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Abdominal CT in patients with AIDS

1D M KOH, MRCP, FRCR, 2B LANGROUDI, MBBS and 2S P G PADLEY, FRCP, FRCR

1Department of Radiology, The Royal Marsden Hospital, Downs Road, Sutton SM2 5PT and 2Department of

Radiology, Chelsea and Westminster Hospital, London SW10 9NH, UK

An estimated 40 million people worldwide are

seropositive for the human immunodeficiency

virus (HIV) [1]. HIV infection is an important

cause of death in both males and females between

the ages of 25 years and 44 years. Although

homosexual men are still frequently affected, HIV

infection is increasing among intravenous (iv)

drug abusers and the heterosexual population.

Widespread prescription of highly active anti-

retroviral treatment (HAART) has resulted ina decrease in the viral load and an increase

in the mean CD4 count of these individuals.

Consequently, morbidity and mortality from

opportunistic infections have declined. HAART

employs a combination of anti-retroviral agents,

acting via different pathways, to inhibit HIV viral

replication. Nevertheless, opportunistic infections

still pose a significant threat to patients newly

diagnosed with the disease and in those who are

refractory to HAART.

Non-specific abdominal symptoms are common

in patients with acquired immune deficiency

syndrome (AIDS). These symptoms include diar-

rhoea, abdominal pain, abdominal distension,

fever, weight loss, abdominal mass, jaundice and

gastrointestinal bleeding. The immunocompro-

mised state predisposes these individuals to a

range of infectious and neoplastic diseases that

can give rise to these symptoms. Unfortunately,

physical examination of patients is often non-

revealing and laboratory test results may be

delayed. Hence, imaging is frequently used to

elucidate the cause of these symptoms. Although

ultrasound is often employed in the initial

assessment, visualization of the retroperitoneum,the mesenteric compartment and the bowel loops

is frequently challenging and often suboptimal. As

a result, CT has assumed a more important role in

the evaluation of abdominal symptoms in patients

with AIDS, especially in those who present

acutely.

Pathological considerations

In AIDS, a reduction in the number of CD4

lymphocytes results in immunosuppression and

exposes individuals to opportunistic infections.The CD4 count is a useful way of quantifying the

degree of immunosuppression, and interpretation

of CT findings should always be made with theknowledge of the patients CD4 count. Certain

diseases are more likely to occur at specific levels

of immunosuppression [2].

Infection with Mycobacterium tuberculosis may

be seen at a higher CD4 count of more than

200 cells ml21. By comparison, disseminated infec-

tion with Mycobacterium avium-intracellulare,

Candida species and cytomegalovirus is unusual

above a CD4 count of 100 cells ml21. Although

malignancies such as lymphoma and Kaposis

sarcoma can occur at varying degrees of immuno-

suppression, they are more common when theCD4 count falls below 200 cell ml21. The likeli-

hood of various abdominal diseases in relation to

the CD4 count is summarized in Table 1.

In addition to unusual opportunistic infections,

patients with AIDS are also susceptible to a range

of bacterial infections that affect the normal

population.

CT in patients with AIDS

CT of the abdomen and pelvis is usually

performed following administration of iv andoral contrast medium. Images should be acquired

craniocaudally in the hepatic portal venous phase,

Summary

N Abdominal symptoms are common in patients

with AIDS. CT is frequently used to evaluate

these symptoms.

N Findings on CT often non-diagnostic but

nevertheless contribute towards patient

management.

N Certain CT signs, together with a knowledge of

the CD4 count, may help to indicate the likely

diagnosis and enable early presumptive

treatment.

N Post-treatment CT may be used to assess the

resolution or progression of disease.

N CT is also useful in detecting intraabdominal

complications arising from the treatment of

AIDS.

Imaging, 14 (2002), 2434 E 2002 The British Institute of Radiology

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approximately 70 s after the beginning of iv

contrast medium delivery. A section thickness of

8 mm or less is optimal.

