Abstract Because of the complex imaging and clinical manifestations of diffuse lung diseases, the diagnosis is often difficult. The pathogenesis, imaging, diagnosis and differential diagnosis of three major types of diffuse lung diseases are analyzed and discussed.
Keywords: diffuse lung disease; diagnosis, differential diagnosis; body layer photography, X-ray computer, Department of Radiology, Henan Provincial People’s Hospital, China, Lei Zhidan
Diffuse lung disease is a group of interstitial and parenchymal lung lesions characterized by extensive multifocal lesions on imaging. It is mainly divided into acute diffuse lung disease in immunocompetent patients, diffuse lung disease caused by non-HIV infectious immune damage and diffuse lung disease in HIV-positive patients.
I. Acute diffuse lung disease in immunocompetent patients
(A) Pulmonary edema
Pulmonary edema is the most common cause of acute diffuse lung disease. It can be divided into hydrostatic (cardiogenic) pulmonary edema and increased vascular permeability (noncardiogenic) pulmonary edema.
1. Hydrostatic pulmonary edema
Interstitial pulmonary edema precedes alveolar edema in hydrostatic edema. The main manifestations of interstitial pulmonary edema are vascular blurring, bronchial cuff sign, K’s B line (thickening of the lobular septa) and subpleural edema distributed along the interlobular fissures. Subpleural edema is more characteristic than the bronchial cuff sign and is easier to visualize than the K’s line. Interstitial pulmonary edema may also be accompanied by redistribution of pulmonary blood, typified by an enlarged upper lobe pulmonary artery larger in diameter than the adjacent bronchus. Alveolar edema usually accumulates in the central or basal part of the lung. In upright patients, there is a clear trend toward a basal distribution. In supine patients, however, pulmonary edema is predominantly distributed posteriorly and may appear as a centrally distributed butterfly wing-shaped solid shadow on chest radiographs. When pulmonary edema is caused by congestive heart failure, it appears as a diffusely distributed solid shadow. Severe pulmonary edema may often be accompanied by a small amount of pleural effusion.
The CT manifestations of hydrostatic pulmonary edema include thickened bronchovascular bundles, thickened lobular septa, and ground glass shadows as well as solid shadows. CT images of ground glass shadows appear as diffuse lesions distributed along the gravitational gradient curve, but they can also be restricted in distribution.
2. Pulmonary edema caused by increased vascular permeability
Increased vascular permeability pulmonary edema is a manifestation of diffuse lung damage, and adult respiratory distress syndrome (ARDS) is the most severe form of vascular permeability edema.
The typical radiological manifestations include a normal-sized cardiac shadow, a normal width of the vascular tip, and patchy lesions in the peripheral air spaces. As the disease progresses, the solid lesions are extensive, the air bronchial sign is more prominent, and pleural effusion is less common. Lobular septal thickening and peripheral bronchial cuff signs may be present, but are less common than cardiogenic edema. In early ARDS, the CT presentation is a combination of ground glass shadows and solid shadows, sometimes with reticular shadows overlapping these images. These parenchymal shadows show a gradient curve that changes along the hypoplasia, i.e., from ventral (minimal opacity) to dorsal (most opacity). However, this is not characteristic of all patients with ARDS. For example, in patients with ARDS caused by pulmonary disease, the concentration shadows of the pulmonary lesions have a similar appearance to the parenchymal shadows of alveolar edema, and the shadows in the non-hypophysis may be due to the primary lesion.
(ii) Infection
Infectious pneumonia is often caused by bacteria or mycoplasma. Although the incidence of diffusely distributed infections is lower than in immunodeficient patients, severe infections of many etiologies can lead to osmotic pulmonary edema with DAD. The main manifestations are diffusely distributed central lobular nodules and intralobular branching structural changes due to fine bronchial filling. The central lobular nodules tend to fuse and resemble patchy shadows, and CT shows more clearly bronchial occlusion due to infection, a sign known as the “bud sign”. Although the “sprout sign” presentation has been traditionally associated with Mycobacterium avium infection, it can also be caused by acute bacterial infections.
Mycoplasma pneumonia is a common cause of group pneumonia. When acute, chest radiographs show focal airspace clouding with a segmental distribution of the lung. On HRCT it often shows nodular shadows and thickened bronchial vascular bundles, while more frequent cases show nodular shadows, reticular shadows and K’s B lines.
