CT manifestations of human immunodeficiency virus (HIV)-related pulmonary infections

CT Manifestations of Human Immunodeficiency Virus (HIV)-Related Pulmonary Infections Rosita M. Shah and Ana M. Salazar The infectious pulmonary complications of acquired immunodefieiency syndrome (AIDS) are reviewed, with emphasis on the spectrum of CT imaging findings and diagnostic accuracy and limitations as reported in the current literature. Changes in epidemiologic trends for common AIDS-related infections and the associated ranges of CD4 lymphocyte counts, when these infections are typically encountered, are discussed. Copyright © 1998 by W.B. Saunders Company

ITH GREATER experience and recognition of changing trends in the acquired immunodeficiency syndrome (AIDS) epidemic, our analysis of pulmonary disease in the human immunodeficiency virus (HIV)-positive patient has become more sophisticated, as is more completely illustrated in the following article by Mason and Muller. It can, however, be argued that, in recognizing a greater variabililty in the manifestations of many HIV-related diseases, we have lost our ability to provide specificity to radiographic diagnosis. It then becomes apparent that the radiologist must also be aware of clinical parameters such as the CD4 lymphocyte count, concurrent medications, and HIV risk factors when considering diagnostic differentials in any given case. The imaging findings of infectious pulmonary complications in AIDS are reviewed with emphasis on more recently recognized radiographic manifestations, common differential diagnosis, and the impact of Clinical factors on diagnosis. Noninfectious complications are briefly discussed in the context of how they might mimic infectious diagnoses. Pattern recognition remains the basis for interpretation and diagnosis on chest radiography (CXR). Yet, false-negative rates as high as 15%, 50% and 60% have been reported in the evaluation of infiltrative interstitial disease, bronchiectasis and emphysema, respectively. 1"3 Limitations reflecting extensive overlap, the presence of coexisting disease, and atypical manifestations of a given disease contribute to the lack of specificity on CXR. Using a pattern approach, Kang et al evaluated the sensitivity and specificity of chest radiography and computed tomography (CT) in the evaluation of AIDS-related pulmonary complications.4 Confident and accurate diagnoses were rendered in 67% of chest radiographic interpretations compared with 87% of CT interpretations.4 In evaluating the accuracy of CT for the diagnosis of specific pulmonary complications of HIV, Hartman et al found an

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overall accuracy of 92%, including 94% for the diagnosis of pneumocystis pneumonia and 90% for the diagnosis of tracheobronchial involvement in Kaposi's sarcoma) Clearly, familiarity with the indications of CT and the significance of imaging findings can contribute to increased specificity in diagnosis when pulmonary disease is encountered in the AIDS patient. HIV-RELATED PULMONARY INFECTIONS

Pneumocystis Carinii A greater recognition of bacterial pneumonia and tuberculosis as initial manifestations of AIDS has coincided with a relative decline in the incidence of Pneumocystis carinii pneumonia (PCP). Several studies show a reduction in hospital admissions for PCP, which was previously held responsible for up to 50% of hospital admissions, to less than 30%. 6,7 Routine PCP prophylaxis is largely responsible for this decline, because up to 60% of PCP cases will recur without preventive measures. 8 The literature reports false-negative rates for the diagnosis of PCP on CXR to be as high as 35% to 39% and, consequently, some patients may undergo bronchoscopy despite normal radiographs. 9,1° In this subset of patients, CT may be beneficial and prevent unneeded interventional diagnostic procedures. Kuhlman has described three dominant patterns of PCP infection at CT, including geographic ground glass attenuation, diffuse ground glass attenuation, and a fine reticular pattern H (Figs 1, 2). When Hartman et al used the presence of ground glass opacity on CT for the diagnosis of

From the Department of Radiology, Medical College of Pennsylvania, and the Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA. Address reprint requests to Rosita M. Shah, MD, Department of Radiology, Medical College of Pennsylvania, 3300 Henry Ave, Philadelphia, PA 19129. Copyright © 1998 by W.B. Saunders Company 0887-2171/98/1902-000558.00/0

Seminars in Ultrasound, CT, and MRI, Vo119, No 2 (April), 1998: pp 167-174

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Fig 1. Pneumocystispneumonia. Geographic pattern of ground glass opacity. Note proximity of normal and abnormal (arrows) secondary pulmonary Iobules.

