Symptoms and Signs

Karaganda State Medical University

Department of Foreign Languages

SIW

Theme: Atherosclerosis

Prepared by: Bagai K.

OM group

Cheeked by:Shubakova M.N.

Karaganda 2014 year

Definition:

• Necrosis of the pulmonary tissue

• Formation of cavities containing necrotic debris or fluid caused by microbial infection.

• The formation of multiple small (<2 cm) abscesses is occasionally referred to as necrotizing pneumonia or lung gangrene.

• Failure to recognize and treat lung abscess is associated with poor clinical outcome

Etiology

· Aspiration of oral secretions (most common)

· Endobronchialobstruction

· Hematogenous seeding of the lungs (less common)

Most lung abscesses develop after aspiration of oral secretions by patients with gingivitis or poor oral hygiene. Typically, patients have altered consciousness as a result of alcohol intoxication, illicit drugs, anesthesia, sedatives, or opioids. Older patients and those unable to handle their oral secretions, often because of neurologic disease, are also at risk. Lung abscesses can also develop secondary to endobronchial obstruction (eg, due to bronchial carcinoma) or to immunosuppression (eg, due to HIV/AIDS or after transplantation and use of immunosuppressive drugs).

A less common cause of lung abscess is necrotizing pneumonia that may develop from hematogenous seeding of the lungs due to suppurative thromboembolism (eg, septic embolism due to IV drug use) or right-sided endocarditis. In contrast to aspiration and obstruction, these conditions typically cause multiple rather than isolated lung abscesses.

Classification:

• Time interval

– Acute: less than 4-6 weeks old

– Chronic: abscesses are of longer duration.

• Origen:

– Primary: Infectious in origin

• caused by aspiration or pneumonia

• healthy host

– Secondary: Caused by a preexisting condition

• Broncheal obstruction, spread from an extrapulmonary site, bronchiectasis, and/or an immunocompromised state.

• Responsible pathogen:

– Aerobic such as Staphylococcus

– Anaerobic

– Fungal sush as Aspergillus

Pathogens:

The most common pathogens of lung abscesses due to aspiration are anaerobic bacteria, but about half of all cases involve both anaerobic and aerobic organisms. The most common anaerobic pathogens are Peptostreptococcus, Fusobacterium, Prevotella, and Bacteroides. The most common aerobic pathogens are streptococci and staphylococci—sometimes methicillin-resistant Staphylococcus aureus (MRSA). Occasionally, cases are due to gram-negative bacteria, especially Klebsiella. Immunocompromised patients with lung abscess are most commonly infected with Pseudomonas aeruginosa and other gram-negative bacilli but also may have infection with Nocardia, Mycobacteriasp, or fungi. Rare cases of pulmonary gangrene or fulminant pneumonia with sepsis have been reported with pathogens such as MRSA, Pneumococcus, and Klebsiella. Some patients, especially those from developing countries, are at risk of abscess due to Mycobacterium tuberculosis, and rare cases are due to amebic infection (with Entamoebahistolytica), paragonimiasis, or infection with Burkholderiapseudomallei.

Introduction of these pathogens into the lungs first causes inflammation, which, over a week or two, leads to tissue necrosis and then abscess formation. The abscess usually ruptures into a bronchus, and its contents are expectorated, leaving an air- and fluid-filled cavity. In about one third of cases, direct or indirect extension (via bronchopleural fistula) into the pleural cavity results in empyema.

Symptoms and Signs

Symptoms of abscess due to anaerobic bacteria or mixed anaerobic and aerobic bacteria are usually chronic (occurring over weeks or months) and include productive cough, fever, night sweats, and weight loss. Patients may also present with hemoptysis and pleuritic chest pain. Sputum may be purulent or blood-streaked and classically smells or tastes foul.

Symptoms of abscess due to aerobic bacteria develop more acutely and resemble bacterial pneumonia. Abscesses due to organisms other than anaerobes (Mycobacteria, Nocardia) lack putrid respiratory secretions and may be more likely to occur in nondependent lung regions.

Signs of lung abscess, when present, are nonspecific and resemble those of pneumonia: decreased breath sounds indicating consolidation or effusion, temperature ≥ 38° C, crackles over the affected area, egophony, and dullness to percussion in the presence of effusion. Patients typically have signs of periodontal disease and a history of a predisposing cause of aspiration, such as dysphagia or a condition causing impaired consciousness.

Pathophysiology:

Primary Lung abscess

• Complication of aspiration

• Caused by mouth anaerobes.

• The patients who develop lung abscess are predisposed to aspiration and commonly have periodontal disease.

• Healthy patients.

• A bacterial inoculum from the gingival crevice reaches the lower airways

• An infection is initiated because the bacteria are not cleared by the patient's host defense mechanism. – Results in aspiration pneumonitis

• Progression to tissue necrosis 7-14 days later, resulting in formation of lung abscess.

Other mechanisms:

Bacteremia

– tricuspid valve endocarditis, causing septic emboli.

– Lemierre syndrome,

• an acute oropharyngeal infection followed by septic thrombophlebitis of the internal jugular vein

Microbiology

Difficult in obtaining material uncontaminated by nonpathogenic bacteria colonizing the upper airway, lung abscesses rarely have a microbiologic diagnosis.

Anaerobic bacteria most significant pathogens

– Peptostreptococcus species,
– Bacteroides species,

– Fusobacterium species,

– microaerophilic streptococci.

Aerobic bacteria

– Staphylococcus aureus,

– Streptococcus pyogenes and S pneumoniae

– Klebsiella pneumoniae,

– Haemophilus influenzae,

– Actinomyces species, Nocardia species, and gram-negative bacilli.

Nonbacterial and atypical bacterial

– usually in the immunocompromised host.

– These microorganisms include parasites (eg, Paragonimus and Entamoeba species), fungi (eg, Aspergillus, Cryptococcus, Histoplasma, Blastomyces, and Coccidioides species), and Mycobacterium species.

Mortality/Morbidity

Most patients with primary lung abscess improve with antibiotics and conservative management, with cure rates documented at 90- 95%. Host factors associated with a poor prognosis

• advanced age,

• debilitation,

• malnutrition,

• human immunodeficiency virus infection or

• other forms of immunosuppression,

• malignancy, and

• duration of symptoms greater than 8 weeks.

The mortality rate for patients with underlying immunocompromised status or bronchial obstruction who develop lung abscess may be as high as 75%.

Aerobic organisms, frequently hospital acquired, are associated with poor outcomes.

– overall mortality rate of lung abscesses caused by mixed gram-positive and gram-negative bacteria at approximately 20

History

• Symptoms depend on whether the abscess is caused by anaerobic or other bacterial infection.

• Anaerobic infection

– Patients often present with indolent symptoms that evolve over a period of weeks to months.

– The usual symptoms are fever, cough with sputum production, night sweats, anorexia, and weight loss.

– The expectorated sputum characteristically is foul smelling and bad tasting.

– Patients may develop hemoptysis or pleurisy

• Other pathogens in lung abscess

– These patients generally present with conditions that are more emergent in nature and are usually treated while they have bacterial pneumonia,

– Present with high fever, malaise, re- occurrence of fever after treating e.g. pneumonia, purulent sputum production, chest pain, signs of severe systemic toxemia.

– Cavitation occurs subsequently as parenchymal necrosis ensues.

– Abscesses from fungi, Nocardia species, and Mycobacteria species tend to have an indolent course and gradually progressive symptom

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