LUNG ABSCESS Flashcards
Which of the following is the most common cause of primary lung abscess?
A) Staphylococcus aureus
B) Anaerobic bacteria
C) Mycobacterium tuberculosis
D) Pseudomonas aeruginosa
Correct Answer: B) Anaerobic bacteria
Rationale:
Primary lung abscesses typically arise from aspiration, and anaerobic bacteria (such as Fusobacterium, Peptostreptococcus, Prevotella, and Bacteroides species) are the predominant causative agents. Staphylococcus aureus and Pseudomonas aeruginosa are more commonly seen in secondary lung abscesses, while Mycobacterium tuberculosis causes cavitary lung disease rather than a true abscess.
Which of the following is the most important risk factor for developing a primary lung abscess?
A) Smoking
B) Aspiration
C) Chronic obstructive pulmonary disease (COPD)
D) Air pollution
Correct Answer: B) Aspiration
Rationale:
Aspiration is the key risk factor for primary lung abscesses, as it allows oropharyngeal secretions containing anaerobic bacteria to enter the lungs. This occurs more frequently in individuals with altered mental status, alcoholism, drug overdose, seizures, or neurological conditions affecting swallowing. Smoking and COPD increase the risk of lung infections but are not the primary causes of lung abscesses.
Which of the following groups is at highest risk for developing a primary lung abscess?
A) Young healthy individuals
B) Middle-aged men with a history of alcohol abuse
C) Patients with bronchial tumors
D) Patients with cystic fibrosis
Correct Answer: B) Middle-aged men with a history of alcohol abuse
Rationale:
Middle-aged men, particularly those with a history of alcohol abuse, are at the highest risk for primary lung abscesses due to an increased likelihood of aspiration. Alcohol impairs the cough reflex and mucociliary clearance, promoting the aspiration of anaerobic oral flora. Patients with bronchial tumors and cystic fibrosis are more likely to develop secondary lung abscesses rather than primary ones.
A 45-year-old male with a history of alcohol use disorder presents with fever, productive cough with foul-smelling sputum, and weight loss for the past three weeks. Chest X-ray shows a cavitary lesion with an air-fluid level in the right lower lobe. Which of the following is the most likely underlying cause?
A) Aspiration of oropharyngeal secretions
B) Mycobacterium tuberculosis infection
C) Hematogenous spread of septic emboli
D) Bronchial carcinoma causing obstruction
Correct Answer: A) Aspiration of oropharyngeal secretions
Rationale:
This patient’s history of alcohol use disorder and symptoms suggest a primary lung abscess caused by aspiration of oropharyngeal secretions containing anaerobic bacteria. Cavitary lesions with air-fluid levels are characteristic of lung abscesses. Mycobacterium tuberculosis can also cause cavitary lung disease but is typically associated with apical involvement. Hematogenous spread of septic emboli is seen in tricuspid valve endocarditis, and bronchial carcinoma is a cause of secondary lung abscess.
Which of the following is the most common location for a primary lung abscess?
A) Apical segments of the upper lobes
B) Anterior segments of the lower lobes
C) Dependent segments of the upper and lower lobes
D) Lingula of the left lung
Correct Answer: C) Dependent segments of the upper and lower lobes
Rationale:
Primary lung abscesses commonly occur in the dependent segments, particularly the posterior segments of the upper lobes and the superior segments of the lower lobes, because aspirated material preferentially deposits in these areas. This occurs due to gravity, particularly when patients aspirate in a recumbent position.
Why is the right lung more commonly affected by primary lung abscesses than the left?
A) The right lung has a larger volume than the left
B) The right mainstem bronchus is less angulated and more vertical
C) The left lung has better clearance mechanisms
D) The right lung has a higher perfusion rate than the left
Correct Answer: B) The right mainstem bronchus is less angulated and more vertical
Rationale:
The right mainstem bronchus has a more direct and vertical trajectory from the trachea compared to the left, making it more prone to aspiration of oropharyngeal contents. This anatomical difference increases the likelihood of a primary lung abscess occurring in the right lung.
Which of the following statements regarding the microbiology of primary lung abscesses is true?
