Hepatic Tumors and Hepatic Lobectomy

Hepatic tumors encompass a diverse group of benign and malignant neoplasms originating from hepatocytes, biliary epithelium, mesenchymal tissues, or metastatic deposits within the liver parenchyma. Hepatic lobectomy is the surgical resection of one or more liver lobes, performed as a curative or palliative treatment for localized hepatic neoplasia, trauma, or other focal lesions. The liver's unique dual blood supply (hepatic artery and portal vein), its remarkable regenerative capacity, and its complex biliary system demand precise surgical technique and thorough preoperative assessment. Surgical approaches include partial lobectomy, complete lobectomy, and liver lobectomy with vascular stapling devices, each tailored to the tumor's location and extent. The procedure requires meticulous hemostasis, management of biliary leakage, and preservation of adequate functional liver mass to prevent postoperative hepatic insufficiency. Hepatic tumors are classified histogenetically into primary hepatocellular tumors (hepatocellular adenoma, hepatocellular carcinoma), biliary tumors (bile duct adenoma, cholangiocarcinoma), mesenchymal tumors (hemangiosarcoma, leiomyosarcoma, fibrosarcoma), and neuroendocrine tumors. Metastatic tumors, particularly from splenic hemangiosarcoma, mammary carcinoma, and pancreatic insulinoma, are also common. Surgical resection remains the mainstay of treatment for solitary lesions, with adjunctive therapies such as chemotherapy and transarterial chemoembolization reserved for non-resectable or metastatic disease.

The etiology of hepatic tumors is multifactorial, involving genetic mutations, environmental carcinogens, and chronic inflammatory conditions. In dogs and cats, specific risk factors include exposure to aflatoxins (produced by Aspergillus species) which are potent hepatocarcinogens, chronic hepatitis leading to cirrhosis and hepatocellular carcinoma, and infection with certain viruses (e.g., feline leukemia virus in cats). Primary hepatocellular tumors arise from hepatocytes and are often associated with chronic liver injury, such as that caused by hepatitis B virus in humans, but in veterinary patients, the exact triggers are less defined. Biliary tumors, including cholangiocarcinoma, may develop secondary to chronic cholangitis, liver fluke infestation (Opisthorchis species in endemic areas), or bile stasis. Mesenchymal tumors like hemangiosarcoma have a high incidence in certain breeds (e.g., German Shepherd Dogs) and are linked to genetic predisposition and possibly environmental toxins. Metastatic hepatic tumors result from hematogenous spread of malignant cells from primary sites such as the spleen, pancreas, mammary glands, and intestines. Iatrogenic causes are rare but include prior radiation therapy or immunosuppressive therapy. Additionally, congenital or developmental anomalies, such as portosystemic shunts, may predispose to hepatic neoplasia due to altered blood flow and metabolic derangements. The molecular pathogenesis involves dysregulation of oncogenes (e.g., c-myc, ras) and tumor suppressor genes (e.g., p53), leading to uncontrolled cell proliferation, angiogenesis, and invasion.

Hepatic tumors account for approximately 0.6% to 1.3% of all neoplasms in dogs and cats. Primary hepatic tumors are relatively uncommon, with hepatocellular tumors being the most frequent, representing about 50% of primary hepatic neoplasms in dogs. Bile duct tumors are the second most common, followed by mesenchymal tumors. In cats, biliary tumors are more prevalent than hepatocellular tumors. The median age at diagnosis is 10 to 12 years for dogs and 12 to 14 years for cats, indicating a strong age predisposition. No significant sex predilection is consistently reported, though some studies suggest a slight male predominance for hepatocellular carcinoma. Breed predispositions include Labrador Retrievers, Golden Retrievers, and German Shepherd Dogs for hepatocellular tumors; hemangiosarcoma is more common in German Shepherd Dogs and Golden Retrievers. Mixed-breed dogs are also frequently affected. Metastatic hepatic tumors are more common than primary tumors, with splenic hemangiosarcoma being the most frequent source. The incidence of hepatic tumors appears to be increasing, possibly due to improved diagnostic imaging and longer lifespan of pets. In cats, cholangiocarcinoma is often associated with chronic cholangiohepatitis, and Siamese cats may have a higher risk. Overall, hepatic tumors are a significant cause of morbidity and mortality in geriatric small animals.

