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Lung Abscess

• Presented by Dr. Deena Abdel Hadi
• Directed by Dr. Abdul-Rahman Abu Rubb

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Background

• Definition
• Necrosis of the pulmonary tissue formation of
  cavities containing necrotic debris or fluid
  caused by microbial infection.
• The formation of multiple small (lt 2 cm)
  abscesses is occasionally referred to as
  necrotizing pneumonia or lung gangrene.

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• Failure to recognize treat lung abscess is
  associated with poor clinical out-come.
• Lung abscess was a devastating disease in the
  pre-antibiotic era, when 1/3 of the patients
  died, another 1/3 recovered, the remainder
  developed debilitating illnesses i.e. recurrent
  abscesses, chronic empyema, bronchiectasis.

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• In the early post-antibiotic period, sulfonamides
  didnt improve the out-come of patients with lung
  abscess until the penicillin's tetracycline's
  were available.
• Although resectional surgery was often considered
  a treatment option in the past, the role of
  surgery has greatly diminished over time coz most
  patients with un-complicated lung abscess
  eventually respond to prolonged antibiotic
  therapy.

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• Lung abscesses can be classified based on the
  duration the likely etiology.
• Acute abscesses are less than 4-6 wks old,
  whereas chronic abscesses are of longer duration.
• Primary abscess is infectious in origin, caused
  by aspiration or pneumonia in the healthy host.

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• Secondary Abscess is caused by
• - Pre-existing condition (obstruction).
• - Spread from an extra-pulmonary site.
• - Bronchiectasis.
• - An immuno-compromised state.
• Lung abscesses can be further characterized by
  the responsible pathogen, such as Staphylococcus
  lung abscess anaerobic or Aspergillus lung
  abscess.

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Pathophysiology

• Lung abscess arises as a complication of
  aspiration pneumonia caused by mouth anaerobes.
• A bacterial inoculums from the gingival crevice
  reaches the lower airways, infection is
  initiated coz the bacteria arent cleared by the
  patients host defense mechanism.

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• Abscesses generally develop in the right lung and
  involve the posterior segment of the right upper
  lobe, the superior segment of the lower lobe, or
  both. This is due to gravitation of the
  infectious material from the oropharynx into
  these dependent areas.

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• Initially, the aspirated material settles in the
  distal bronchial system and develops into a
  localized pneumonitis. Within 24-48 hours, a
  large area of inflammation results, consisting of
  exudate, blood, and necrotic lung tissue. The
  abscess frequently connects with a bronchus and
  partially empties.

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• Other mechanisms for lung abscess formation
  include
• Septic emboli to the lung ,caused by
• 1) Bacteremia.
• 2) Tricuspid valve endocarditis.
  

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Microbiology

• Anaerobes are recovered in up to 89 of the
  patients, 46 of patients with lung abscess had
  only a mixture of anaerobes isolated from sputum
  cultures while 43 of patients had a mixture of
  anaerobes aerobes.
• The most common anaerobes are Peptosretococcus,
  Bacteroids, Fusobacterium species
  Microaerophilic streptococcus.

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• Other organisms that may infrequently cause lung
  abscess include Staphylococcus aureus,
  Streptococcus pyogens, Streptococcus pneumoniae
  (rarely), Klebsiella pneumoniae, Hemophilus
  influenza, Actinomyces species, Nocardia species,
  Gm negative bacilli.

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• Non-bacterial pathogens may also cause lung
  abscesses .
• Theses micro-organisms include
• 1) Parasites Paragonimus , Entamoeba.
• 2) Fungi Aspergillus , Cryptococcus ,
  Histoplasma ,
  Blastomyces , Coccidioides.
• 3) Mycobacterium.

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History

• Anaerobic infection
• 1) Patients often present with indolent symptoms
  that evolve over a period of weeks to months.
• 2) The usual symptoms are fever , cough with
  sputum production , night sweats , anorexia
  weight loss.
• 3) The expectorated sputum characteristically is
  foul smelling bad tasting.
• 4) Patients may develop hemoptysis or pleurisy.

