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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.
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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.
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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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