A) They are most commonly caused by Streptococcus pneumoniae
B) They are typically monomicrobial infections
C) They often involve anaerobic bacteria and microaerophilic streptococci
D) They require specialized culture techniques for definitive diagnosis in most cases
Correct Answer: C) They often involve anaerobic bacteria and microaerophilic streptococci
Rationale:
Primary lung abscesses are polymicrobial infections, commonly involving anaerobic bacteria (e.g., Fusobacterium, Bacteroides, Peptostreptococcus, Prevotella) and microaerophilic streptococci. While specialized culture techniques can improve pathogen identification, they are not always necessary for treatment decisions. Streptococcus pneumoniae is a common cause of pneumonia but is not a major pathogen in lung abscesses.
A 55-year-old male with a history of poor dental hygiene and chronic alcohol use presents with fever, weight loss, and a foul-smelling productive cough. Chest imaging reveals a cavitary lesion with an air-fluid level in the right lower lobe. Which of the following is the most likely diagnosis?
A) Tuberculosis
B) Nocardiosis
C) Putrid lung abscess
D) Lung cancer with cavitation
Correct Answer: C) Putrid lung abscess
Rationale:
A putrid lung abscess is characterized by foul-smelling breath, sputum, or empyema, which is highly suggestive of an anaerobic infection. This condition is most commonly seen in patients with alcohol use disorder and poor oral hygiene due to aspiration of anaerobic bacteria.
A putrid lung abscess refers to cases with foul-smelling breath, sputum, or empyema; these manifestations are essentially diagnostic of an anaerobic lung abscess.
Which of the following is the most common bacterial cause of secondary lung abscesses?
A) Pseudomonas aeruginosa
B) Mycobacterium tuberculosis
C) Fusobacterium necrophorum
D) Legionella pneumophila
Correct Answer: A) Pseudomonas aeruginosa
Rationale:
Secondary lung abscesses have a broader microbiological spectrum than primary lung abscesses. Gram-negative bacteria, particularly Pseudomonas aeruginosa and other gram-negative rods, are the most common pathogens in secondary lung abscesses. Fusobacterium necrophorum is associated with Lemierre’s syndrome, Mycobacterium tuberculosis is a cause of cavitary lung disease but not true lung abscesses, and Legionella pneumophila is primarily associated with atypical pneumonia.
Which of the following symptoms is most suggestive of an anaerobic lung abscess?
A) Sudden onset of high fever and dyspnea
B) Foul-smelling sputum with a chronic course
C) Dry cough with wheezing
D) Hemoptysis and pleuritic chest pain
Correct Answer: B) Foul-smelling sputum with a chronic course
Rationale:
Anaerobic lung abscesses tend to have a chronic and indolent presentation, with night sweats, fatigue, and anemia. A putrid (foul-smelling) sputum is highly suggestive of anaerobic infection, often due to polymicrobial flora. High fevers and rapid progression are more characteristic of non-anaerobic pathogens, such as Staphylococcus aureus (Option A). Dry cough and wheezing (Option C) are more typical of asthma or viral infections, while hemoptysis and pleuritic pain (Option D) suggest pulmonary embolism or tuberculosis.
A 65-year-old man with poor dentition and history of alcohol use disorder presents with fever, productive cough, and weight loss. Imaging shows a thick-walled cavitary lesion with an air-fluid level in the right lung. What is the most likely etiology of his lung abscess?
A) Aspiration of anaerobic bacteria
B) Mycobacterial infection
C) Septic emboli from tricuspid valve endocarditis
D) Cryptogenic organizing pneumonia
Correct Answer: A) Aspiration of anaerobic bacteria
Rationale:
The most common cause of primary lung abscess is aspiration of anaerobic bacteria, particularly in patients with alcohol use disorder and poor dentition, as they have an increased risk of aspirating oral flora. The right lung is more frequently affected due to the anatomy of the right mainstem bronchus. Mycobacteria (Option B) and septic emboli (Option C) can cause cavitary lesions but typically present differently. Cryptogenic organizing pneumonia (Option D) is an inflammatory disease that does not typically form lung abscesses.
Which of the following is the first-line antibiotic treatment for a primary lung abscess?
A) Metronidazole alone
B) Clindamycin or a β-lactam/β-lactamase inhibitor combination
C) Azithromycin
D) Ceftriaxone monotherapy
Correct Answer: B) Clindamycin or a β-lactam/β-lactamase inhibitor combination
Rationale:
Clindamycin (600 mg IV three times daily, then 300 mg PO four times daily) and β-lactam/β-lactamase inhibitor combinations (e.g., ampicillin-sulbactam, amoxicillin-clavulanate) are the preferred regimens. Metronidazole alone (Option A) is ineffective because it does not cover microaerophilic streptococci. Azithromycin (Option C) and ceftriaxone (Option D) do not provide adequate anaerobic coverage needed for treating a lung abscess.
