A 66-year-old homeless man with a history of smoking and cirrhosis due to alcoholism presents to the hospital with a productive cough and fever for one month. He has traveled around Arizona and New Mexico but has never left the country. His complete blood count (CBC) is notable for a white blood cell count of 13,000. His chest X-ray reveals a 1.7-cm right upper lobe cavitary lung lesion (see Figure 1). What is the best approach to this patient’s cavitary lung lesion?
Cavitary lung lesions are relatively common findings on chest imaging and often pose a diagnostic challenge to the hospitalist. Having a standard approach to the evaluation of a cavitary lung lesion can facilitate an expedited workup.
A lung cavity is defined radiographically as a lucent area contained within a consolidation, mass, or nodule.1 Cavities usually are accompanied by thick walls, greater than 4 mm. These should be differentiated from cysts, which are not surrounded by consolidation, mass, or nodule, and are accompanied by a thinner wall.2
The differential diagnosis of a cavitary lung lesion is broad and can be delineated into categories of infectious and noninfectious etiologies (see Figure 2). Infectious causes include bacterial, fungal, and, rarely, parasitic agents. Noninfectious causes encompass malignant, rheumatologic, and other less common etiologies such as infarct related to pulmonary embolism.
The clinical presentation and assessment of risk factors for a particular patient are of the utmost importance in delineating next steps for evaluation and management (see Table 1). For those patients of older age with smoking history, specific occupational or environmental exposures, and weight loss, the most common etiology is neoplasm. Common infectious causes include lung abscess and necrotizing pneumonia, as well as tuberculosis. The approach to diagnosis should be based on a composite of the clinical presentation, patient characteristics, and radiographic appearance of the cavity.
Guidelines for the approach to cavitary lung lesions are lacking, yet a thorough understanding of the initial approach is important for those practicing hospital medicine. Key components in the approach to diagnosis of a solitary cavitary lesion are outlined in this article.
Diagnosis of Infectious Causes
In the initial evaluation of a cavitary lung lesion, it is important to first determine if the cause is an infectious process. The infectious etiologies to consider include lung abscess and necrotizing pneumonia, tuberculosis, and septic emboli. Important components in the clinical presentation include presence of cough, fever, night sweats, chills, and symptoms that have lasted less than one month, as well as comorbid conditions, drug or alcohol abuse, and history of immunocompromise (e.g. HIV, immunosuppressive therapy, or organ transplant).
Given the public health considerations and impact of treatment, tuberculosis (TB) will be discussed in its own category.
Tuberculosis. Given the fact that TB patients require airborne isolation, the disease must be considered early in the evaluation of a cavitary lung lesion. Patients with TB often present with more chronic symptoms, such as fevers, night sweats, weight loss, and hemoptysis. Immunocompromised state, travel to endemic regions, and incarceration increase the likelihood of TB. Nontuberculous mycobacterium (i.e., M. kansasii) should also be considered in endemic areas.
For those patients in whom TB is suspected, airborne isolation must be initiated promptly. The provider should obtain three sputum samples for acid-fast bacillus (AFB) smear and culture when risk factors are present. Most patients with reactivation TB have abnormal chest X-rays, with approximately 20% of those patients having air-fluid levels and the majority of cases affecting the upper lobes.3 Cavities may be seen in patients with primary or reactivation TB.3
Lung abscess and necrotizing pneumonia. Lung abscesses are cavities associated with necrosis caused by a microbial infection. The term necrotizing pneumonia typically is used when there are multiple smaller (smaller than 2 cm) associated lung abscesses, although both lung abscess and necrotizing pneumonia represent a similar pathophysiologic process and are along the same continuum. Lung abscess is suspected with the presence of predisposing risk factors to aspiration (e.g. alcoholism) and poor dentition. History of cough, fever, putrid sputum, night sweats, and weight loss may indicate subacute or chronic development of a lung abscess. Physical examination might be significant for signs of pneumonia and gingivitis.
Organisms that cause lung abscesses include anaerobes (most common), TB, methicillin-resistant Staphylococcus aureus (MRSA), post-influenza illness, endemic fungi, and Nocardia, among others.4 In immunocompromised patients, more common considerations include TB, Mycobacterium avium complex, other mycobacteria, Pseudomonas aeruginosa, Nocardia, Cryptococcus, Aspergillus, endemic fungi (e.g. Coccidiodes in the Southwest and Histoplasma in the Midwest), and, less commonly, Pneumocystis jiroveci.4 The likelihood of each organism is dependent on the patient’s risk factors. Initial laboratory testing includes sputum and blood cultures, as well as serologic testing for endemic fungi, especially in immunocompromised patients.
Imaging may reveal a cavitary lesion in the dependent pulmonary segments (posterior segments of the upper lobes or superior segments of the lower lobes), at times associated with a pleural effusion or infiltrate. The most common appearance of a lung abscess is an asymmetric cavity with an air-fluid level and a wall with a ragged or smooth border. CT scan is often indicated when X-rays are equivocal and when cases are of uncertain cause or are unresponsive to antibiotic therapy. Bronchoscopy is reserved for patients with an immunocompromising condition, atypical presentation, or lack of response to treatment.
For those cavitary lesions in which there is a high degree of suspicion for lung abscess, empiric treatment should include antibiotics active against anaerobes and MRSA if the patient has risk factors. Patients often receive an empiric trial of antibiotics prior to biopsy unless there are clear indications that the cavitary lung lesion is related to cancer. Lung abscesses typically drain spontaneously, and transthoracic or endobronchial drainage is not usually recommended as initial management due to risk of pneumothorax and formation of bronchopleural fistula.
