Acquired immunodeficiency syndrome (aids)

disorder caused by infection with the HIV virus. Some, but not all, patients will experience an acute virus-like illness after their initial infection. During the second phase, the duration of which is variable, the patient is an asymptomatic carrier. The last phase of the disease is characterized by opportunistic infections, malignant tumours and neurological disease. Gastrointestinal and hepatobiliary symptoms are very frequent in patients with AIDS and may occur during the first and last phases of the disease. Many lesions in the gastrointestinal tract are superficial lesions of the mucosa and they can be satisfactorily visualized by double contrast barium radiography. For the evaluation of visceral organs or the abdominal cavity, affected by infection or by malignancy CT, and, to a lesser extent, ultrasound are the preferred methods.

Biliary disease

This is also called AIDS cholangiopathy. In the biliary system AIDS may cause acute acalculous cholecystitis, cholangitis and, more rarely, lymphoma or Kaposis sarcoma. Acute acalculous cholecystitis may be caused by CMV infection, fungal or protozoal parasitic infection (see cholecystitis acute acalculous). Ultrasound, CT or MRI will show a thickened gallbladder wall in the absence of stones. The cholangitis is mostly caused by cryptosporidiosis or cytomegalic virus (CMV). The cholangiographic abnormalities of the bile ducts, visualized on either ERCP or MRCP, include irregular contours due to mucosal thickening, short strictures, beading and papillary stenosis.

Colitis

Colitis caused by CMV (the usual colitis in this situation) involves predominantly the caecum and the ascending colon but also the terminal ileum. It causes oedema and ulcerations of the mucosa and wall thickening. These changes can best be visualized by barium studies but also by CT which will demonstrate marked thickening of the wall of the colon with low attenuation and, following intravenous contrast administration, enhancement of the layers of the colon wall. Mycobacterium tuberculosis colitis in patients with AIDS is characterized by thickening of the ileocaecal valve and the medial wall of the caecum and terminal ileum, as demonstrated by barium studies and by CT. CT will also show enlarged mesenteric lymph nodes in the ileocaecal area. Histoplasmosis may cause either ulcerative changes or mass lesions located mainly in the terminal ileum and the caecum. CT will usually reveal enlarged regional hypoattenuating lymphnodes in these circumstances.

Enteropathy

This enteropathy is usually related to opportunistic infections of the small bowel caused by cryptosporidiosis or Mycobacterium avium-intracellulare (MAI). Barium studies will reveal dilution of the contrast medium and irregular fold thickening, either limited to a segment of the small bowel or involving its entire length. CT may demonstrate enlarged regional mesenterial and retroperitoneal lymph nodes in the case of MAI infection.

Hepatic abnormalities

Liver involvement includes infectious hepatitis, lymphoma of the liver and Kaposis sarcoma. Viral hepatitis, usually hepatitis B, is common in patients with AIDS. However, the most frequent infection is caused by MAI. Other causes of infectious hepatitis in AIDS patients are histoplasmosis, cytomegalovirus, cryptococcosis or Pneumocystis carinii. The microabscesses and granulomas consequent on these infections may be visible on CT as small, rounded, low attenuation, nonenhancing areas, possibly with peripheral ring enhancement. Lymphoma lesions in the liver of AIDS patients are usually solitary and large at the time of the diagnosis. Kaposis sarcoma has a predilection for the periportal regions of the liver and occurs in 10 - 15% of patients. Ultrasound, CT and MRI will clearly demon virus (CMV). Oesophageal tuberculosis in AIDS patients is secondary to extension from enlarged and caseating mediastinal tuberculous lymph nodes. It is therefore generally limited to the upper or midportion of the oesophagus at the level of the mediastinal lymph nodes. Also, see oesophagitis infectious mycobacterial.

ALB