When the tuberculosis bacilli spread with the blood, it can produce cornified tuberculosis. It can occur as a result of initial infection or secondary infection. It can present clinically as a chronic form with nonspecific symptoms or as an acute form with rapid deterioration or even death. On HRCT, cornified TB presents as nodules approximately 1-5 mm in size with well-defined and randomly distributed margins; such nodules are most often considered secondary lobular nodules. A portion of the tuberculosis nodules, compared to the nodules of mycoplasma and bacterial pneumonia, tend to be distributed more adjacent to the subpleural space. Ground-glass shadows are more common in pulmonary tuberculosis and thickening of the lobular septa and intralobular septa, but ground-glass shadows are more common in fulminant disease.
(iii) Eosinophilic pneumonia
Acute eosinophilic pneumonia is a disease of acute fever, often associated with severe hypoxia, bilateral parenchymal lung lesions with or without peripheral eosinophilia, and elevated eosinophils in bronchoalveolar lavage fluid, among other changes. HRCT shows ground glass shadows and septal thickening. It is more similar to hydrostatic pulmonary edema, but the cardiac shadow is normal and there is no vascular redistribution in this disease.
(iv) Allergic pneumonia
Hypersensitivity pneumonitis (HP) is also a common diffuse lung disease. Patients with acute and subacute HP present with dry cough, fever, and chills, while chronic cases may have progressive dyspnea. Acute HP presents with bilateral solid shadows and is mostly distributed in the middle and lower lung fields. In recovered and subacute disease, small nodular lesions may be observed, and ground glass shadows are occasionally seen. Pulmonary hilar and mediastinal lymph node enlargement with pleural effusion is rare. Blurred margins of lobar central nodules and/or widely distributed ground glass shadows are characteristic of subacute HP, and lobar central nodules and ground glass shadows are frequently diffusely distributed with a predominant distribution in the middle and lower lung fields.
(E) Pulmonary hemorrhage
Diffuse pulmonary hemorrhage can be caused by systemic lupus erythematosus, Welch’s hematoma, idiopathic ferritin-containing hyperemia, mitral stenosis, and leptospirosis. Diffuse pulmonary hemorrhage can result in widely distributed airspace lesions, mainly around the hilum and significantly in the middle and lower lung fields. After more than a few days of acute hemorrhage, the airspace shadows may gradually clear and show a reticulonodular pattern of distribution. HRCT of acute hemorrhage shows solid and ground glass shadows, and in some cases also mild lobular septal thickening, but pleural effusion is rare. In the subacute phase, it may show a diffuse distribution of small nodular and reticular shadows, thus showing a progression from alveolar to interstitial and gradually replacing the initial alveolar shadows.
(F) Acute interstitial pneumonia
Acute interstital penumonitis (AIP) is a diffuse lung disease that causes idiopathic diffuse alveolar damage and is characterized clinically by severe hypoxemia and radiologically by progressive diffuse parenchymal clouding. Chest radiographs show diffuse solid pulmonary shadows in both lungs, which may occasionally be confined to the upper lobe or lower lung fields. Chest CT often shows extensive ground-glass and solid shadows that may follow a dorsal to ventral gradient. Concurrent distended bronchial dilatation and structural deformation are common features of the disease. Such changes are more pronounced when the disease progresses.
II. Diffuse lung disease due to non-HIV infectious immune damage
The systemic immune system is divided into local mechanical defenses, activated systemic defenses and specific response system (humoral and cellular immune defenses). When it encounters damage, pulmonary complications are very common.
(A) Damage to local mechanical defenses
1. Airway mechanical defenses include the filtering action of the nose and pharyngeal isthmus, the mobile action of cilia in the trachea and bronchi, and the coughing action. When they are damaged, they can produce recurrent sinusitis, pneumonia, bronchitis and bronchiectasis, as well as fine bronchiectasis. The main manifestations of bronchiectasis are bronchial thickening (>2 mm) and wall irregularities, and are most valuable when they occur in the outer bands. The filling pattern of thinning of the bronchial lumen shown on thin-section CT is associated with concurrent small airway duct lesions, and is consistent with the diagnosis of small airway lesions when hyperinflation of the invaded lung segment and thinning of the lumen is evident on inspiratory scans. Thin-layer CT of bronchial dilatation shows a loss of the normal progressive thinning of the bronchi from coarse to thin, the impression sign and its 1.5 times larger than the accompanying pulmonary artery, etc.
