1-Introduction. 2-Pathology and Pathogenesis. 3-Clinical Manifestations. 4-Diagnosis. 5-Treatment. 6-Prognosis.

Pulmonary abscesses are localized areas composed of thick-walled purulent material formed as a result of lung infection that lead to destruction of lung parenchyma, cavitation, and central necrosis.

Lung abscesses are much less common in children than in adults. A primary lung abscess occurs in a previously healthy patient with no underlying medical disorders. A secondary lung abscess occurs in a patient with underlying or predisposing conditions.

A number of conditions predispose children to the development of pulmonary abscesses, including aspiration, pneumonia, cystic fibrosis, gastroesophageal reflux, tracheoesophageal fistula, immunodeficiencies,FB, seizures, and a variety of neurologic diseases.

In children, aspiration of infected materials or a foreign body is the predominant source of the organisms causing abscesses. Initially, pneumonitis impairs drainage of fluid or the aspirated material. Inflammatory vascular obstruction occurs, leading to tissue necrosis, liquefaction, and abscess formation.

If the aspiration event occurred while the child was recumbent, the right and left upper lobes and apical segment of the right lower lobes are the dependent areas most likely to be affected. In a child who was upright, the posterior segments of the upper lobes were dependent and therefore are most likely to be affected.

Primary abscesses are found most often on the right side, Whereas secondary lung abscesses, particularly in immunocompromised patients, have a predilection for the left side.

Both anaerobic and aerobic organisms can cause lung abscesses. Most lung abscesses arise as a complication of aspiration pneumonia and are caused by species of anaerobes that are normally present in the gingival crevices. Common anaerobic bacteria that can cause a pulmonary abscess include Bacteroides spp, Fusobacterium spp, and Peptostreptococcus spp.

Abscesses can be caused by aerobic organisms such as Streptococcus spp, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.

Aerobic and anaerobic cultures should be part of the work-up for all patients with lung abscess. Fungi can also cause lung abscesses, particularly in immunocompromised patients.

Non-bacterial pathogens can produce lung abscess including parasites (eg, Paragonimus westermani and Entamoeba histolytica) Many fungi (eg, Aspergillus spp, Cryptococcus neoformans, Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis)

The most common symptoms of pulmonary abscess in pediatric population are 1-Cough 2-Fever 3-Tachypnea 4-Dyspnea 5-Chest pain 6-Vomiting 7-Sputum production 8-Weight loss 9-Hemoptysis.

Physical examination typically reveals : 1-Tachypnea 2-Dyspnea 3-Retractions with accessory muscle use, 4-Decreased breath sounds, and 5-Dullness to percussion in the affected area. 6-Crackles and, occasionally, a prolonged expiratory phase may be heard on lung examination.

Diagnosis is most commonly made on the basis of chest radiography.

A chest CT scan can provide better anatomic definition of an abscess, including location and size.

An abscess is usually a thick-walled lesion with a low- density center progressing to an air-fluid level. Abscesses should be distinguished from pneumatoceles, which often complicate severe bacterial pneumonias and are characterized by thin- and smooth-walled, localized air collections with or without air-fluid level Pneumatoceles often resolve spontaneously with the treatment of the specific cause of the pneumonia.

The determination of the etiologic bacteria in a lung abscess can be very helpful in guiding antibiotic choice. Although Gram stain of sputum can provide an early clue as to the class of bacteria involved, sputum cultures typically yield mixed bacteria and are therefore not always reliable.

Attempts to avoid contamination from oral flora include direct lung puncture, percutaneous (aided by CT guidance). Bronchoscopic aspiration should be avoided as it can be complicated by massive intrabronchial aspiration. To avoid invasive procedures in previously normal hosts, empiric therapy can be initiated in the absence of culturable material.

Conservative management is recommended for pulmonary abscess. The duration of therapy is controversial. Some treat for three weeks as a standard and others treat based upon the response. The practice is to continue antibiotic treatment until the chest x-ray shows a small, stable residual lesion or is clear.

Most experts advocate a 2- to 3-wk course of parenteral antibiotics for uncomplicated cases, followed by a course of oral antibiotics to complete a total of 4-6 wk.

Antibiotic choice should include agents with aerobic and anaerobic coverage.

Treatment regimens should include : 1-Penicillinase-resistant agent active against S. aureus and anaerobic coverage, typically with clindamycin. If gram-negative bacteria are suspected or isolated, an aminoglycoside should be added.

For severely ill patients or those whose status fails to improve after 7-10 days of appropriate antimicrobial therapy, surgical intervention should be considered.

Minimally invasive percutaneous aspiration techniques, often with CT guidance, are the initial and, often, only intervention required. In rare complicated cases, thoracotomy with surgical drainage or lobectomy and/or decortication may be necessary.

Overall, prognosis for children with primary pulmonary abscesses is excellent. The presence of aerobic organisms may be a negative prognostic indicator, particularly in those with secondary lung abscesses.

Most children become asymptomatic within 7-10 days. Radiologic abnormalities usually resolve in 1-3 m.

Lung abscess is defined as necrosis of the pulmonary parenchyma. Most lung abscesses arise as a complication of aspiration pneumonia. Lung abscesses are classified into a primary lung abscess and secondary lung abscess.

A lung abscess is typically diagnosed when a chest radiograph. Better anatomic definition can be achieved with computed tomographic (CT) scans. Treatment regimens should include agents active against S. aureus, anaerobic coverage and gram negative if suspected. Continue antibiotic treatment until the chest x-ray shows a small, stable residual lesion or is clear.

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