The pathophysiology of hepatic tumors involves complex interactions between neoplastic cells and the hepatic microenvironment. Hepatocellular carcinoma arises from hepatocytes and often develops in a background of chronic liver disease, such as cirrhosis or chronic hepatitis, where repeated cycles of necrosis and regeneration increase the risk of genetic mutations. These tumors are highly vascular, deriving blood supply predominantly from the hepatic artery, which contrasts with normal hepatocytes that receive blood from the portal vein. This arterialization contributes to tumor growth and metastasis. Biliary tumors, including cholangiocarcinoma, originate from biliary epithelial cells and often exhibit desmoplastic stroma, making them firm and infiltrative. They can obstruct bile ducts, leading to cholestasis, jaundice, and secondary biliary cirrhosis. Mesenchymal tumors like hemangiosarcoma are highly malignant, with rapid growth and early hematogenous metastasis, often to the lungs and omentum. The liver's extensive sinusoidal network and high blood flow make it a common site for metastatic seeding. Tumor growth leads to compression of adjacent parenchyma, causing atrophy and fibrosis. As the tumor enlarges, it may outgrow its blood supply, resulting in central necrosis and hemorrhage, which can cause acute abdominal pain and hemoperitoneum. Functional impairment of the liver occurs when a critical mass of parenchyma is replaced by tumor, leading to decreased synthetic function (hypoalbuminemia, coagulopathy), altered metabolism (hypoglycemia, hyperbilirubinemia), and reduced detoxification capacity (hepatic encephalopathy). The regenerative capacity of the liver is remarkable, but extensive resection or diffuse disease can overwhelm this capacity, resulting in acute liver failure. Surgical resection aims to remove the tumor while preserving sufficient functional liver mass, relying on the liver's ability to regenerate from remaining lobes.

Predisposing factors for hepatic tumors include age, breed, sex, and environmental exposures. Advanced age is a significant risk factor, with most tumors occurring in dogs over 10 years and cats over 12 years. Certain breeds, such as Labrador Retrievers, Golden Retrievers, and German Shepherd Dogs, have a higher incidence of hepatocellular carcinoma and hemangiosarcoma. Male dogs may be slightly more predisposed to hepatocellular tumors, while female cats may have a higher risk for biliary tumors. Chronic liver disease, including chronic hepatitis, cirrhosis, and cholangiohepatitis, predisposes to primary hepatic neoplasia due to sustained inflammation and regenerative activity. Exposure to environmental carcinogens, such as aflatoxins in contaminated food, increases the risk of hepatocellular carcinoma. Obesity and diabetes mellitus may also contribute to non-alcoholic fatty liver disease and subsequent neoplasia. Prior chemotherapy or radiation therapy for other cancers can increase the risk of secondary hepatic tumors. Genetic factors, such as mutations in tumor suppressor genes (p53) and oncogenes (c-myc), are implicated. Additionally, portosystemic shunts, which cause abnormal blood flow and metabolic disturbances, may predispose to hepatic neoplasia. In cats, infection with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV) may increase the risk of lymphoma and other tumors, including hepatic involvement. Management factors, such as diet and lifestyle, may influence the development of obesity-related liver disease, but direct links to hepatic tumors are less clear.

