Fig. 6.63 A-C. Cerebral cryptococcosis. A A section of the brain showing multiple cystic lesions. B Cryptococcus neoformans cell in cerebrospinal fluid. India ink,x1200. C A small cryptococcal lesion in the brain: there is no inflammatory reaction, the lesion consists of small capsule-deficient cryptococcus cells. Mayer's mucicarmine, x256. A-C from Bittencourt and Londero 1995)

Fig.6.64 A-C. Candidiasis of the esophagus. A The barium filled esophagus of a patient with chronic leukemia on steroid therapy. There are multiple nodules along the esophagus caused by granulomas and a matrix of hyphae and yeast forms. These may retain the barium for 30-60 min. The esophagus is edematous and normal peristalsis is lost. Both the mucosa and the peristalsis will return to normal within a few days of appropriate therapy. AFIP 229498-250. B A similar but less severe infection in a 79-year-old man who also had leukemia. AFIP 239498-249. C A man from India with marked esophagitis. The radiological appearance mimics varices, but when due to candidiasis the nodules are most prominent at the top of the esophagus whereas varices occur in the lower half. (C courtesy of Dr. A. Gajaraj, Madras, India)

Candidiasis of the Biliary Tract and Liver

Candidiasis of the biliary tract is unusual. Fungus balls may be shown by cholangiography or ultrasonography. It is difficult to distinguish the images from any other cholangitis.

In the liver, Candida causes microabscesses from hematogenous spread. These can be demonstrated by ultrasonography or CT, and some will enhance with intravenous contrast. Four patterns of hepatosplenic candidiasis have been described on ultrasonography. The early abscesses are surrounded by a hypoechoic ring which surrounds an inner hyperechoic ring: the outer zone is fibrous tissue, the inner is inflammatory cells. There is a central hyperechoic necrotic area, caused by the fungi. Larger abscesses have a more typical target appearance (bull's eye), but when most patients are scanned, these stages will be past and the finding on ultrasonography will be of multiple hypoechoic foci. Later again, as healing occurs there is further fibrosis and calcification. The foci become more echogenic and there may be acoustic shadowing in some cases.

The CT findings are similar: the microabscesses show as multiple low attenuated foci scattered throughout the liver and spleen. As they heal, calcification may be detected. MRI shows the same pattern, but the calcification may not be recognized.

Candidiasis of the Genitourinary Tract

The most common of all fungal infections of the urinary tract is Candida: On scanning (ultrasonography CT, or MRI), the same pattern of microabscesses seen in the liver will be found in the kidneys. In acute candidiasis, the findings resemble any acute pyelonephritis. The fungi may produce filling defects on the mucosa of the renal collecting system (Fig. 6.66A), mimicking small radiolucent calculi, blood clots, or even epithelial tumors. In immunodeficient patients, particularly diabetics, the fungal mass can be large enough to cause obstruction (Fig. 6.66 B, C). CT or ultrasonography will show these changes clearly and demonstrate that the renal outline is deformed. In neonatal renal candidiasis, ultrasonography is not a reliable way to indicate the need for treatment or assess its success and need for continuation. There is no correlation between the sonographic findings and apparent deterioration during treatment. If there have been renal abscesses which heal, calcification may follow, as in the liver or spleen. A few patients have had candidal interstitial cystitis, causing trabeculation and thickening of the urinary bladder and dilatation of the collecting system.

None of these imaging changes are really diagnostic in the urinary tract: urinary tests may be misleading and percutaneous aspiration biopsy may be necessary.

Intracerebral Candidiasis

Intracerebral candidiasis is almost always the result of dissemination. CT and MRI will show multiple microabscesses, with enhancing ring or nodular lesions. These are indistinguishable from any other infection, and do not have any specific distribution.