PCR the diagnostic accuracy was 94%. 5 Of 32 immunocompromised patients studied by Brown, including those with HIV-positive and HIVnegative serologies, ground glass opacity was the dominant pattern in 15 (47%). 12 This pattern also occurred in patients with cytomegalovirus (CMV) pneumonitis, bronchiolitis obliterans and organizing pneumonia (BOOP), drug reactions, lymphoma, and edema. The corresponding pathological findings were variable, ranging from a fine interstitial infiltrate, to intra-alveolar filling, or a combination of these findings. These investigators concluded that the presence of ground glass opacity is a manifestation of the underlying morphological changes, without a specifc histological correlate, potentially limiting the specificty of radiographic diagnosis, t2 In the AIDS patient with ground glass opacity, CMV pneumonitis remains the primary differential diagnosis, but is uncommon at CD4 lymphocyte counts greater than 50 cells/mm3.13 Cystic complications of PCP may be more readily observed at CT, with reported incidences of

Fig 2. Pneumocystispneumonia. Diffuse ground glass opacity, Note preservation of normal pulmonary vascular pattern.

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10% to 34% on chest radiographs. 14,~5These cysts are most commonly multiple, thin-walled, subpleural, and upper lobe in distribution (Fig 3). As many as 35% of patients will present with spontaneous pneumothoraces, with high mortality rates, approaching 50% in one series. 15 Chronic parenchymal PCP has more recently been recognized, manifested by a prolonged clinical course in which persistent radiographic abnormalities are detected, corresponding to pathological findings of interstitial fibrosis and honeycombing. In disseminated PCP infections, CT may show mediastinal nodal calcifications.

Mycobacterium Tuberculosis Since 1993, pulmonary Mycobacterium tuberculosis (MTB) infection has been a component of the AIDS surveillance case definition.16 Along with recognition of an increasing incidence of pulmonary tuberculosis following the onset of the AIDS epidemic, it is now recognized that the rate of death with tuberculosis as a concurrent illness has increased dramatically. Between 1982 and 1990, an increase in the death rates from 0.61 to 2.82/ 100,000 represents an increase of 362%. 17 The diagnosis of pulmonary tuberculosis, therefore, remains a primary concern. Differences in the radiographic appearance of HIV-positive and HIV-negative patients with pulmonary MTB are well-established. In comparing 42 HIV-positive patients with 42 HIV-negative age-, race- and sex-matched controls, Leung et al found a higher prevalence of adenopathy, miliary and extrapulmonary disease, as well as a lower occurrence of cavitation and typical reactivation disease patterns amongst the HIV-positive patients.18 Normal CXRs

Fig 3. Complicated pneumocystis pneumonia with cysts. Note multiple thin-walled cysts (arrows) in upper lobe distribution snd small right pneumothorax (curved arrow),

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Fig 4. Parenchymal involvement with MTB. Diffuse miliary type nodules and para-aortic adenopathy are evident (arrows), Fig 6. Tuberculous empyema, Note Ioculated, thick-walled right pleural collection (arrows).

also were noted in 15% of the HIV-positive patients, whereas all the CXRs were abnormal in the HIV-negative group. However, CT showed abnormalities that could assist the diagnosis in all of the HIV-positive patients, including isolated or multiple nodules and adenopathy.18 At CT, nodular opacities, observed in 81% of the patients studied by Leung represented the most common parenchymal abnormality of pulmonary MTB 18 (Fig 4). Miliary and centrilobular distributions were noted. Lymphadenopathy was noted in 74%. Peripheral rim enhancement is a feature of tuberculous adenopathy of both HIV-positive and HIV-negative patients, occurring in up to 83% of cases 19 (Fig 5). Other findings that can be expected at CT include focal or rnultifocal consolidation, peribronchial thickening, and pleural effusions (Fig 6). Cavitation is described in only 19% of HIV-positive patients with TB, compared with greater than 50% in immunocompetent hosts.18 The imaging findings of MTB infection are widely believed to vary with the degree of imrnuno-