Common indications for the use of CT includeabdominal pain, pyrexia of uncertain origin, and

diagnosis or follow-up of intraabdominal malig-

nancy [3]. CT is particularly helpful in the

evaluation of patients presenting with acute abdo-

minal symptoms [4, 5]. However, CT was found

to be less useful when it was used as a screening

examination for HIV seropositive individuals

presenting to the hospital, since it did not

always improve outcome or reduce the length of

the hospital stay [6].

Common CT findings include hepatomegaly,

splenomegaly and lymphadenopathy. Unfortu-

nately, these radiological signs are non-specific.Consequently, a definitive diagnosis is made on

CT in only 12% of cases, although findings on CT

frequently contribute to the patients management

[3]. The CT findings, together with knowledge of

the CD4 count, allow a presumptive diagnosis to

be made and early treatment to be instituted

before microbiological or histological confirma-

tion becomes available. Where the diagnosis is

uncertain, CT can also be used to guide the

biopsy of abnormal tissue for definitive micro-

biological or histological diagnosis.

Certain radiological findings on CT have beenshown to indicate a poorer prognosis. These

include hepatic masses, grossly enlarged lymph

nodes and ascites [7], presumably reflecting a

greater degree of immunosuppression. The more

common CT findings of splenomegaly, hepato-

megaly and lymphadenopathy have no prognostic

implications [7].

Patients treated for malignancies such as

lymphoma and Kaposis sarcoma may be mon-

itored for radiological response using CT. In

patients with infective diseases, a repeat CT with

worsening clinical symptoms will help in the earlydetection of complications, allowing appropriate

management decisions to be made.

The cardinal CT features of the infections and

malignancies commonly encountered in patients

with AIDS are summarized below. Emphasis is

placed on those CT findings that may be helpful

in distinguishing one disease entity from the other.

InfectionsInfection can result from a variety of viruses,

bacteria or protozoans. Although opportunistic

infections are common, there is also an increased

incidence of non-opportunistic infections.

Mycobacterium tuberculosis andMycobacterium avium-intracellulare

Infection with Mycobacterium tuberculosis

(MTB) or Mycobacterium avium-intracellulare

(MAI) can be acquired through primary infection

or secondary to reactivation disease. In most casesof disseminated infection, it is thought that these

are likely to represent new primary infection

rather than reactivation disease.

There is considerable overlap in the CT features

of MTB and MAI infection. However, MAI

infection usually occurs at a greater degree of

immunosuppression when the CD4 count falls

below 50100 cells ml21.

The cardinal imaging features of both MTB

and MAI infections include lymphadenopathy,

hepatomegaly, splenomegaly and focal lesions

within the liver, spleen or kidneys.

Peritoneal disease is not unusual, especiallywith MTB, and may be a primary presentation.

Peritonitis resulting from mycobacterial infection

has been classified into wet, dry plastic or

fibrotic-fixed types depending on the imaging

features [8]. Ascites resulting from MTB infection

is classically, but not invariably, high in attenua-

tion (2545 HU) [8] (Figure 1).

Table 1. Abdominal diseases in relation to the CD4count

Disease CD4 count(cells ml21)

N Mycobacterium tuberculosis(extrapulmonary)

,200

N Mycobacterium avium-intracellulare ,100N Cytomegalovirus ,100N Candidiasis ,100N Histoplasmosis ,100N Pneumocystis carinii (extrapulmonary) ,200N Cryptosporidiosis ,200N Kaposis sarcoma ,200N Non-Hodgkins lymphoma ,200

Adapted from [20].

Figure 1. Mycobacterium tuberculosis (MTB) infectionand ascites. 43-year-old man with MTB infection

showing multiple retroperitoneal lymph nodes asso-ciated with peritoneal nodules. High attenuationascites are also shown.

Abdominal CT in AIDS patients

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Abdominal lymphadenopathy can be observed

in all patients with MTB and MAI infections [9].

However, the appearance of the abdominal lymph

nodes may be useful in distinguishing MTB infec-

tion from MAI infection [9, 10]. MAI typically

incites less tissue response, granuloma formation

and caseation, resulting in a lower incidence of

necrotic (low attenuation) lymph nodes. Lymph

nodes with central low attenuation are typical of

MTB infection and have a reported frequency of

up to 93% [9, 10] (Figure 2).Hepatomegaly is not an infrequent finding in

MAI infection, with a reported frequency of

3645% [911]. There appears to be an equal

incidence of splenomegaly in MTB infection and

MAI infection [9, 10].

