Case
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?
Overview
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.
Figure 1. Right upper lobe cavitary lung lesion
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.
(click for larger image)Table 1. Patient traits and radiologic appearance suggesting specific etiologies of cavitary lung lesions
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