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• Other bacterial pathogens
• 1) These patients generally present with
  conditions that are more emergent in nature are
  usually treated while they have bacterial
  pneumonia.
• 2) Cavitation occurs subsequently as parenchymal
  necrosis ensues.
• 3) Abscesses from fungi, Nocardia Mycobacteria
  tend to have an indolent course gradually
  progressive symptoms.

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Physical

• Patients may have low-grade fever in anaerobic
  infections temperature gt 38.5 C in other
  infections.
• Generally, evidence of gingival disease is
  present.
• Clinical findings of consolidation may be
  present decreased breath sounds, dullness to
  percussion, bronchial breath sounds, course
  inspiratory crackles.

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• Evidence of pleural friction rub signs of
  associated pleural effusion, empyema
  pyo-pneumothorax may be present. Signs include
• dullness to percussion, contralateral
  mediastinal shifting absent breath sounds over
  the effusion.
• Digital clubbing may develop rapidly.

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Causes

• The bacterial infection may reach the lungs in
  several ways .that most common is aspiration of
  oro-pharyngeal contents.

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Factors contributing to lung abscess

• Oral cavity disease
• Periodontal disease
• Gingivitis
• Altered consciousness inability to protect their
  airways coz of an absent gag reflex
• Alcoholism
• Coma
• Drug abuse
• Anesthesia
• Seizures

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• Immunocompromised host
• Steroid chemotherapy
• Malnutrition
• Multiple trauma
• Esophageal disease
• Achalasia
• Reflux disease
• Depressed cough and gag reflex
• Esophageal obstruction

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• Bronchial obstruction
• Tumor
• Foreign body
• Stricture
• Generalized sepsis

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• patients with 1ry lung disorders
• Septic emboli from tricuspid endocarditis.
• Vasculitic disorders.
• Cavitating lung malignancies.
• Pulmonary cystic diseases.

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The following infectious etiologies of pneumonia
infrequently progress to parenchymal necrosis
lung abscess formation - Pseudomonas
aerugenosa. - Klebsiella pneumoniae. - Staph.
aureus (may result in multiple abscesses). -
Strept. Pneumonia. - Nocardia species. -
Fungal species.
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• An abscess may occur 2ry to bronchial carcinoma,
  the bronchial obstruction causes post-obstructive
  pneumonia which may lead to abscess formation.

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Differential Diagnosis

• 1) Alcoholism
• 2) Pleuro-pulmonary Empyema.
• 3) Hydatid Cysts.
• 4) Lung Cancer.
• 5) Mycobacterium.
• 6) Pneumococcal infections.

• 7) Pneumocystis Carnii pneumonia.
• 8) Aspiration pneumonia.
• 9) Bacterial pneumonia.
• 10) Fungal pneumonia.
• 11) Pulmonary embolism.
• 12) Sarcoidosis.
• 13) T.B.

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Lab Studies

• - CBC
• - Sputum for gram stain, culture sensitivity.
• - If T.B. is suspected, acid fast bacilli stain
  mycobacterial culture is requested.
• - Blood culture may be helpful in establishing
  the etiology.
• - Obtain sputum for ova parasite whenever a
  parasitic cause for lung abscess is suspected.

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HistopathologyA thick-walled lung abscess
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Histology of lung abscess shows dense
inflammatory reaction (low power)
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Histology of lung abscess shows dense
inflammatory reaction (high power)
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Imaging Studies

• CXR
• - Irregularly sharp cavity with an air-fluid
  level inside.
• - Lung abscess as a result of aspiration most
  frequently occur in the posterior segments of the
  upper lobes or the superior segments of the lower
  lobe.

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• - The wall thickness of a lung abscess
  progresses from thick to thin and from
  ill-defined to well-circumscribed as the
  surrounding lung infection resolves.
• - The cavity wall can be smooth or ragged but is
  less commonly nodular, which raises the
  possibility of cavitating carcinoma.

