Imaging 14:24-34 (2002)
© 2002 The British Institute of Radiology
Abdominal CT in patients with AIDS
D M Koh, MRCP, FRCR1,
B Langroudi, MBBS2 and
S P G Padley, FRCP, FRCR2
1 Department of Radiology, The Royal Marsden Hospital, Downs Road, Sutton SM2 5PT and 2 Department of Radiology, Chelsea and Westminster Hospital, London SW10 9NH, UK
 |
Summary
|
|---|
- Abdominal symptoms are common in patients with AIDS. CT is frequently used to evaluate these symptoms.
- Findings on CT often non-diagnostic but nevertheless contribute towards patient management.
- Certain CT signs, together with a knowledge of the CD4 count, may help to indicate the likely diagnosis and enable early presumptive treatment.
- Post-treatment CT may be used to assess the resolution or progression of disease.
- CT is also useful in detecting intraabdominal complications arising from the treatment of AIDS.
|
Introduction
|
|---|
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 in a 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 diarrhoea, abdominal pain, abdominal distension, fever, weight loss, abdominal mass, jaundice and gastrointestinal bleeding. The immunocompromised 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 the knowledge of the patient's 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 µl-1. By comparison, disseminated infection with Mycobacterium avium-intracellulare, Candida species and cytomegalovirus is unusual above a CD4 count of 100 cells µl-1. Although malignancies such as lymphoma and Kaposi's sarcoma can occur at varying degrees of immunosuppression, they are more common when the CD4 count falls below 200 cell µl-1. The likelihood 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 and oral contrast medium. Images should be acquired craniocaudally in the hepatic portal venous phase, 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 include abdominal pain, pyrexia of uncertain origin, and diagnosis or follow-up of intraabdominal malignancy [3]. CT is particularly helpful in the evaluation of patients presenting with acute abdominal 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. Unfortunately, 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 patient's 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 confirmation becomes available. Where the diagnosis is uncertain, CT can also be used to guide the biopsy of abnormal tissue for definitive microbiological or histological diagnosis.
Certain radiological findings on CT have been shown 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, hepatomegaly and lymphadenopathy have no prognostic implications [7].
Patients treated for malignancies such as lymphoma and Kaposi's sarcoma may be monitored for radiological response using CT. In patients with infective diseases, a repeat CT with worsening clinical symptoms will help in the early detection 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.
|
Infections
|
|---|
Infection 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 and Mycobacterium 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 cases of 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 50–100 cells µl-1.
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, especially with 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 attenuation (25–45 HU) [8] (Figure 1).
View larger version (117K):
[in this window]
[in a new window]
|
Figure 1. Mycobacterium tuberculosis (MTB) infection and ascites. 43-year-old man with MTB infection showing multiple retroperitoneal lymph nodes associated with peritoneal nodules. High attenuation ascites are also shown.
|
|
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 infection 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).
View larger version (64K):
[in this window]
[in a new window]
|
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 the retroperitoneum and small bowel mesentery. (b) In another 38-year-old man with MTB infection, lymph nodes within the retroperitoneum show typical central low attenuation.
|
|
Hepatomegaly is not an infrequent finding in MAI infection, with a reported frequency of 36–45% [9–11]. 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% [9–11] and for MAI infection it ranges from 3.5% to 9% [9–11].
For focal splenic lesions, the corresponding incidence is 30–59% for MTB infection and 6.7–7% for MAI infection [9–11] (Figure 3). Focal renal lesions are also more common in MTB infection [9]. Pancreatic and adrenal involvement is rarely evident on imaging in either group.
View larger version (99K):
[in this window]
[in a new window]
|
Figure 3. Focal splenic lesions. In this 33-year-old man with abdominal Mycobacterium tuberculosis infection there are multiple low attenuation lesions within the spleen. This appearance is, however, non-specific in the patient with AIDS.
|
|
Proximal small bowel thickening is a feature of MAI infection and the appearance resembles Whipple's disease, both histologically and radiologically [9, 12, 13]. Thickening of the terminal ileum is more typical of MTB infection (Figure 4) [14].
View larger version (103K):
[in this window]
[in a new window]
|
Figure 4. Terminal ileitis. In this 44-year-old man with Mycobacterium tuberculosis infection there is concentric thickening of the terminal ileum.
|
|
Recently, a new fastidious species, Mycobacterium genevense (MG), has been isolated [15] from HIV seropositive patients. It is a recognized cause of abdominal disease but it is radiologically and clinically indistinguishable from MAI infection [16]. Treatment for both MG and MAI infections are similar.
