Volume 7, Case 3
Rachel O. Newton-Weaver, MD
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
This is a 5 year old, male who initially developed fever (Tmax 40 degrees C) ten days ago along with coughing, a sore throat and mild back pain. He was seen at his health center seven days ago and a throat culture was done at that time (eventually negative). Over the next five days he continued to have fever and cough. His mother noted him to have decreased appetite, increased fatigue and shallow breathing. He did not have any ill contacts, trauma, aspiration/choking episodes or foreign travel. His past medical history is negative. He has not had his 5 year old immunizations, but he was up to date prior to this.
He presented to his primary care physician earlier today at which time his vital signs were recorded as: T 37.5, P 120, RR 48, BP 100/56 and oxygen saturation 95-98% in room air. Although he does not appear to be toxic or in obvious distress, he is making soft grunting noises and has shallow respirations with diminished breath sounds bilaterally.
A chest radiograph is ordered.
View chest radiograph.
Other lab studies done as an outpatient: CBC WBC 23,000, 73% segs, 10% bands, 11% lymphocytes and 6% monocytes, Hgb 10.6, Hct 31.2. ESR 56. His chemistry panel is normal.
The chest radiograph demonstrates a large well circumscribed consolidated lesion of the right middle lobe with an air fluid level.
Arrangements for hospitalization at a children's hospital are made. Upon admission, he develops shaking chills with a temperature of 41 degrees C. VS P 104, RR 52, BP 123/63 and oxygen saturation 96% in room air. He is alert, cooperative and active with some tachypnea and shallow respirations noted. He does not appear to be toxic. Oral mucosa moist, without lesions and no dental caries. Neck is supple without lymphadenopathy. Heart regular without murmur. Lung exam is significant for mild tachypnea, shallow respirations, decreased breath sounds at both bases (right > left). No rhonchi, rales, wheeze or retractions are auscultated. Abdomen with normal bowel sounds, no hepatosplenomegaly. Skin shows healing insect bites on his lower legs with no impetiginous lesions present.
A CT scan of the patient's chest confirms the presence of a 8 x 6 x 8 cm thick walled mass in the RML and RLL consistent with an abscess. He is started empirically on clindamycin and cefotaxime.
Cultures of the abscess fluid isolate non-typable Hemophilus influenzae (beta lactamase negative) sensitive to ampicillin, cefotaxime, ciprofloxacin and trimethoprim/sulfa. He was continued on clindamycin and ampicillin. He became afebrile within 6 days of starting intravenous antibiotics and remained so for the rest of his hospital stay. After two weeks of IV antibiotics, he was changed to oral amoxicillin to be continued for another two weeks. His blood culture remained negative.
Discussion
A lung abscess is defined as an area of necrotic material within a thick walled cavity. The incidence, morbidity and mortality of lung abscesses has fallen due to improved antibiotic therapy and improved early diagnostic capabilities. Overall, lung abscess remains a relatively uncommon disease in the pediatric population.
Pathogenesis
Risk factors for the development of a lung abscess are aspiration, immunodeficiency and hematogenous spread. Aspiration is the most important factor predisposing a child to lung abscess (1). In children, a lung abscess may also be a complication of a necrotizing pneumonia. Aspiration occurs in children with neurologic disorders, altered mental status, impaired cough mechanisms, swallowing dysfunction or even foreign body aspiration. Most lung abscesses related to aspiration are polymicrobial and include anaerobes. Hematogenous spread occurs with emboli, right sided endocarditis and bacteremia.
Immunodeficiency in children occurs secondary to myeloproliferative disorders, chemotherapy, chronic granulomatous disease, hyper IgE syndrome, etc. Among pediatric patients, HIV-1 infection has not been reported as a risk factor (2). Additionally, immotile cilia disorders and cystic fibrosis can increase the risk for a lung abscess.
A lung abscess can have a well defined fibrotic wall that may converge on adjacent structures causing compression or dissection of the borders. Dissection into a bronchus results in an air fluid level. Dissection into the plural space forms a purulent effusion and if an abscess dissects into the mediastinum, compression of large vessels and the heart may occur.
Microbiology
The organisms associated with lung abscesses have evolved as antibiotic therapy and our ability to isolate organisms have improved. In normal children with no known underlying disease, the most common organisms are anaerobic bacteria, Staph aureus, Strep pneumoniae and Strep pyogenes (group A strep). Gram negative organisms include non-typable H. influenza, Klebsiella and Pseudomonas. Anaerobic organisms are the predominate organism isolated from children with neurologic disorders (often due to aspiration) and include Bacteroides and Peptostreptococcus. Mycobacterium tuberculosis should also be considered.