Fig 5, Tuberculous lymphadenopathy, Note low-density lymphnodes (arrows) with central low attenuation and peripheral rim enhancement, involving aortopulmonic window and right paratracheal mediastinum,

suppression as manifested by the CD4 lymphocyte count. At counts greater than 200 cells/mm 3, the appearance of MTB in the HIV-positive patient is that of typical postprimary disease, including cavitation and apical consolidation2° (Fig 7). This appearance accounts for 20% to 30% of MTB infection in AIDS patients. At CD4 lymphocyte counts less than 200 cells/ram3, a greater incidence of features of primary disease are reported, including adenopathy, pleural effusions, and noncavitary consolidation (Fig 8). Up to 40% of AIDS patients will present with this pattern. 2° The appearance of MTB at CD4 counts of less than 50 cells/mm 3 is more controversial. Atypical appearances are reported, including diffuse reticular or reticulonodular infiltrates. Of more recent concern is the development of multidrug-resistant MTB, with reported prevalences in some parts of the country as high as 33% to 56%, contributing to a mortality of 80% in these patients. 21 In comparing 33 patients with drug-

Fig 7. Reactivation pattern of pulmonary TB. Note cavitary left upper lobe consolidation with additional foci of early consolidation from bronchogenic spread (arrows).

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Fig 9. Mycobacterium avium-intracellulare complex. Illdefined mass-like areas of consolidation are observed in both upper lobes. Additional images showed extensive bilateral hilar adenopathy, Radiographic findings and clinical symptoms resolved with treatment. Fig 8, Primary pattern of pulmonary TB. Noncavitary right upper lobe consolidation is associated with low density subcarinal lymph nodes (arrow) and small right pleural effusion (curved arrow),

sensitive MTB to 36 patients with multidrugresistant MTB, Lessnau found little difference in the initial CXR manifestations between the groups. 22 However, following 2 weeks of treatment, worsening of the radiographic findings was associated with a 95% probability of multidrug-resistant MTB. Although the CT imaging findings of multidrugresistant MTB have not been described, it is reasonable to consider resistant disease in the patient undergoing CT for apparent progression of pulmonary MTB.

Atypical Mycobacterial Infections Nontuberculous mycobacterial infections reported in AIDS include Mycobacterium avium intracellulare (MAI) complex, M kansasii, M fortuiturn, M chelonei, and M gordonae. MAI complex, present in 50% of patients at autopsy, represents the most common atypical mycobacterial infection occurring in end-stage AIDS. 23 Although organisms are frequently recovered from the lungs, clinical and radiographic evidence of parenchymal involvement is uncommon. Adenopathy is the most common positive finding described with MAI. Parenchymal abnormalities include patchy, cavitary or noncavitary, alveolar infiltrates and nodular opacities 24 (Fig 9). Description of the radiographic findings directly attributable to the atypical mycobacterial infections is complicated, because many patients will have coexistent infections or neoplasms.

Cytomegalovirus Isolated in 72% of autopsy subjects, 80% of which had evidence of CMV pneumonitis, 25 cytomegalovirus (CMV) is the most common viral infection in AIDS. Documentation of CMV pneumonitis, however, may be difficult to obtain clinically, because isolation of viral inclusions from alveolar epithelium is required. Less than 25% of CMV infections are diagnosed premortem. With longer survival in end-stage HIV infection and the utilization of steroids in management of other pulmonary complications, including PCP, CMV pneumonitis has achieved greater clinical recognition. As many as 16% of deaths in AIDS may be attributed to CMV pneumonitis. 26 Ground glass opacity and nodular patterns, occurring in up to one half of the 21 patients studied by McGuinness et al, represents the most common CT findings of CMV pneumonitis 27 (Fig 10). Masslike focal consolidation, peribronchial thickening, and reticular interstitial abnormalities were also de-

