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Scintigraphy: hepatic for PSS

ISSN 2398-2942


Introduction

  • Use of radionucleotide allows some assessment of function and structure of organ.
  • 99MTc (technetium) is rapidly absorbed through the colonic mucosa → portal blood stream (<15% of original dose is absorbed).
  • Absorbed Tc is unaffected in liver or heart and in normal animal radioactivity appears in liver within 8-10 sec after administration of radionucleotide.
  • A 6-12 sec delay should occur before radioactivity is seen in the heart depending on the circulation time, ie patient size.
  • Used commonly in human medicine.

Uses

  • Assessing portosystemic shunts Congenital portosystemic shunt (CPSS) :
    • Investigation of suspected portosystemic shunt.
    • Assessing shunt magnitude.
    • Evaluating efficacy of surgical ligation of shunt.

Advantages

  • Non-invasive.
  • Quantifies magnitude of shunt flow.

Disadvantages

  • Cost.
  • Limited availability.
  • Radiation hazard (minimal).
  • May not identify location of shunt.
  • Requires patient to be isolated for a period after injection of radionucleotide.

Alternative techniques

  • Alternative techniques for evaluating portosystemic shunt:
    • Ultrasonographic examination of shunt Ultrasonography: liver.
    • Portovenography for radiological assessment.
    • Biochemical assessment of shunt.
  • Splenic vein injection of radionucleotide:
    • Anesthetized patient placed in right lateral recumbency and needle introduced into splenic vein using ultrasonographic guidance.
    • Inject 300-600 ul Tc macroaggregate and take one image of liver.
    • Inject same volume into cephalic vein and take 10 minute count of liver and lungs.
    • Shunt index = CPM lungs/(CPM lungs + liver).
    • In normal dogs MAA trapped in liver so shunt index is close to 0.
    • In PSS shunt index 0.69-1.00.

Time required

Preparation

  • 30 minutes to administer enema and adequately prepare patient.

Procedure

  • A few minutes to perform study.
  • Additional time to analyze data.

Decision taking

Criteria for choosing test

  • Is the examination appropriate?
  • Can you make the diagnosis without it?
  • Will your management of the case be affected by the outcome of the examination?

Requirements

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Preparation

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Technique

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Aftercare

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Meyer H P, Rothuizen J, van den Brom W E et al (1994) Quantitation of portosystemic shunting in dogs by ultrasound-guided injection of 99MTc-macroaggregates into a splenic vein. Res Vet Sci 57 (1), 58-62 PubMed.
  • Van Vechten B J, Komtebedde J & Koblik P D (1994) Use of transcolonic portal scintigraphy to monitor blood flow and progressive post-operative attenuation of partially ligated single extrahepatic portosystemic shunts in dogs. JAVMA 204 (11), 1770-1774 PubMed.