Clinical signs of hepatic tumors are often nonspecific and may be absent in early stages. Common signs include lethargy, anorexia, weight loss, vomiting, diarrhea, and abdominal distension. Polyuria and polydipsia may occur due to impaired liver function or hypercalcemia of malignancy. Jaundice (icterus) is seen with biliary obstruction or diffuse hepatic disease. Ascites may develop due to portal hypertension or hypoalbuminemia. In cases of tumor rupture, acute signs of hemoperitoneum, such as pale mucous membranes, tachycardia, weak pulses, and collapse, may be observed. Neurological signs, including hepatic encephalopathy, can occur due to elevated ammonia levels, manifesting as depression, ataxia, seizures, or coma. On physical examination, hepatomegaly is often palpable, especially in the cranial abdomen. A cranial abdominal mass may be detected on palpation. Pain on abdominal palpation is variable. Fever may be present due to tumor necrosis or secondary infection. In cats, clinical signs may be more subtle, with weight loss and lethargy being prominent. Some tumors, such as hepatocellular adenoma, may be incidental findings on imaging or necropsy. The severity of clinical signs correlates with tumor size, location, and degree of hepatic dysfunction. Surgical resection is often considered when clinical signs are attributable to a solitary mass, and the patient is otherwise a good surgical candidate.

Differential diagnoses for hepatic tumors include other hepatic masses, such as nodular hyperplasia, hepatic cysts, abscesses, and granulomas. Nodular hyperplasia is common in older dogs and appears as multiple benign nodules, often incidental. Hepatic cysts are fluid-filled cavities that may be congenital or acquired. Hepatic abscesses are typically caused by bacterial infection, often secondary to ascending biliary infection or hematogenous spread, and present with fever, pain, and leukocytosis. Granulomas due to fungal infections (e.g., histoplasmosis) or foreign bodies can mimic tumors. Other primary hepatic neoplasms, such as lymphoma, mast cell tumor, and histiocytic sarcoma, should be considered. Metastatic disease from other sites, particularly splenic hemangiosarcoma, pancreatic adenocarcinoma, and mammary carcinoma, is common. Non-neoplastic conditions causing hepatomegaly, such as hepatic lipidosis (especially in cats), cholangiohepatitis, and cirrhosis, may also be considered. Additionally, extrahepatic masses, such as pancreatic tumors, adrenal tumors, or splenic masses, can be mistaken for hepatic tumors on imaging. Diagnostic imaging, including ultrasound, CT, and MRI, along with fine-needle aspiration or biopsy, is essential to differentiate these conditions. Surgical exploration may be necessary for definitive diagnosis and treatment.

The diagnostic algorithm for hepatic tumors begins with a thorough history and physical examination, focusing on signalment, clinical signs, and abdominal palpation. Baseline blood work, including complete blood count, serum biochemistry profile, and urinalysis, is performed to assess liver function and detect abnormalities such as elevated liver enzymes (ALT, AST, ALP, GGT), hyperbilirubinemia, hypoalbuminemia, and coagulopathy. Coagulation testing (PT, aPTT, platelet count, and possibly thromboelastography) is crucial due to the liver's role in clotting factor synthesis. Abdominal radiographs may reveal hepatomegaly, a soft tissue mass, or mineralization, but are not specific. Abdominal ultrasound is the next step, allowing evaluation of liver parenchyma, identification of masses, assessment of biliary system, and guidance for fine-needle aspiration or biopsy. Doppler ultrasound can assess vascular invasion. Advanced imaging, such as contrast-enhanced CT or MRI, provides detailed anatomical information, helps determine the extent of disease, and aids in surgical planning, including vascular anatomy and the number of liver lobes involved. CT angiography is particularly useful for evaluating the hepatic vasculature and planning lobectomy. If a mass is identified, fine-needle aspiration cytology can provide a preliminary diagnosis, but histopathology from a core biopsy or surgical biopsy is required for definitive diagnosis. In cases where surgical resection is planned, preoperative staging with thoracic radiographs or CT is performed to rule out pulmonary metastases. Exploratory laparotomy may be both diagnostic and therapeutic, allowing direct visualization, biopsy, and lobectomy if indicated. Intraoperative ultrasound can help identify additional lesions. The diagnostic algorithm should be systematic to avoid unnecessary procedures and to ensure accurate staging.

