Thoracic Imaging 2003 - Society of Thoracic Radiology

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application. The untreated patient with sarcoid will improve 50
to 90 percent of the time with Radiographic stage 1 disease. The
untreated patient with Stage 2 disease will improve 30 to 70
percent of the time. Only 10 to 20 percent of untreated patients
with Stage 3 disease will improve, and there is no improvement
in those with untreated Stage 4 disease, [5]. It is important to
note that there may be considerable discrepancy between the
severity of the radiographic abnormalities and the patient’s
symptoms, [5].
The clinical diagnosis of sarcoid requires a compatible clinical
and radiographic presentation, biopsy evidence of sarcoid
granulomas, usually from transbronchial biopsies of the lung,
and the exclusion of other diseases capable of producing a similar
clinical, radiographic, and histological picture, [1-5].
Systemic corticosteroid therapy is clearly indicated for cardiac
disease, neurological disease, eye disease that is refractory
to topical therapies, and hypercalcemia, [1]. Most physicians
feel that progressive symptomatic pulmonary and extrapulmonary
disease should be treated with systemic corticosteroids,
[1]. Cytotoxic agents, antimalarial agents, and lung transplantation
are useful in select patients with advanced sarcoid, [1].
The diagnostic yield of endomyocardial biopsies is low in
sarcoid patients. Sarcoid patients with symptomatic cardiac dysfunction,
ECG abnormalities, thallium 201 imaging defects, or
MR evidence of myocardial disease should be presumed to have
cardiac sarcoidosis in the presence of a negative endomyocardial
biopsy, [1]. It is important in older sarcoid patients to
exclude coronary artery disease as cause of their cardiac illness.
Sarcoid is a multisystem disease and, for this reason, careful
clinical evaluation of the entire patient must be done. This clinical
review includes the peripheral lymph nodes, skin, spleen,
liver, eyes, central nervous system, musculoskeletal system, gastrointestinal
tract, bone marrow, parotid glands, reproductive
organs, kidneys, and the endocrine system, [1-5].
Physiology
The pulmonary physiology of sarcoid is usually a predominantly
restrictive ventilatory process, with reductions in vital
capacity (VC) and diffusion capacity (DLCO), [4]. Physiology
testing cannot distinguish alveolitis from fibrosis, [4]. Serial
physiological testing is quite valuable in monitoring the course
of an individual patient’s pulmonary sarcoid, [4]. An obstructive
component of the lung physiology is detected in one-third or
more of sarcoid patients with lung involvement with reductions
in FEVI and expiratory flow rates, [4]. Central and small airway
involvement accounts for the obstructive physiology observed in
these sarcoid patients.
Typical Radiographic and CT Observations in the Thorax
The most common radiographic presentation is Stage 1 sarcoid
with bilateral symmetric hilar lymphadenopathy and mediastinal
lymphadenopathy in an asymptomatic patient, [5].
Mediastinal lymph node enlargement usually is seen in the right
paratracheal, aortopulmonary window, and subcarinal regions.
Anterior mediastinal lymph node enlargement is unusual in sarcoid
unlike lymphoma patients, [5]. CT demonstrates lymphadenopathy
better than radiography and often demonstrates
additional regions of lymph node involvement. CT is more sensitive
than radiography for the detection of lymph node calcifications
in sarcoid, [5].
The typical radiographic observations in Stage 2 or 3 sarcoid
are nodules, linear/reticular opacities and ground glass opacities
with a mid and upper lung zone distribution [5]. HRCT examination
demonstrates a perilymphatic distribution of irregular,
small discrete nodules, 2 to 10 mm in size, that predominate in
both the mid and upper lung zones and in the central portion of
the lung. This perilymphatic distribution of nodules results in
nodules that are associated with the bronchovascular structures,
interlobular septae, and pleural surfaces. Peribronchial wall
thickening is common on HRCT, as well as interlobular septal
thickening and ground glass opacities. Nodules larger than 10
mm in size may be seen but are less common.
Radiographic Stage 4 sarcoid has marked upper lobe volume
loss, architectural distortion of the lung, conglomerant mass formation,
cyst formation, honeycombing, traction bronchiectasis,
and emphysema, [51. Pulmonary fibrosis and honeycombing
with an upper lobe predominance develops in 20 % of sarcoid
patients. HRCT examinations show similar findings but to better
advantage than radiography.
Plain radiography and CT may show severe bronchial stenosis
or irregularity in patients with endobronchial sarcoid. Central
airway observations on CT include regular or irregular bronchial
wall thickening, luminal narrowing or occlusion, and displacement
of central bronchial structures by adjacent lymphadenopathy,
[51. 3D reconstructions of multidetector spiral CT datasets
can show central bronchial stenosis for endobronchial stent
placements, [5].
Less Common Radiographic and CT Observations in the
Thorax
Radiographic and CT examinations of patients may demonstrate
a number of observations that are less commonly associated
with pulmonary sarcoidosis. These include a solitary mass,
multiple masses, focal consolidation, cavity formation, pleural
thickening, pleural effusion, and pleural calcifications, [4,5].
The presence of cavities may indicate a different process than
sarcoid including necrotizing sarcoid granulomatosis, superinfection,
or vasculitis, [4,5]. Mycetomas may developing in
upper lobe bullae and cysts in Stage 4 sarcoid. These mycetomas
may present with life threatening hemoptysis. A pattern
of pulmonary fibrosis indistinguishable from IPF has also been
described in sarcoid, [4,51. Though unusual, unilateral lung and
intrathoracic lymph node disease have also been described in
sarcoid and are indistinguishable radiographically from infectious
granulomatous disease and intrathoracic malignancies,
[4,51. Pulmonary arterial hypertension is seen in less than 5%
of patients and usually in patients with Stage 4 disease, [4,51.
There is an increased rate of sarcoid recurring in a transplanted
lung compared to other diseases that undergo lung
transplantation therapy, [1,[8]. The frequency of recurrency has
been reported to be as high as 35%, [8]. Posttransplantation
immunosuppression therapy is reported to control the recurring
sarcoidosis, [I]. Myocardial imaging is helpful in the 5% of
patients suspected of having cardiac sarcoid, [1]. Thallium 201
myocardial imaging is superior to Doppler echocardiography if
the detection of segmental wall motion abnormalities of the left
ventricle that correspond to sarcoid induced granulomas or
fibrosis in the myocardium, [1]. MR imaging of the heart has
recently been shown to be effective in the detection of myocardial
sarcoid lesions and the MR imaging findings may be helpful
in monitoring the response of the myocardium to steroid
therapy, [9].
Differential Diagnosis
The differential diagnosis of pulmonary sarcoid includes
conditions that have preferential involvement of the perilymphatic
space of the lungs and lymph node involvement in the
hila of the lungs and in the mediastinum. This includes infectious
granulornatous diseases, Berylliosis, lymphorna, leukemia,
and lymphangitic carcinomatosis, Asymmetric involvement of
the lung and intrathoracic lymph nodes usually excludes malignant
and infectious diseases of the thorax. Lymphangitic carcinomatosis
has recently been shown to have more involvement of
the interlobular septae and subpleural space on HRCT than
either lymphoma or sarcoid, [10]. Almost all patients with thoracic
malignancies are symptomatic as opposed to asympto-