Liver Lobe Torsion

Liver lobe torsion is a rare and potentially life-threatening surgical condition characterized by the rotation of a hepatic lobe around its vascular pedicle, leading to vascular compromise, ischemia, venous congestion, and parenchymal necrosis. The torsion typically involves the caudate or left lateral lobe in dogs, and less commonly the right lateral or quadrate lobes. The condition results in a strangulating obstruction of the portal vein, hepatic artery, and bile duct, causing rapid hepatocellular injury and release of inflammatory mediators. Clinically, it presents as an acute abdomen with signs of shock, vomiting, and abdominal pain. Surgical intervention, usually lobectomy, is the definitive treatment. The condition is most frequently reported in large-breed dogs, particularly those with deep-chested conformations, and has been associated with trauma, gastric dilatation-volvulus, and congenital ligamentous laxity. Early recognition and aggressive surgical management are critical for a favorable outcome.

The exact etiology of liver lobe torsion is often idiopathic, but several predisposing factors have been identified. Anatomical variations, such as a congenitally absent or elongated hepatic ligament (e.g., falciform ligament, coronary ligament, triangular ligaments), can allow excessive mobility of a lobe. Trauma, including blunt abdominal trauma, can cause displacement and subsequent torsion. In some cases, torsion occurs secondary to other intra-abdominal pathologies, such as gastric dilatation-volvulus (GDV), which can alter the position of the liver and its ligaments. Neoplastic masses within a lobe may increase its weight and predispose to torsion. Additionally, iatrogenic causes, such as prior abdominal surgery that disrupts ligamentous attachments, have been reported. The exact biomechanical trigger is unknown, but it is hypothesized that sudden changes in intra-abdominal pressure or body position may initiate the rotation.

Liver lobe torsion is a rare condition in dogs and cats. It is most commonly reported in large and giant breed dogs, including the German Shepherd, Great Dane, and Saint Bernard, though any breed can be affected. There is no clear sex predilection, but some studies suggest a slight male predominance. The condition is more frequently diagnosed in middle-aged to older animals, with a median age of around 6-8 years. In cats, it is extremely rare, with only a few case reports. The condition is often associated with concurrent diseases such as GDV, which may be due to the shared anatomical and conformational risk factors. The true incidence is unknown, but it is considered an uncommon cause of acute abdomen in small animal practice.

The pathophysiology of liver lobe torsion involves a cascade of events initiated by the rotation of the lobe around its pedicle. The rotation causes partial or complete obstruction of the portal vein, hepatic artery, and bile duct. Initially, venous outflow obstruction leads to congestion and increased intraparenchymal pressure, resulting in hepatocyte hypoxia and ischemic injury. Arterial inflow may be partially maintained, leading to a congested, swollen, and painful lobe. As the torsion progresses, arterial blood flow is compromised, leading to ischemic necrosis and infarction. The release of intracellular contents, including enzymes and inflammatory cytokines, into the systemic circulation contributes to a systemic inflammatory response syndrome (SIRS) and can lead to septic peritonitis if the necrotic lobe becomes infected. The necrotic tissue may also serve as a nidus for bacterial translocation. If left untreated, the condition can progress to hypovolemic shock, disseminated intravascular coagulation (DIC), and death.

Predisposing factors for liver lobe torsion include anatomical variations such as congenital absence or elongation of the hepatic ligaments, which allow excessive mobility of the lobes. Deep-chested and large-breed dogs are at higher risk due to their conformational anatomy, which may predispose to ligamentous laxity. Trauma, particularly blunt abdominal trauma, can cause displacement of the liver and initiate torsion. Concurrent conditions such as gastric dilatation-volvulus (GDV) are associated with an increased risk, possibly due to the abnormal positioning of the stomach and liver during GDV. Neoplastic masses within a lobe can increase its weight and alter its center of gravity, making torsion more likely. Prior abdominal surgery that disrupts ligamentous attachments may also predispose to torsion. Additionally, strenuous exercise or sudden changes in body position may trigger torsion in susceptible individuals.

