Message to Massive Liver Tumors in Dogs: We are not afraid of you!

Tumors of the liver are frequently seen in dogs, with the most common being the hepatocellular carcinoma. Affected dogs present for non-specific clinical signs and the tumors can become very large before being discovered. Massive liver tumors are defined as large tumors that are confined to one lobe of the liver.(1) (Fig. 1) 

Fig. 1: Large hepatocellular carcinoma of the liver in a dog

Prior to availability of surgical stapling devices such as the Thoracoabdominal Stapler (TA), liver lobectomy was tedious, risky, and associated with significant blood loss. The stapling device has made removal of even very large hepatic tumors safer and much faster resulting is less morbidity and mortality. (Fig. 2)

Fig. 2: Large liver mass in a dog being removed using
an older version of the thoracoabdominal stapling device

Diagnosis

Dogs with liver tumors present with non-specific signs such as lethargy, anorexia, and weight loss. A large cranial abdominal mass is usually palpable on physical examination. Diagnostic imaging is indicated including plain film abdominal radiographs (Fig. 3), abdominal ultrasound, and thoracic radiographs to look for metastatic lesions.

Fig. 3: Plain film abdominal radiograph of a liver tumor in a 12 year old Labrador retriever (arrow)
(photo courtesy of Dr. Laura Lemmons)

CT scan can also be performed (Fig. 4), however it may not provide more significant information than radiographs and ultrasound.

Fig. 4: CT scan of a 10 year old golden doodle with a large right sided liver
mass.(arrow) The mass was surgically removed and histopathology revealed a hepatic adenoma.

Preoperative Care

Appropriate preoperative diagnostics are necessary to rule out metabolic diseases and metastasis of primary liver tumors.  Preoperative hemograms and coagulation status should be assessed since many liver and biliary diseases can cause deficiency of clotting factors.  Serum proteins should also be evaluated.  The patient's fluid and electrolyte status should be considered and abnormalities corrected before surgery.  Significant blood loss can occur during or after partial hepatectomy which may require blood tranfusion.

Applied Anatomy

The liver is divided into 6 lobes, the caudate, right lateral, right medial, quadrate, left lateral, and left medial. 

Fig. 5: Normal gross anatomy of the canine liver lobes.

The liver has a dual blood supply, receiving circulation from both the portal vein and the hepatic arteries.  Major hepatic portal vein branches are the right lateral trunk, right medial branch, and left lateral trunk supplying the left lobes.  The liver portal vasculature can also be classified as right divisional (caudate and right lateral), central divisional (right medial and quadrate), and left divisional (left medial and left lateral). Six to eight major hepatic veins drain into the caudal vena cava.  The liver is attached to other structures in the abdomen via the triangular ligaments and the hepatogastric and hepatoduodenal ligaments.

Surgical Approaches

The liver is best approached via a ventral midline celiotomy.  Although rarely done, a right or left paracostal incision can be combined with the midline approach for large liver masses or other conditions that require greater exposure.  Caudal ventral midline sternotomy can be combined with the midline abdominal incision if necessary for cranially located masses.

Partial hepatectomy

Liver lobectomy using surgical staples is the procedure of choice for most surgeons. Complete or partial lobectomy can be performed. Omental adhesions to the mass will require hemostasis and sharp dissection to release them from the tumor. The Ligasure or electrocautery device is useful for hemostasis. After exposing the mass, incise triangular ligaments as needed to mobilize the liver lobe. Be cautious working around the hepatoduodenal ligament since the hepatic arteries and common bile duct are in the region. Caudal traction on the liver lobe is necessary to accurately place the stapler proximal to the tumor. (Figs. 6,7)

Fig. 6: Surgical removal of a large hepatocellular carcinoma
in a dog using the Thoracoabdominal stapler. 

Large hemostatic clips may be needed to control occasional arterial bleeders that were not adequately compressed by the staples. The Ligasure device can also be used to control liver bleeding. 

Fig. 7: Liver mass in same dog as in Fig. 3; histopathology of the
mass revealed an hepatic adenoma.

The liver has a remarkable ability to regenerate. Up to 60-70% of the liver tissue mass can be removed without impacting liver function.

Postoperative Care and Complications

Liver surgery patients should be closely monitored and supported after liver surgery.  Postoperative hemorrhage is possible and should be monitored via the patient's color, heart rate, peripheral PCV (measured several hours after surgery), and evidence of bleeding from the incision or blood in the abdominal cavity.  Routine postoperative supportive care with intravenous fluids and analgesics is administered. In the absence of complications, most dogs can be discharged from the hospital the day after surgery.

Prognosis
The prognosis for dogs after removal of massive liver tumors, even hepatocellular carcinoma if completely excised, is very good. In one study of 42 dogs, mortality rate was only 4.8% and median postoperative survival was greater than 1460 days.(1)  In contrast, dogs treated without surgery had a median survival was 270 days.

References

1. Julius M. Liptak, BVSc, MvetClinStud; William S. Dernell, DVM, MS, DACVS; Eric Monnet, DVM, PhD, DACVS; Barbara E. Powers, DVM, PhD, DACVP; Annette M. Bachand, PhD; Juanita G. Kenney; Stephen J. Withrow, DVM, DACVS, DACVIM. Massive hepatocellular carcinoma in dogs:48 cases (1992–2002) JAVMA, Vol 225, No. 8, October 15, 2004