Evaluation of Donor Liver Biopsy for Transplant
*These cases are accessioned and administratively executed in the same manner as a routine frozen.
**The surgpath requisition is required upon receipt along with proper patient and specimen identification labeling.
***Make a copy of the frozen worksheet for the Gift of Hope representative. And make a copy of the Gift of Hope paperwork for our UofC records
****Freeze liver core and wedge biopsies in separate blocks
Who You Gonna Call?
Please contact Dr. Hart first, followed by Dr. Alpert. If neither Liver pathologist is available, then contact the Surg Path Attending on call.
Preparation of the Slides
The biopsy should be blotted dry before rapid freezing to reduce ice crystal artifact. Standard 4-5 micron sections and H&E staining is all that is required. Oil red O stains are not necessary and in fact are often misleading, leading to overestimation of degree of steatosis. Slides should be prepared from ALL samples. Cut and stain 3 slides. Give one slide to the harvesting team to show to their own pathologist at a later date.
Evaluation of the Histology
Macrovesicular Steatosis
The degree of macrovesicular steatosis is estimated by the pathologist as the percentage of hepatocytes throughout the biopsy that contain a large lipid droplet. The percentage should reflect the entire biopsy (not the worst area). Ice crystal artifact can produce uniform medium sized vacuoles within hepatocytes can that resemble large droplet fat vacuoles. One clue to the recognition of this artifact is the uniformity of this change through the biopsy (or a part of the biopsy).
Microvesicular Steatosis
Microvesicular steatosis is quite difficult to recognize on frozen section, and there is no convincing data that indicate that it significantly impacts post-transplant graft function. If the surgeon insists on a percent microvesicular steatosis is is best to record 0%.
Other Donor Biopsy Pathology
The presence of hepatocyte necrosis should be evaluated and reported if present. Centrilobular necrosis may be subtle if it is recent. It causes slight shrinkage and smudginess of hepatocytes with condensation of the cytoplasm and mild nuclear hyperchromasia. It most often occurs as a consequence of hepatic ischemia related to the use of a high dose of pressor agents and/or the development of hypernatremia and other metabolic derangements preceding the development of brain death. At an earlier stage there may be random individual apoptotic hepatocytes (acidophil bodies), but this degree of hepatocyte injury probably won’t cause significant post-transplant graft dysfunction.
A mild degree of portal mononuclear cell infiltration is acceptable, and the cause is generally never learned (donors are screened for HBV and HCV hepatitis). It is possible that chronic intermittent biliary obstruction, celiac disease, or prior resolved episodes of HBV or HCV hepatitis are responsible for these infiltrates in some donor organs. Unexplained heavy portal or lobular inflammatory cell infiltrates should be mentioned to the surgeon and likely will lead to rejection of the organ.
Significant portal and/or centrilobular fibrosis (stage 2 or worse) is generally unacceptable, except for recipients in fulminant hepatic failure. Remember that more abundant portal fibrous tissue is expected in the portal tracts that are quite close to the hepatic capsule.
Lobular inflation is generally not a contraindication to transplant unless it is quite florid or if an actual abscess is present. Scattered neutrophils in the sinusoids generally represents so-called “surgical hepatitis” and is not a pathologic process that prevents use of the donor organ.
Mass Lesions in Donor Organs
On rare occasions small mass lesions may be identified by the transplant surgeon at the time or organ harvest. Bile duct hamartomas (von Meyenberg complexes) even if numerous, are not a contraindication to the use of an organ. Likewise, bile duct adenomas are regarded as completely benign lesions that pose no risk to the recipient. These two lesions are often recognized by the surgeon as small well circumscribed subcapsular nodules are often ignored. Walled off hyalinized granulomas are also regarded as innocuous lesions, but the presence of caseating or necrotizing granulomas should probably lead to rejection of the donor organ. Small cavernous hemangiomas are common incidental findings (approximately 1% of livers at autopsy) and are usually easily recognized by both surgeons and surgical pathologists.
The presence of focal nodular hyperplasia is also not a contraindication to the use of a donor organ, as these lesions have no malignant potential. Small lesions often do not exhibit a central scar with an obvious abnormal vessel, so the diagnosis rests upon recognition of the “focal cirrhosis” pattern of fibrous septa containing proliferating bile ductules. Although not well studied, organs containing hepatic adenomas have also been utilized after complete excision of the mass. Naturally, confident exclusion of a well differentiated hepatocellular carcinoma must be assured, and this can be problematic by frozen section examination. Thus, many of these organs end up not be used.
The Bottom Line
- There is no universally accepted threshold for the degree of macrovesicular steatosis that makes a cadaveric donor organ unusable.
- Microvesicular steatosis cannot be reliably recognized in routine frozen sections and there is no convincing data to suggest that it’s presence adversely affects donor organ function.
- Other histologic features that should be assessed include the degree of hepatocyte necrosis and fibrosis.
- The presence of mild non-specific chronic portal inflammation is acceptable for transplantation.
References
Donor Biopsy Evaluation
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Macrovesicular Steatosis in Donor Liver Biopsies
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Microvesicular Steatosis in Donor Biopsies
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- Andert A et al. Grade of donor liver microvesicular steatosis does not affect the postoperative outcome after liver transplantation. Hepatobiliary Pancreat Dis Int 2017;16:617-23.
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