Clinical signs of liver lobe torsion are often acute and severe, reflecting the rapid onset of vascular compromise and necrosis. Common signs include acute abdominal pain, vomiting (often non-productive), anorexia, lethargy, and depression. Animals may exhibit signs of shock, such as pale mucous membranes, tachycardia, weak pulses, and prolonged capillary refill time. Abdominal distension may be present, especially if there is concurrent GDV or peritoneal effusion. On abdominal palpation, a painful cranial abdominal mass may be detected. Fever may be present due to inflammation and necrosis. In some cases, the condition may be subacute or chronic, with intermittent signs of abdominal pain and vomiting. If peritonitis develops, signs may worsen, with progression to septic shock.

Differential diagnoses for liver lobe torsion include: 1) Gastric dilatation-volvulus (GDV): presents with acute abdominal distension, non-productive vomiting, and shock; radiographs show a gas-filled stomach with a 'double bubble' sign; torsion of the liver may be a concurrent finding. 2) Acute pancreatitis: causes vomiting, abdominal pain, and elevated pancreatic enzymes; imaging may show a normal liver but pancreatic changes. 3) Biliary tract disease (cholecystitis, bile duct obstruction): may cause jaundice, vomiting, and abdominal pain; ultrasonography reveals biliary distension or gallstones. 4) Hepatic neoplasia (e.g., hepatocellular carcinoma, hemangiosarcoma): can cause a mass effect and abdominal pain; imaging and biopsy are diagnostic. 5) Splenic torsion: presents with acute abdominal pain and a palpable splenic mass; imaging shows an enlarged spleen with a characteristic 'whirl sign' on ultrasound. 6) Intestinal obstruction or volvulus: causes vomiting and abdominal pain; radiographs may show dilated loops of bowel. 7) Peritonitis (septic or sterile): can cause fever, abdominal pain, and effusion; abdominocentesis and cytology are helpful. 8) Traumatic liver injury: may cause hemorrhage and abdominal pain; history of trauma and imaging findings differentiate. 9) Diaphragmatic hernia: can cause respiratory distress and abdominal organ displacement; thoracic radiographs may show herniated liver. 10) Acute hepatitis or cholangiohepatitis: may cause vomiting, jaundice, and elevated liver enzymes; liver biopsy is diagnostic.

The diagnostic algorithm for liver lobe torsion begins with a thorough history and physical examination, focusing on the presence of acute abdominal pain, vomiting, and signs of shock. Initial stabilization with intravenous fluids and analgesics is essential. Baseline blood work, including a complete blood count, serum biochemistry, and coagulation profile, should be performed. Abdominal radiographs may reveal a soft tissue mass in the cranial abdomen, loss of serosal detail, or concurrent GDV. Abdominal ultrasonography is the most useful imaging modality, as it can demonstrate a torsed liver lobe with a characteristic 'whirl sign' of the vascular pedicle, as well as Doppler evidence of absent or reduced blood flow. If ultrasonography is inconclusive, computed tomography (CT) with contrast can provide detailed vascular anatomy and confirm the diagnosis. In unstable patients, exploratory laparotomy may be both diagnostic and therapeutic. Definitive diagnosis is made at surgery by identifying the torsed lobe, which appears congested, dark, and necrotic.

Laboratory findings in liver lobe torsion are non-specific but may include: 1) Complete blood count: leukocytosis with a left shift, or leukopenia in severe cases; hemoconcentration may be present due to dehydration. 2) Serum biochemistry: elevated liver enzymes (ALT, AST, ALP, GGT) due to hepatocellular injury and cholestasis; hyperbilirubinemia may occur if bile duct obstruction is present; hypoglycemia can result from hepatic dysfunction; azotemia may be prerenal or renal. 3) Coagulation profile: prolonged PT and aPTT, and elevated D-dimers, indicating DIC, which is common in severe cases. 4) Blood gas analysis: metabolic acidosis due to lactic acidosis from tissue hypoperfusion. 5) Inflammatory biomarkers: elevated C-reactive protein (CRP) and serum amyloid A (SAA) may be present. 6) Abdominocentesis: if peritoneal effusion is present, fluid analysis may show a modified transudate or exudate with high protein and cellularity, and possibly bacteria if peritonitis has developed.

