Gastrointestinal Manifestations of Acquired Immunodeficiency Syndrome

Radiologic-Pathologic Correlation

Abstract Introduction

Opportunistic Infections AIDS-Associated Neoplasms Conclusion

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AIDS-Associated Neoplasms

Kaposi Sarcoma

Kaposi sarcoma is a tumor composed of spindle cells and vascular clefts with extravasated red blood cells. The spindle cells of Kaposi sarcoma are generally believed to originate from the malignant proliferation of endothelial cells of lymphatic or blood vessels, which would explain the multicentric nature of the tumor (86). The HIV regulatory protein, trans-activator target (TAT), which is important for viral replication, is hypothesized to cause proliferation of Kaposi sarcoma cells (86).

Kaposi sarcoma is the most common AIDS-related tumor in homosexual men and in populations in parts of Africa (63,87). The gastrointestinal tract is the third most common site of Kaposi sarcoma, after the skin and lymph nodes. Kaposi sarcoma of the gastrointestinal tract is usually clinically silent and appears concurrently with or after cutaneous disease. However, primary gastrointestinal Kaposi sarcoma without skin lesions has been reported (88). The diagnosis of gastrointestinal Kaposi sarcoma is made based on endoscopic visualization of a submucosal mass or masses of a red-purple color, which is typical of Kaposi sarcoma; confirmation is made histologically with biopsy specimens.

Kaposi sarcoma can involve any part of the gastrointestinal tract from the oropharynx to the rectum. The most common radiologic finding in the gastrointestinal tract is of multiple submucosal masses, with or without central ulceration ("target" or "bull's-eye" lesions) (Figure 11). Plaquelike lesions or small nodules are less common radiologic findings and are best detected with double-contrast barium studies (89). Intussusception is an uncommon manifestation of Kaposi sarcoma but does occur (90).

Kaposi sarcoma may involve almost any solid organ within the abdomen. However, detection of these lesions at imaging is uncommon, except in the lymph nodes. Abdominal and pelvic lymphadenopathy are common features of Kaposi sarcoma (Figure 12). At dynamic sequential bolus CT, these enlarged nodes may show high attenuation (compared with that of adjacent skeletal muscle) secondary to the high vascularity of the tumor (91). Kaposi sarcoma of the gallbladder may manifest as wall thickening detected with US or CT (Figure 12). However, this finding is not specific.

Non-Hodgkin Lymphoma

Non-Hodgkin lymphoma occurs more frequently in patients with AIDS than in the normal population. These neoplasms are not derived from HIV-infected CD4 cells but rather are generally B-cell lymphomas. Non-Hodgkin lymphoma is the second most common AIDS-associated neoplasm and occurs in 4% 10% of AIDS patients (92). The calculated risk of developing non-Hodgkin lymphoma is about 60 times greater in individuals with AIDS than in the general population in the United States (93). AIDS-associated non-Hodgkin lymphoma occurs in all AIDS risk groups, unlike Kaposi sarcoma, which has a higher incidence in homosexual men.

The distinguishing feature of AIDS-associated non-Hodgkin lymphoma is the presence of widely disseminated disease, including a high frequency of extranodal involvement at initial presentation. The most frequent sites of extranodal involvement include the central nervous system, gastrointestinal tract, and bone marrow (94). The diagnosis of non-Hodgkin lymphoma is made based on histologic and immunohistologic findings, which usually include evidence of B-cell origin, high or intermediate grade, and multiclonality.

Within the gastrointestinal tract, the stomach and small bowel are the two most frequent sites of involvement by non-Hodgkin lymphoma, although all segments may be involved, and multifocality is not uncommon. Radiologic findings of gastric non-Hodgkin lymphoma include circumferential or focal thickening of the gastric wall and mural masses with or without ulceration. The radiologic manifestations of small bowel non-Hodgkin lymphoma include diffuse or focal bowel wall thickening and excavated masses. Intussusception occurs (Figure 13) but is uncommon (95).

Primary esophageal lymphoma in AIDS patients is unusual but does occur. It is usually aggressive and may mimic squamous cell carcinoma (96) (Figure 14). Although primary anorectal lymphoma is very unusual in the general population, it occurs frequently in patients with AIDS, especially homosexual men (97). A perianal mass and diffuse or focal rectal wall thickening are common radiologic findings at this site (Figure 15).

The liver is also a common site of non-Hodgkin lymphoma in the abdomen in AIDS patients. Solitary or multiple lesions of various sizes may be detected with either US or CT. A characteristic US finding is that of a mass that is hypoechoic compared with the adjacent hepatic parenchyma (Figure 16). CT shows various patterns of enhancement after intravenous contrast material administration, including no enhancement, a thin enhancing rim, or diffuse enhancement (98) (Figure 16). Non-Hodgkin lymphoma in AIDS patients is found less commonly in the spleen than in the liver. A common finding at CT is that of single or multifocal low-attenuation lesions (98) (Figure 17).

Other Neoplasms

Cloacogenic carcinoma arises from the cloacogenic epithelium, which is found in the transition zone between anal and rectal mucosa. The gastrointestinal literature suggests an increase in the occurrence of anorectal carcinoma in homosexual men (99,100). However, the frequency of cloacogenic carcinoma is not substantially greater in patients with AIDS (101).

Smooth-muscle tumors of the gastrointestinal tract and liver in AIDS patients have been reported (102,103,104). However, there is no epidemiologic data that indicate an increased prevalence of smooth-muscle tumors in the AIDS population.

Hodgkin disease has been reported in AIDS patients (105), but it has not been included in the list of AIDS-defining illnesses by the Centers for Disease Control.

Abstract Introduction

Opportunistic Infections AIDS-Associated Neoplasms Conclusion

Source Information References