Additional pediatric resources: GeneralPediatrics.com | PediatricEducation.org | SearchingPediatrics.com
Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed
Etiology/Pathophysiology:
The initial infection with the bacterium Mycobacterium Tuberculosis
is acquired via an airborne route. If the initial infection is not
walled off, it may spread via bronchogenic spread with multiple
pulmonary foci, lymphatic spread to more distant lymph nodes and
hematogenous (miliary) spread to kidneys, lungs, liver, and meninges.
Pathology:
The classic finding is caseating necrosis.
Imaging Findings:
The initial focus has localized air space consolidation and then
spreads from the periphery via lymphatic channels to regional lymph
nodes where the lymph nodes enlarge after several weeks. If the
infection involutes the lesion can calcify with the Ghon focus being
the calcified peripheral lung focus and the Ranke complex being the
calcified peripheral lung focus and the calcified central lymph
nodes. If resistance fails to develop and there is no involution the
initial peripheral focus can extend to occupy an entire segment or
lobe. Often there may be an associated pleural effusion. Primary TB
has its peripheral foci scattered throughout the lung fields.
Secondary, or reinfection, TB has 90% of its lesions in apices. The
lungs may take 4 years to clear after therapy. The classic picture of
primary TB is air space disease associated with hilar/mediastinal
adenopathy and pleural effusion.
DDX:
References:
Additional pediatric resources: GeneralPediatrics.com | PediatricEducation.org | SearchingPediatrics.com
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