Chest Radiology: Randomly Distributed Lung Diseases and More
Review of chest radiology lung diseases that are randomly distributed, centrally distributed and more.
Chest Radiology: Randomly Distributed Lung Diseases and More
Diffuse, Central, RML/lingula, and/or Randomly Distributed Lung Diseases:
Granulomatosis with polyangiitis: Triad is commonly tested although not super common and consists of upper respiratory tract, lung (95% involvement), and renal involvement. Expect random nodules with cavitation on chest CT with additional
history of renal or upper respiratory tract abnormalities including hematuria and hemoptysis. Pulmonary hemorrhage around nodules may happen and would look like ground-glass surrounding the nodule. Labs show c-ANCA positivity.
Goodpasture syndrome/antiglomerular basement membrane antibody disease: An
autoimmune pulmonary renal syndrome most common in younger men with diffuse alveolar hemorrhage from the pulmonary capillary inflammation (pulmonary capillaritis). Chest imaging shows bilateral coalescent airspace opacities that may mimic pulmonary edema but results from pulmonary hemorrhage (pulmonary edema=fluid in alveolar spaces/Goodpasture syndrome=blood in alveolar spaces). Recurrent episodes of pulmonary hemorrhage can lead to fibrosis and hemosiderosis (iron deposition) causing appearance of multiple small nodules. More advanced disease may present with crazy paving. Need to exclude infection before you treat with steroids.
Eosinophilic granulomatosis with polyangiitis: Is an eosinophilic lung
disease and most patients have associated asthma and eosinophilia. Expect migratory lung opacities that are transient. If see nodules with cavitation think granulomatosis with polyangiitis instead of this. May have additional cardiac, renal, CNS, GI
involvement. Treat with steroids.
ANCA:
c-ANCA think granulomatosis with polyangiitis first
p-ANCA think Goodpasture syndrome, eosinophilic granulomatosis with polyangiitis first
Hypersensitivity pneumonitis (HP): Results from a type 3 hypersensitivity reaction (type 1 hypersensitivity reaction is asthma) resulting from an immune reaction to an antigen with hundreds of known antigens that can cause HP. Smoking may be protective against hypersensitivity pneumonitis due to diminished antibody response (the antibodies throw in the towel due to the constant barrage of cigarette smoke), but I still do not advocate cigarette smoking. Has acute, subacute, and chronic phases. List of possible antigens is extensive and includes many farm/food preparation entities (mushroom worker’s lung, cheese worker’s lung, bird fancier’s lung), many industrial activities (wine maker’s lung, machine operator’s lung), the classic hot tub lung, and some interesting ones such as saxophone lung and shower curtain
disease.
Acute HP is rare, requires a significant inhalational event (such as caught in dust storm
without mask or rescued from house fire with lots of smoke inhalation), presents with edema and centrilobular nodules, diffuse alveolar damage/hemorrhage, and is indistinguishable from DIP but history will be very different (acute massive inhalation event is acute HP, chronic smoking is DIP).
Subacute HP presents with many ill-defined ground-glass nodules and mosaic attenuation. No or only minimal fibrosis but you start to see changes from inflamed airways (mosaic attenuation resulting from air trapping). Subacute HP is most common for the head cheese sign, and this is a sign that you should associate with HP. This results from the mixture of mosaic attenuation, normal lung, and ground-glass opacities. You need to know what this looks like so look it up.
Chronic HP: Fibrosis in lungs from long-term exposure presenting with dyspnea, finger clubbing, etc. On CT expect pulmonary fibrosis and honeycombing, mosaic attenuation from airway narrowing, ground-glass opacities. This may spare the lung bases unlike UIP/NSIP.
Mosaic attenuation: lung pattern with areas of varying pulmonary parenchymal attenuation resulting from reduced ventilation (air trapping), reduced perfusion (oligemia), mixture of above, or parenchymal problems.
Pneumocystis jiroveci pneumonia (PJP): Presents primarily in HIV/AIDS patients or less commonly in otherwise immunocompromised or bone marrow transplant patients. CT shows ground-glass opacities, septal thickening (therefore a possible crazy paving pattern) and possible cysts/blebs/pneumatoceles that form in area of infection. Expect CD4 count <200. Groundglass opacities most common in perihilar/mid lung zones. There is a cystic variation that is upper lobe predominant with bilateral upper lobe cysts and pneumothorax risk. Don’t forget about the diffuse gallium-67 pulmonary uptake that is classic for this and frequently tested. Lack of gallium-67 uptake = no PJP.