2. The local defense of alveoli mainly relies on macrophage defense. When the macrophages of the alveoli fail to remove excessive surface active substances, it can lead to periodic protein accumulation, a pathological process called pulmonary alveolar proteinosis (PAP). The disease often presents with chronic dyspnea and a dry cough. The chest radiograph often shows a progression from patchy to diffuse ground-glass density and can progress to more fused solid lesions. Thin-section CT shows diffuse polygonal, restricted ground-glass shadows or solid shadows, producing typical paving-stone-like changes.
(ii) Activated local defense damage
When activated local defenses fail to respond to invading factors, neutrophils and eosinophils reach the site of invasion and produce activated local defenses. When this degree of immunity is compromised, the important complications are Gram-negative bacteria and opportunistic fungal infections. Bacterial lung infections frequently present with more acute symptoms of fever, cough, and chest pain. Chest radiographs often show rapidly progressive focal or multifocal solid lesions 24-48 hours after infection, and cavitary manifestations often suggest staphylococcal, septic emboli, or anaerobic infections. Its important differential diagnosis is opportunistic fungal infection, which tends to progress more slowly than the vast majority of bacterial infections.
(iii) Damage to the cellular and humoral regulatory systems
The activated immune system includes both humoral and cellular systems. When it is defective, it is prone to complicate opportunistic fungal, cytomegalovirus (CMV), and Pneumocystis carinii infections. This will be discussed later in the context of typical complications resulting from various degrees of immunosuppression.
(iv) Bone marrow transplantation (BMT)
Diffuse lung disease is a common cause of morbidity and mortality in BMT recipients, with an incidence of approximately 40-60%. The three important time periods after transplantation are the neutropenic phase (first 30 days), the early phase (30-100 days), and the late phase (after 100 days). Typical infectious and non-infectious pulmonary complications often occur when immunosuppression improves.
1. During the neutropenic phase, the most common infections during this stage are bacterial and opportunistic fungi, with three other important non-infectious complications: pulmonary edema, diffuse alveolar damage, and drug toxicity. A serious infectious complication is invasive fungal infections, especially Aspergillus. Fungal infections account for 12-45% of pneumonia in patients with BMT. Its radiological manifestations are nodules/masses with faint margins as well as solid lesions. Its progression is slower than most bacterial lung lesions, and the cavity frequently progresses, showing the typical air crescent sign. On thin-section CT, an early sign of Aspergillus infection is a faintly margined nodule with surrounding ground glass shadows (halo sign.) Another typical sign of airway mycobacterial infection is the focal or multifocal treponema sign. Bacterial infections are common at this stage, but the lesions are more limited, with imaging showing focal or multifocal areas of solidity and a tendency to progress or recover rapidly.
Pulmonary edema is a combination of both capillary leak and hydrostatic edema. The typical imaging presentation is a diffuse symmetrical ground glass/solid shadow with septal lines, a small amount of pleural effusion and an enlarged cardiac shadow.
Approximately 21% of autografts have diffuse alveolar hemorrhage (DAH), which is a serious complication with a mortality rate of 50%-80%.DAH typically occurs during the phase where the immunization and recovery time curves intersect (7-21 days post-transplant). Chest radiographs show rapidly progressive diffuse solid lesions, usually within 24 hours of onset. It is typified by gradual recovery of bleeding without recovery of infectious causative organisms in the bronchoalveolar lavage (BAL).
2. Early stage. At this stage, the risk of Aspergillus infection decreases, while the risk of bacterial pneumonia increases. At the same time, the risk of CMV infection appears at this stage. The most common non-infectious complications are idiopathic pneumonia syndrome and drug toxicity.
CMV pneumonia occurs in 10%-40% of BMT recipients, most commonly at 6-12 weeks post-transplant. There is a high incidence in patients with allografts and severe graft-versus-host disease (GVHD). Patients with progressive lesions have a mortality rate of almost 85%. Chest radiographs show sparse ground-glass shadows in the middle and lower lung fields, with thin-section CT better demonstrating the ground-glass process and often accompanied by small randomly distributed nodules that are pathologically consistent with small foci of hemorrhage.