Fig 10. CMV pneumonia. Ill-defined pulmonary nodules (arrows) are noted, Rapid progression resulted in death,

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scribed. Clearly, these findings overlap with those described for PCP and MTB. When nodularity is associated with ground glass opacity, CMV should be considered over PCP, especially in the patient with CD4 lymphocyte counts of less than 50 cells/ram 3 or concurrently being treated with steroids. The presence of adenopathy strongly suggests alternative diagnoses or coexistent tuberculous infection. CT may show bronchiectasis as the only evidence of CMV infection. 27 Bacterial Pneumonia Perhaps related to the widespread use of PCP prophylaxis, bacterial pneumonia is increasingly recognized as a complication of HIV infection and, since 1993, recurrent bacterial pneumonia has been a component of the AIDS case surveillance definition. 16 Hirschtick et al reported HIV-positive patients to be five times as likely as HIV-negative cohorts to develop bacterial pulmonary infections when studied prospectively over a 5-year period. 28 Similarly, the rate of infection was five times greater in patients with CD4 lymphocyte counts of less than 200 cells/mm 3 compared to those with counts greater than 500 cells/mm 3. Spneumoniae, S aureus, and H influenzae are the most commonly isolated agents. 28 Focal lobar consolidation was the most common pattern of parenchymal disease, observed radiographically in 50% of AIDS patients with pyogenic pulmonary infections studied by Amorosa. 29 Rapidly progressive bronchiectasis has been described as a complication of isolated and recurrent bacterial pneumonia 3° (Fig 11). The extreme immunosuppression observed in

Fig 11. Bronchiectasis secondary to S pneumoniae infection. Cyllindrical bronchiectasis (curved arrows) and patchy consolidation are observed following documented pneumococcal pneumonia,

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end-stage HIV infection also predisposes to unusual bacterial infections. Bacillary angiomatosis and peliosis was first described in 1983 as a proliferative vascular lesion affecting skin, bone, lymphatic tissues, and brain. 31 Rochalimaea henselae was confirmed as the etiologic agent in 1993, with a history of close contact with cats noted as an epidemiologic factor. 32 Lung nodules associated with bronchovascular bundles and cavitary masses have been described as the most common radiographic manifestation of pulmonary bacillary angiomatosis, with lymphadenopathy a common accompanying feature. On contrast-enhanced studies, marked enhancement is reported? 3 Community-acquired pneumonia due to P auruginosa has recently been reported as a cause of cavitary consolidation in AIDS patients with endstage HIV infection. Of 16 patients studied by Schuster and Harris, 11 of 15 (73%), had cavitary consolidations. The mean CD4 count was 27 cells/mm 3. 34 Fungal Infections As many as 50% of chest radiograph results are normal in the presence of disseminated fungal infection. When abnormalities are present, small miliary type nodules and reticulonodular interstitial patterns are most common. 35Unlike in immunocompetent hosts, in whom focal consolidation is identified in up to 75% of patients, this pattern occurrs in less than 10% of HIV-positive patients. 36 Likewise, pleural effusions and adenopathy are uncommon in the immunocompromised host. C neoformans is the most common opportunistic fungal infection in AIDS. CT findings of pulmonary cryptococcosis as described by Sider and Westcott include interstitial and segmental alveolar opacities. 37 Alveolar opacities seem to occur at a later stage and indicate a worse prognosis. Cavitation and multiple nodules have also been described, but are more common in the immunocompetent host (Fig 12). In endemic areas, H capsulatum can be an important fungal pathogen. 38 Conces et al found that small nodules seen radiographically in cases of pulmonary histoplasmosis in AIDS, when correlated with histopathologic features, most commonly represented extension of macrophages into the alveoli. 38 These investigators noted the usual absence of granulomas. The development of invasive pulmonary aspergillosis implies significant quantitative or qualitative

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Fig 12. Cryptococcal lung abscess. Heterogeneous consolidation with cavitation (arrow) is identified in superior segment left lower lobe.

