Schistosomiasis (urinary tract manifestations)
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Bladder schistosomiasis, also known as bilharzia of the bladder, is an infection by the Schistosoma flukeworm and is a major health problem in developing parts of the world predisposing individuals to bladder squamous cell carcinoma.
Schistosomiasis is very common, affecting over 200 million people, with the vast majority (85%) in Africa. It is prevalent in tropical and subtropical areas, especially in rural regions 2,3.
There are five species of the blood fluke (trematode worm) Schistosoma species that cause disease in humans 3:
- Schistosoma haematobium
- S. mansoni
- S. japononicum
- S. intercalatum
- S. mekongi
Larvae are released from snails (intermediate host) into water and penetrate human skin (definitive host) exposed to the infected water. These larvae travel to the lungs and liver of the human host, where they reside until they mature.
After maturation, the adult worm pairs travel to the pelvic veins. Eggs are deposited in the bladder wall vessels and incite a granulomatous response that results in polypoid lesions. The eggs may go on to incite a chronic inflammatory response and fibrosis, which is an important predisposing factor for squamous cell carcinoma (SCC).
Imaging findings mirror the pathologic course.
In the acute phase, nodular bladder wall thickening is observed at urography or cross-sectional imaging.
The chronic phase is characterized by a contracted, fibrotic, thick-walled bladder with calcifications. These calcifications are typically curvilinear and represent the large numbers of calcified eggs within the bladder wall. A mass may be secondary to inflammation or complicating carcinoma, typically SCC.
Theses calcifications may extend to the ureters.