Sunday, May 18, 2014

Answer to Case 304

Answer:  Rotifer

Thank you to everyone who wrote in with suggested diagnoses for this case.  Rotifers are microscopic animals found in fresh water sources worldwide including  ponds, bird baths, and rain gutters.  There are also a few species that live in saltwater.  When alive, rotifers have a corona with cilia that sweep food into the found.

In this particular case, the fixative used in the cytology preparation has likely caused the corona to retract so that it is not clearly visible. The rotifers are clearly a contaminate here - either of the original urine specimen (most likely) or in the reagents used for staining. Unless these little guys start showing up in multiple other cytology specimens in this laboratory, then this is probably a one-time contamination and nothing for the lab to worry about.  I would simply recommend examining the procedure for collecting urine specimens to make sure that the instructions clearly state to avoid contamination with toilet water (the likely source of the rotifers).

Some readers suggested that this was a cyclops - a similar appearing organism (crustacean) found in freshwater sources.  It can be differentiated from rotifers by the presence of 2 antennae. Copepods are important as an intermediate host for certain human-infecting parasites such as Dracuncula medinensis, Gnathostoma spp., Diphyllobothrium latum and Spirometra spp.  Interestingly, my very first Case of the Week featured a cyclops containing Dracuncula medinensis larvae! The answer to this case is HERE.

If you are interested in reading more about critters you can find in pond water, you may want to check out Microbus which has nice line drawings of many common microscopic organisms.

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