The incidence of focal lesions in the liver and

spleen is higher in MTB infection than MAI

infection. The frequency of focal hepatic lesions in

MTB infection ranges from 11% to 19% [911]

and for MAI infection it ranges from 3.5% to 9%

[911].

For focal splenic lesions, the corresponding

incidence is 3059% for MTB infection and

6.77% for MAI infection [911] (Figure 3).

Focal renal lesions are also more common in

MTB infection [9]. Pancreatic and adrenal invol-

vement is rarely evident on imaging in either

group.

Proximal small bowel thickening is a feature ofMAI infection and the appearance resembles

Whipples disease, both histologically and radi-

ologically [9, 12, 13]. Thickening of the terminal

ileum is more typical of MTB infection (Figure 4)

[14].

Recently, a new fastidious species, Mycobac-

terium genevense (MG), has been isolated [15]

from HIV seropositive patients. It is a recognized

cause of abdominal disease but it is radiologi-

cally and clinically indistinguishable from MAI

(a) (b)

Figure 2. Mycobacterium avium-intracellulare (MAI) and Mycobacterium tuberculosis (MTB) lymphadenopathy.(a) In this 36-year-old man with MAI infection, there are discrete lymph nodes of uniform attenuation within theretroperitoneum and small bowel mesentery. (b) In another 38-year-old man with MTB infection, lymph nodes

within the retroperitoneum show typical central low attenuation.

Figure 3. Focal splenic lesions. In this 33-year-oldman with abdominal Mycobacterium tuberculosis infec-

tion there are multiple low attenuation lesions withinthe spleen. This appearance is, however, non-specificin the patient with AIDS.

Figure 4. Terminal ileitis. In this 44-year-old manwith Mycobacterium tuberculosis infection there isconcentric thickening of the terminal ileum.

D M Koh, B Langroudi and S P G Padley


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infection [16]. Treatment for both MG and MAI

infections are similar.

Cytomegalovirus

Cytomegalovirus is a common cause of life-

threatening opportunistic infection in patientswith AIDS. The disease frequently results from

reactivation of previous latent infection and

usually occurs when the CD4 count falls below

100 cells ml21. The manifestation of disease

depends on the severity of infection, which results

in varying degrees of inflammation, vasculitis and

fibrosis. In the abdomen, the colon is the

commonest site of involvement, followed by the

small bowel, the oesophagus and the stomach.

The caecum and the ascending colon are most

frequently affected by colitis, although a panco-

litis can result in severe infection. Barium enema

typically demonstrates multiple ulcers withnormal intervening mucosa. The CT findings

reflect the degree of inflammation, with concentric

thickening of the colonic wall, narrowing of the

intestinal lumen and pericolic inflammatory

changes [17] (Figure 5). The ulcer may be visible

on CT and, in severe cases, toxic megacolon,

pneumatosis coli and bowel perforation [17] are

recognized complications. Lymphadenopathy,

either within the mesentery or the retroperito-

neum, is usually absent [17].

The antrum is usually the site of disease in the

stomach, appearing as bowel wall thickening onCT. On barium studies there is thickening of the

gastric folds associated with superficial or deep

ulcerations [18]. Rarely, the infection may man-

ifest as a polypoidal mass (cytomegalovirus

pseudotumour), simulating neoplasia such as

lymphoma, carcinoma or Kaposis sarcoma [19].

Cytomegalovirus is also a cause of biliary peri-

ductal fibrosis leading to stenosis of the distal

common bile duct and intrahepatic biliary

strictures and dilatation. The appearance is

indistinguishable from the AIDS-related cholan-

giopathy caused by cryptosporiodiosis.

Candidiasis

The oesophagus is the commonest site of

involvement by candidiasis in patients with

AIDS. Disseminated systemic candidiasis is less

common because of the relative preservation of

neutrophil function [20].