Cytomegalovirus
Cytomegalovirus is a common cause of life-threatening opportunistic infection in patients with AIDS. The disease frequently results from reactivation of previous latent infection and usually occurs when the CD4 count falls below 100 cells µl-1. 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 pancolitis can result in severe infection. Barium enema typically demonstrates multiple ulcers with normal 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 retroperitoneum, is usually absent [17].
View larger version (121K):
[in this window]
[in a new window]
|
Figure 5. Cytomegalovirus colitis. CT in this 34-year-old with colitis shows concentric thickening of the ascending colon. There is minimal pericolic inflammatory change. Note the absence of significant lymphadenopathy within the retroperitoneum.
|
|
The antrum is usually the site of disease in the stomach, appearing as bowel wall thickening on CT. On barium studies there is thickening of the gastric folds associated with superficial or deep ulcerations [18]. Rarely, the infection may manifest as a polypoidal mass (cytomegalovirus pseudotumour), simulating neoplasia such as lymphoma, carcinoma or Kaposi's sarcoma [19].
Cytomegalovirus is also a cause of biliary periductal fibrosis leading to stenosis of the distal common bile duct and intrahepatic biliary strictures and dilatation. The appearance is indistinguishable from the AIDS-related cholangiopathy 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 oesophageal involvement. Infection of the oesophagus results in extensive ulceration, with multiple oesophageal plaques throughout the oesophagus. This gives rise to the typical diffuse irregular appearance on the barium oesophagram as shown in Figure 6. The appearance on CT is, however, non-specific, with thickening of the oesophageal wall. In severe infection, a mass-like lesion may 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.
View larger version (92K):
[in this window]
[in a new window]
|
Figure 6. Candidiasis. Barium oesophagram in this 26-year-old man with diffuse mucosal irregularity giving rise to a shaggy appearance typical of oesophageal candidiasis.
|
|
Pneumocystis carinii
Pneumocystis carinii is a protozoan-like organism. 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 µl-1. 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 central punctate 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.
View larger version (95K):
[in this window]
[in a new window]
|
Figure 7. Pneumocystis carinii. This man with previous pneumocystis infection of the kidneys demonstrates multiple, well defined, punctate calcifications within the renal parenchyma bilaterally.
|
|
Histoplasmosis
Histoplasmosis is caused by the fungus Histoplasma capsulatum. In regions of the world where histoplasmosis is endemic, disseminated histoplasmosis may occur when the CD4 count falls to less than 100 cells µl-1. 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 histoplasmosis 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 inflammation can result in strictures resembling carcinoma. Low attenuation lymph nodes, resembling MTB lymphadenitis, within the mesentery or retroperitoneum are common [24]. Hepatosplenomegaly, 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 µl-1. 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.
View larger version (117K):
[in this window]
[in a new window]
|
Figure 8. Cryptosporidiosis. 45-year-old man with microbiologically proven cryptosporidiosis. There are multiple loops of fluid-filled small bowel showing concentric wall thickening.
|
|
Cryptosporidiosis and cytomegalovirus are causes of AIDS-related cholangiopathy, which results in dilatation of the intrahepatic and extrahepatic bile ducts as seen in Figure 9. The presence of papillary stenosis on endoscopy is useful in distinguishing the condition from primary sclerosing cholangitis [26]. Infections with Cryptosporidium and cytomegalovirus are also known to give rise to acalculous cholecystitis, with thickening of the gall bladder wall and pericholecystic fluid collection [27].
View larger version (121K):
[in this window]
[in a new window]
|
Figure 9. AIDS cholangiopathy. There is mild dilatation of the intrahepatic ducts on CT in this patient with an enlarged liver. Endoscopic retrograde cholangiopancreatography (not shown) revealed multiple strictures of the intrahepatic ducts, resembling sclerosing cholangitis.
|
|
Infection with Isospora belli, a protozoan, can result in a gastrointestinal disease that is clinically and radiologically indistinguishable from cryptosporidiosis [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 infection is a cutaneous lesion, which may be mistaken for Kaposi's sarcoma [30]. Other sites of involvement 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, Kaposi's sarcoma or metastases. The disease may also manifest as enhancing abdominal lymphadenopathy on contrast enhanced CT, resembling that of Kaposi's sarcoma.
View larger version (132K):
[in this window]
[in a new window]
|
Figure 10. Bacillary angiomatosis. This 36-year-old man demonstrates several low attenuation lesions within the liver and spleen, associated with lymphadenopathy in the retroperitoneum.
|
|
Other infections
Other 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 pyelonephritis 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.
