Major clinical complication pneumonia are necrotizing pneumonia, lung abscess, pleural effusion and empyema. Necrotizing pneumonia (NP) is characterized by necrosis and liquefication, and cavitation of the lung parenchyma from an infectious pathogen. Nearly 4% of all community-acquired pneumonia are necrotizing, although studies retrospectively evaluating the incidence have found it to be increasing during the past 20 years. Common presenting symptoms include fever, tachypnea, and cough, and have been shown to have more elevated white blood cell counts and inflammatory marker that take longer to normalize, a longer duration of symptoms despite initiation of therapy, and a longer hospital stay. Necrotizing pneumonia is usually secondary to pneumococcus, Staphylococcus aureus or less commonly Pseudomonas aeruginosa infections. Diagnosis of NP requires CT imaging. Conservative management of NP with antibiotics results in good outcomes and there is no indication that surgical resection is necessary for the proper treatment of NP.
 Pleural effusions develop in approximately 40% of children hospitalized with bacterial pneumonia. Pleural effusion occurs when an inflammatory response to pneumonia cause an increase in permeability of the pleura with an accumulation of fluid in the pleura space. There is increased capillary permeability after parenchymal lung injury, favoring the migration of inflammatory cells (neutrophils, lymphocytes, and eosinophils) into the pleural space. When bacteria enter the pleural space, pus appears, characterizing empyema. The child presents usually more severe signs of pneumonia or after a few days of usually pneumonia symptoms children deteriorate clinically with persistent fever or respiratory distress and pleuritic pain is common. On physical examination there is reduce air entry and dullness to percussion over the affected area. Radiographic finding may progress to complete hemithorax opacification with mediastinal contralateral deviation. Streptococcus pneumonia is considered to be the most common cause of parapneumonic effusion (PPE) and empyema. Among other organisms that cause are methicillin-sensitive Staphylococcus aureus (MSSA), S pyogenic, Haemophilus influenzae type b, Mycoplasma pneumoniae, Pseudomonas aeruginosa, and Mycobacterium tuberculosis in older children. Smaller effusions less than 10 mm thick can usually be managed with antibiotics alone, and these should especially cover S. pneumoniae. Staphylococcus aureus should be considered when pneumatoceles are present and the child is toxic. Antibiotics alone should not be the main strategy for managing effusions that are enlarging, or those that are big enough to cause respiratory distress. Therapeutic options besides antibiotics are thoracentesis, chest drain insertion with or without the instillation of fibrinolytic agents, and surgical techniques, such as video-assisted thoracoscopic surgery (VATS), and standard thoracotomy with decortication. 
 Another possible complication of pneumonia is lung abscess. A pulmonary abscess is a thick-walled cavity that contains purulent liquid. The pathogenesis of lung abscess begins with inflammation of the parenchyma which progresses to necrosis, cavitation, and abscess formation. Primary abscesses are associated with a pulmonary infection, especially due to gram-positive cocci, and gram-negative bacteria. Secondary abscesses most  cause of S. pneumoniae and S. aureus. The initial clinical presentation of lung abscess is like that of uncomplicated pneumoniae. A main difference from usual pneumonia is that it progresses indolently. A typical patient may show tachypnea, dullness to percussion, locally reduce air entry, and localized inspiratory crackles. Plain chest radiography usually confirms the diagnosis. A cavity with thick walls and an air-fluid level is the characteristic finding. A contrast-enhanced CT scan is usually considered the investigation of choice, being able to better define a thick wall cavity filled with fluid. The mainstay of treatment is the use of a parenteral antibiotic. Ampicillin-sulbactam or a cephalosporin with clindamycin (if CA-MRSA is suspected) are the usual choices to cover the most prevalent pathogen. Surgery is the last resource after medical therapy has failed.