Imaging plays a crucial role in the diagnosis of liver lobe torsion. Abdominal radiographs may show a soft tissue opacity in the cranial abdomen, loss of serosal detail due to effusion, or displacement of adjacent organs. However, radiographs are often non-specific. Abdominal ultrasonography is the preferred imaging modality. On ultrasound, the torsed liver lobe appears enlarged, hypoechoic, and may have a 'whirl sign' at the hilus, representing the twisted vascular pedicle. Color Doppler can demonstrate absent or reduced blood flow to the affected lobe. Ultrasonography can also identify concurrent conditions such as GDV or biliary obstruction. Computed tomography (CT) with intravenous contrast is highly sensitive and can show a non-enhancing, enlarged liver lobe with a twisted pedicle. CT is particularly useful in stable patients when the diagnosis is uncertain. Magnetic resonance imaging (MRI) is rarely used but can provide detailed soft tissue contrast. In emergency situations, exploratory laparotomy may be performed without advanced imaging if the patient is unstable.

Cytological and histopathological evaluation of the affected liver lobe is typically performed after surgical resection. Grossly, the torsed lobe is dark red to black, swollen, and friable. Histopathology reveals extensive hemorrhagic infarction, coagulative necrosis, and congestion. There may be evidence of neutrophilic infiltration and bacterial colonization if secondary infection has occurred. In chronic cases, fibrosis and hemosiderin deposition may be seen. Cytology of peritoneal fluid may show a suppurative inflammation with degenerate neutrophils and intracellular bacteria if peritonitis is present. Histopathology is also important to rule out underlying neoplasia, which may have predisposed to torsion. If a mass is present, it should be submitted for histopathological evaluation to determine the tumor type and surgical margins.

Treatment of liver lobe torsion is primarily surgical and involves resection of the affected lobe (lobectomy). Preoperative stabilization is critical and includes aggressive intravenous fluid therapy with crystalloids (e.g., lactated Ringer's solution at 10-20 ml/kg bolus, then 5-10 ml/kg/hr) to correct shock, and colloids (e.g., hydroxyethyl starch at 5-10 ml/kg) if hypoproteinemia is present. Pain management with opioids (e.g., hydromorphone 0.05-0.1 mg/kg IV, or fentanyl CRI at 2-5 mcg/kg/hr) is essential. Broad-spectrum antibiotics (e.g., ampicillin 22 mg/kg IV q8h and enrofloxacin 10 mg/kg IV q24h) should be administered if peritonitis is suspected. Surgical approach is via a cranial midline celiotomy. The abdomen is explored, and the torsed lobe is identified. The vascular pedicle is isolated, and the lobe is removed using a stapling device (e.g., TA stapler) or by ligating the vessels with absorbable suture (e.g., 2-0 or 3-0 polydioxanone). Partial lobectomy may be performed if the torsion is limited to a portion of the lobe. The abdomen is lavaged with warm sterile saline, and a closed-suction drain may be placed if peritonitis is present. Postoperative care includes continued fluid therapy, analgesia, and monitoring for complications such as DIC, sepsis, and hepatic insufficiency. In cases of concurrent GDV, gastropexy should be performed.

The prognosis for liver lobe torsion is guarded to good, depending on the timeliness of surgical intervention and the presence of concurrent disease. If surgery is performed early before the onset of severe necrosis and systemic complications, the prognosis is good, with many animals making a full recovery. However, if the condition is advanced, with significant necrosis, peritonitis, or DIC, the prognosis is poor. Reported mortality rates range from 20% to 50%. Negative prognostic indicators include the presence of septic peritonitis, DIC, and delayed surgical treatment. With prompt surgical resection and aggressive postoperative care, the long-term prognosis is generally favorable, as the remaining liver lobes can regenerate and compensate for the loss of function.

Postoperative follow-up for liver lobe torsion includes monitoring for complications such as hemorrhage, bile peritonitis, and infection. Patients should be hospitalized for at least 24-48 hours postoperatively, with continuous monitoring of vital signs, packed cell volume, total protein, and blood glucose. Serial abdominal ultrasonography may be performed to assess for fluid accumulation or abscess formation. Suture removal is typically 10-14 days after surgery. Activity should be restricted for 2-4 weeks to allow for healing. Liver function should be monitored with serum biochemistry, including liver enzymes and bile acids, at 2-4 weeks postoperatively and then as needed. Long-term follow-up is generally not required if the animal recovers uneventfully, but periodic check-ups are recommended to ensure no recurrence or development of other hepatic issues.

