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Lung abscess
This document discusses lung abscess, including its definition, causes, microbiology, risk factors, clinical presentation, diagnosis and treatment. A lung abscess is a localized infection and necrosis of lung tissue, often caused by aspiration of oral or gastric contents, that produces a cavity within the lung. It commonly presents with cough, sputum production and fever. Diagnosis is made through chest imaging showing a lung cavity. Treatment involves prolonged use of antibiotics active against the typical bacterial causes, such as clindamycin and metronidazole, for 4-6 weeks.
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Introduces the topic of lung abscess by Passant Abdul Nasser Dorgham.
Defines lung abscess as a microbial infection leading to lung cavity formation, often presenting with cough and purulent sputum.
Describes necrotizing pneumonia with multiple small cavities in lung tissue.
Clarifies that hydatid cysts should not be confused with multiple lung abscesses.
Classifies lung abscesses as acute or chronic and primary (80%) vs secondary based on health status.
Details the bacteria commonly causing lung abscesses, focusing on anaerobes from the mouth.
Lists mycobacteria, fungi, and parasites that can also lead to lung abscess formation.
Lists various non-infectious conditions, including neoplasms and pulmonary infarction leading to abscess-like cavities.
Discusses additional non-infectious causes of cavity formation, including vasculitis and developmental issues.
Explains mechanisms of lung abscess formation, mainly as a complication of aspiration pneumonia.
Outlines the time frame (1-2 weeks) for tissue necrosis and abscess formation post-aspiration.
Notes that 1/3 of lung abscess cases may develop empyema.
Lists major risk factors including aspiration, poor dental health, and airway obstruction.
Describes symptoms such as fever, cough, and pleuritic chest pain associated with lung abscess.
Chronic conditions including weight loss and clubbing appear 8-12 weeks after abscess onset.
Identifies clinical signs including consolidation and potential perforation into pleural space.
Details symptoms of an amebic lung abscess typically linked to liver abscess.
Discusses radiological findings associated with lung abscess, including initial consolidation.
Notes the finding of consolidation in the right upper lobe on lateral chest views.
Describes CT scan features of lung abscess, such as decreased attenuation and rim enhancement.
Shows that lung abscess size may decrease over time with associated cavitation.
Illustrates the appearance of a lung abscess with air fluid level at the right upper lobe.
Documents cases of pneumonia complicated by necrosis and lung abscess formation.
Describes a patient with foul-smelling sputum and radiographic evidence of lung abscess.
Explains the role of ultrasound in detecting peripheral lung abscesses.
Details methods for obtaining uncontaminated samples for anaerobic culture in lung abscess.
Lists relevant laboratory studies to assess lung abscess, including blood tests and cultures.
Discusses potential complications resulting from lung abscess, such as empyema and respiratory failure.
Lists conditions to differentiate from lung abscess, including cavitating lung cancer and infections.
Describes treatment protocols, emphasizing the use of clindamycin for anaerobic lung infections.
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Lung abscess
- 1. Lung Abscess by | PassantAbdul Nasser Dorgham
- 3. Definition: • Microbial infectioncauses suppurative necrosis of the lung parenchyma producing a cavity. Often communicate with large airways resulting in cough, expectoration of purulent sputum and AFL on imaging studies . • May be more than one cavity, but usually one is large and dominant . • More common in pre-antibiotic era with progression bacterial pneumonia +/- empyema
- 4. • Necrotizing pneumonia: oftenused to describe similar pathologic process with multiple small (<2cm) cavities in contiguous areas of the lung .