Isolating organisms remains difficult. Bronchoscopy is useful only if the abscess has ruptured. Direct needle aspiration can be used if the abscess is near the margins of the chest wall and this is aided with CT and ultrasound guidance. Complications of this recovery technique include pneumothorax, hemothorax and empyema. Sputum is not reliable, especially if the abscess has not ruptured, and it is also very difficult to obtain in a child.
Signs and Symptoms
The most common clinical finding is fever. Additional symptoms include cough (productive if the abscess has ruptured and foul smelling sputum if the organism is anaerobic), dyspnea, chest pain, shoulder pain, anorexia and malaise. Acute onset of symptoms is associated with bacterial organisms while subacute presentations are typical in patients with tuberculosis and fungal abscesses (2). The course of a lung abscess before medical intervention may be surprisingly indolent and may last several weeks (1).
On physical examination, findings are not always consistent or specific, especially in children, but include tachypnea, decreased breath sounds and rales.
Diagnosis
Chest radiographs usually reveal a well circumscribed radiodense cavity with an air fluid level that is confirmed with a lateral decubitus views. The width of the air fluid level is usually of equal length on both frontal and lateral chest radiographs, and its walls are thick with an uneven shaggy appearance (3). Atelectasis may be seen if the abscess compresses nearby lung parenchyma. Initially the lung abscess appears as a solid lesion within the parenchyma (5).
Computed tomography is useful in the diagnosis of a lung abscess especially in cases where there may be multiple or small abscesses, to differentiate an abscess from a tumor, and to pinpoint the location of an abscess in proximity to other structures. Classic findings on CT include a thick ragged wall, central fluid and surrounding parenchymal consolidation. Distinctive features of a lung abscess are well marginated edges, greater density of the abscess compared to water and contrast enhancement in adjacent tissue (1).
Ultrasound examination shows a thick irregular wall with a blurred outer margin and an oval or round shape that forms an acute angle with the chest wall. However, with ultrasound, a peripheral lung abscess may contain low level echoes and thus can mimic a pleural effusion. Voluntary hyperventilation causes symmetric movement of the anterior and posterior walls of an abscess cavity, while a pleural effusion causes asymmetric movement (3).
The location of a lung abscess may be dependent on the patient's position especially if aspiration is involved. Supine position at time of aspiration commonly results in an abscess located in the upper lobes and apical aspects of the lower lobes, while the erect position causes basilar portions of the upper lobes to be affected. The right lung is usually affected twice as often as the left because of the anatomic position of the bronchus (4).
Blood cultures are positive in less than 10% of cases (2). Leukocytosis and elevated ESR are nonspecific. A PPD should be placed in all patients suspected of lung abscess.
Differential Diagnosis
A lung abscess appearance on a chest radiograph can be confused with a pneumatocele, infected congenital cyst, loculated empyema, bronchopleural fistula or pulmonary sequestration. Metastatic disease from Ewing sarcoma or osteosarcoma can be associated with pulmonary lesions with central necrosis.
Treatment
The treatment of choice for lung abscess is conservative medical management, with the length of therapy dictated by the patient's clinical course and documented radiographic improvement (4). In most cases, the need for surgery is limited to cases of failed antibiotic therapy or to an abscess complicated by rupture into adjacent tissue (2).
Recommended antibiotic regimes include coverage against both penicillinase producing Staph aureus and anaerobes (5). If aspiration is suspected or the patient is immunocompromised, there should be coverage for gram negative organisms. Patients with cystic fibrosis need coverage for Pseudomonas with an anti-pseudomonal beta lactam (piperacillin or ceftazidime) plus an aminoglycoside. Intravenous antibiotic coverage should continue until the patient is nontoxic and afebrile for 48-72 hours at which time oral therapy may be considered (2). Two to three weeks of antibiotic treatment are recommended.
Surgical intervention includes thoracentesis, guided percutaneous needle aspiration and chest tube thoracostomy (if the pleural space requires drainage) which is recommended if antibiotic therapy fails, a large abscess is present or for critically ill or deteriorating patients. In extreme cases, wedge resection or lobectomy may be needed.
Prognosis
The outcome for pediatric patients is usually very good when lung abscesses are uncomplicated, and recovery is more rapid than in adults (2). A study focusing on follow-up of patients with primary pulmonary abscess who received only antibiotics, showed most of them to have normal pulmonary function tests, normal growth and no other significant lower respiratory tract disease (6). Chest radiographs should be followed but complete resolution may take up to 6 months.
References