Lung Abscess Slide gangrene

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

Necrosis of the pulmonary tissue & formation of
cavities containing necrotic debris or fluid
caused by microbial infection.

The formation of multiple small (< 2 cm)
abscesses is occasionally referred to as
necrotizing pneumonia or lung gangrene.
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].

In the early post-antibiotic period, sulfonamides didn’t
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.
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.

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.
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 aren’t cleared by the patient’s host
defense mechanism.

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

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.

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


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.
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.

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.

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.
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.
Patients may have low-grade fever in anaerobic
infections & temperature > 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].

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.


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

Factors contributing to lung abscess

  Oral cavity disease
  Periodontal disease

  Altered consciousness[ inability to protect their
  airways coz of an absent gag reflex]
  Drug abuse
Immunocompromised host
Steroid chemotherapy
Multiple trauma

Esophageal disease
Reflux disease
Depressed cough and gag reflex
Esophageal obstruction           20
Bronchial obstruction
Foreign body

Generalized sepsis

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

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.                                     23
 An abscess may occur 2ry to bronchial
carcinoma, the bronchial obstruction causes
post-obstructive pneumonia which may lead
to abscess formation.

       Differential Diagnosis

1) Alcoholism         7) Pneumocystis Carnii
2) Pleuro-pulmonary   pneumonia.
   Empyema.           8) Aspiration pneumonia.
3) Hydatid Cysts.     9) Bacterial pneumonia.
4) Lung Cancer.       10) Fungal pneumonia.
5) Mycobacterium.     11) Pulmonary embolism.
6) Pneumococcal       12) Sarcoidosis.
   infections.        13) T.B.
              Lab Studies

- 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
- Obtain sputum for ova & parasite whenever a
  parasitic cause for lung abscess is suspected.
A thick-walled lung abscess

Histology of lung abscess shows dense inflammatory
                reaction (low power)

Histology of lung abscess shows dense inflammatory
              reaction (high power)

             Imaging Studies

- 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.

 - 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.
- 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.

  Pneumococcal pneumonia
complicated by lung necrosis &
      abscess formation

A lateral CXR shows air fluid level
 (characteristic of lung abscess)

A 54 yr old pt. developed cough with foul-
  smelling sputum production. A CXR
shows lung abscess in the left lower lobes.

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.

CXR of a patient who had foul-smelling & bad
tasting sputum, an almost diagnostic feature of
            anaerobic lung abscess

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.

   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.


- 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.

               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

- 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.                                         42
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.

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.
              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.

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.              46

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.

The End
Thank You


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