- 5. • Hydatid cysts>> do not mistaken this for multiple abscesses No air fluid level
- 6. Classification Onset andduration : acute < 1month, chronic > 1 month Primary lung abscess or Secondary lung abscess : o Primary lung abscess: used when abscess develops in individuals prone to aspiration or in general good health 80% of lung abscess is primary o Secondary lung abscess: • obstructive airway neoplasm • treatment that compromises host immune defense mechanisms
- 7. Microbiology : Bacteria oUsually: mouthflora anaerobes, Most frequently isolated anaerobes: • Peptostreptococcus, • Fusobacterium nucleatum, • Prevotella melaningogenica o Less common: • Staphylococcus aureus, . Streptococcus pyogenes, • Pseudomonas aeruginosa, Klebsiella pneumoniae , • Streptococcus pneumoniae • gram-negative bacilli, such as E. coli , Haemophilus influenzae type B • Legionella,, Nocardia asteroides
- 8. Microbiology : Mycobacteria •M. tuberculosis, M. avium complex, • M. kansasii, other mycobacteria Fungi • Aspergillus spp., Histoplasma capsulatum, • Pneumocystis carinii, Coccidioides immitis, • Blastocystis hominis , cryptococcus Parasites • Entamoeba histolytica, • Paragonimus westermani, • Strongyloides stercoralis (post-obstructive)
- 9. Non-infectious Causes (cavityformation causes): Neoplasms Primary lung cancer(pulmonary adenocarcinoma), metastatic carcinoma, Lymphoma Pulmonary infarction Due to bland embolus (may be secondarily infected in <5%) Septic embolism • Tricuspid endocarditis due to S. aureus • jugular venous septic phlebitis due to Fuso-bacterium necrophorum (Lemierre syndrome)
- 10. Non-infectious Causes (cavityformation causes): Vasculitis Wegener's granulomatosis, rheumatoid lung nodule Airway disease Bullae, blebs, or cystic bronchiectasis Developmental Pulmonary sequestration Other Sarcoidosis, transdiaphragmatic bowel herniation giving appearance of cavity with airfluid level Bronchiectasis (honey comb appearance ) cavitations
- 11. Pathophysiology : Mostoccur as a complication of aspiration pneumonia and are poly microbial due to anaerobic bacteria that are normal oral flora Initial aspiration lung insult may be due to direct chemical injury from aspirated stomach acid or to areas of obstruction due to aspirated particulate matter (food) Following the obstruction the gases result from the putrifaction and the anaerobic organisms will result in lung cavity which could be progressive Secondary bacterial infection then may occur.
- 12. If thebacterial inoculum is large/virulent or lung defense mechanisms (mucociliary apparatus,alveolar macrophages) compromised, infection can occur without prior insult to the lung . studies of patients with known time of aspiration suggest that tissue necrosis with lung abscess formation takes at least 1 week and up to 2 weeks to develop. Aspirated bacteria are carried by gravity to dependent portions of the lung. Due to bronchus/carina anatomy, occur most frequently in posterior segment of RUL then posterior segment of LUL and then the superior segments of RUL/LLL
- 13. 1/3 developempyema due to direct extension . Amebic lung abscess typically occurs in RLL due to direct extension of liver abscess through the diaphragm
- 14. Risk Factors forlung abscess: Predisposition to aspiration 45% of health adults aspirate during sleep; 70% of patients with AMS aspirate 1ml of saliva with > 109 live bacteria. Patients with chronic COPD Poor dentition with gingivitis resulting in an unusually high density of oral anaerobic organism particular in gingival crevices . Airway Obstruction • Neoplasm: 50% of lung abscesses in patients >50 areassociated with lung carcinoma (post- obstruction vs. necrotic tumor) Foreign bodies, extrinsic compression (enlarged lymph node) Patients with cell-mediated immunity (AIDS, transplant) Neutropenic patients Patients with prosthetic cardiac valves or vegetative endocarditis
- 16. Clinical features :(symptoms ) • The onset may be abrupt or gradual. • Symptoms include fever, sweating, cough and chest pain simulating pneumonia. • The cough is often non productive at first or may produce mucoid or mucopurulent expectorate from bronchial inflammation close to the abscess area and sometimes there is blood streaking. • If this happens suddenly in large quantities, this denotes a rupture of the abscess cavity into the bronchus and blood streaking is common.
- 17. • Pleuritic chestpain, especially with coughing is common because the abscess is near to the pleura. • Weight loss, anaemia, and clubbing or pulmonary osteo arthropathy appear when the abscess becomes chronic (8-12 weeks after onset).