Oral thrush frequently accompanies oesopha-

geal involvement. Infection of the oesophagus

results in extensive ulceration, with multiple oeso-

phageal plaques throughout the oesophagus. This

gives rise to the typical diffuse irregular appear-

ance on the barium oesophagram as shown in

Figure 6. The appearance on CT is, however,

non-specific, with thickening of the oesophagealwall. In severe infection, a mass-like lesion may

Figure 5. Cytomegalovirus colitis. CT in this 34-year-old with colitis shows concentric thickening of the

ascending colon. There is minimal pericolic inflamma-tory change. Note the absence of significant lymph-adenopathy within the retroperitoneum.

Figure 6. Candidiasis. Barium oesophagram in this

26-year-old man with diffuse mucosal irregularitygiving rise to a shaggy appearance typical of oesopha-geal candidiasis.



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result, resembling carcinoma [21]. In disseminated

disease, haematogenous spread of the infection

can lead to microabscesses within the liver, spleen

and kidneys. These appear on CT as multiple foci

of low attenuation.

Pneumocystis carinii

Pneumocystis carinii is a protozoan-like organ-

ism. Infection predominantly affects the lungs in

patients with AIDS and is more common in those

individuals with a CD4 count of less than

100 cells ml21. Rarely the liver, kidneys (Figure 7),

spleen, adrenal glands and abdominal lymph

nodes [20] may be affected in disseminated

Pneumocystis carinii infection. Extrapulmonary

dissemination of infection occurs in less than 1%

of patients with AIDS [22]. On CT, involvement

of the liver and spleen appear as multiple, small,

low attenuation lesions, which may show centralpunctate or rim calcifications [23]. These low

attenuation lesions have been shown to contain

clusters of trophozoites and eosinophilic material

[21]. Involvement of lymph nodes leads to nodal

enlargement, which may also calcify [22]. Pancreatic

involvement is very rare, but has been reported.

Histoplasmosis

Histoplasmosis is caused by the fungus Histo-

plasma capsulatum. In regions of the world where

histoplasmosis is endemic, disseminated histoplas-mosis may occur when the CD4 count falls to less

than 100 cells ml21. Disseminated histoplasmosis

may be a consequence of primary infection or

reactivation disease, which is not dissimilar to the

pathogenesis of disseminated MTB infection.

Although the chest is the usual portal of infection,

the chest radiograph is normal in up to 40% of

cases [21].

The radiological findings of disseminated histo-

plasmosis on CT mimic that of MTB infection

[24]. The bowel is involved in the majority (75%)

of cases [25], with the ascending colon being most

frequently affected and the terminal ileum to

a lesser degree. CT typically reveals concentric

thickening of the diseased bowel, associated with

perienteric inflammatory change. The inflam-

mation can result in strictures resembling carci-

noma. Low attenuation lymph nodes, resembling

MTB lymphadenitis, within the mesentery or

retroperitoneum are common [24]. Hepato-

splenomegaly, adrenal enlargement and peritoneal

nodularity have also been reported [24].

Cryptosporidiosis

Cryptosporidiosis is not uncommon in AIDS

patients with a CD4 count of less than

200 cells ml21. Cryptosporidia are intracellular

parasites that infect the epithelial cells of the

gastrointestinal tract, resulting in hypersecretion

and diarrhoea. The infection has a predilection

for the proximal small bowel, resulting in non-

specific thickening of the duodenum, jejenum and

proximal ileum [20]. Multiple loops of fluid-filled

and thickened small bowel loop can be identified

on CT (see Figure 8). Lymphadenopathy is not a

feature of the disease [20]. On barium follow-

through, mucosal fold thickening, mucosal fold

effacement and dilution of barium are well

recognized features.

Cryptosporidiosis and cytomegalovirus are

causes of AIDS-related cholangiopathy, which

results in dilatation of the intrahepatic and extra-

hepatic bile ducts as seen in Figure 9. The pres-

ence of papillary stenosis on endoscopy is useful

Figure 7. Pneumocystis carinii. This man with pre-

vious pneumocystis infection of the kidneys demon-strates multiple, well defined, punctate calcificationswithin the renal parenchyma bilaterally.