View larger version (68K):
[in this window]
[in a new window]
|
11 (a) Pyelonephritis. This patient presented with acute flank pain. Note the striated nephrogram within the slightly enlarged kidneys, typical of acute pyelonephritis. (b) Pancreatitis. In another patient receiving protease inhibitor, there is enlargement and heterogeneity of the head of the pancreas associated with stranding of the peripancreatic fat. The appearance is consistent with acute pancreatitis.
|
|
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 pancreatitis. Pancreatitis in these patients is associated with a high mortality. The imaging features on CT are similar to the findings in an immunocompetent patient with pancreatitis (Figure 11b
).
|
AIDS-related neoplasia
|
|---|
Patients with AIDS are at increased risk of developing neoplasms such as Kaposi's sarcoma and lymphoma. In addition, there is also an increase in the incidence of squamous cell anorectal carcinoma.
Kaposi's sarcoma
Kaposi's sarcoma is the commonest tumour to affect patients with AIDS [20]. It occurs in up to 20% of the susceptible population, and is more common amongst homosexual men than in other patients with AIDS [20]. The tumour consists of 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 disease progression, 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 dissemination 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, mycobacterial infections and AIDS-related lymphadenopathy.
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-Hodgkin's 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-Hodgkin's lymphoma is frequently 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 multiple extranodal 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-Hodgkin's 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 be similarly 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, resembling peritoneal carcinomatosis [20].
View larger version (91K):
[in this window]
[in a new window]
|
Figure 12. (a) Lymphoma. There are two low attenuation lesions within an enlarged liver. There is no appreciable enhancement of these lesions. (b) CT demonstrates a solitary lesion in a normal-sized spleen. Lymphoma may present as multiple, small, splenic, low attenuation foci, splenic enlargment or a focal solitary lesion, as demonstrated here. (c) There are multiple masses of low attenuation within the kidneys. The appearance is typical of lymphomatous involvement of the kidneys.
|
|
Lymphadenopathy is characteristically bulky [38]. However, cases may be difficult to distinguish from other causes of lymphadenopathy in the patient with AIDS. A percutaneous lymph node biopsy is usually needed to arrive at a definitive diagnosis.
The frequency of Hodgkin's disease is not increased in the presence of HIV. Nevertheless, Hodgkin's disease can arise in AIDS patients and there is also a higher incidence of extranodal involvement and more aggressive behaviour 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 intraepithelial 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).
View larger version (133K):
[in this window]
[in a new window]
|
Figure 13. Anorectal carcinoma. Post-intravenous gadolinium T1 weighted axial MR image showing an enhancing soft tissue mass arising from the left of the anal canal, breaching the external sphincter.
|
|
|
Treatment-related conditions
|
|---|
Urolithiasis associated with protease inhibitors
Indinavir sulphate is a widely used protease inhibitor used to treat patients with HIV infection. 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 stones are not visible on the abdominal radiograph [40], urolithiasis is usually confirmed by performing an excretory intravenous urogram, ultrasound or CT (Figure 14).
View larger version (123K):
[in this window]
[in a new window]
|
Figure 14. Urolithiasis. Excretory urogram demonstrating left ureteric obstruction in a patient receiving indinavir. The obstruction spontaneously resolved after 48 h.
|
|
Unlike stones of urate, oxalate or cystine, pure indinavir stones are radiolucent and cannot be visualized on unenhanced CT [39–41]. 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 conservatively with hydration [42]. Surgical intervention is rarely necessary. However, metabolic screen can help to identify and correct factors that predispose to stone formation, reducing the risk of future recurrence.
HIV-related lipodystrophy syndrome
The treatment of HIV using HAART is associated with a lipodystrophy syndrome, characterized 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.
View larger version (136K):
[in this window]
[in a new window]
|
Figure 15. Lipodystrophy. In this 38-year-old man receiving protease inhibitor, note the relative paucity of subcutaneous fat compared with the generous intraabdominal fat deposition. The appearance is typical of AIDS-related lipodystrophy.
|
|
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 abdomen in patients with AIDS. Findings on CT are frequently non-specific. Common CT findings include hepatomegaly, splenomegaly and lymphadenopathy. CT findings of ascites, large focal hepatic lesions and extensive lymphadenopathy are associated with a poorer prognosis.
Certain CT findings may be helpful in indicating 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 Kaposi's sarcoma is associated with high attenuation lymph nodes following iv contrast medium administration. 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 frequently needed to confirm the diagnosis.