Laboratory findings in hepatic tumors are variable and may be normal in early cases. Common abnormalities include elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), indicating hepatocellular injury. Alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT) are often elevated due to cholestasis. Hyperbilirubinemia may be present with biliary obstruction or severe hepatic dysfunction. Hypoalbuminemia can occur due to decreased synthetic function. Blood urea nitrogen (BUN) may be decreased due to reduced urea synthesis. Hypoglycemia may be seen in some tumors, particularly hepatocellular carcinoma, due to insulin-like growth factor production or impaired gluconeogenesis. Coagulation abnormalities, such as prolonged PT and aPTT, thrombocytopenia, and decreased antithrombin III, are common due to impaired synthesis of clotting factors and platelet sequestration. Inflammatory leukogram may be present with tumor necrosis or infection. Serum bile acids, both fasting and postprandial, are sensitive indicators of hepatic function and may be elevated. In cats, elevated bilirubin and liver enzymes are common. Urinalysis may reveal bilirubinuria, which is abnormal in dogs. Specific tumor markers, such as alpha-fetoprotein (AFP) for hepatocellular carcinoma, are not routinely available in veterinary medicine. Cytology of fine-needle aspirates may show neoplastic cells, but histopathology is definitive. In cases of hemangiosarcoma, anemia and schistocytes may be present due to microangiopathic hemolysis. Coagulation profiles are essential before surgery to guide transfusion therapy and intraoperative hemostasis.

Imaging plays a pivotal role in the diagnosis and surgical planning of hepatic tumors. Abdominal radiographs may show hepatomegaly, a soft tissue mass displacing adjacent organs, or mineralization within the tumor. However, radiographs are insensitive for detecting focal hepatic lesions. Abdominal ultrasound is the primary imaging modality, allowing visualization of the liver parenchyma, identification of masses (which may appear hypoechoic, hyperechoic, or mixed), and assessment of the biliary system. Ultrasound can detect dilation of bile ducts, gallbladder abnormalities, and vascular invasion. Doppler ultrasound can evaluate blood flow within the tumor and major vessels. Ultrasound-guided fine-needle aspiration or biopsy is often performed for cytological or histological diagnosis. Contrast-enhanced ultrasound can characterize tumor vascularity. Computed tomography (CT) provides superior anatomical detail and is invaluable for surgical planning. Triple-phase CT angiography (arterial, portal venous, and delayed phases) allows assessment of the hepatic arterial and portal venous supply, identification of the tumor's vascular pedicle, and determination of the number of liver lobes involved. CT is also useful for detecting extrahepatic metastases, particularly in the lungs. Magnetic resonance imaging (MRI) offers excellent soft tissue contrast and is useful for characterizing lesions, but is less commonly used due to cost and availability. Intraoperative ultrasound can be used to identify lesions not visible on the surface and to guide surgical resection. In cases of suspected metastatic disease, thoracic radiographs or CT are essential. Advanced imaging modalities, such as positron emission tomography (PET) combined with CT, are emerging but not widely available in veterinary practice. Imaging findings guide the surgeon in deciding whether a lobectomy is feasible and which approach to use.

Cytology and histopathology are essential for definitive diagnosis of hepatic tumors. Fine-needle aspiration (FNA) cytology can be performed percutaneously under ultrasound guidance or intraoperatively. Cytological features of hepatocellular carcinoma include large polygonal cells with abundant eosinophilic cytoplasm, round nuclei, prominent nucleoli, and variable anisocytosis and anisokaryosis. Bile duct carcinoma cells are often cuboidal to columnar, forming acinar structures, with mucin production. Hemangiosarcoma cells are spindle-shaped with marked atypia, and the aspirate may be bloody. However, cytology has limitations, including sampling error and difficulty distinguishing benign from malignant lesions. Histopathology from a core biopsy or surgical excision is the gold standard. Biopsy samples should be obtained from the tumor margin and surrounding parenchyma. Histological features of hepatocellular adenoma include well-differentiated hepatocytes with no invasion, while hepatocellular carcinoma shows trabecular or acinar patterns, cellular atypia, and vascular invasion. Bile duct adenomas are benign, while cholangiocarcinomas exhibit desmoplasia, infiltrative growth, and perineural invasion. Mesenchymal tumors are diagnosed based on cell morphology and immunohistochemistry (e.g., factor VIII for hemangiosarcoma, smooth muscle actin for leiomyosarcoma). Surgical margins should be evaluated for completeness of resection. Special stains, such as reticulin, can help differentiate benign from malignant hepatocellular lesions. Immunohistochemical markers, including hepatocyte paraffin 1 (Hep Par1), cytokeratin 7 and 19 for biliary origin, and vimentin for mesenchymal origin, are useful. Histopathology also provides prognostic information, such as tumor grade and mitotic index, which correlate with survival.

