Ascariasis laboratory tests: Difference between revisions
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==Laboratory Findings == | ==Laboratory Findings == | ||
The diagnosis of ascariasis can be done via the following methods:<ref name="Principles and Practice">Durand, Marlene (2015). "Chapter 288:Intestinal Nematodes (Roundworms)". Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases Updated Edition, Eighth Edition. Elsevier. pp. 3199–3207. ISBN 978-1-4557-4801-3.</ref><ref name="Ferri's Clinical Advisor">Ferri, Fred (2017). "Chapter:Ascariasis". Ferri's Clinical Advisor 2017. Elsevier. pp. 117–117. ISBN 978-0-3232-8048-8.</ref> | The diagnosis of ascariasis can be done via the following methods:<ref name="Principles and Practice">Durand, Marlene (2015). "Chapter 288:Intestinal Nematodes (Roundworms)". Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases Updated Edition, Eighth Edition. Elsevier. pp. 3199–3207. ISBN 978-1-4557-4801-3.</ref><ref name="Ferri's Clinical Advisor">Ferri, Fred (2017). "Chapter:Ascariasis". Ferri's Clinical Advisor 2017. Elsevier. pp. 117–117. ISBN 978-0-3232-8048-8.</ref> | ||
* Microscopic identification of eggs in the stool is the common method for diagnosing ascariasis and simple smears are often adequate because of the high output of eggs produced daily by gravid female worms. Stool concentration procedures such as Kato-Katz thick smear or formalin-ethyl acetate sedimentation can also be done | * Microscopic identification of eggs in the stool is the common method for diagnosing ascariasis and simple smears are often adequate because of the high output of eggs produced daily by gravid female worms. Stool concentration procedures such as Kato-Katz thick smear or formalin-ethyl acetate sedimentation can also be done. Ascaris larvae can also be found in sputum or gastric aspirates during pulmonary migration, before eggs are present in feces. | ||
* Adult worms are occasionally passed in the stool or through the mouth or nose and are easily recognizable by their macroscopic characteristics. | * Adult worms are occasionally passed in the stool or through the mouth or nose and are easily recognizable by their macroscopic characteristics. | ||
===Macroscopic Findings=== | ===Macroscopic Findings=== | ||
Revision as of 16:05, 2 March 2017
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Imtiaz Ahmed Wani, M.B.B.S
Overview
Laboratory Findings
The diagnosis of ascariasis can be done via the following methods:[1][2]
- Microscopic identification of eggs in the stool is the common method for diagnosing ascariasis and simple smears are often adequate because of the high output of eggs produced daily by gravid female worms. Stool concentration procedures such as Kato-Katz thick smear or formalin-ethyl acetate sedimentation can also be done. Ascaris larvae can also be found in sputum or gastric aspirates during pulmonary migration, before eggs are present in feces.
- Adult worms are occasionally passed in the stool or through the mouth or nose and are easily recognizable by their macroscopic characteristics.
Macroscopic Findings
(Images courtesy of Dr. Imtiaz Ahmed Wani)
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Enterotomy for worm removal -
Ascaris lumbricoides caused gangrene of ileum (shown worms removed from a child)
Microscopic Findings
Below are several Ascaris eggs seen in wet mounts. Diagnostic characteristics:
Fertilized eggs (A, B on the right, D, F, G, H) are rounded, have a thick shell, with an external mammillated layer that is often stained brown by bile. In some cases, the outer layer is absent (decorticated eggs:E, F on the right, G). Size: approximately 60 µm in diameter when spherical, and up to 75 µm when ovoid.
Unfertilized eggs (B on the left, C, E) are elongated and larger (up to 90 µm in length); their shell is thinner; and their mammillated layer is more variable, either with large protuberances (C) or practically none (E); these eggs contain mainly a mass of refractile granules.
A: Fertilized Ascaris egg, still at the unicellular stage. Eggs are normally at this stage when passed in the stool. Complete development of the larva requires 18 days under favorable conditions.
B: Unfertilized and fertilized eggs (left and right, respectively).
C: Unfertilized egg. Prominent mammillations of outer layer.
D: Fertilized egg. The embryo can be distinguished inside the egg.
E: Unfertilized egg with no outer mammillated layer (decorticated).
F: Three fertilized eggs (one decorticated, on the right) of Ascaris lumbricoides.
G, H: Two fertilized eggs from the same patient, where embryos have begun to develop (this happens when the stool sample is not processed for several days without refrigeration). The embryos in early stage of division (4 to 6 cells) can be clearly seen. Note that the egg in G has a very thin mammillated outer layer.
I: Egg containing a larva, which will be infective if ingested.
J: Larva hatching from an egg.
References
- ↑ Durand, Marlene (2015). "Chapter 288:Intestinal Nematodes (Roundworms)". Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases Updated Edition, Eighth Edition. Elsevier. pp. 3199–3207. ISBN 978-1-4557-4801-3.
- ↑ Ferri, Fred (2017). "Chapter:Ascariasis". Ferri's Clinical Advisor 2017. Elsevier. pp. 117–117. ISBN 978-0-3232-8048-8.