487

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Intraabdominal Mycobacterium tuberculosis vs Mycobacterium avium-intracellulare Infections Patients with AIDS: Distinction

in Based

on CT Findings

D. Randall

Radin1

Abdominal CT scans of 71 patients with AIDS who had proved disseminated infection due to Mycobacterium tuberculosis (27 patients) or Mycobacterium avlum-intracellulare

(44 patients) used

were reviewed

to distinguish

the two

retrospectively

to identify radiologic

infections.

findings

CT

in patients

features with

that can be

disseminated

M.

included focal lesions in the liver (1 1%), spleen (30%), kidneys (19%), pancreas (7%), and gastrointestinal tract (15%) and lymph nodes with central or diffuse low attenuation (93%). CT findings in patients with disseminated M. avium-intracellulare included marked hepatomegaly (20%); marked splenomegaly (14%); focal lesions in the

tuberculosis

liver (9%), spleen (7%), and kidneys (2%); diffuse jejunal wall thickening (18%); lymph nodes with central low attenuation (14%); and enlarged lymph nodes exclusively of homogeneous soft-tissue density (55%). The presence of focal visceral lesions and low-attenuation lymph nodes suggests disseminated M. tuberculosis, whereas marked hepatic and splenic enlargement, diffuse jejunal wall thickening, and enlarged soft-tissue-density lymph nodes suggest dissemmated M. avium-intracellulare. Recognition of these CT features can lead to a tentative diagnosis so that appropriate therapy can be instituted before the results of mycobacterial cultures become available.

AJR 156:487-491,

March

1991

Disseminated infections due to Mycobacterium avium-intracellulare (MAI) [1 ] and Mycobacterium tuberculosis (MTB) [2] in patients with AIDS were first reported in 1 982 and 1983, respectively. In 1987, the Centers for Disease Control included disseminated extrapulmonary infection by both MAI and MTB in a list of diseases that indicate a diagnosis of AIDS in patients with laboratory evidence of infection with human immunodeficiency virus (HIV) [3]. Distinction between MTB and MAI infection is important because of the therapeutic implications [1 4]. Standard antimycobacterial therapy is far more effective in AIDS patients with MTB infection than in those with MAI infection. Findings in one large series suggest that clinical features and findings on chest radiographs may help to distinguish between MTB and MAI infection in HIV-infected patients [4]. Abdominal CT findings in AIDS patients with disseminated mycobactenal infection have been described in several studies and review articles [5-i 0]. However, a comparative study of abdominal CT findings in MTB and MAI infection has not yet been reported. ,

Received July 25, 1990: September 13, 1990.

accepted

after revision

Department of Radiology, University of Southem California School of Medicine, L. A. CountyUSC Medical Center, 1200 N. State St., Los Angeles, CA 90033-1084. Address reprintrequests to

D. R. Radin. 0361 -803x/91/1

c

American

563-0487

Roentgen

Ray Society

Materials

and Methods

According to mycobactenology laboratory records at our hospital, cultures of specimens from lymph node biopsies, bone marrow biopsies, or blood yielded MTB in 173 patients and MAI in 373 patients between February 1 985 and February 1990. An abdominal CT examination done during the same hospital admission during which the biopsy with positive mycobacterial results was performed was available for 33 patients with MTB infection and

45 patients

with

MAI

infection.

Medical

records

of these

78 patients

were

reviewed.

Six

RADIN

488

TABLE

1: Clinical

Features

of 71 Patients

AJR:156,

with AIDS and Disseminated

Number (%)

Feat u re

with

MTB

Mycobacterial

of Patients (n = 27)

Number with

March

1991

Infection

(%) of Patients (n = 44)

MAI

HIV risk factor 1 8 (67)

Homosexuality

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IV drug use

Homosexuality Other

and IV drug use

Unknown

illness

Concurrent AIDS-defining illness Disseminated mycobacterial infection

as only AIDS-defining Note.-MTB

patients

with MTB infection

1 1 patients

(with

Mycobacterium

=

and one patient

AIDS-defining

known

MAI

tuberculosis;

with

MAI infection

were

illness

extracutaneous

were

Kaposi

involvement

sarcoma

in

in only one pneumonia

patient); lymphoma (three patients); Pneumocystis carinll (24 patients); cytornegalovirus infection (nine patients); esophageal candidiasis (four patients); cryptococcosis (two patients); and histoplasmosis, toxoplasmosis, and cryptospondiosis (one patient each). CT examinations of the 71 patients were performed on a Picker 1 200 SX scanner. Slices 1 0 mm thick 15-mm intervals. IV contrast medium