*If you see similar clinical history and imaging findings and they ask about CMV remember this can look very similar to PJP pneumonia, but CMV does not have the cystic pattern with PJP.
Pulmonary amyloidosis: Presents with multiple calcified pulmonary nodules. There are other forms that can look like other things in the lungs but the one I would be most familiar with for the Core Exam is the nodular variant with nodules that have central and/or irregular calcifications with slow growth over years. Sjogren syndrome association. Nodules can look like pulmonary hamartomas.
Lymphangioleiomyomatosis: Expect a history of a woman of childbearing age with tuberous sclerosis. Diagnosis is based on “possible”, “probable” or “definite” LAM which is combination of imaging findings and other criteria such as biopsy, things like associated renal angiomyolipoma, thoracic or abdominal chylous effusion, so forth. CT findings alone without the other supporting factors is “possible” LAM. Imaging shows multiple uniformly distributed thin-walled cysts, may have associated chylous pleural effusion. Extra-thoracic findings include abdominal chylous ascites, renal AMLs, uterine fibroids, splenic cysts, and cystic hygroma. Risks include recurrent pneumothorax.
Acute interstitial pneumonia/ARDS: Results from alveolar injury with leakage of fluid into the alveolar space, i.e., non-cardiogenic pulmonary edema. ARDS requires both the imaging findings and respiratory failure that is of non-cardiac or volume-overload etiology. Many things can cause this including viral illness and entities like burn injuries, pancreatitis, post-traumatic, head injury, etc. Expect some involvement of groundglass opacities in all 5 lobes with some normal areas of lung as well. CT may show a gradient effect where dependent lungs show consolidation on background of groundglass in the middle and normal lung in the non-dependent lung. If
unresolved but the patient survives can lead to rapid fibrosis within weeks and the minority of patients will recover completely. Would look like UIP pattern that developed in weeks rather than years.
Miliary tuberculosis: Tuberculosis was previously discussed. Miliary pattern is random nodules throughout both lungs. Differential considerations for a miliary pattern include hematogenous metastases such metastatic thyroid cancer, melanoma, or renal cell carcinoma.
Pulmonary alveolar proteinosis: An intrinsic lipoid pneumonia with abnormal surfactant clearance with a highly tested, classic look that is crazy paving pattern in both lungs with batwing appearance on chest x-rays. Male smokers are at particularly high risk. Cause is the abnormal proliferation two pneumocytes that make fat like surfactant that become ingested by macrophages that don’t work correctly due to autoimmune issues and can test for anti-GM-CSF antibodies. Treatment includes intubation with therapeutic lavage of each lung with large amounts (10-15 liters) of fluid. If see this in the first year of life remember association with
lymphoid tissue hypoplasia presenting with low lymphocyte counts and reduced/absent thymic tissue. Classic is imaging findings worse than expected for clinical presentation. Superimposed infection is a concern.
Crazy paving: admixture of ground-glass opacities with inter- and intralobular septal thickening. For board purposes this is most classic for pulmonary alveolar proteinosis (PAP), but may also be seen with ARDS and other infectious/inflammatory processes such as bacterial pneumonia, Goodpasture syndrome, UIP, COP, etc.
.
Pulmonary edema: May have cardiac and non-cardiac causes. Lots of classic radiograph
findings like Kerley lines, batwing opacification, pleural effusions, etc. CT expect ground-glass opacities, often central, interlobular septal thickening, possible superimposed consolidation and pleural effusions.
*Imaging appearance like diffuse pulmonary hemorrhage, pulmonary alveolar proteinosis (see above) and diffuse pneumonia/infection. Diffuse hemorrhage does not have a pleural effusion and typically no increase in the dependent lung.
Mycobacterium avium complex (MAC): The most common nontuberculous mycobacteria in North America. May present with a cavitary pattern, nodular bronchiectasis pattern, and a hypersensitivity pneumonitis pattern. Cavitary pattern can mimic TB and is most common in older men with COPD, presents with thick-walled cavities with adjacent consolidation and possible tree-in-bud opacities. Nodular bronchiectasis pattern is most common in older, thin women and has the classic tendency to present in the right middle lobe and lingula (Lady Windermere syndrome) which is more likely indolent. This may also present with a hypersensitivity pneumonitis pattern and MAC is likely to be the etiology of “hot tub lung”.
Patients with bronchiectasis more at risk (cystic fibrosis/alpha 1 antitrypsin). Get a sputum culture to confirm the diagnosis. Treatment/clearance of disease can be difficult, like TB.