Figure 8. Cryptosporidiosis. 45-year-old man with

microbiologically proven cryptosporidiosis. There aremultiple loops of fluid-filled small bowel showing con-centric wall thickening.



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in distinguishing the condition from primary

sclerosing cholangitis [26]. Infections with Crypto-

sporidium and cytomegalovirus are also known to

give rise to acalculous cholecystitis, with thicken-

ing of the gall bladder wall and pericholecystic

fluid collection [27].

Infection with Isospora belli, a protozoan, can

result in a gastrointestinal disease that is clinically

and radiologically indistinguishable from crypto-

sporidiosis [28]. The two conditions may be

differentiated by microscopic stool examination

or intestinal biopsy.

Bacillary angiomatosis

Bacillary angiomatosis results from an infection

by Bartonella henselae, an organism belonging

to the group Rickettsiales. Infection results in

prominent vascular proliferation and hence the

named entity. The infection is found almost

exclusively in HIV seropositive patients, with a

prevalence of 1.2 per 1000 [29].

The most common manifestation of the infec-tion is a cutaneous lesion, which may be mistaken

for Kaposis sarcoma [30]. Other sites of involve-

ment include the mucous membrane, bones,

lymph nodes, intestine, liver, spleen and brain

[30]. In the liver and spleen, CT may reveal

multiple, low attenuation lesions (Figure 10). In

some cases, peliosis of the liver can occur [31].

Low attenuation liver lesions are very non-specific

in patients with AIDS, and may also result from

microabscesses caused by variety of infections,

lymphoma, Kaposis sarcoma or metastases. The

disease may also manifest as enhancing abdom-inal lymphadenopathy on contrast enhanced CT,

resembling that of Kaposis sarcoma.

Other infectionsOther infections of the gastrointestinal tract

include amoebiasis, giardiasis, salmonellosis and

Campylobacter infections. These infections may

occur with increased severity compared with the

non-immunocompromised population.

Renal infections such as pyogenic pyelonephri-

tis and renal abscesses are not uncommon. The

CT imaging features of pyelonephritis include

renal enlargement, striated nephrogram or poorly

functional kidneys (Figure 11a). Renal abscess is

recognized as a focal, low attenuation area within

the kidney.The pancreas may be affected by opportunistic

infections such as toxoplasmosis, cytomegalovirus

and MTB. However, pancreatitis may also result

as a complication of anti-retroviral treatment.

Treatment with protease inhibitors results in

hyperlipidaemia, which predisposes to acute pan-

creatitis. Pancreatitis in these patients is asso-

ciated with a high mortality. The imaging features

on CT are similar to the findings in an immuno-

competent patient with pancreatitis (Figure 11b).

AIDS-related neoplasia

Patients with AIDS are at increased risk of

developing neoplasms such as Kaposis sarcoma

and lymphoma. In addition, there is also an increase

in the incidence of squamous cell anorectal

carcinoma.

Kaposis sarcoma

Kaposis sarcoma is the commonest tumour to

affect patients with AIDS [20]. It occurs in up to

20% of the susceptible population, and is morecommon amongst homosexual men than in other

patients with AIDS [20]. The tumour consists of

Figure 9. AIDS cholangiopathy. There is mild dilata-tion of the intrahepatic ducts on CT in this patientwith an enlarged liver. Endoscopic retrograde cholan-giopancreatography (not shown) revealed multiplestrictures of the intrahepatic ducts, resembling scleros-

ing cholangitis.

Figure 10. Bacillary angiomatosis. This 36-year-oldman demonstrates several low attenuation lesionswithin the liver and spleen, associated with lymph-adenopathy in the retroperitoneum.



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clusters of spindle cells and vascular spaces. It

is believed that an HIV regulatory protein is

responsible for the uncontrolled proliferation of

the sarcoma cells.

The skin is the most frequent site of disease,

and this usually precedes involvement of the solid

organs and intestinal tract [32]. Although any

segment of the gastrointestinal tract may be

involved, the duodenum is most commonly

affected [33]. The lesions appear on barium

studies as submucosal nodules, which may

undergo central umbilication [33]. With diseaseprogression, the lesions may appear mass-like,

associated with bowel wall thickening, and can be

detected on CT.