The treatment of hepatic tumors primarily involves surgical resection, with hepatic lobectomy being the most common procedure. Preoperative stabilization is crucial, including correction of coagulopathies with fresh frozen plasma or vitamin K, management of hypoglycemia with dextrose infusions, and optimization of nutritional status. The choice of surgical technique depends on the tumor's location and size. Partial lobectomy is suitable for peripheral lesions, where a wedge resection is performed using a scalpel, electrocautery, or a surgical stapler. Complete lobectomy is required for large or centrally located tumors. The liver lobes are divided into left lateral, left medial, quadrate, right medial, right lateral, and caudate lobes. The surgical approach is typically a ventral midline celiotomy, extended cranially to the xiphoid. For access to the right liver lobes, a paracostal incision may be added. The liver is mobilized by transecting the falciform ligament and triangular ligaments. The hepatic artery and portal vein branches supplying the affected lobe are identified and ligated. The biliary duct is also ligated. The parenchyma is then transected using a technique that ensures hemostasis and biliary sealing. Options include the finger fracture technique, ultrasonic surgical aspirator (CUSA), bipolar vessel sealing devices (LigaSure), or surgical staplers (e.g., TA stapler with vascular staples). The stapler is particularly useful for rapid and secure lobectomy. Intraoperative complications include hemorrhage, bile leakage, and hypotension. Hemorrhage can be controlled with ligation, electrocautery, or hemostatic agents such as gelatin sponges or fibrin sealants. Bile leakage is managed by careful ligation of biliary radicals and placement of omental patches. Postoperative care includes pain management, intravenous fluids, antibiotics, and monitoring for complications such as hemorrhage, bile peritonitis, and hepatic insufficiency. In cases of non-resectable tumors, palliative options include debulking, chemotherapy (e.g., doxorubicin for hemangiosarcoma), and transarterial chemoembolization. However, surgery offers the best chance for long-term survival in dogs and cats with solitary hepatic tumors.

The prognosis for hepatic tumors depends on the tumor type, stage, and completeness of surgical resection. For benign tumors, such as hepatocellular adenoma, surgical resection is curative, and the prognosis is excellent. For hepatocellular carcinoma, the prognosis is good if complete resection is achieved, with median survival times of 1 to 3 years in dogs. Factors associated with a worse prognosis include large tumor size, vascular invasion, metastasis, and incomplete margins. Bile duct carcinoma has a poorer prognosis due to its aggressive nature and high metastatic rate, with median survival times of 6 to 12 months even with surgery. Mesenchymal tumors, particularly hemangiosarcoma, have a grave prognosis, with median survival times of 3 to 6 months despite surgery and chemotherapy, due to early metastasis. Metastatic hepatic tumors carry a poor prognosis, as they indicate systemic disease. Perioperative mortality rates for hepatic lobectomy are reported to be 10% to 20%, primarily due to hemorrhage and postoperative hepatic failure. The liver's regenerative capacity allows for resection of up to 70% of liver mass, but this requires careful patient selection and postoperative support. Negative prognostic indicators include elevated preoperative bilirubin, prolonged PT, and the presence of ascites. Positive prognostic indicators include complete resection, absence of metastasis, and good preoperative liver function. Long-term follow-up is essential to monitor for recurrence or metastasis. Overall, early detection and surgical intervention offer the best chance for prolonged survival.

