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[Dioctophyme renale]

Dioctophyme renale is known as the giant kidney worm, and parasitizes a wide range of primarily fish-eating carnivorous mammals (including mustelids).  As humans are not the usual definitive host for D. renale, the parasite does not usually present the way it would in its natural definitive hosts.  Although there have been a few cases in humans with kidney involvement, often the larvae wind up in subcutaneous nodules and do not develop any further.

A	B

A, B: Cross-sections of larvae of D. renale in a subcutaneous nodule, stained with hematoxylin and eosin (H&E).  Images courtesy of the Laboratory of Parasitology, National Public Health Research Center in Vilnius, Lithuania.

C	D

C, D: Higher-magnification of the specimens shown in Figures A and B, showing a close-up of the characteristic intestine, with cuboidal, uninucleate cells, pigment, and microvilli.

E	F

E: Higher-magnification of the specimens shown in Figures A-D.  Shown in this image are the tall, polymyarian muscle cells, the characteristic ventral chord with a U-shaped row of nuclei (black arrow), and three pseudocoelomic membranes (red arrows).
F: Close-up of Figure A, showing the ventral chord (black-arrow).