Involvement of the solid organs such as the

liver and the spleen can be subtle on CT. The

tumour typically infiltrates along the vessels, and

CT is frequently normal in these individuals [33].

Hepatosplenomegaly may be the sole abnormality

on CT [34]. Less frequently, there may be

multiple, small, low attenuation nodules, which

enhance variably with iv contrast medium [34].

Unlike lymphoma and metastases, these nodules

are frequently hyperechoeic on ultrasound [20].

Lymphadenopathy occurs with nodal dissemi-

nation of disease. High attenuation lymph nodes

following administration of iv contrast medium

are typical of nodal involvement [35]. However,

the lymph nodes may be of soft tissue attenuation

and therefore indistinguishable from other causes

of lymphadenopathy such as lymphoma, myco-

bacterial infections and AIDS-related lymphade-

nopathy.

AIDS-related lymphoma

Lymphoma is the second most common

malignancy in patients with AIDS [20]. Patients

with AIDS are at a much higher risk of

developing non-Hodgkins lymphoma compared

with the general population. The pathogenesis of

lymphoma is uncertain, but is believed to be the

result of B-cell proliferation induced by HIV or

the Epstein-Barr virus [20].

AIDS-related non-Hodgkins lymphoma is fre-

quently aggressive, poorly differentiated, high

grade and carries a poorer prognosis compared

with the disease affecting the normal population

[36]. The disease is usually widely disseminated at

the time of diagnosis, frequently affecting multipleextranodal sites such as bone, brain, abdominal

viscera and gastrointestinal tract [20, 37].

Within the abdomen, the liver, spleen, kidneys,

lymph nodes and gastrointestinal tract are most

frequently affected [37] (Figure 11). The disease

may less frequently affect the pancreas or adrenal

glands [36]. Non-Hodgkins lymphoma of the

liver and spleen appear as hepatosplenomegaly,

often with accompanying low attenuation lesions

[37] (Figures 12a,b). These focal lesions may

demonstrate no, rim or diffuse enhancement on

contrast enhanced CT. Involved kidneys may besimilarly enlarged and infiltrated (Figure 12c).

The stomach and proximal small bowel are

most frequently affected along the gastrointestinal

tract [38]. Typical CT findings include bowel wall

thickening and mural masses [38]. Rarely, the

patient may present with multiple peritoneal

nodules and infiltration of the omentum, resem-

bling peritoneal carcinomatosis [20].

Lymphadenopathy is characteristically bulky

[38]. However, cases may be difficult to distin-

guish from other causes of lymphadenopathy in

the patient with AIDS. A percutaneous lymphnode biopsy is usually needed to arrive at a

definitive diagnosis.

(a) (b)

11Figure 11. (a) Pyelonephritis. This patient presented with acute flank pain. Note the striated nephrogram within theslightly enlarged kidneys, typical of acute pyelonephritis. (b) Pancreatitis. In another patient receiving proteaseinhibitor, there is enlargement and heterogeneity of the head of the pancreas associated with stranding of theperipancreatic fat. The appearance is consistent with acute pancreatitis.



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The frequency of Hodgkins disease is not

increased in the presence of HIV. Nevertheless,

Hodgkins disease can arise in AIDS patients

and there is also a higher incidence of extra-

nodal involvement and more aggressive beha-

viour of the disease compared with the normal

population [20].

Anorectal carcinoma

There is an increased incidence of anorectal

carcinoma in patients with AIDS. The majority

of these are squamous cell carcinomas [39].

Immunosuppression is associated with anal intra-epithelial dysplasia, which can transform into an

invasive cancer. Like lymphoma, these cancers are

frequently locally invasive and aggressive at the

time of diagnosis. MRI is useful in the diagnosis,

staging and follow-up of these tumours (Figure 13).

Treatment-related conditions

Urolithiasis associated with proteaseinhibitors

Indinavir sulphate is a widely used proteaseinhibitor used to treat patients with HIV infec-

tion. However, its use is associated with an

increased incidence of crystallization and stone

formation within the urinary tract, occurring in

up to 20% of patients receiving the treatment [40].