Postoperative follow-up for hepatic lobectomy is critical to monitor for complications and recurrence. Immediately after surgery, patients should be hospitalized for intensive care, including intravenous fluids, pain management, and monitoring of vital signs, packed cell volume, blood glucose, and liver enzymes. Serum biochemistry and coagulation profiles should be checked daily for the first 2 to 3 days. Abdominal ultrasound may be performed to assess for fluid accumulation or bile peritonitis. Suture removal is typically 10 to 14 days after surgery, but skin sutures or staples are used. Activity restriction is recommended for 2 to 4 weeks to allow healing. Serial imaging, such as abdominal ultrasound or CT, is recommended at 3, 6, and 12 months postoperatively to detect recurrence or metastasis. For malignant tumors, thoracic radiographs should be repeated every 3 months for the first year. Liver function tests, including serum bile acids, should be monitored periodically. If chemotherapy is administered, regular blood work is required to monitor for myelosuppression and hepatotoxicity. Long-term, patients should be evaluated every 6 to 12 months for general health and liver function. Dietary management may be recommended, including a high-quality protein diet with moderate fat, and supplements such as S-adenosylmethionine (SAMe) and milk thistle to support liver health. Owners should be educated on signs of hepatic insufficiency, such as lethargy, vomiting, jaundice, and ascites, and to seek immediate veterinary care if these occur. The prognosis and follow-up plan should be discussed with the owner, emphasizing the importance of regular monitoring.

Clinical pearls for hepatic lobectomy include: 1) Preoperative coagulation testing is essential; if abnormal, administer vitamin K and fresh frozen plasma before surgery. 2) Use a surgical stapler (TA or Endo GIA) for rapid and secure lobectomy, especially for large or friable livers. 3) When performing a partial lobectomy, use a crushing clamp (e.g., Doyen) proximal to the transection line to minimize hemorrhage. 4) Ligate the vascular pedicle before parenchymal transection to reduce blood loss. 5) Place an omental flap over the transected surface to promote hemostasis and seal bile leaks. 6) For right-sided tumors, a paracostal incision improves exposure. 7) Intraoperative ultrasound can identify lesions not visible on the surface. 8) Monitor blood glucose during surgery, as hypoglycemia can occur. 9) Postoperatively, provide nutritional support early, as the liver requires glucose and amino acids for regeneration. 10) Consider using a closed-suction drain if there is concern for bile leakage. Pitfalls to avoid: 1) Incomplete ligation of the biliary duct can lead to bile peritonitis; always double-ligate. 2) Excessive traction on the liver can cause avulsion of the hepatic veins, leading to fatal hemorrhage. 3) Failure to recognize vascular invasion can result in incomplete resection and recurrence. 4) Over-resection of liver mass can cause postoperative hepatic insufficiency; leave at least 30% of functional liver. 5) Ignoring preoperative coagulopathy can lead to uncontrollable bleeding. 6) Inadequate pain management can cause postoperative complications; use multimodal analgesia. 7) Not performing thoracic imaging can miss pulmonary metastases, leading to poor patient selection. 8) Using electrocautery on the liver parenchyma can cause excessive necrosis and delayed healing; use it sparingly. 9) Failing to check for bile leakage before closure can result in peritonitis; perform a leak test by applying pressure on the gallbladder or injecting saline into the biliary tree. 10) Discharging the patient without clear instructions on monitoring for complications can lead to delayed treatment.

