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Background: The liver possesses remarkable regenerative abilities following parenchymal injury. This study aimed to assess and document the microscopic regenerative changes in the rat liver using a partial hepatectomy model.

Methodology: Adult male Sprague Dawley rats weighing approximately 200-300 grams were subjected to partial hepatectomy, leaving approximately 70% future liver remnant. The rats were euthanized at designated time intervals (1/2 hour, 48 hours, 72 hours, 7 days, 11 days, and 14 days) for histological analysis of the liver.

Results: Liver regeneration was observed within 1 week of partial hepatectomy. Cytoplasmic vacuolization increased until day 7, but decreased significantly during the regenerative process. Disruption of cytoplasmic membranes and blurring of cell-to-cell and cell-to-sinusoidal space boundaries decreased notably from day 11. Necrosis involving central veins and portal tracts was observed on the first day after hepatectomy. By day 7, the portal tract exhibited granulomatous inflammation with conglomerates of epithelioid macrophages forming giant cells. The sinusoidal spaces displayed increased lymphocyte volume on day 7. Patchy portal inflammation consisting of lymphocytes, plasma cells, occasional eosinophils, and monocytes was observed from day 7 post-hepatectomy.

Conclusion: In this partial hepatectomy animal model, the inflammatory cascade was evident through confluent necrosis affecting approximately 10% of the hepatic parenchyma, along with subcapsular infarction. Cytoplasmic vacuolization affected approximately 50% of the cells. The study documented various histological changes during the post-hepatectomy period, demonstrating the initiation of hepatocyte regeneration within one week.