A patient with a primary lung abscess has been on clindamycin for 5 days with persistent fevers. Imaging shows an enlarging abscess. What is the next best step?
A) Switch to metronidazole monotherapy
B) Continue antibiotics for another week before reassessing
C) Perform additional studies to rule out a secondary lung abscess
D) Discontinue antibiotics and initiate steroids
Correct Answer: C) Perform additional studies to rule out a secondary lung abscess
Rationale:
Failure to improve after 7 days of appropriate therapy raises suspicion for an underlying secondary cause, such as malignancy or foreign body obstruction. Continuing antibiotics alone (Option B) without identifying the cause may lead to unnecessary delays in appropriate treatment. Metronidazole monotherapy (Option A) is inadequate, and steroids (Option D) are not indicated for treating lung abscesses.
What is the recommended duration of antibiotic therapy for primary lung abscesses?
A) 5–7 days
B) 10–14 days
C) 3–4 weeks to as long as 14 weeks
D) Antibiotics are only required until fever resolves
Correct Answer: C) 3–4 weeks to as long as 14 weeks
Rationale:
Lung abscess treatment requires prolonged antibiotic therapy until imaging shows that the abscess has cleared or regressed to a small scar. Shorter durations (Options A & B) are insufficient to ensure complete resolution. Stopping antibiotics based on fever resolution alone (Option D) is incorrect, as imaging confirmation is necessary.
Which of the following situations would most likely require surgical intervention or percutaneous drainage?
A) A lung abscess measuring 7 cm in diameter
B) A 3-cm abscess responding to antibiotics
C) A patient defervescing after 5 days of antibiotic therapy
D) A 2-cm abscess in an immunocompromised host
Correct Answer: A) A lung abscess measuring 7 cm in diameter
Rationale:
Abscesses larger than 6–8 cm are less likely to resolve with antibiotics alone and may require percutaneous drainage or surgical resection. Smaller abscesses (Options B & D), even in immunocompromised patients, may still respond to antibiotics. Patients improving with antibiotic therapy (Option C) typically do not need invasive procedures.
Which of the following is a potential complication of percutaneous drainage of a lung abscess?
A) Bronchiectasis
B) Pulmonary hypertension
C) Pneumothorax
D) Pulmonary fibrosis
Correct Answer: C) Pneumothorax
Rationale:
Percutaneous drainage carries risks, including pneumothorax, hemothorax, and bacterial contamination of the pleural space. Bronchiectasis (Option A) and pulmonary hypertension (Option B) are not direct complications of drainage. Pulmonary fibrosis (Option D) may develop after chronic infections, but it is not a specific complication of the procedure.
Which of the following is a potential complication of a large lung abscess?
A) Pneumatoceles and bronchiectasis
B) Pulmonary embolism
C) Aortic dissection
D) Pleural effusion without infection
Correct Answer: A) Pneumatoceles and bronchiectasis
Rationale:
Large abscesses may lead to persistent cystic changes (pneumatoceles) or bronchiectasis due to prolonged lung tissue destruction. Pulmonary embolism (Option B) and aortic dissection (Option C) are unrelated to lung abscess pathology. Pleural effusion (Option D) can occur, but empyema (infected pleural fluid) is a more relevant complication.
Which of the following factors is associated with poor prognosis in lung abscesses?
A) Abscess size <3 cm
B) Age <40 years
C) Presence of aerobic bacteria
D) Symptoms lasting less than 5 days
Correct Answer: C) Presence of aerobic bacteria
Rationale:
Other poor prognostic factors include
age >60, the presence of aerobic bacteria, sepsis at presentation, symptom duration of >8 weeks, and abscess size >6 cm.
A patient with a lung abscess and history of alcohol use disorder presents with foul-smelling sputum. What is the most likely causative pathogen?
A) Pseudomonas aeruginosa
B) Mycobacterium tuberculosis
C) Anaerobic bacteria (e.g., Fusobacterium, Bacteroides)
D) Legionella pneumophila
Correct Answer: C) Anaerobic bacteria (e.g., Fusobacterium, Bacteroides)
Rationale:
Foul-smelling sputum is highly suggestive of an anaerobic lung abscess, often due to aspiration pneumonia in patients with poor dentition, alcohol use, or altered consciousness. Pseudomonas (Option A) is more common in hospital-acquired infections. TB (Option B) and Legionella (Option D) do not typically cause putrid-smelling sputum.
