Teaching Case

A 34-year-old male immigrant from South America, with a twelve-year history of Human Immunodeficiency Virus (HIV) infection, was hospitalised because of generalised malaise, 20-kg weight loss, and abdominal distension. His immune function was sufficiently preserved (309 CD4 cells/mmc) on antiretroviral treatment.

At emergency department admission, plain abdominal radiographs acquired disclosed centralisation of some moderately distended enteric loops, suggesting the presence of ascites underlying abdominal distension.
Unenhanced and contrast-enhanced multidetector CT showed minimal peritoneal effusion, associated with diffuse solid, moderately enhancing thickening (maximum thickness 1.5-2 cm) of the peritoneal serosa, including some nodularities compressing the liver, and massive involvement of the omentum, porta hepatis, and mesentery. Lymphadenopathies as well as lesions in the brain, thorax and solid organs were excluded. Percutaneous aspiration biopsy performed on two different peritoneal nodularities diagnosed CD20+, high proliferative index B-cell lymphoma. Bone marrow biopsy and liquoral cytology yielded negative results.
Chemotherapy including corticosteroids plus alternating antiblastic drugs allowed prompt clinical improvement. At treatment completion, CT restaging disclosed disappearance of all peritoneal, omental, and mesenterial changes, with minimal residual ascites. Four months later, no residual abnormalities were visible at follow-up CT.

The introduction of highly active antiretroviral therapy (HAART) in 1995 has resulted in a dramatic improvement in immune function and survival of patients infected with the Human Immunodeficiency Virus (HIV). Whereas the incidence of Kaposi’s sarcoma and uterine cervix cancer has significantly decreased, non-Hodgkin lymphoma (NHL) is increasingly diagnosed and is currently the most prevalent Acquired Immunodeficiency Syndrome (AIDS)-defining malignancy. NHL occurs in all risk groups, usually in the mid or late phases of HIV systemic infection, without any clear relationship with the degree of immune suppression measured by the CD4 cell count. In HIV-positive patients, the disease extent and patterns of involvement differ from those observed in lymphoma in the general population. Typically a high-grade, poorly differentiated B-cell lymphoma, HIV-related NHL is often widely disseminated at presentation, invariably including extranodal disease [1, 4].
Almost exclusively encountered in immunocompromised patients, peritoneal lymphomatosis (PL) is a very uncommon, atypical manifestation of NHL. Usually, PL primarily involves and remains confined to the body cavity of origin, is often aggressive and associated with a poor prognosis [1, 3, 4, 5, 6].
Although ultrasound can readily detect the presence of peritoneal effusion, nowadays contrast-enhanced multidetector CT (MDCT) represents the mainstay imaging modality to investigate suspected abdominal or systemic opportunistic disorders in HIV-infected patients, as it provides simultaneous, comprehensive assessment of the solid organs, peritoneal surfaces and omentum, gastrointestinal viscera, lymph nodes, and urogenital tract [2].
Cross-sectional imaging findings of PL include diffusely thickened peritoneal surfaces with multifocal nodules and masses, in association with ascites and omental caking. Additionally, diffuse lymphomatous infiltration of the mesentery may cause small bowel fixation and straightening of the mesenteric vasculature [3, 4, 5, 6].
Alternatively, the diagnosis of peritoneal carcinomatosis should be considered, since the two entities are often radiologically indistinguishable on the basis of their CT appearance, so that pathologic proof is necessary [7, 5].