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Fig 14. Aspergilloma in preexisting PCP cavity. Heterogeneous, septated mass (arrows) is noted within thin-walled cavity. Note groundglass opacity throughout lungs, consistent with PCR (Courtesy of Dr. Barry Gross, University of Michigan.)

impairment of macrophages and leukocytes. In AIDS, this occurs only in end-stage disease, such that invasive aspergillus has not been widely reported as a complication of HIV infection. Staples et al reported cavitary nodules or masses as the most common manifestation of invasive aspergillus at C T 39 (Fig 13). Many of the cavities had wall thicknesses approaching 1 cm. In six of eight patients, an upper lobe distribution was noted. Other findings at CT included noncavitary nodules, consolidation, and pleural effusions. 39 In five of 10 patients studied by these investigators, preexisting cavities or cysts were documented, presumedly posing a risk factor for the development of invasive aspergillosis 39 (Fig 14). Aspergillus is the most common fungal etiology associated with airway disease in AIDS, occurring in up to 10% of HIV-positive patients with pulmo-

nary aspergillosis. 4° Necrotizing tracheobronchitis, obstructing bronchopulmonary aspergillosis, and chronic cavitary aspergillosis, noted to be otherwise uncommon, can occur as primary manifestations of airway involvement in aspergillosis in the patient with AIDS (Fig 15).

Fig 13. Invasive aspergillosis. Widespread, cavitary and noncavitary ill-defined pulmonary nodules (curved arrows) are noted.

Fig 15. Airway involvement secondary to aspergillosis. Extensive central bronchiectasis (arrows) is noted on 10 mm standard (A) and 1.5 mm HRCT (B) images.

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NEOPLASTIC MIMICS OF PULMONARY INFECTIONS IN AIDS

Kaposi's Sarcoma Kaposi's sarcoma (KS) is the most commonly identified malignancy in AIDS, strongly associated with the homosexual transmission of HIV. Pulmonary involvement can be observed in up to 50% of patients with typical cutaneous lesions and has been recently reported in 13% of patients without skin manifestations.41,42As a malignancy of probable lymphatic endothelial origin, when there is involvement of the pulmonary parenchyma, KS has an obvious distribution along bronchovascular bundles. This distribution, including dominant findings of peribronchial thickening and nodularity, is more readily apparent on CT (Fig 16). Wolff et al have described the CT findings of KS, including symmetric perihilar ill-defined nodules or flame-shaped lesions.43 In the presence of pleural effusions, which occur in two-thirds of patients, and lymphadenopathy, present in 50% of patients, KS can closely mimic pulmonary infection with MTB .43

AIDS-Related Lymphoma AIDS-related lymphoma (ARL) occurs as a manifestation of late HIV disease. 13Adenopathy is identified as the primary pattern in 25% of patients, with parenchymal lesions being more common, including rapidly growing, sharply marginated nodules, diffuse interstitial patterns, and dominant ill-defined masses or mass-like consolidation.44 These findings, either in isolation or in combina-

Fig 16. Kaposi's sarcoma. Peribronchial thickening and ill-defined pulmonary nodules (arrows) mimic MTB infection.

tion with adenopathy, can mimic more common infectious diagnoses of MTB or fungal pneumonia. SUMMARY

The infectious pulmonary complications of AIDS remain a significant source of morbidity and mortality, for which prompt recognition and diagnosis are required. Although the chest radiograph is the only imaging study required in the majority of cases, some patients will undergo further evaluation by CT. Familiarity with the spectrum of imaging findings on CT can contribute to a greater degree of diagnostic accuracy and confidence level.4,5 The radiologist should be aware of the role of CT in the evaluation of patients with normal or nonspecific CXR findings, the effect of advancing immunosuppression on the radiographic manifestations of certain disease processes, especially MTB, and the significant overlap between the manifestations of AiDS-related neoplasms and certain infections.