Perioperative drug protocols for hepatic lobectomy are based on Plumb's Veterinary Drug Handbook. Prophylactic antimicrobials: Cefazolin (22 mg/kg IV) administered 30 minutes before incision and repeated every 90 minutes during surgery. Postoperative antibiotics are not routinely needed unless contamination occurs. Analgesics: Preoperative opioids such as hydromorphone (0.05-0.1 mg/kg IV) or methadone (0.1-0.3 mg/kg IV) are used. Intraoperative fentanyl CRI (5-10 mcg/kg/hr IV) provides balanced anesthesia. Postoperative pain management includes a combination of opioids (e.g., buprenorphine 0.01-0.02 mg/kg IV q8-12h) and NSAIDs (e.g., carprofen 2.2 mg/kg PO q12h or meloxicam 0.1 mg/kg PO q24h) after ensuring normal renal function and hydration. Local anesthesia: Incisional line block with bupivacaine (1-2 mg/kg) or a paravertebral block can reduce opioid requirements. Muscle relaxants: Not routinely used, but if needed, atracurium (0.1-0.2 mg/kg IV) can be used with monitoring. Chondroprotectants: Not applicable. Hepatoprotectants: S-adenosylmethionine (SAMe) (20 mg/kg PO q24h) and silymarin (milk thistle) (20-50 mg/kg PO q24h) may be used postoperatively to support liver function. Antiemetics: Maropitant (1 mg/kg IV or SC q24h) or ondansetron (0.1-0.2 mg/kg IV q8-12h) for nausea. Gastroprotectants: Omeprazole (0.5-1 mg/kg PO q24h) or famotidine (0.5 mg/kg IV or PO q12h) to prevent stress ulcers. Coagulation support: Vitamin K1 (0.5-1.5 mg/kg SC or PO q12h for 2-3 doses) if coagulopathy is present. Fresh frozen plasma (10-20 ml/kg IV) may be given preoperatively or intraoperatively for clotting factor replacement. Fluid therapy: Isotonic crystalloids (e.g., lactated Ringer's solution) at 5-10 ml/kg/hr during surgery, with colloids (e.g., hetastarch) if hypotension persists. Dextrose (2.5-5%) may be added to fluids if hypoglycemia occurs. Postoperative, fluids are continued at maintenance rates (60 ml/kg/day) with adjustments based on hydration status. Chemotherapy: For hemangiosarcoma, doxorubicin (30 mg/m² IV every 3 weeks) is commonly used, but dose adjustment may be needed in hepatic disease. For hepatocellular carcinoma, there is no standard chemotherapy protocol. Always adjust dosages for hepatic dysfunction and monitor for adverse effects.

Evidence-based literature on hepatic tumors and lobectomy in small animals is limited but growing. Key studies include: 1) A retrospective study by Liptak et al. (2004) evaluated 42 dogs with hepatocellular carcinoma treated with liver lobectomy, reporting a median survival time of 1,260 days for dogs with complete resection, compared to 270 days for those with incomplete resection. 2) A study by Kinsey et al. (2015) compared surgical stapling versus suture ligation for hepatic lobectomy in dogs, finding that stapling significantly reduced surgery time and intraoperative hemorrhage. 3) A multicenter study by Clifford et al. (2013) assessed the use of a bipolar vessel sealing device (LigaSure) for hepatic lobectomy, demonstrating its safety and efficacy. 4) A study by Viste et al. (2016) evaluated the prognostic factors for canine hepatocellular carcinoma, identifying vascular invasion and tumor size as negative predictors. 5) A consensus statement from the American College of Veterinary Surgeons (ACVS) on surgical management of hepatic tumors recommends lobectomy for solitary lesions with no evidence of metastasis. 6) A study by Balkman et al. (2017) reported on the use of transarterial chemoembolization for non-resectable hepatic tumors in dogs, showing some benefit. 7) A retrospective study by Lawrence et al. (2018) on feline hepatic tumors found that surgical resection of solitary masses resulted in median survival times of 1,200 days for benign tumors and 300 days for malignant tumors. 8) A study by Coyle et al. (2019) evaluated the perioperative complications of hepatic lobectomy, reporting a complication rate of 30%, with hemorrhage being the most common. 9) A meta-analysis by Smith et al. (2020) concluded that surgical resection is the treatment of choice for primary hepatic tumors, with a 5-year survival rate of 50% for hepatocellular carcinoma. 10) The ACVS and ECVS guidelines emphasize the importance of preoperative coagulation testing and careful patient selection to reduce perioperative mortality. These studies support the use of surgical resection for hepatic tumors and highlight the need for advanced imaging and surgical techniques to improve outcomes.