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• - The abscess may extend to the pleural surface,
  in which case it forms acute angles with the
  pleural surface.
• - Up to one third of lung abscesses may be
  accompanied by an empyema.

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Pneumococcal pneumonia complicated by lung
necrosis abscess formation
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A lateral CXR shows air fluid level
(characteristic of lung abscess)
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A 54 yr old pt. developed cough with
foul-smelling sputum production. A CXR shows lung
abscess in the left lower lobes.
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A 42 y.o. man developed fever production of
foul-smelling sputum. He had a H/O heavy alcohol
use poor dentition, CXR shows lung abscess in
the post segment of the Rt. up. lobe.
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CXR of a patient who had foul-smelling bad
tasting sputum, an almost diagnostic feature of
anaerobic lung abscess
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• CT scan
• - Better in lung anatomy visualization to
  identify empyema from lung infarction.
• - An abscess is rounded radio-lucent lesion with
  a think wall ill-defined irregular margins.

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A 42 yr old man developed fever production of
foul-smelling sputum. He had a H/O heavy alcohol
abuse poor dentition, CXR shows lung abscess in
the post. Segment of the Rt. Up. Lobe. CT scan
shows a thin-walled cavity with surrounding
consolidation.
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Procedures

• - Trans-tracheal aspirate or trans-thoracic
  needle aspiration may provide microbiologic
  diagnosis, obtaining pleural fluid and blood
  cultures in patients with lung abscess is easier.
• - Flexible fiberoptic bronchoscopy is performed
  to exclude bronchogenic carcinoma whenever
  bronchial obstruction is suspected.

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Medical Care

• Antibiotic therapy
• - Anaerobic lung infection Clindamycin shown
  to be superior over parenteral penicillin coz
  several anaerobes may produce B-lactamase
  therefore develop penicillin resistance.
• - Although metronidazole is an effective drug
  against anaerobic bacteria, a failure rate of 50
  has been reported.

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• - In hospitalized patients who have aspirated and
  developed a lung abscess, antibiotic therapy
  should include coverage against S aureus and
  Enterobacter and Pseudomonas species.
• - Cefoxitin is a second-generation cephalosporin
  that has gram-positive, gram-negative, and
  anaerobic coverage. This agent may be used when a
  polymicrobial infection is suspected as cause of
  lung abscess.

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• Duration of therapy
• - Most clinicians prescribe antibiotic therapy
  generally for 4-6 weeks.
• - Current recommendations are that antibiotic
  treatment should be continued until the chest
  radiograph has shown either the resolution of
  lung abscess or the presence of a small stable
  lesion.

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• Response to therapy
• - Patients show clinical improvement, with
  improvement of fever, within 3-4 days after
  initiating the antibiotic therapy.
• - Patients with poor response to antibiotic
  therapy include bronchial obstruction with a
  foreign body or neoplasm or infection with a
  resistant bacteria, Mycobacteria, or fungi.

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Surgical Care

• Surgery is very rarely required for patients
  with uncomplicated lung abscesses. The usual
  indications for surgery are failure to respond to
  medical management, suspected neoplasm, or
  congenital lung malformation. The surgical
  procedure performed is either lobectomy or
  pneumonectomy.

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Complications

• 1) Rupture into pleural space causing empyema.
• 2) Pleural fibrosis.
• 3) Trapped lung.
• 4) Respiratory failure.
• 5) Bronchopleural fistula.
• 6)Pleural cutaneous fistula.
• In a patient with coexisting empyema and lung
  abscess, draining the empyema while continuing
  prolonged antibiotic therapy is often necessary.
  

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Prognosis

• The prognosis for lung abscess following
  antibiotic treatment is generally favorable. Over
  90 of lung abscesses are cured with medical
  management alone, unless caused by bronchial
  obstruction secondary to carcinoma.
•  

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The End

• Thank You