REFERENCES l. Gaensler EA, Carrngton CB: Open biopsy for chronic diffuse infiltrative lung disease: Clinical roentographic and physiologic correlations in 502 patients. Ann Thorac Surg 30:411-426, 1980 2. Currie DC, Goldman JM, Cole PJ, et al: Comparison of narrow section CT and CXR in chronic ABPA. Clin Radiol 38:593-560, 1987 3. Thurlbeck WM, Simon G: Radiographic appearance of the chest in emphysema. AJR 130:429-440, 1978 4. Kang EY, Staples CA, McGuiness G, et al: Detection and differential diagnosis of pulmonary infections and tumors in patients with AIDS: Value of chest radiography versus CT. AJR 166:15-19, 1996 5. Hartman TE, Primack SL, Muller NL, et al: Diagnosis of thoracic complications in AIDS: Accuracy of CT. AJR 162:547553, 1994

6. Chein SM, Rawji M, Mintz S, et al: Changes in hospital admissions patterns in patients with HIV infection in the era of Pneumocystis carinii prophylaxis. Chest 102:1035-1039, 1992 7. Pitkin AD, Grant AD, Foley NM, et al: Changing patterns of respiratory disease in HIV-positive patients in a referral center in the United Kingdom between 1986-7 and 1990-1. Thorax 48:204-207, 1993 8. Gallant JE, Moore RD, Chaisson RE: Prophylaxis for opportunistic infections in patients with HIV infection. Ann Intern Med 120:932-944, 1994 9. Barrett TF, Birnbaum NS, Shaney LB, et al: Pneumocystis carinii pneumonia studied by gallium-67 scanning. Radiology 154:791-793, 1985 10. Opravil M, Marincek B, Fuchs WA, et al: Shortcomings of chest radiography in detecting Pneumocystis carinii pneumonia. JAIDS 7:39-45, 1994

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11. Kuhlman JE, Kavuru M, Fishman EK: Pneumocystis carinii pneumonia: Spectrum of parenchymal CT findings. Radiology 175:711-714, 1990 12. Brown MJ, Miller RR, Muller NL: Acute lung disease in the immunocompromised host: CT and pathologic examination findings. Radiology 190:247-254, 1994 13. Crowe SM, Carlin JB, Stewart Kl, et al: Predictive value of CD4 lymphocyte numbers for the development of opportunistic infections and malignancies in HIV-infected persons. J AIDS 4:770-776, 1991 14. Sandhu JS, Goodman PC: Pulmonary cysts associated with Pneumocystis carinii pneumonia in patients with AIDS. Radiology 173:33-35, 1989 15. Chow C, Templeton PA, White CS: Lung cysts associated with Pneumocystis pneumonia: Radiographic characteristics, natural history, and complications. AJR 161:527-531, 1993 16. Centers for Disease Control: 1993 revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR 41:1-12, 1992 17. Braun MM, Cote TR, Rabkin CS: Trends in death with tuberculosis during the AIDS era. JAMA 269:2865-2868, 1993 18. Leung AN, Brauner MW, Gamsu G, et al: Pulmonary tuberculosis: Comparison of CT findings in HIV-seropositive and HIV-seronegative patients. Radiology 198:687-691, 1996 19. Lee KS, Im JG: CT in adults with tuberculosis of the chest: Characteristic findings and role in management. AJR 164:1361-1367, 1995 20. Greenberg SD, Frager D, Suster B, et al: Active pulmonary tuberculosis in patients with AIDS: Spectrum of radiographic findings (including a normal appearance). Radiology 193:115-119, 1994 21. Freiden TR, Sterling T, Pablos-Mendez A, et al: The emergence of drug-resistant tuberculosis in New York City. N Engl J Med 328:521-526, 1993 22. Lessnau KD, Gorla M, Talavera W: Radiographic findings in HIV-positive patients with sensitive and resistant tuberculosis. Chest 106:687-689, 1994 23. Aronchick JM, Miller WT Jr: Disseminated nontuberculous mycobacterial infections in immunosupressed patients. Semin Roentgeno128:150-157, 1993 24. Fishman JE, Schwartz DS, Sala GJ: Mycobacterium kansasii pulmonary infection in patients with AIDS: Spectrum of chest radiographic findings. Radiology 204:171 - 175, 1997 25. Wallace JM, Hannah J: Cytomegalovirus pneumonitis in patients with AIDS: Findings in an autopsy series. Chest 92:198-203, 1987 26. McKenzie R, Travis WD, Dolan SA, et al: The causes of death in patients with human immunodeficiency virus infection: A clinical and pathologic study with emphasis on the role of pulmonary diseases. Medicine 70:326-341, 1991 27. McGuinness G, Scholes IV, Garay SM, et al: Cytomegalovirus pneumonitis: Spectrum of parenchymal CT findings with pathologic correlation in 21 AIDS patients. Radiology 192:451459, 1994

