Holes in the lungs form when tissue is destroyed by infection, disease, or abnormal air pockets. The medical term for these holes is “cavitary lesions” or “cavities,” and they show up on chest X-rays or CT scans as dark, hollow spaces where solid lung tissue should be. The causes range from bacterial infections and tuberculosis to chronic lung disease, cancer, and autoimmune conditions.
How Lung Tissue Breaks Down
Healthy lung tissue is spongy and filled with tiny air sacs that exchange oxygen and carbon dioxide. A hole forms when something destroys that tissue from the inside out. In infections, the body’s own immune response often does the damage: white blood cells flood the area, release powerful enzymes (protein-dissolving chemicals, fat-dissolving chemicals, and others), and break down both the invading organism and the surrounding lung tissue. The destroyed tissue either liquefies and gets coughed up or dies and leaves behind a hollow space.
In non-infectious causes like cancer, the center of a tumor can outgrow its blood supply, starving itself of oxygen. The tissue in the middle dies and breaks apart, leaving a cavity. About 10% to 20% of all lung cancers show up on imaging with this kind of hollowed-out appearance.
Tuberculosis
Tuberculosis (TB) is one of the most recognized causes of lung cavities worldwide and has been studied for over a century. When TB bacteria infect the lungs, the immune system walls them off in dense clumps of dead tissue called caseous necrosis, named for its cheese-like consistency. This solid plug can sit in the lung for weeks or longer without changing.
The cavity forms not because the bacteria eat through the tissue, but because the body’s own enzymes eventually liquefy it. Research has shown that the TB bacteria actually produce substances that slow this liquefaction process down. Once those inhibitors diffuse away, host enzymes (including those from immune cells called macrophages) dissolve the dead tissue. The liquefied material drains into the airways, gets coughed out, and leaves behind an open cavity. This cavity then becomes an ideal environment for the bacteria to multiply in large numbers, which is why cavitary TB is highly contagious.
Bacterial Lung Abscess
A lung abscess is essentially a pocket of pus inside the lung, and it’s the most common infectious cause of lung cavities in many clinical settings. It typically starts when bacteria from the mouth or throat are accidentally inhaled into the lungs, which is why it often follows aspiration events like choking, heavy sedation, or alcohol intoxication.
The bacteria involved are usually anaerobes, organisms that thrive without oxygen and normally live in the mouth and gums. The most common culprits include species of Peptostreptococcus, Bacteroides, and Fusobacterium. These bacteria trigger a localized infection that destroys the surrounding tissue, forming a walled-off cavity filled with infected fluid. Less commonly, Staphylococcus aureus can cause lung abscesses, sometimes producing multiple cavities at once. Klebsiella pneumoniae is another cause, particularly in people with alcohol use disorder or diabetes.
Fungal Infections
Several types of fungi can cause or inhabit lung cavities. The most well-known is Aspergillus fumigatus, which causes a condition called aspergilloma. Rather than creating the cavity itself, this fungus typically moves into a pre-existing hole, one left behind by TB, a prior abscess, or another lung disease. Inside that cavity, the fungus grows into a dense ball of fungal material that’s often visible on X-rays as a round mass sitting inside the hollow space.
Other fungi can actively destroy lung tissue to create cavities on their own. These include the organisms responsible for histoplasmosis, coccidioidomycosis (valley fever), and blastomycosis. These infections tend to occur in specific geographic regions. Histoplasmosis is common in the Ohio and Mississippi River valleys, coccidioidomycosis in the desert Southwest, and blastomycosis around the Great Lakes and Southeast. People with weakened immune systems face additional risks from fungi like Cryptococcus and the organisms that cause mucormycosis.
Emphysema and Air-Filled Cysts
Not all holes in the lungs come from infection. Emphysema, most often caused by long-term smoking, gradually destroys the walls of the tiny air sacs in the lungs. As these walls break down, small air sacs merge into larger and larger spaces, creating permanent holes that can’t exchange oxygen effectively.
Two specific types of air-filled holes deserve mention. A bleb is a small pocket of trapped air between the lung surface and its outer lining, typically found in the upper portions of the lung. When blebs grow larger or merge together, they form what’s called a bulla. Bullae can become quite large, sometimes compressing the healthy lung tissue around them. Both blebs and bullae can rupture without warning, releasing air into the chest cavity and causing a collapsed lung (pneumothorax). This is the reason some young, otherwise healthy people, particularly tall, thin men, experience a sudden collapsed lung seemingly out of nowhere.
Lung Cancer
Cavities in the lung aren’t always caused by infection. Between 10% and 20% of lung cancers develop a hollow center, usually because the tumor grows faster than its blood supply can keep up. The tissue at the core becomes oxygen-starved, dies, and breaks down. Squamous cell carcinoma, one of the main types of lung cancer, is particularly prone to forming cavities. On imaging, a cancerous cavity often has thick, irregular walls, which helps distinguish it from the thinner, smoother walls of an infectious abscess, though the distinction isn’t always clear-cut.
Because a cavitary lesion can look similar whether it’s caused by infection or cancer, doctors often need a biopsy or additional testing to tell the difference. This is especially important when someone has risk factors for both, such as a history of smoking combined with possible TB exposure.
Autoimmune and Inflammatory Causes
The immune system itself can attack lung tissue and create holes. Granulomatosis with polyangiitis (GPA), formerly called Wegener’s granulomatosis, is a condition in which the immune system produces antibodies that mistakenly target healthy cells. This triggers inflammation in blood vessels throughout the body, including those in the lungs. The inflamed tissue forms clumps called granulomas that can destroy healthy lung tissue, leaving behind cavities. GPA also commonly affects the sinuses and kidneys, so lung cavities appearing alongside sinus problems or kidney issues can be an important diagnostic clue.
Other autoimmune conditions can cause similar damage. Rheumatoid arthritis occasionally produces lung nodules that cavitate, and sarcoidosis can create cavitary lesions in rare cases. Without treatment, ongoing inflammation from these conditions leads to progressive scarring and loss of functional lung tissue.
Parasitic and Rare Causes
In certain parts of the world, parasites can create cyst-like holes in the lungs. Echinococcus, a tapeworm acquired from contact with infected dogs or livestock, forms fluid-filled cysts that can grow to several centimeters. Paragonimus, a lung fluke contracted by eating undercooked freshwater crabs or crayfish, burrows into lung tissue and creates cavities as it matures. Amebic infections from Entamoeba histolytica, more commonly associated with liver abscesses, can occasionally extend into the lungs and produce cavitary disease.
These causes are rare in North America and Europe but are important to consider in travelers or immigrants from endemic regions in Southeast Asia, sub-Saharan Africa, and parts of South America.
How Lung Cavities Are Found
Most lung cavities are discovered on a chest X-ray or CT scan, often during workup for symptoms like a persistent cough, coughing up blood, unexplained fevers, or weight loss. The appearance of the cavity gives doctors initial clues about the cause. Thin-walled cavities suggest infections or benign cysts, while thick, irregular walls raise concern for cancer. A round mass sitting inside a cavity, sometimes shifting position when the patient moves, points toward a fungal ball.
Because so many different conditions can create similar-looking holes, pinpointing the cause usually requires combining imaging findings with blood tests, sputum cultures, and sometimes a tissue biopsy. The patient’s history matters enormously: where they’ve lived, what they’ve been exposed to, whether they smoke, and how their immune system is functioning all help narrow the possibilities.