Drug toxicity occurs at any time during the first 100 days and results in capillary leaky pulmonary edema, allergic reactions, diffuse alveolar damage (DAD), or a nonspecific interstitial pneumonia. The imaging presentation is dependent on the main pathological changes. Allergic reactions are manifested by a thin patchy or diffuse ground glass shadowing process, and the patient has a dry cough, dyspnea, and more febrile symptoms. In the presence of persistent exposure, the shadows become more solid or reticular changes, and progressive nonspecific interstitial pneumonia is considered if there is dilatation of the traction fine bronchi and structural deformation.
Idiopathic pneumonia syndrome is a progressive diffuse alveolar damage (DAD) in which the cause of infection cannot be found and has a high mortality rate (70%). Plain radiographs show progressively worsening patchy ground glass shadows and pulmonary solid lesions that become more confluent and diffuse after a few days or weeks. CT shows subtle areas of structural distortion and reticular shadows consistent with early fibrosis. The typical clinical signs are progressive hypoxia and restrictive pulmonary dysfunction, and the combination of typical imaging abnormalities and negative infectious BAL is consistent with the diagnosis of idiopathic pneumonia syndrome.
3. Late stage. Most late complications occur in chronic GVDH receptors, and infections are common, mainly bacterial infections with podoconiosis, CMC pneumonia, and Aspergillus infections. Non-infectious complications are Bronchiolitis obliterans (BO) and Bronchiolitis obliterans with organizing pneumonia (BOOP). Lymphoproliferative disease is an uncommon complication.
BO-like reactions occur in approximately 10% of allograft recipients, and BO occurs when inflammation causes necrosis of the fine bronchial mucosal surface. BOOP is the disease to be considered when chronic GVHD response is significant. The pathology is characterized by proliferation of granulation tissue in the fine bronchi adjacent to the alveolar lumen and alveolar sacs. Dry cough, dyspnea and hypothermia are frequent signs and symptoms. Plain films often show focal to multifocal solid shadows as well as nodular shadows with faint margins. Thin-section CT shows areas of ground glass density, and BOOP may have characteristic mild bronchial and fine bronchial dilatation distributed along the bronchoalveolar periphery.
(V) Parenchymal organ transplantation
The main complications of parenchymal organ transplantation are infection and posttransplant lymphoproliferative disorder (PTLD).
1. Lung transplantation
The earliest complication of lung transplantation is reperfusion edema. Its progression within the first 72 hours is hypoxic and its radiological manifestation is capillary leaky pulmonary edema, which often subsides within 1 week. Acute rejection often occurs 7-30 days after transplantation and often shows bilateral basal solidity, thickening of the septal line and pleural effusion. Late onset may show normal chest radiographs or underlying patchy ground glass shadows. Bacterial pneumonia is the most common infection after lung transplantation and heart-lung transplantation. CMV pneumonia is the second most common infection after transplantation, with its incidence peaking approximately 1-4 months after transplantation.
BO is a very common manifestation of chronic heteroreactivity and often develops at any time after 3 months of transplantation, with an incidence ranging from 10% to 70%. Its typical radiographic presentation is hyperinflation of the lungs/multilobes, expiratory air trapping and thickening of the bronchial walls. A valuable CT scan for BO is an expiratory scan, and when the patient’s lung volume changes decrease within 1 second of forceful exhalation, the diagnosis of BO is considered.
Lymphoproliferative disease is a multigroup disease that arises after transplantation and is strongly associated with Epstein-Barr virus (EBV), often occurring within the first year after transplantation. It frequently invades the same graft site, but can also be involved extrapulmonarily. The radiological presentation is variable, but multiple nodules/masses with indistinct margins, thickened septal lines, and enlarged mediastinal and hilar lymph nodes are suggestive of the diagnosis.
2. Liver and kidney transplantation.
Its main complication is infection, often bacterial in the first 30 days, especially nosocomial infections. Although CMV pneumonia is common in lung transplantation, it should also be considered in liver and kidney transplantation. A common infection 6 months after transplantation is a bacterial infection. There is an important risk of post-transplant malignancy, the most common being carcinoma, such as skin and liver cancer. This is followed by PTLD, which is a risk for all recipients of parenchymal organ transplants. Its incidence approximates 6%.