were obtained at 1 0-mm or was administered in all but

seven cases. The studies were reviewed retrospectively and evaluated for liver and spleen size; the presence of hepatic, splenic, renal, pancreatic, adrenal, and gastrointestinal lesions and ascites; and the location, size, and density of abdominal lymph nodes. Of the 27 patients with MTB infection, involvement of abdominal lymph nodes was proved by percutaneous fine-needle aspiration in nine patients and autopsy in three patients. Follow-up CT examination after antituberculous therapy showed resolution of abdominal adenopathy in one patient. In seven of the 14 patients without direct evidence of abdominal nodal involvement, MTB was cultured from peripheral lymph node biopsy specimens. Splenic lesions in three patients and renal and pancreatic lesions in one patient each were confirmed to be due to MTB by fine-needle aspiration or autopsy. Of the 44 patients with MAI infection, involvement of abdominal lymph nodes was proved by percutaneous fine-needle aspiration of softtissue-density nodes in three patients and necrotic nodes in three patients. Involvement of nodes less than 10 mm in diameter was found at autopsy in one patient. Biopsy specimens of peripheral nodes yielded MAI in two patients. Hepatic lesions were confirmed at autopsy in one patient.

Results Abdominal

disseminated

CT findings mycobacterial

5 (11) 0 (0)

(4)

0

(0)

2 (7)

31 (70)

2 (7) 23 (85)

5 (11) 8 (18)

=

Mycobacterium

avium-intracellulare:

HIV

=

human

immu-

virus.

.

nonmycobactenal

2 (7) 2 (7)

illness

excluded because of a lack of serologic proof of HIV infection. All but one of the 71 patients with AIDS who had disseminated mycobactenal infection were men. The 27 patients with MTB ranged in age from 21 to 54 years (average, 35 years). The 44 patients with MAI ranged in age from 25 to 53 years (average, 35 years). HIV risk factors and the temporal relationship of mycobacterial infection to nonmycobacterial AIDS-defining illness are indicated in Table 1 Kaposi sarcoma was the only previous or concurrent disease in the four MTB patients with nonmycobacterial AIDS-defining illness. Extracutaneous Kaposi sarcoma was documented in only one of these four patients. Previous and concurrent diseases in the 36 MAI patients with

35 (80) 4 (9)

1

Previous AIDS-defining

nodeficiency

4 (1 5)

in the 71 patients with infection are presented

AIDS and in Tables

TABLE 2: Abdominal CT in 71 Patients with AIDS and Disseminated Mycobacterial Infection: Extranodal Findings

(%) of Patients

Number

CT Findin

g

Number

with MTB

with MAI

(n=27) Hepatomegaly Mild (1 9-20

cm cephalocau-

dal diameter) Marked (21 -24 cm cephalocaudal diameter) Splenomegaly Mild (1 4-1

5 cm cephalocau-

(%)

of Patients (n=44)

5 (1 9)

20 (45)

5 (1 9)

1 1 (25)

0

(0)

9 (20)

7

(26)

10 (23)

7 (26)

4

(9)

0

(0)

6 (14)

12 (44) 3(11) 8 (30)

6 (14) 4 (9) 3 (7)

dal diameter) Marked (1 6-21 cm cephalocaudal diameter)

Focal lesions in solid viscera Liver Spleen Kidney

5 (1 9)

1

Pancreas Adrenal abnormalities

2 (7) 0 (0)

0 (0) 0 (0)

Gastrointestinal

4 (15)

8 (18)

5 (1 9)

5 (11)

tract abnormali-

(2)

ties

Ascites Note.-MTB

=

Mycobacterium

tuberculosis

; MAI

=

Mycobacterium

av-

ium-intracellulare.

2 and 3. Although hepatomegaly and splenomegaly were seen in a minority of patients in each group, marked enlargement occurred only in patients with MAI. Because only one third of these MAI patients had other diseases commonly associated with hepatosplenomegaly (lymphoma, cytomegalovirus infection, histoplasmosis), it is likely that MAI infection was responsible for the marked hepatic and splenic enlargement in most instances. CT evidence of focal involvement of solid abdominal viscera was far more frequent in patients with MTB. CT showed one or more round or oval hypodense lesions between several millimeters and 2 cm in diameter in the liver, spleen, kidneys, and/or pancreas in 1 2 (44%) of the 27 MTB patients (Fig. 1) but in only six (1 4%) of the 44 MAI patients (Fig. 2). These parenchymal lesions had a similar appearance in both groups of patients but tended to be more numerous in the patients with MTB. A striking finding was the

AJR:156,

March

MYCOBACTERIAL

1991

TABLE 3: Abdominal Nodal Findings

CT in 71 Patients

CT Findin Solid

nodes

g

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node nodes