This week's case was generously donated by Dr. José Poloni. The following was found in a stool specimen. Identification? Significance?
(you may need to click twice on the video below to play)
This week's case was generously donated by Dr. Neil Anderson. The following structure was retrieved from the common bile duct during endoscopic retrograde cholangiopancreatography (ERCP). The patient is a refugee from Tanzania who presented with intermittent abdominal pain, distended gallbladder and hepatosplenomegaly. This was one of many "worm like" structures noted on ERCP. Unfortunately this object appeared to tear during removal. The portion submitted measures several centimeters in length. No identifying external structures were identified.
Dr. Anderson's team tried to express eggs from this structure but was unsuccessful. In an effort to learn more about the nature of this object, a portion of it was submitted for histopathologic processing. Representative sections revealed the following:
What is the most likely identification?
Answer to Parasite Case of the Week 633: Fasciola hepatica
Although the fluke was sadly torn in half during retrieval, it has all of the features that allows us to identify it:
As a trematode - it has the flat, leaf-like body shape of a platyhelminth belonging to the Trematoda phylum. On histopathologic examination, trematodes have an outer tegument (with microvillus border, and often with spines), spongy parenchyma with no large cavities, and a digestive tract. Cestodes have a similar appearance, but may have a large cavity (depending on the species and stage), do NOT have a digestive tract or tegumental spines, and have calcareous corpuscles in the stroma.
I don't believe I see see ovarian tubules in this section, although it is hard to tell from this image alone. I also don't see any eggs. This would make sense as Dr. Anderson was not able to express any eggs from the portion of the fluke that he received in the laboratory.
As Fasciola hepatica specifically - the large size of this structure allows us to identify it as either Fasciola hepatica or F. gigantica. We can further identify this fluke as F. hepatica based on the presence of pointed tegumental spines. F. gigantica, in comparison, has tegumental spines with blunt/flattened ends. Other morphologic features (e.g., overall size of the adult and its eggs, features of the acetabulum) can also be used to differentiate F. hepatica and F. gigantica.
Thanks again to Dr. Anderson for sharing this case with us!