Pseudoparasitic Liesegang structures in perirenal hemorrhagic cysts.

Periodic structures with equally spaced radial striations identified as Liesegang-like rings were seen in two male patients' hemorrhagic perirenal cysts. The patients, one 48 and the other 60 years old, had acute right-flank pain and anemia; both had nephrectomy. The rings, initially believed to represent parasites (Dioctophyma renale), were from 8 to 500 micron in diameter and had uniform, pink-tan, radially striated double walls. Multiple small rings within a larger ring predominated in one case. Morphologically, the rings differed from D. renale when compared with specimens from animals infected naturally or experimentally with the giant kidney worm. Histochemical and immunoperoxidase tests for iron, calcium, mucopolysaccharides, amyloid, keratin, and hemoglobin had negative results. Energy-dispersive x-ray elemental analysis demonstrated no detectable elements; ultrastructurally, however, the rings displayed a fine fibrillary composition with a concentric and radial pattern. These rings are believed to be an end product of a phenomenon resembling or are, in fact, the Liesegang phenomenon. Because these Liesegang-like structures may be mistaken for parasites on fine-needle aspiration or surgical specimens of hemorrhagic areas, pathologists should be aware of them.