Clinical pearls: 1) Always consider liver lobe torsion in large-breed dogs presenting with acute abdomen, especially if there is a history of GDV or trauma. 2) Ultrasonography is the most valuable diagnostic tool; look for the 'whirl sign' and absent Doppler flow. 3) In unstable patients, do not delay surgery for advanced imaging; exploratory laparotomy is both diagnostic and therapeutic. 4) When performing lobectomy, use a stapling device to minimize hemorrhage and reduce surgical time. 5) Always explore the entire abdomen for concurrent conditions, especially GDV. Pitfalls: 1) Failure to recognize the condition early can lead to fatal complications such as DIC and septic peritonitis. 2) Incomplete resection of the torsed lobe can lead to continued necrosis and peritonitis. 3) Inadequate preoperative stabilization can increase the risk of anesthetic complications. 4) Overlooking concurrent biliary tract injury can lead to bile peritonitis. 5) Not providing appropriate postoperative monitoring for DIC and hepatic insufficiency can result in delayed complications.

Perioperative drug protocols for liver lobe torsion are based on Plumb's Veterinary Drug Handbook. Preoperative: 1) Analgesia: hydromorphone (0.05-0.1 mg/kg IV) or methadone (0.1-0.2 mg/kg IV) for pain; may be repeated as needed. 2) Antibiotics: ampicillin (22 mg/kg IV q8h) and enrofloxacin (10 mg/kg IV q24h) or cefazolin (22 mg/kg IV q2h during surgery) for prophylaxis and treatment of peritonitis. 3) Fluid therapy: lactated Ringer's solution (10-20 ml/kg bolus, then 5-10 ml/kg/hr) to restore perfusion; colloids (hydroxyethyl starch 5-10 ml/kg) if hypoproteinemia. Intraoperative: 1) Continue antibiotics, redose cefazolin every 2 hours. 2) Analgesia: fentanyl CRI (2-5 mcg/kg/hr) or lidocaine CRI (25-50 mcg/kg/min) for multimodal analgesia. 3) Antiemetics: maropitant (1 mg/kg IV) to prevent vomiting. Postoperative: 1) Analgesia: fentanyl CRI (2-5 mcg/kg/hr) for 12-24 hours, then transition to oral tramadol (2-5 mg/kg PO q8-12h) or carprofen (2.2 mg/kg PO q12h) for 3-5 days. 2) Antibiotics: continue for 7-10 days if peritonitis was present. 3) Gastroprotectants: pantoprazole (1 mg/kg IV q24h) or omeprazole (1 mg/kg PO q12h) to prevent stress ulcers. 4) Hepatoprotectants: S-adenosylmethionine (SAMe) (20 mg/kg PO q24h) and silymarin (10-20 mg/kg PO q8h) may be considered. 5) Anticoagulants: if DIC is present, consider low-molecular-weight heparin (dalteparin 100-150 IU/kg SC q8-12h) or fresh frozen plasma (10-20 ml/kg IV) to replace clotting factors.

Liver lobe torsion is a rare condition, and the literature consists mainly of case reports and small case series. A retrospective study by Schwartz et al. (2006) reported 13 cases of liver lobe torsion in dogs, with the caudate lobe being most commonly affected. The study found that concurrent GDV was present in 31% of cases, and the overall mortality rate was 38%. Another case series by Tobias and Johnston (2012) described 10 cases, highlighting the importance of early surgical intervention. A review by Fossum (2018) emphasizes that the condition is often misdiagnosed preoperatively, and exploratory laparotomy is frequently required for diagnosis. There are no prospective clinical trials due to the rarity of the condition. Consensus guidelines from the ACVS recommend prompt surgical resection and aggressive postoperative care. The use of stapling devices for lobectomy has been shown to reduce surgical time and hemorrhage in experimental studies. Overall, the evidence supports surgical resection as the treatment of choice, with a guarded to good prognosis if performed early.