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28. Hirschtick RE, Glassroth J, Jordan MC, et al: Bacterial pneumonia in persons infected with the human immunodeficiency virus. N Engl J Meal 333:845-851, 1995 29. Amorosa JK, Nahass RG, Nosher JL, et al: Radiologic distinction of pyogenic pulmonary infection from Pneumocystis carinii pneumonia in AIDS patients. Radiology 175:721-724, 1990 30. McGuinness G, Naidich DP, Garay S, et al: AIDSassociated bronchiectasis: CT features. J Comput Assist Tomogr 17:260-266, 1993 31. Stoler MH, Bonfiglio TA, Steigbigel RT, et al: An atypical subcutaneous infection associated with the acquired immune deficiency syndrome. Am J Clin Pathol 80:714-718, 1983 32. Tappero JW, Mohle-Boetani J, Koehler JE, et al: The epidemiology of bacillary angiomatosis and bacillary peliosis. JAMA 269:770-775, 1993 33. Moore EH, Russel LA, Klein JS, et al: Bacillary angiomatosis in patients with AIDS: Multiorgan imaging findings. Radiology 197:67-72, 197 34. Schuster MG, Norris AH: Community-acquired Pseudomonas aeruginosa pneumonia in patients with HIV infection. AIDS 8:1437-1441, 1994 35. Johnson PC, Hamill RJ, Sarosi GA: Clinical review: Progressive disseminated histoplasmosis in the AIDS patient. Semin Respir Infect 4:139-146, 1989 36. Miller WT Jr, Edelman JM, Miller WT: Cryptococcal pulmonary infection in patients with AIDS: Radiographic appearance. Radiology 175:725-728, 1990 37. Sider L, Westcott MA: Pulmonary manifestations of cryptococcosis in patients with AIDS: CT manifestations. J Thorac Imaging 9:78-84, 1994 38. Conces DJ, Stockberger SM, Tarver RE}, et al: Disseminated histoplasmosis in AIDS: Findings on chest radiographs. AJR 160:15-19, 1993 39. Staples CA, Kang EY, Wright JL, et al: Invasive pulmonary aspergillosis in AIDS: radiographic, CT and pathologic findings. Radiology 196:409-414, 1995 40. McGuiness G, Gruden JF, Bhalla M, et ah AIDS-related airway disease. AJR 168:67-77, 1997 41. Meduri GU, Stover DE, Lee M, et al: Pulmonary Kaposi's sarcoma in the acquired immune deficiency syndrome: Clinical, radiographic, and pathologic manifestations. Am J Med 81:11-18, 1986 42. Gruden JF, Huang L, Webb WR, et al: AIDS-related Kaposi sarcoma of the lung: Radiographic findings and staging system with bronchoscopic correlation. Radiology 195:545-552, 1995 43. Wolff SD, Kuhlman JE, Fishman EK: Thoracic Kaposi sarcoma in AIDS: CT findings. J Comput Assist Tomogr 17:60-62, 1993 44. Dodd GD, Greenler DR Confer SR: Thoracic and abdominal manifestations of lymphoma occurring in the immunocompromised patient. Radiol Clin North Am 30:597-610, 1992