Main»Pulmonary Fungus And Tuberculosis

Pulmonary Fungus And Tuberculosis

Pulmonary Fungus and Tuberculosis

1. Fungal Infections of the lung

A. Indications for Thoracic Surgical Intervention
1) Establish a diagnosis
2) Failure of medical therapy
3) Fungal disease vs. lung carcinoma
B. Fungal Infections of the Lung
1) The three major mycotic infections are histoplasmosis, coccidiomycosis, and blastomycosis
2) The fungal agent in each case is dimorphic: exists in nature as mycelium (mold) that bears infectious spores, which enter host and develop into a yeast-like phase that is the tissue pathogen
3)These fungi require special staining and culture methods

Amphotericin B is primary therapy for all three fungal infections

C. Histoplasmosis
1) Systemic disease caused by H. capsulatum, which is found in soil with high concentration of fecal material of chickens, pigeons and bats
2) Endemic areas are the valleys of Ohio, Missouri, and Mississippi rivers
3) Occurs as an intracellular yeast and is seen best on silver stain
4) Farmers, construction workers, and people who enjoy outdoor activities are the most at risk by inhaling spores
5) 1 in 2000 people will develop chronic pulmonary disease
6) Most cases of primary histoplasmosis are asymptomatic or mild flu-like syndrome
7) Progressive pulmonary disease associated with chronic lung disease occurs in middle-aged men
8) CXR demonstrates dense nodules with central calcification
9) Chronic cavitary histoplasmosis is less common
10) Mediastinal histoplasmosis results in fibrosing mediastinitis, which is the most frequent benign etiology of SVC obstruction
11) Healed histoplasmosis causes a solitary pulmonary nodule, which can be confused with carcinoma
12) Indications for surgery:
a) Chronic cavitary pulmonary disease - persistent thick-walled cavity after 2g to 3g course of Amphotericin B for 2-3 months
b) Fibrosing mediastinitis with middle lobe syndrome
c) SVC syndrome
D. Coccidiomycosis
1) Causative agent is C. immitis
2) Endemic areas are the Southwestern USA and Mexico
3) The spherules have a thin wall containing endospores which are seen on wet mount slides
4) Infection occurs after spore inhalation and 60% of patients are asymptomatic
5) Acute valley fever is characterized by pneumonitis, erythema nodosum, and arthralgias
6) Only 5% of patients with symptomatic pulmonary disease develop irreversible bronchiectasis, pulmonary nodules, pulmonary abscesses or residual cavities
7) The most frequent long-term complication is a chronic cavitary lesion (solitary, thin-walled)
8) CXR demonstrates nonspecific infiltrates, hilar adenopathy, or pleural effusions
9) Diagnosis is made by serologic testing for IgM or IgG antibodies; a rising titer suggests possible dissemination
10) The most important extra pulmonary manifestation is meningitis
11) Most patients require no therapy
12) Amphotericin B is indicated if there is severe, prolonged pulmonary disease; primary disease with risk of dissemination (pregnancy, immunosuppression); symptomatic, chronic cavitary disease; and as an adjuvant to surgical resection
13) Indications for surgery:
a) Enlarging cavitary lesion
b) Hemoptysis
c) Secondary infection
14) Peri-operative Amphotericin B is recommended for these patients
E. Blastomycosis
1) Causative agent is B. dermatitides
2) The endemic areas are the southeastern and southwestern USA, mostly the Ohio and -->3) Mississippi river valleys and the Great Lakes area
4) Classically seen as a round, thick-walled single yeast cell on staining
5) Acute infection typically involves the lower lobes and is asymptomatic, or can result in influenza-like syndrome
6) Chronic infection typically involves the upper lobes and results in a pyogranulomatous process
7) The most common extrapulmonary manifestation is cutaneous ulcers
8) Chronic, disseminated disease typically involves the skin and ribs
9) Primary treatment is typically Amphotericin B - 2 to 2.5g over 2-3 months or ketoconazole as an alternative agent
10) Indications for surgery:
1) Rule out malignancy
2) Drainage of large cavitary abscesses
3) Closure of bronchopleural fistulas
F. Other Fungal and Opportunistic Infections of the Lung
1) Cryptococcosis
a) Caused by C. neoformans, found in soil contaminated by pigeon droppings
b) India ink staining reveals round, budding yeast which has gelatinous polysaccharide capsule
c) Primarily involves the bronchopulmonary tree, with special predilection for the meninges
d) Lesions often involve the lower lobes and are solid
e) Amphotericin B and 5-fluorocytosine are both effective medical treatment
f)Always examine CSF if C. neoformans is isolated from sputum or surgical specimen
g) 10% of patients develop cryptococcal meningitis after resection of a pulmonary lesion
2) Aspergillosis
a) Most are caused by A. fumigatus, an organism found in hay and grains
b) Appears as mixture of coarse, fragmented hyphae and ball-like clusters on histology
c) Three clinical syndromes occurs: aspergillar bronchitis, aspergilloma, and invasive aspergillosis
d) Aspergillomas are the most common surgically resected lesion of this type and usually occur in a upper lobe cavity
e) These may be asymptomatic for years or cause hemoptysis
f) Hemoptysis occurs in 50% of patients with Aspergilloma, in 10% the hemoptysis is severe and recurrent
g) Once hemoptysis develops, the aspergilloma should be resected
h) Medical therapy usually not effective because Amphotericin penetrates aspergillus cavities poorly
i) Prophylactic resection in asymptomatic patients is generally not indicated because of significant complication rate
3) Actinomyocis
a) Causative agent is usually A. israelii, a microaerophilic organism
b) Appears as branching hyphae which contain "sulfur granules"
c) Thoracic infection occurs after aspiration of oropharyngeal organisms
d) Presents as empyema, infiltrate, consolidation, or hilar mass
f) Treatment of choice is high dose penicillin for 1-3 months
4) Nocardiosis
a) Causative agent is N. asteroides
b) Appears as long-branching filaments that can be confused with M. tuberculosis
c) Opportunistic infection which occurs in immunocompromised patients
d) CXR shows solitary nodules, nonspecific infiltrates, or cavitations
e) Chest wall sinus tracts and empyema may occur, as well as CNS dissemination
f) Treatment of choice is sulfadiazine, sulfisoxasolem, minocycline, or Bactrim for --->g) 2-3 months
5) Candidiasis
a) Causative agent is C. albicans, which is normal flora in GI tract, oral cavity, and --->b) female genital tract
c) Most common fungal infection in humans
d) Becomes invasive in immunocompromised host
e) Can cause deep thoracic infections or endocarditis
f) Treatment of choice is Amphotericin B
6) Protozoal Infections
a) Most common causative agent is P. carinii
b) Occurs as a diffuse interstitial pneumonitis in immunocompromised patients
c) CXR shows diffuse infiltrates radiating from the hilum
d) Often causes hypoxemia, hypocapnia, and pneumothoraces
e) Open lung biopsy may be required to establish diagnosis
f) Treatment of choice is pentamidine or Bactrim
7) Pulmonary Echinococcosis
a) Causitive agent is T. echinococcus, a small tapeworm
b) Reults in intrathoracic cyst that can rupture, causing asphyxiation or allergic --->c) reaction
d) CXR shows homogenous, oval shaped densities with clearly defined borders
e) Surgical therapy involves cystectomy or pericystectomy with instillation of --->f) formalin or 10% NaCl solution
f) Some success has been reported with medical treatment using benzimidazole derivatives