(vi) Corticosteroid therapy
Chronic steroid therapy can affect the cellular immune system, thereby increasing the risk of some viruses (e.g., CMV) and Pneumocystis carinii infection. Pneumocystis carinii pneumonia (PCP) is a common complication, more common than HIV-associated PCP, and has a shorter duration, presenting with respiratory symptoms for only 3-5 days, whereas patients with HIV-associated PCP often present with symptoms for more than 2-4 weeks. BAL in steroid-like PCP may be negative because a small amount of fungal infection in the lungs is complicated by a high number of neutrophils in this immune state. In contrast, HIV-associated PCP has a massive fungal filling process, and the diagnosis is often made by finding Pneumocystis carinii in saliva or BAL specimens alone. The diagnosis of PCP should be considered when a patient with steroidal immune suppression system has imaging manifestations of diffuse ground glass solid shadows, especially when the patient has severe hypoxia.
III. Diffuse pulmonary disease in HIV-positive patients
(A) Infectious lung disease
1, bacterial infection: In recent years, infectious airway disease and pneumonia have surpassed PCP among the most common causes of lung infections in HIV-positive patients. bacterial pneumonia often occurs early in the course of HIV disease, but the risk of progression of this infection increases markedly as the CD4 count decreases. The typical presentation of bacterial pneumonia is fever and coughing sputum. The imaging presentation in most cases is a limited solid shadow distributed by lobe and segment of the lung in single or multiple sites, with an atypical presentation of bilateral diffuse shadows. Bacterial pneumonia develops more rapidly in AIDS than in the normal population, and abscess formation associated with bacteremia is more common. Patients with purulent airway infections frequently present with fever, dyspnea, and coughing symptoms. Chest radiographs are often normal, but may also show thickened bronchial walls. Extensive bronchiectasis may resemble an interstitial lesion and present with a predominant reticulonodular shadow that is often symmetrical in its lower lobe distribution. Central shadows, which represent inflammatory secretions filling the fine bronchi. This sign is called the “bud sign”. Although septic infection is the most common cause of proliferative small airway disease in patients with AIDS, viral and mycobacterial infections can also have a similar presentation.
2. Pneumocystis carinii pneumonia (PCP)
PCP is the most common lung infection that threatens survival. Typical PCP occurs with a CD4 cell count <200/mm2. It is usually an insidious onset of fever, dry cough and dyspnea. The typical chest radiograph shows diffuse interstitial images around the hilum bilaterally or symmetrically, which can be finely granular, reticular and ground glass shadows. The typical HRCT presentation is an extensive ground glass image, often in a patchy or restricted form, with a predominant distribution along the mid-axis of the lung or around the hilum. typical presentations of PCP also include cystic lesions, spontaneous pneumothorax and solid images in the upper lobe distribution. Residual fibrosis is seen although radiological abnormalities usually resolve 2 weeks after treatment. This subtype is classified as chronic PCP when interstitial fibrosis is the predominant radiological manifestation and the process lasts for months to years.
3.Tuberculosis (TB)
Individuals with HIV have a 50-200 times higher risk of TB infection than the general population, and TB can contribute to the course of AIDS. TB can occur at any stage of HIV infection. Complicated TB is often one of the first manifestations of HIV infection. Symptoms include cough, night sweats and weight loss. Its radiological manifestations depend on the degree of immunosuppression during the period when the lesion is evident. In the early stages, when CD4 is >200 cells/mm3, the imaging features are typically associated with secondary TB, showing shadows associated with cavities and often confined to the apical, posterior, and upper parts of the lungs. When the patient is immunocompromised, the typical imaging presentation is initial infectious TB, including solid changes and lymph node enlargement. This presentation is often seen in patients with CD4 cell counts <200 cells/mm3. Enlarged lymph nodes often show a central hypodensity with peripheral enhancement. Compared to normal hosts, nodules in AIDS patients tend to show enlarged lymph nodes, diffuse pulmonary lesions, bronchial spread, cornified lesions and extrapulmonary lesions. These manifestations increase with the degree of immunosuppression.
4.Fungal infection
The common causative agent of pulmonary fungal infections in patients with AIDS is Cryptococcus novelis. The infection occurs in the late stages of immunosuppression (CD4 <100/mm3). Radiological manifestations are nonspecific and include reticular or reticulonodular shadows, nodular and focal solid lesions, with possible lymph node enlargement and pleural effusion.
