Answer for BIR CoW 22 July 2018
LUNG ABSCESS
Findings
CXR PA VIEW Radioopacity seen in left lower lung zone with loss of silhouette of left hemidiaphragm and blunting of left costophrenic and cardiophrenic angles. Cavity with air fluid level seen within the radioopacity. Patchy radioopacity seen in right lower zone.
Discussion
Lung abscesses are circumscribed collections of pus within the lungs. They are often complicated to manage and difficult to treat and, in some cases, may be life-threatening. Epidemiology The elderly, immunocompromised, malnourished, debilitated, and those who do not have access to antibiotics are particularly susceptible and have the worst prognosis. Clinical presentation 1. Acute (<6 weeks) 2. Chronic (>6 weeks) Fever, cough and shortness of breath. Peripheral abscesses may also cause pleuritic chest pain. If chronic, symptoms include weight loss and constitutional symptoms. In some cases, erosion into a bronchial vessel may result in haemoptysis. Divided into primary and secondary as they differ in aetiology, microbiology and prognosis. Primary abscess: develops as a result of primary infection of the lung. They most commonly arise from aspiration, necrotising pneumonia or chronic pneumonia, e.g. pulmonary tuberculosis, immunodeficiency In patients who develop abscesses as a result of aspiration, mixed infections are most common, including anaerobes. Organisms prone to causing necrotising pneumonia resulting in cavitation and abscess formation include: 1. Staphylococcus aureus 2. Klebsiella sp: Klebsiella pneumonia 3. Pseudomonas sp 4. Proteus sp In immunocompromised patients additional organisms implicated include : 1. Candida albicans: pulmonary candidiasis 2. Legionella micdadei and Legionella pneumophila: Legionella pneumonia 3. Pneumocystis carinii (uncommon): Pneumocystis jirovecii pneumonia Secondary abscess: develops as a result of another condition like: 1. bronchial obstruction: bronchogenic carcinoma, inhaled foreign body 2. haematogenous spread: bacterial endocarditis, IV drug use 3. direct extension from adjacent infection: mediastinum, subphrenic, chest wall Radiographic features As aspiration is the most common cause of pulmonary abscesses, the superior segment of the right lower lobe is the most common site of infection. Plain radiograph • Cavity containing a gas-fluid level. • Abscesses are round in shape and appear similar in both frontal and lateral projections. • All margins are equally well seen, although adjacent consolidation may make the assessment of this difficult. CT • Most sensitive and specific imaging modality • Abscesses vary in size and are generally rounded in shape. The may contain only fluid or have a gas-fluid level. Typically there is surrounding consolidation. • The wall of the abscess is typically thick and the luminal surface irregular. • Bronchial vessels and bronchi can be traced as far as the wall of the abscess, whereupon they are truncated. Treatment and prognosis 1. Prolonged antibiotics and physiotherapy with postural drainage. 2. Bronchoscopy - in establishing bronchial patency to improve drainage 3. Surgical resection - In cases that are refractory to conservative management or those complicated by haemoptysis, empyema or suspected malignancy 4. Percutaneous drainage under CT guidance - patients refractory to conventional therapy Differential diagnosis 1. empyema (see empyema vs pulmonary abscess) 2. bronchogenic carcinoma (cavitating) 3. pulmonary metastasis: with necrosis 4. pulmonary cavitating granulomatous disease (e.g. granulomatosis with polyangiitis) 5. large infected pneumatocele: infected emphysematous bulla 6. cavitating pneumonia / necrotising pneumonia LUNG ABSCESS VS.EMPYEMA LUNG ABSCESS Round in shape Round in all projections Air fluid level remains same in lateral projection Acute angle with chest wall Abruptly interrupts bronchovascular structures No split pleura sign Thick irregular walls Adjacent lung shows consolidation EMPYEMA Lentiform Air fluid level changes in lateral projection Obtuse angle with chest wall Distorts and compresses adjacent lung Split pleura sign present Smooth walls Adjacent lung usually normal
Findings
CXR PA VIEW Radioopacity seen in left lower lung zone with loss of silhouette of left hemidiaphragm and blunting of left costophrenic and cardiophrenic angles. Cavity with air fluid level seen within the radioopacity. Patchy radioopacity seen in right lower zone.
