouth, throat, tongue, or salivary glands, lacking the mucus produced in airways.

Blood mixed with mucus may come from the nose if nasal mucus is drawn into the mouth. Persistent bloody or blood-tinged sputum always requires medical evaluation, as it may be an early sign of lung cancer, especially in men over 40 or smokers.

Excess mucus in airways triggers coughing to clear them and maintain patency. Mucous or frothy sputum, odorless, is a clean product of numerous airway mucus glands. Mucus production can increase due to infections, inflammation, irritant gases, dust, cold, or sudden temperature changes.

These causes typically lead to temporary, short-term excess mucus production. Rarely, chronic, excessive mucus production occurs due to heightened gland activity or increased gland numbers, leading to frequent coughing to keep airways clear, as seen in chronic bronchitis.