5.Viral infection
Cytomegalovirus (CMV) is the most common viral infection in the lungs of patients with AIDS, occurring in the late stages of immunosuppression (CD4 <100/mm3). The disease is more likely to occur in patients with HIV transmitted by sexual contact. The most common imaging findings are ground glass shadows and solid alveolar lesions; others may include nodules, masses, and small airway lesions.
(ii) Non-infectious lung diseases
1. Kaposi’s sarcoma (KS)
Among AIDS-associated tumors KS is the first to be described. The CD4 cell count in pulmonary KS is usually <100/mm3. The common symptoms are dyspnea and cough, while hemoptysis is rare. The typical chest radiograph shows thickened bronchovascular bundles in the perihilar region. When the tumor grows, reticulonodular shadows may appear and are mainly located in the lower lobes. Interstitial nodules and parenchymal nodules with blurred margins may fuse into dense areas of solid alveolar changes, and thickened lobular septa are common. Pleural effusions are also frequently seen, unilaterally or bilaterally, and their volume can vary. Enlargement of the mediastinal and hilar lymph nodes is shown on chest radiographs in a minority of cases, but hilar and mediastinal lymphadenopathy is seen in up to 50% of cases on CT. Chest CT shows a typical bronchovascular bundle pattern accompanied by parenchymal lung shadowing. Although the imaging is highly suggestive of the disease, there is some overlap with other diseases. Gallium mono-thallium radionuclide imaging is helpful in differentiating KS from other diseases. kS has an affinity for thallium and does not absorb gallium. When gallium scans are negative in patients with abnormal chest films and CT, it helps to further confirm the absence of other tumors and the coexistence of infection. On MRI, KS has the typical presentation of high signal on T1WI, significant attenuation of signal intensity on T2WI, and significant signal enhancement after gadolinium injection.
2.Lymphoma
Non-Hodgkin’s lymphoma (NHL) is the second most common malignancy in AIDS, accounting for 2%-10% of HIV-positive patients, and the risk of developing NHL is 113 times higher than in the general population and occurs in younger patients, whose CD4 counts are usually below 100/mm3. When the lungs and pleura are affected, the most common symptoms There is cough, dyspnea and inflammatory pleural pain. The most common radiological presentation consists of multiple intrapulmonary nodules (40%-55%), solid areas (27%-40%) and pleural effusions (33%-73%). Reticular shadows and masses are also relatively common. The diameter of the nodules varies from 0.5-5.0 M. Air bronchial signs are common, and a halo sign of ground glass density around the nodules is seen on HRCT. The incidence of mediastinal and hilar lymph node enlargement is 3%-54%. Its rare forms are pleural effusion without soft tissue tumors, pericardial effusion and peritoneal effusion. Other abnormalities include intraluminal lesions in the airway cavity and intrusion of extrathoracic masses into the mediastinum.
3. Lymphocytic interstitial pneumonia
Lymphocytic interstitial pneumonia (LIP) is characterized by nodules around bronchial vessels resulting from infiltration of mature lymphocytes and plasma cells into the interstitial space of the lung. It is usually associated with cough and insidious episodes of respiratory distress with low fever. The typical chest radiograph presentation consists of fine or coarse reticular shadows and nodular shadows associated with alveolar components. ct shows 2-4L nodules with indistinct margins, often distributed along the peribronchial vessels, and with bilateral areas of ground glass density. In most cases, thickened bronchovascular bundles, thickened septal lines, small subpleural nodules and cystic air spaces are observed. Lymph node enlargement is often massive and can be quite variable. In children with LIP, solid changes in the air spaces and dilated fine bronchi may also occur.
4. Nonspecific interstitial penumonia (NSIP)
The symptoms of NSIP are usually mild cough, fever, and dyspnea. Compared to PCP, which appears much earlier in the HIV process, its CD4 count remains normal. Radiological manifestations include fine reticular, reticulonodular and ground glass shadows in the hilar region or diffusely distributed in both lungs. The primary diagnosis is to exclude opportunistic bacterial infections or tumors.
IV. Summary
Diffuse lung disease is complex, with both interstitial and substantive lesions, and there are many similarities in clinical symptoms and signs, and many overlapping imaging changes, making the diagnosis very difficult. The diagnosis of many diseases often requires transbronchial puncture biopsy, transthoracic puncture biopsy or even open lung biopsy. However, by mastering the knowledge of various diseases, combined with laboratory data, clinical symptoms, signs and imaging manifestations, the diagnosis can be narrowed down to a greater extent.
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