Amoebic liver abscess other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]

Overview

Other Diagnostic Tests

Needle aspiration

  • Needle aspiration is used to differentiate between amoebic and pyogenic liver abscess
  • The ultrasound and CT are used to guide percutaneous aspiration and drainage.
  • The aspirated fluid is odorless unless secondarily infected
  • The pathognomonic of the aspirate is the reddish-brown anchovy paste appearance, which indicates that the abscess has been present for weeks.
  • The trophozoites are present only in the wall of the abscess. Rest of abscess is composed of lysed leukocytes.
Laboratory Method Findings
Microscopy
  • Microscopic techniques include 1. Wet preparation 2. Concentration 3. Permanently stained smears[1]
  • Less reliable method than culture or antigen detection test[2][3]
  • Minimum three stool samples are examined for ova and parasites within 10days of sample collection as organisms are excreted intermittently[4]
  • Presence of RBCs in trophozoites is diagnostic of Entamoeba histolytica
  • The specificity of the test is low as the trophozoites containing RBCs are not present in all cases and E dispar may also contain RBCs in trophozoites[5][6]
Wet (Saline) preparation
  • Very insensitive method (<10%) Procedure
  • The sample is a fresh specimen that should be examined within 1 hr of collection
  • The test is positive when RBCs in trophozoites are detected
  • It is not used in patients without acute dysentery as trophozoites will not contain RBCs
 Concentration Technique
  • It is helpful in detecting cysts in the stool sample in asymptomatic carriers
 Permanently stained smears
  • This is an important method for identification and recovery of Entamoeba species
Culture Methods
  • The specimens for the culture of E histolytica include fecal specimens, rectal biopsy specimens or liver abscess aspirates.
  • There are two culture techniques. They are xenic and axenic systems.[7]
  • Culture of E histolytica is less sensitive than microscopy as a detection method.
  • Parasite cultures are expensive, labor intensive and difficult to maintain in the diagnostic laboratory.
  • Culture is not recommended as the routine diagnostic test due to overgrowth of other organisms like bacteria and fungi in the culture media.
Isoenzyme analysis
Antibody Detection Tests
Antigen Detection Tests
Immunochromatographic Assays

DNA-Based Diagnostic Tests

Laboratory Methods Findings
Manual Methods
Automated Methods
Conventional PCR
Real-Time PCR
Microarray Development
Typing Methods

References

  1. ↑ Huston CD, Haque R, Petri WA (1999). "Molecular-based diagnosis of Entamoeba histolytica infection". Expert Rev Mol Med. 1999: 1–11. doi:doi:10.1017/S1462399499000599 Check |doi= value (help). PMID 14987356.
  2. ↑ Tanyuksel M, Petri WA (2003). "Laboratory diagnosis of amebiasis". Clin Microbiol Rev. 16 (4): 713–29. PMC 207118. PMID 14557296.
  3. ↑ Krogstad DJ, Spencer HC, Healy GR, Gleason NN, Sexton DJ, Herron CA (1978). "Amebiasis: epidemiologic studies in the United States, 1971-1974". Ann Intern Med. 88 (1): 89–97. PMID 619763.
  4. ↑ Li E, Stanley SL (1996). "Protozoa. Amebiasis". Gastroenterol Clin North Am. 25 (3): 471–92. PMID 8863036.
  5. ↑ González-Ruiz A, Haque R, Aguirre A, Castañón G, Hall A, Guhl F; et al. (1994). "Value of microscopy in the diagnosis of dysentery associated with invasive Entamoeba histolytica". J Clin Pathol. 47 (3): 236–9. PMC 501902. PMID 8163695.
  6. ↑ Strachan WD, Chiodini PL, Spice WM, Moody AH, Ackers JP (1988). "Immunological differentiation of pathogenic and non-pathogenic isolates of Entamoeba histolytica". Lancet. 1 (8585): 561–3. PMID 2894495.
  7. ↑ Clark CG, Diamond LS (2002). "Methods for cultivation of luminal parasitic protists of clinical importance". Clin Microbiol Rev. 15 (3): 329–41. PMC 118080. PMID 12097242.
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