Empyema

Empyema Microchapters
Patient Information
Overview
Classification Subdural empyema Pleural empyema
Differential Diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Prince Tano Djan, BSc, MBChB [2]

Overview

Empyema may be classified according to the etiology, anatomical location, and pathological course of the disease. Primary thoracic empyema occurs most commonly as iatrogenic empyema without associated pneumonia whereas secondary empyema occurs more commonly secondary to pneumonia. Empyema necessitans is a spontaneous discharge of an empyema that has burrowed through the parietal pleura into the chest wall to form a subcutaneous abscess that may eventually rupture through the skin. On the basis of anatomical location, empyema may be classified depending on the affected organ including the following: gallbladder empyema, subdural empyema, joint empyema, and empyema cystitis. Empyema is most frequently caused by bacteria. Causes may be tuberculous or nontuberculous. Tuberculous empyema is the most common cause of empyema necessitans with majority of affected patients immunocompromised. There are 3 stages of empyema which are important in terms of the laboratory findings. These are exudative, fibrinopurulent, and organizing.

Empyema classification

Classification by Organ System or Location of Empyema

Pleural empyema

Pleural empyema is also called empyema thoracis. Thoracic empyema arises from an infection within the lung. It must be differentiated from an abscess, which is a collection of necrotic and suppurated tissue located in the parenchyma of an organ. Empyema is most commonly used to refer to pus collection in the pleural cavity although several other organs can be affected including the brain, gallbladder, joints, and urinary bladder. Thoracic empyema arises from an infection within the lung, often associated with parapneumonic effusions. Parapneumonic effusions may be uncomplicated or complicated effusions. Complicated parapneumonic effusion results when bacteria invade the pleural space with a resultant formation of an empyema.

Gallbladder empyema

Gallbladder empyema is also called suppurative cholecystitis which may complicate acute/chronic cholecystitis whereby pus collects in the gall bladder lumen. It is common in people with diabetes and atherosclerotic disease. Gallbladder empyema normally results from an obstruction of the cystic duct hampering drainage of bile from the gall bladder, which becomes secondarily infected.

Subdural empyema

Subdural empyema is a life-threatening infection, consisting of a localized collection of purulent material, typically unilateral, between the dura mater and the arachnoid mater. Subdural empyema may be classified according to location of the infection into 2 groups: intracranial and spinal, with intracranial being the more common of the two groups, accounting for 95% of subdural empyema patients. Subdural empyema accounts for approximately 15-25% of focal central nervous system infections. In 2014, the incidence of subdural empyema was estimated to be less than 1 case per 100,000 individuals, with a male predominance. The most common pathogens of intracranial subdural empyema are anaerobic and microaerophilic Streptococci, compared to spinal subdural epmyema, which may be caused by either Streptococci or Staphylococcus aureus. If left untreated, subdural empyema frequently evolves into severe fever, headache, nausea, vomiting, seizures, coma, and subsequent death. Complications to subdural empyema include status epilepticus, neurological deficits, and thrombosis. Prognosis is generally good with antimicrobial therapy. Physical examination of patients with subdural empyema is usually remarkable for fever, facial pain, and altered mental status. MRI is the primary imaging study of epidural abscess, with CT scan as a secondary alternative. Treatment of subdural empyema requires a combined medical and surgical approach. In order to evacuate the pus, burr hole placement or craniotomy may be used to treat the subdural empyema. The preferred surgical mainstay of treatment for subdural empyema is craniotomy.

Subdural empyema  is rare, however it may complicate one-third of all intracranial infections. Subdural empyema may follow pansinusitis, mastoiditis, orbital cellulitis, and after surgery for lumbar lipomyelomeningocele manifesting with seizures, focal neurological deficits and altered mentatal status and possible progression to coma.

Joint empyema

This usually occurs after superimposed infection of the sinovial fluid following some procedures (e.g. post-lumbar or sacroiliac discectomy and instrumentation or surgery).

Empyema cystitis

This type of empyema may complicate a dysfunctional or an obstructed urinary bladder. Empyema cystis may be treated by intermittent self-catherterization or vaginal vesicostomy for empyema of dysfunctional bladder.

