Primary Alveolar Echinococcosis of the Kidney

Abstract

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Alveolar echinococcosis (AE), which is caused by the larval stage of** ** Echinococcus multilocularis , is a rare and aggressive parasitic disease1. Over 95% of cases involve the liver, with primary extrahepatic AE being exceptionally uncommon2. Here, we present a rare case of primary renal AE in a 67-year-old asymptomatic Moroccan man.

The lesion was incidentally detected on thoraco-abdomino-pelvic computed tomography (CT). Abdominal CT revealed a calcified cystic mass in the right kidney, associated with renal atrophy (Figure 1). The liver and other abdominal organs showed no signs of lesions (Figure 2). Serology using an indirect hemagglutination test forE. granulosus yielded a negative result. However, an Anti-Echinococcus EUROLINE-Western Blot IgG assay tested positive for antibodies against theE. multilocularis-specific antigen Em95 (Figure 3), confirming the diagnosis of AE.

FIGURE 1:Abdominal tomography showing a calcified cyst in the right kidney with atrophy.

FIGURE 2:Abdominal tomography showing the liver without cystic or solid lesions.

FIGURE 3:Western blot analysis showing the presence of antibodies against *E. multilocularis-*specific antigen Em95.

To our knowledge, this represents the first case of primary renal AE reported in Morocco and the second described worldwide3. Isolated renal AE is a clinical mimic that can easily be misdiagnosed as a renal tumor based solely on imaging4. Maintaining a high index of suspicion is essential in non-endemic regions and cases with atypical presentations. Specific immunoblotting is a valuable noninvasive tool for distinguishing AE from other cystic renal lesions and for guiding appropriate management, which typically involves a combination of surgery and long-term albendazole therapy4.