- 18. Signs : Consolidationdue to pneumonia surrounding the abscess is the most frequent finding. Inspiratory rales and pleural rub may be heard. Rarely the amphoric or cavernous breath sounds are heard Rupture into the pleural space produces signs of effusion or hydro pneumothorax. Digital clubbing may develop rapidly. Then aspiration results will reveal the infecting organism.
- 19. Amebic lung abscess: • Patients who develop an amebic lung abscess often have symptoms • associated with a liver abscess. • These may include right upper quadrant pain and fever. • After perforation of the liver abscess into the lung, the patient may develop a cough and expectorate a chocolate or anchovy paste–like sputum that has no odor.
- 20. Radiological diagnosis : •Consolidation due to pneumonia surrounding the abscess is the most frequent finding. • A dense shadow is the initial finding before rupture. • Later this opacity develops a cavity with fluid level. May have smooth and regular walls. • Chest films may also reveal associated primary lesions, (bronchogenic carcinoma). • Malignant abcess shows eccenteric cavitation with thick rough irregular walls.
- 21. lateral view showRt upper lobe consolidation
- 22. Contrast-enhanced (CT) scan demonstrateslarge focal area of decreased attenuation with rim enhancement (arrow) characteristic of lung abscess.
- 23. Lateral chest radiographs3 weeks later show decreased size of lung abscess and development of cavitation with fluid level . The patient was a 43-year-old woman with lung abscess secondary to Haemophilus infection
- 24. A cavity withan air fluid level at apical segment of upper lobe of right lung due to lung abscess.
- 25. Pneumococcal pneumonia complicated by lungnecrosis and abscess formation. A lateral chest radiograph shows air-fluid level characteristic of lung abscess.
- 26. A 54-year-old patient developedcough with foul-smelling sputum production. A chest radiograph shows lung abscess in the left lower lobe, superior segment.
- 27. Ultrasonography Peripheral lung abscesseswith pleural contact or included inside a lung consolidation are detectable using lung ultrasonography Lung abscess appears as a rounded hypo- echoic lesion with an outer margin.
- 28. Diagnostic material uncontaminatedby bacteria colonizing the upper airway may be obtained for anaerobic culture from the following: Blood cultures are infrequently positive in patients with lung abscess. Transtracheal aspirateBlood culture Pleural fluid (if empyema present) Transthoracic pulmonary aspirate Surgical specimens Fiberoptic bronchoscopy with protected brush Bronchoalveolar lavage with quantitative cultures Expectorated sputum and other methods of sampling the upper airway do not yield useful results for anaerobic culture because the oral cavity is extensively colonized with anaerobes. Procedures: Flexible fiberoptic bronchoscopy is performed to exclude bronchogenic carcinoma whenever bronchial obstruction is suspected.
- 29. Laboratory Studies: complete whiteblood cell count with differential may reveal leukocytosis. Gram stain, culture, and sensitivity. If tuberculosis is suspected, ZeilNelsen and mycobacterial culture is requested. Routine investigations: e.g blood glucose , liver functions tests , renal functions test, electrolytes
- 30. Complications of lungabscess : Rupture into pleural space causing empyema Pleural fibrosis Trapped lung Respiratory failure Bronchopleural fistula Pleural cutaneous fistula In a patient with coexisting empyema and lung abscess, draining the empyema while continuing prolonged antibiotic therapy is often necessary.
- 31. Differential diagnosis: Cavitatinglung cancer Localized empyema Infected bulla containing a fluid level Infected congenital pulmonary lesion, • such as bronchogenic cyst or sequestration Pulmonary hematoma Cavitating pneumoconiosis Hiatus hernia Lung parasites (eg, hydatid cyst, Paragonimus infection) Actinomycosis Wegener granulomatosis and other vasculitides Cavitating lung infarcts Cavitating sarcoidosis
- 32. Treatment : Several anaerobesmay produce beta- lactamase , develop resistance to penicillin. Clindamycin is the treatment of choice Flagyl as monotherapy is inferior to clindamycin as it is not active against micro aerophilic streptococci and anaerobic cocci that are common constituents of anaerobic lung infection (which are sensitive to Penicillin)…. So we can combine flagyl with penicilin. Do not forget that treatment should continue from 4-6 weeks