CT is also useful in the follow-up of patients with abdominal diseases, especially in those with underlying malignancies. Abdominal diseases in patients with AIDS can also result from the treatment they are receiving. Urolithiasis, pancreatitis and lipodystrophy syndrome can result from treatment with protease inhibitor and are readily recognized on CT.
|
References
|
|---|
-
Mann JM. A global epidemic out of control? In: Mann JM, Tarantola DJM, Netter TW, editors. AIDS in the world. Cambridge, MA: Harvard University Press, 1992:1–7.
-
Crowe SM, Carlin JB, Stewart KL, et al. Predictive value of CD4 lymphocytic number for the development of opportunistic infections and malignancies in HIV infected persons. J Acquir Immune Defic Syndr 1991;4:770–6.
-
Sansom H, Seddon B, Padley SP. Clinical utility of abdominal CT scanning in patients with HIV disease. Clin Radiol 1997;52:698–703.[Medline]
-
Wyatt SH, Fishman K. The acute abdomen in individuals with AIDS. Radiol Clin North Am 1994;32:1023–43.[Medline]
-
Wu CM, Davis F, Fishman EK. Radiologic evaluation of the acute abdomen in the patient with acquired immunodeficiency syndrome (AIDS): the role of CT scanning. Semin Ultrasound CT MR 1998;19:190–9.[Medline]
-
Rosen MP, Sher S, Bhorade R, et al. Screening admission CT scans in patients with AIDS—a randomised trial. Eff Clin Pract 1999;3:101–7.
-
Knollman FD, Maurer J, Grunewald T, et al. Abdominal CT features and survival in acquired immunodeficiency. Acta Radiol 1997;38:970–7.[Medline]
-
Suri S, Gupta S, Suri R. Computed tomography in abdominal tuberculosis. Br J Radiol 1999;72:92–8.[Abstract]
-
Radin DR. Intraabdominal Mycobacterium tuberculosis vs Mycobacterium avium-intracellulare infections in patients with AIDS: distinction based on CT findings. AJR 1991;156:487–91.[Abstract/Free Full Text]
-
Nyberg DA, Federle MP, Jeffrey RB, Bottles K, Wofsy CB. Abdominal CT findings of disseminated Mycobacterium avium-intracellulare in AIDS. AJR 1985;145:297–9.[Abstract/Free Full Text]
-
Radin R. HIV infection: analysis in 259 consecutive patients with abnormal abdominal CT findings. Radiology 1995;197:712–22.[Abstract]
-
Strom RL, Gruninges RP. AIDS with Mycobacterium avium-intracellulare lesions resembling those of Whipple's disease. N Engl J Med 1983;309:1323–4.[Medline]
-
Vincent ME, Robbins AH. Mycobacterium avium-intracellulare complex enteritis: pseudo-Whipple disease in AIDS. AJR 1985;144:921–2.[Free Full Text]
-
Balthazar EJ, Cordon R, Hulnick D. Ileocaecal tuberculosis: CT and radiologic evaluation. AJR 1990;154:499–503.[Abstract/Free Full Text]
-
Bottger EC, Teske A, Kirschner P, Bost S, Chang HR, Beer V, et al. Disseminated Mycobacterium genavense infection in patients with AIDS. Lancet 1992;340:76–80.[Medline]
-
Pechere M, Opravil M, Wald A, et al. Clinical and epidemiologic features of infection with Mycobacterium genavense. Swiss HIV Cohort Study. Arch Intern Med 1995;155:400–4.[Abstract]
-
Murray JG, Evans SJJ, Jeffrey PB, Halvorsen RA. Cytomegalovirus colitis in AIDS: CT features. AJR 1995;165:67–71.[Abstract/Free Full Text]
-
Farman J, Lerner ME, Ng C, et al. Cytomegalovirus gastritis: protean radiologic features. Abdom Imaging 1992;17:202–6.
-
Laguna F, Garcia-Samaniego J, Alonso MJ, et al. Pseudotumoral appearance of cytomegalovirus esophagitis and gastritis in AIDS patients. Am J Gastroenterol 1993;88:1108–11.[Medline]
-
Redvanly RD, Silverstein JE. Intra-abdominal manifestations of AIDS. Radiol Clin North Am 1997;35:1083–125.[Medline]
-
Pantogang-Brown L, Nelson AM, Brown AE, Buerton DC, Buck JL. Gastrointestinal manifestations of acquired immunodeficiency syndrome. Radiologic–pathologic correlation. Radiographics 1995;15:1155–78.[Abstract]
-
Raviglione MC. Extrapulmonary pneumocystosis: the first 50 cases. Rev Infect Dis 1990;12:1127–38.[Medline]
-
Radin DR, Baker EL, Klatt EC, et al. Visceral and nodal calcification in patients with AIDS-related Pneumocystis carinii infection. AJR 1990;154:24–31.
