Liver: Evaluation of Allograft Prior to Transplantation



Liver: Evaluation of Allograft Prior to Transplantation










Each component of the liver parenchyma is evaluated systematically: Portal tracts with duct image, artery and vein, portal-lobular interface image, hepatocytes image, and sinusoids image.






Degree of inflammation image in portal tracts may be overestimated and the portal-lobular interface may appear blurred image on frozen sections, which are usually thicker than standard paraffin sections.


SURGICAL/CLINICAL CONSIDERATIONS


Goal of Consultation



  • Evaluation of a donor liver prior to transplantation


Change in Patient Management



  • Pathologic findings are used to decide whether or not liver is suitable for transplantation



    • Unlike kidney transplantation, there is no alternative should the allograft fail


    • Livers with a high risk of allograft failure will not be used for transplantation


Clinical Setting



  • There is a shortage of donor livers available for transplantation


  • Criteria for acceptance have been expanded to include organs at a greater risk of reduced function or graft failure


  • The following features are no longer used to exclude a liver from consideration



    • Age (> 60 years), viral hepatitis, steatosis, alcohol abuse, acute infection, hypotension, hypoxemia, cardiovascular disease, chronic renal failure


  • Histologic evaluation of liver is helpful to predict organs at greatest risk



    • Degree of macrovesicular steatosis is most useful criteria for accepting or rejecting a graft


SPECIMEN EVALUATION


Gross



  • Either a wedge biopsy (≥ 1.5 cm²) or a cutting needle biopsy (≥ 2 cm in length) from anterior-inferior edge of kidney is performed



    • If a gross mass lesion is present, separate biopsy of noninvolved liver also should be evaluated


    • Needle biopsy is preferred for evaluating fibrosis



      • Subcapsular liver sampled in wedge biopsy often has thick trabeculae that may be mistaken for advanced fibrosis


  • Biopsy should be processed as quickly as possible



    • Fat is diminished after even a few minutes of exposure to air


    • Saline can cause distortion (chromatin clumping and edema of extracellular spaces)


Frozen Section



  • Tissue should be gently blotted dry to reduce ice crystal artifact


  • Representative slides should be retained by recipient institution to aid in evaluating graft after transplantation


FEATURES TO BE EVALUATED


Macrovesicular Steatosis



  • Single, dominant, lipid vacuole displacing nucleus to periphery of cell


  • Usually centrilobular


  • Severity is graded



    • Mild: < 30% of hepatocytes


    • Moderate: 30-60% of hepatocytes



      • Increased risk of complications


      • Liver may be accepted for transplant in some settings


    • Severe: > 60% of hepatocytes



      • Absolute contraindication for transplantation due to high risk of graft malfunction


Microvesicular Steatosis



  • Numerous small lipid droplets that do not cause displacement of nucleus to periphery of cell



    • Nucleus is located in center of cell


  • Graded in same manner as macrovesicular steatosis


  • Minimal effect on graft function



    • Common finding


Fibrosis



  • Portal and periportal fibrosis may be difficult to evaluate on frozen sections


  • Bridging fibrosis is easily detected



  • Nodularity of liver and bridging fibrosis are indicative of cirrhosis and are a contraindication to transplantation


Necrosis



  • Apoptotic hepatocytes (acidophil bodies)


  • Centrilobular necrosis


  • Reported as



    • Focal (< 10%) or extensive (≥ 10%)


    • Mild or severe


Mass Lesions



  • Benign lesions are not a contraindication for transplantation



    • Biopsy away from mass should also be evaluated


  • Carcinoma



    • Detection of tumor cells is absolute contraindication for transplantation


Portal Inflammation



  • Mild chronic inflammation of portal triad is common in hospitalized patients; not a contraindication


  • Severe lymphoplasmacytic portal infiltrate with interface hepatitis (piecemeal necrosis) should raise possibility of viral hepatitis


  • Reported as mild, moderate/severe


Iron Deposition



  • Hepatocellular siderosis



    • Coarse, dark brown granular pigment in periportal hepatocytes; graded semiquantitatively 1-4+


    • Grades > 2 may be contraindication for transplantation



      • Organs from patients with hereditary hemochromatosis or secondary iron overload can be used if fibrosis is not advanced


  • Kupffer cell siderosis



    • Common finding; typically mild, cannot be detected easily on frozen section


Other Pigments



  • Lipofuscin (very fine brown granules in centrilobular hepatocytes)


  • Bile (green to gold/brown granules) in perivenular hepatocytes or within canaliculi


Granulomas



  • Nonnecrotizing fibrotic granulomas may be residue of prior infection (e.g., histoplasmosis); not contraindication to transplant


  • Necrotizing granulomas may indicate current infection and lead to rejection of organ for transplant


Congestion



  • Dilated sinusoids alone are a nonspecific finding


  • Atrophy of perivenular hepatocytes and sinusoidal dilatation often consequence of terminal ischemic injury


Duct Damage



  • Seen in primary biliary disorders, such as primary biliary cirrhosis and primary sclerosing cholangitis


  • Ductular proliferation is also indirect evidence of duct damage


Thrombi



  • Rarely seen in central or portal veins


REPORTING


Frozen Section



  • Features reported



    • Steatosis: Presence or absence and percent of hepatocytes affected



      • Minimal or mild (up to 30% of hepatocytes) may be acceptable for transplantation


      • Severe (> 60%) is associated with a nonfunctioning graft


    • Extent of inflammation &/or hepatocyte necrosis



      • Mild focal necrosis may occur during harvesting of organ


      • Severe or extensive necrosis is associated with graft failure


    • Fibrosis: Presence or absence


    • Alcohol-induced injury: Associated with compromise of graft weeks to years after transplantation



      • Fibrosis


      • Moderate to severe fatty change


      • Marked hepatocytic necrosis with or without cholestasis


      • Mallory hyaline/ballooning degeneration


  • Biopsies consisting entirely or predominantly of capsule are inadequate for evaluation



    • Additional biopsy should be requested


PITFALLS


Superficial Biopsy

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Liver: Evaluation of Allograft Prior to Transplantation

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