2. Pulmonary Tuberculosis

A. Etiology
1) M. tuberculosis is a virulent organism transmitted by airborne droplets that can rapidly destroy lung tissue if left untreated
2) Three million deaths occur worldwide due to TB
3) The incidence had been declining until 1985 and is now rising
4) Resectional therapy is becoming increasingly utilized with the rise in multidrug resistant organisms
B. Diagnosis
1) Classic symptoms include night sweats, fever, cough, and occasionally hemoptysis
2) Tuberculosis is most common cause of severe hemoptysis
3) Asphyxiation rather than hypovolemia is usual cause of death from hemoptysis
4) The diagnosis is made by acid-fast staining and culture of the sputum
5) The Ghon complex is characterized by a peripheral lesion with associated hilar adenopathy
6) Other forms of mycobacterium, most commonly M. avium, can cause indolent infections that attack diseased pulmonary tissue
C. Medical Therapy
1) First line drug therapy includes isoniazid, ethambutol, pyrazinamide, and streptomycin
2) A minimum of 3 drugs should be initiated when the diagnosis is made
3) The preferred regimen is isoniazid and rifampin for 6 months, with pyrazinamide for 2 months
4) If the sputum is positive after 3 months of treatment, either the patient is noncompliant or the organism is an uncommon mycobacterium or is resistant; the patient should be recultured
5) Pure tuberculous effusions almost always resolve spontaneously or respond promptly to chemotherapy
6) Tube thoracostomy rarely provides a cure because dense pleural reaction interferes with full re-expansion of the underlying lung
D. Indications for Surgical Resection
1) Persistently positive sputum cultures with cavitation after 5-6 months of continuous optimal chemotherapy with 2 or more drugs
2) Localized pulmonary disease cause by M. avium-intracellulare; other atypical mycobacterium or M. tuberculosis which is drug resistant
3) Mass lesion of the lung in an area of tuberculous involvement
4) Massive life-threatening hemoptysis or recurrent severe hemoptysis (massive = 600 cc or more/24 hr, severe = 200 cc/24 hr)
5) Bronchopleural fistula in association with mycobacterial infection that does not respond to tube thoracostomy
E. Contraindications to Resection in TB
1) Widespread pulmonary or endobronchial disease
2) Children with mycobacterial disease
3) FEV1 less than 800-1,000 cc
4) Active endobronchial disease, as this interferes with healing of bronchial stump (pre-op bronchoscopy in all patients prior to resection)
G. Operative Management
1) Lobectomy or pneumonectomy usually necessary with active mycobacterial disease
2) Extrapleural pneumonectomy for extensive pulmonary parenchymal disease with chronic empyema (rare)
3) Complications of resection include empyema with or without broncho-pleural fistula and bronchogenic spread of mycobacterial disease
4) Both complications aremore frequent when the sputum is positive at the time of operation