Lung abscesses should be followed to resolution with serial chest imaging. If the lung abscess does not resolve, it would be appropriate to consult thoracic surgery, interventional radiology, or pulmonary, depending on the location of the abscess and the local expertise with transthoracic or endobronchial drainage and surgical resection.
Septic emboli. Septic emboli are a less common cause of cavitary lung lesions. This entity should be considered in patients with a history of IV drug use or infected indwelling devices (central venous catheters, pacemaker wires, and right-sided prosthetic heart valves). Physical examination should include an assessment for signs of endocarditis and inspection for infected indwelling devices. In patients with IV drug use, the likely pathogen is S. aureus.
Oropharyngeal infection or indwelling catheters may predispose patients to septic thrombophlebitis of the internal jugular vein, also known as Lemierre’s syndrome, a rare but important cause of septic emboli.5 Laboratory testing includes culture for sputum and blood and culture of the infected device if applicable. On chest X-ray, septic emboli commonly appear as nodules located in the lung periphery. CT scan is more sensitive for detecting cavitation associated with septic emboli.
Diagnosis of Noninfectious Causes
Upon identification of a cavitary lung lesion, noninfectious etiologies must also be entertained. Noninfectious etiologies include malignancy, rheumatologic diseases, pulmonary embolism, and other causes. Important components in the clinical presentation include the presence of constitutional symptoms (fevers, weight loss, night sweats), smoking history, family history, and an otherwise complete review of systems. Physical exam should include evaluation for lymphadenopathy, cachexia, rash, clubbing, and other symptoms pertinent to the suspected etiology.
Malignancy. Perhaps most important among noninfectious causes of cavitary lung lesions is malignancy, and a high index of suspicion is warranted given that it is commonly the first diagnosis to consider overall.2 Cavities can form in primary lung cancers (e.g. bronchogenic carcinomas), lung tumors such as lymphoma or Kaposi’s sarcoma, or in metastatic disease. Cavitation has been detected in 7%-11% of primary lung cancers by plain radiography and in 22% by computed tomography.5 Cancers of squamous cell origin are the most likely to cavitate; this holds true for both primary lung tumors and metastatic tumors.6 Additionally, cavitation portends a worse prognosis.7
Clinicians should review any available prior chest imaging studies to look for a change in the quality or size of a cavitary lung lesion. Neoplasms are typically of variable size with irregular thick walls (greater than 4 mm) on CT scan, with higher specificity for neoplasm in those with a wall thickness greater than 15 mm.2
When the diagnosis is less clear, the decision to embark on more advanced diagnostic methods, such as biopsy, should rest on the provider’s clinical suspicion for a certain disease process. When a lung cancer is suspected, consultation with pulmonary and interventional radiology should be obtained to determine the best approach for biopsy.
Rheumatologic. Less common causes of cavitary lesions include those related to rheumatologic diseases (e.g. granulomatosis with polyangiitis, formerly known as Wegener’s granulomatosis). One study demonstrated that cavitary lung nodules occur in 37% of patients with granulomatosis with polyangiitis.8
Although uncommon, cavitary nodules can also be seen in rheumatoid arthritis and sarcoidosis. Given that patients with rheumatologic diseases are often treated with immunosuppressive agents, infection must remain high on the differential. Suspicion of a rheumatologic cause should prompt the clinician to obtain appropriate serologic testing and consultation as needed.
Pulmonary embolism. Although often not considered in the evaluation of cavitary lung lesions, pulmonary embolism (PE) can lead to infarction and the formation of a cavitary lesion. Pulmonary infarction has been reported to occur in as many as one third of cases of PE.9 Cavitary lesions also have been described in chronic thromboembolic disease.10
Other. Uncommon causes of cavitary lesions include bronchiolitis obliterans with organizing pneumonia, Langerhans cell histiocytosis, and amyloidosis, among others. The hospitalist should keep a broad differential and involve consultants if the diagnosis remains unclear after initial diagnostic evaluation.
Back to the Case
The patient’s fever and productive cough, in combination with recent travel and location of the cavitary lesion, increase his risk for tuberculosis and endemic fungi, such as Coccidioides. This patient was placed on respiratory isolation with AFBs obtained to rule out TB, with Coccidioides antibodies, Cyptococcal antigen titers, and sputum for fungus sent to evaluate for an endemic fungus. He had a chest CT, which revealed a 17-mm cavitary mass within the right upper lobe that contained an air-fluid level indicating lung abscess. Coccidioides, cryptococcal, fungal sputum, and TB studies were negative.
The patient was treated empirically with clindamycin given the high prevalence of anaerobes in lung abscess. He was followed as an outpatient and had a chest X-ray showing resolution of the lesion at six months. The purpose of the X-ray was two-fold: to monitor the effect of antibiotic treatment and to evaluate for persistence of the cavitation given the neoplastic risk factors of older age and smoking.
The best approach to a patient with a cavitary lung lesion includes assessing the clinical presentation and risk factors, differentiating infectious from noninfectious causes, and then utilizing this information to further direct the diagnostic evaluation. Consultation with a subspecialist or further testing such as biopsy should be considered if the etiology remains undefined after the initial evaluation.
Drs. Rendon, Pizanis, Montanaro, and Kraai are hospitalists in the department of internal medicine at the University of New Mexico School of Medicine in Albuquerque.
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- Harris H, Barraclough R, Davies C, Armstrong I, Kiely DG, van Beek E Jr. Cavitating lung lesions in chronic thromboembolic pulmonary hypertension. J Radiol Case Rep. 2008;2(3):11-21.
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