Differential Diagnosis

Causes of lung cavities	Differentiating Features	Differentiating radiological findings	Diagnosis confirmation
Malignancy (Primary lung cancer)	Elderly male or female Chronic smokers Presents with a low-grade fever, absence of leukocytosis, systemic complaints weight loss, fatigue Absence of factors that predispose to gastric content aspiration, no response to antibiotics within 10 days Hemoptysis is commonly associated with bronchogenic carcinoma	A coin-shaped lesion with thick wall(>15mm) is seen on CXR with less ground glass opacities Bronchoalveolar lavage cytology shows malignant cells	Biopsy of lung
Pulmonary Tuberculosis	Mostly in endemic areas Symptoms include productive cough, night sweats, fever, and weight loss	CXR and CT demonstrates cavities in the upper lobe of the lung	Sputum smear positive for acid-fast bacilli and nucleic acid amplification tests (NAAT) is used on sputum or any sterile fluid for rapid diagnosis and is positive for mycobacteria.
Necrotizing Pneumonia	Any age group Acute, fulminant life threating complication of prior infection >100.4 °F fever, with hemodynamic instability Worsening pneumonia-like symptoms	CXR demonstrates multiple cavitary lesions Pleural effusion and empyema are common findings	CBC is positive for causative organism
Loculated empyema	Children and elderly are at risk Pleuritic chest pain, dry cough, fever with chills Dullness to percussion decreased breath sounds, and reduced vocal resonance on examination	Empyema appears lenticular in shape and has a thin wall with smooth luminal margins	Thoracocentesis
Granulomatosis with polyangiitis (Wegener's)	Women are more commonly effected than man Kidneys are also involved Upper respiratory tract symptoms, perforation of nasal septum, chronic sinusitis, otitis media, mastoiditis. Lower respiratory tract symptoms (e.g. hemoptysis, cough, dyspnea) Renal symptoms, hematuria, red cell casts	Pulmonary nodules with cavities and infiltrates are a frequent manifestation on CXR	Positive for P-ANCA Biopsy of the tissue involved shows necrotizing granulomas
Rheumatoid nodule	Elderly females of 40-50 age group Manifestation of rheumatoid arthritis Presents with other systemic symptoms including symmetric arthritis of the small joints of the hands and feet with morning stiffness are common manifestations	Pulmonary nodules with cavitation are located in the upper lobe (Caplan syndrome) on X-ray	Positive for both rheumatoid factor and anticyclic citrullinated peptide antibody.
Sarcoidosis	More common in African-American females Often asymptomatic except for enlarged lymph nodes Associated with restrictive lung disease Erythema nodosum Lupus pernio (skin lesions on face resembling lupus) Bell palsy Epithelioid granulomas containing microscopic Schaumann and asteroid bodies	On CXR bilateral adenopathy and coarse reticular opacities are seen CT of the chest demonstrates extensive hilar and mediastinal adenopathy Additional findings on CT include fibrosis (honeycomb, linear, or associated with bronchial distortion), pleural thickening, and ground-glass opacities.	Biopsy of lung shows non-caseating granuloma
Bronchiolitis obliterans (Cryptogenic organizing pneumonia)	Rare condition and mimics asthma, pneumonia and emphysema It is caused by drug or toxin exposure, autoimmune diseases, viral infections, or radiation injury People working in industries are at high risk Presents with fever, cough, wheezing, and shortness of breath over weeks to months	Common appearance on CT is patchy consolidation,often accompanied by ground-glass opacities and nodules.	Biopsy of the lung Pulmonary function tests demonstrate low fev1/fvc
Langerhans cell Histiocytosis	Exclusively afflicts smokers, with a peak age of onset of between 20 and 40 years Clinical presentation varies, but symptoms generally include months of dry cough, fever, night sweats, and weight loss Skin is involved in 80% of the cases, scaly erythematous rash is typical	Thin-walled cystic cavities are the usual radiographic manifestation, observed in over 50% of patients by either CXR or CT scans.	Biopsy of the lung