-
Radin DR. Disseminated histoplasmosis: abdominal CT findings in 16 patients. AJR 1991;157:955–8.[Abstract/Free Full Text]
-
Clarkston WK, Bonacini M, Peterson I. Colitis due to Histoplasma capsulatum in the acquired immune deficiency syndrome. Am J Gastroenterol 1991;86:913–6.[Medline]
-
Schneiderman DJ, Cello JP, Laing FC. Papillary stenosis and sclerosing cholangitis in the acquired immune deficiency syndrome. Ann Intern Med 1987;106:546–9.
-
Texidor HS, Godwin TA, Ramirez EA. Cryptosporidiosis of the biliary tract in AIDS. Radiology 1991;180:51–6.[Abstract]
-
Goodgame RW. Understanding intestinal spore forming protozoa: cryptosporidia, microsporidia, isospora and cyclospora. Ann Intern Med 1996;124:429–41.[Abstract/Free Full Text]
-
Plettenberg A, Lorenzen T, Burtsche BT, et al. Bacillary angiomatosis in HIV-infected patients—an epidemiological and clinical study. Dermatology 2000;201:326–31.[Medline]
-
Webster GF, Cockerell CJ, Friedman-Kien AE. The clinical spectrum of bacillary angiomatosis. Br J Dermatol 1992;126:535–41.[Medline]
-
Moore EH, Russell LA, Klein JS, et al. Bacillary angiomatosis in patients with AIDS: multiorgan imaging findings. Radiology 1995;197:67–72.[Abstract]
-
Nyberg DA, Federle MP. AIDS related Kaposi sarcoma and lymphomas. Semin Roentgenol 1987;2:54–6.
-
Wall SE, Friedman SL, Margulis AR. Gastrointestinal Kaposi's sarcoma in AIDS. Radiographic manifestations. J Clin Gastroenterol 1984;6:165–71.[Medline]
-
Luburich P, Bru C, Ayuso MC, et al. Hepatic Kaposi sarcoma in AIDS: US and CT findings. Radiology 1990;175:157–60.[Abstract]
-
Herts HR, Meigbow AJ, Birnbaum BA, et al. High attenuation lymphadenopathy in AIDS patients: significance of findings at CT. Radiology 1992;185:777–81.[Abstract]
-
Ziegler JL, Beckstead JA, Volberding PA, et al. Non-Hodgkin's lymphoma in 90 homosexual men: relationship to generalised lymphadenopathy and the acquired immunodeficiency syndrome. N Engl J Med 1984;311:565–70.[Abstract]
-
Townend RR. CT of AIDS related lymphoma. AJR 1991;156:969–74.[Abstract/Free Full Text]
-
Radin DR, Esplin JA, Levine AM, Ralls PW. AIDS related non-Hodgkin's lymphoma: abdominal CT findings in 112 patients. AJR 1993;160:1122–39.
-
Barrett WL, Callahan TD, Orkin BA. Perianal manifestations of human immunodeficiency virus infection: experience with 260 patients. Dis Colon Rectum 1998;41:606–11.[Medline]
-
Schwartz BF, Schenkman N, Armenakas NA, Stoller ML. Imaging characteristics of indinavir calculi. J Urol 1999;161:1085–7.[Medline]
-
Blake SP, McNicholas MM, Raptopoulos V. Non-opaque crystal depostion causing ureteric obstruction in patients with HIV undergoing indinavir therapy. AJR 1998;171:717–20.[Abstract/Free Full Text]
-
Sundaram CP, Saltzmann B. Urolithiasis associated with protease inhibitor. J Endourol 1999;13:309–12.[Medline]
-
Gellett LR, Haddon L, Maskell GF. CT appearances of HIV-related lipodystrophy syndrome. Br J Radiol 2001;74:382–3.[Abstract/Free Full Text]
-
Miller KD, Jones E, Yanovski JA, Shankar R, Feuerstein I, Falloon J. Visceral abdominal fat accumulation associated with the use of indinavir. Lancet 1998;351:871–5.[Medline]
This article has been cited by other articles:
|
|
|
|
 
Answers to multiple-choice questionnaire: Imaging in AIDS/HIV [from Imaging 14(1)]
Imaging,
June 1, 2002;
14(3):
246 - 249.
[Full Text]
[PDF]
|
|
|
Top
Summary
Introduction