Discussion
Lung abscesses are circumscribed collections of pus within the lungs. They are often complicated to manage and difficult to treat and, in some cases, may be life-threatening. Epidemiology The elderly, immunocompromised, malnourished, debilitated, and those who do not have access to antibiotics are particularly susceptible and have the worst prognosis. Clinical presentation 1. Acute (<6 weeks) 2. Chronic (>6 weeks) Fever, cough and shortness of breath. Peripheral abscesses may also cause pleuritic chest pain. If chronic, symptoms include weight loss and constitutional symptoms. In some cases, erosion into a bronchial vessel may result in haemoptysis. Divided into primary and secondary as they differ in aetiology, microbiology and prognosis. Primary abscess: develops as a result of primary infection of the lung. They most commonly arise from aspiration, necrotising pneumonia or chronic pneumonia, e.g. pulmonary tuberculosis, immunodeficiency In patients who develop abscesses as a result of aspiration, mixed infections are most common, including anaerobes. Organisms prone to causing necrotising pneumonia resulting in cavitation and abscess formation include: 1. Staphylococcus aureus 2. Klebsiella sp: Klebsiella pneumonia 3. Pseudomonas sp 4. Proteus sp In immunocompromised patients additional organisms implicated include : 1. Candida albicans: pulmonary candidiasis 2. Legionella micdadei and Legionella pneumophila: Legionella pneumonia 3. Pneumocystis carinii (uncommon): Pneumocystis jirovecii pneumonia Secondary abscess: develops as a result of another condition like: 1. bronchial obstruction: bronchogenic carcinoma, inhaled foreign body 2. haematogenous spread: bacterial endocarditis, IV drug use 3. direct extension from adjacent infection: mediastinum, subphrenic, chest wall Radiographic features As aspiration is the most common cause of pulmonary abscesses, the superior segment of the right lower lobe is the most common site of infection. Plain radiograph • Cavity containing a gas-fluid level. • Abscesses are round in shape and appear similar in both frontal and lateral projections. • All margins are equally well seen, although adjacent consolidation may make the assessment of this difficult. CT • Most sensitive and specific imaging modality • Abscesses vary in size and are generally rounded in shape. The may contain only fluid or have a gas-fluid level. Typically there is surrounding consolidation. • The wall of the abscess is typically thick and the luminal surface irregular. • Bronchial vessels and bronchi can be traced as far as the wall of the abscess, whereupon they are truncated. Treatment and prognosis 1. Prolonged antibiotics and physiotherapy with postural drainage. 2. Bronchoscopy - in establishing bronchial patency to improve drainage 3. Surgical resection - In cases that are refractory to conservative management or those complicated by haemoptysis, empyema or suspected malignancy 4. Percutaneous drainage under CT guidance - patients refractory to conventional therapy Differential diagnosis 1. empyema (see empyema vs pulmonary abscess) 2. bronchogenic carcinoma (cavitating) 3. pulmonary metastasis: with necrosis 4. pulmonary cavitating granulomatous disease (e.g. granulomatosis with polyangiitis) 5. large infected pneumatocele: infected emphysematous bulla 6. cavitating pneumonia / necrotising pneumonia LUNG ABSCESS VS.EMPYEMA LUNG ABSCESS Round in shape Round in all projections Air fluid level remains same in lateral projection Acute angle with chest wall Abruptly interrupts bronchovascular structures No split pleura sign Thick irregular walls Adjacent lung shows consolidation EMPYEMA Lentiform Air fluid level changes in lateral projection Obtuse angle with chest wall Distorts and compresses adjacent lung Split pleura sign present Smooth walls Adjacent lung usually normal
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!