Answer to Case 201

Answer:  Schistosoma hematobium (haematobium) egg.

This egg has the characteristic terminal spine and is usually found in urine or bladder wall biopsies.  I've also seen an extensive case involving the ureters, renal pelvis of the kidneys, and the appendix (so eggs could potentially be found in stool as well).  Eggs of S. hematobium  are large, measuring 112-170 micrometers in length.

Of note, the eggs of less common species, S. intercalatum, are similar in appearance, but are larger (140-240 micrometers) in length, have a slightly longer, slightly curved terminal spine, and often have a prominent bulge in the middle of the egg (equatorial bulge). They are found in stool and not urine.