Patients with crystal uropathy usually present

with acute flank pain and dysuria. Since indinavir

Figure 13. Anorectal carcinoma. Post-intravenous

gadolinium T1 weighted axial MR image showing anenhancing soft tissue mass arising from the left of theanal canal, breaching the external sphincter.

(a)

(c)

(b)

Figure 12. (a) Lymphoma. There are two lowattenuation lesions within an enlarged liver. There isno appreciable enhancement of these lesions. (b) CTdemonstrates a solitary lesion in a normal-sizedspleen. Lymphoma may present as multiple, small,splenic, low attenuation foci, splenic enlargment or afocal solitary lesion, as demonstrated here. (c) Thereare multiple masses of low attenuation within the kid-neys. The appearance is typical of lymphomatousinvolvement of the kidneys.



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stones are not visible on the abdominal radio-

graph [40], urolithiasis is usually confirmed by

performing an excretory intravenous urogram,

ultrasound or CT (Figure 14).

Unlike stones of urate, oxalate or cystine, pure

indinavir stones are radiolucent and cannot be

visualized on unenhanced CT [3941]. Mixed

indinavir and calcium stones may be radiopaque.

The secondary signs of obstruction resulting from

indinavir stones can also be minimal [41]. Hence,

indinavir stones are best diagnosed on CT

following iv contrast medium administration to

delineate the presence of a stone or obstruction in

patients who are receiving such treatment [41].

The majority of HIV seropositive patients with

symptomatic urolithasis can be treated conserva-

tively with hydration [42]. Surgical intervention is

rarely necessary. However, metabolic screen can

help to identify and correct factors that predis-

pose to stone formation, reducing the risk offuture recurrence.

HIV-related lipodystrophy syndrome

The treatment of HIV using HAART is

associated with a lipodystrophy syndrome, char-

acterized by wasting of the peripheral fat of the

extremities, facial and gluteal area with increased

central adiposity within the abdomen (Figure 15),

breast and cervicothoracic region [43]. There is

usually associated hyperlipidaemia and insulin

resistance [43]. Accumulation of intraabdominal

fat results in symptoms such as abdominal

distension and pain.

Abdominal CT has been used to quantify these

changes by measuring the ratio of visceral adipose

tissue to total adipose tissue. Patients receiving

indinavir treatment have a higher visceral to total

adipose tissue ratio, and this ratio increases with

the duration of treatment [44].

Conclusions

CT is increasingly utilized in the evaluation of

infective and neoplastic conditions of the abdo-

men in patients with AIDS. Findings on CT are

frequently non-specific. Common CT findings

include hepatomegaly, splenomegaly and lymph-

adenopathy. CT findings of ascites, large focal

hepatic lesions and extensive lymphadenopathy

are associated with a poorer prognosis.

Certain CT findings may be helpful in indicat-ing the underlying diagnosis. Lymph nodes with

central low attenuation are typical but not

pathognomonic of MTB infection. Thickening

of the caecum and ascending colon is a feature of

cytomegalovirus infection. Disseminated Kaposis

sarcoma is associated with high attenuation lymph

nodes following iv contrast medium administra-

tion. CT may allow a presumptive diagnosis to

be made and treatment to be instituted before

microbiological or histological results become

available. Nevertheless, a tissue biopsy is fre-

quently needed to confirm the diagnosis.CT is also useful in the follow-up of patients

with abdominal diseases, especially in those with

Figure 14. Urolithiasis. Excretory urogram demon-

strating left ureteric obstruction in a patient receivingindinavir. The obstruction spontaneously resolvedafter 48 h.

Figure 15. Lipodystrophy. In this 38-year-old manreceiving protease inhibitor, note the relative paucity

of subcutaneous fat compared with the generousintraabdominal fat deposition. The appearance istypical of AIDS-related lipodystrophy.



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underlying malignancies. Abdominal diseases in

patients with AIDS can also result from the

treatment they are receiving. Urolithiasis, pan-

creatitis and lipodystrophy syndrome can result

from treatment with protease inhibitor and are

readily recognized on CT.

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