Therapeutic Management
Both medical and surgical treatments have been reported for the management of GB MC, with surgery (cholecystectomy with retrograde lavage of the common bile duct), considered the treatment of choice in all cases of GB MC.
Cholecystotomy or chole- cystoenterostomy are not recommended as recurrence can be a problem and necrosis of the GB wall may not be visually evident during surgery but can lead to postoperative GB rupture and bile peritonitis. Discretion can be used in determining the timing of surgery in dogs with an intact GB. Dogs without clinical signs and that do not have signs of GB leakage on abdominal ultrasound can have surgery on an elective basis. In dogs with clinical signs, however surgery should be considered more urgent and in cases of GB rupture with or without bile peritonitis, surgery should be considered an emergency procedure.Long-term prognosis is excellent for patients that survive the perioperative period. Unfortunately, the perioperative prognosis for dogs having undergone surgery is guarded with the mortality rates ranging from 21% to 32% (Pike et al. 2004; Worley, Hottinger, and Lawrence 2004; Aguirre et al. 2007). No concrete preoperative survival prognosticators have been demonstrated and even dogs with biliary tract rupture and bile peritonitis have been shown not to fare worse than those with an intact GB. Postoperatively, hypotension and a high serum lactate have been shown to be very highly associated with mortality (Malek et al. 2013). Common postoperative complications include pneumonia, pancreatitis, pulmonary thromboembolism, and bile peritonitis. Preoperative and postoperative pancreatitis as a reported complication in fact has a high enough incidence to warrant recommendation of preventative measures such as withholding food 24-48 hours postsurgery and close monitoring of pain and comfort levels in the perioperative period.
Samples of the liver, GB wall, and bile should be routinely collected during surgery for histopathology and bacterial culture. Copious abdominal lavage is indicated if bile spillage has occurred during surgery or if biliary tract rupture is present.Postoperative management should include a broad-spectrum antibiotic until bacterial culture results are available, intravenous fluid therapy, antiemetic and gastro-protective agents in symptomatic patients, adequate analgesia, and close monitoring of blood pressure, serum lactate, heart rate, and respiratory rate. Long-term management should also include a low-fat diet and ursodiol. Often antibiotic therapy is continued for at least 2 weeks postoperatively. Many patients with GB MCs also have a degree of histopathological liver abnormalities evident on biopsy including bile duct hyperplasia, portal fibrosis, cholangiohepatitis, nodular regeneration, and hepatocellular vacuolar changes. Despite these changes, in most patients liver enzyme activities return to normal after surgery. Concurrent liver disease does however remain in some patients, which may require ongoing long-term medical management. In addition, in all patients, concurrent endo- crinopathies and dyslipidemias should be addressed.
Medical therapy in the majority of cases is unable to transform a semisolid MC into liquid bile and should only ever be considered in patients that are asymptomatic and have normal liver enzyme activities. One report however does claim successful management of two symptomatic dogs with clinical signs attributable to GB MC's and underlying hypothyroidism, but in this report the authors do caution that surgery is still the preferred method of management (Walter et al. 2008). Medical management may also unfortunately have to be considered in symptomatic patients when the pet owner has severe cost constraints that preclude surgery or when the pet owner considers the perioperative mortality rates unacceptable. Medical management however can never be considered in patients with confirmed biliary rupture with or without bile peritonitis or where ultrasonographic signs of extrahepatic biliary obstruction are present.
When embarking on medical treatment in symptomatic patients it is also imperative that the pet owner be warned of the possible need for surgery in the future either if medical management is unsuccessful in alleviating or controlling clinical signs to acceptable levels or if biliary rupture/extrahepatic bile duct obstruction subsequently occurs.Medical management consists of feeding a low-fat diet and the use of ursodiol (1015 mg/kg SID) as well as broad-spectrum antibiotics and analgesic agents if required (buprenorphine, tramadol). Some patients may also benefit from the use of antiemetic agents (metoclopramide, maropitant) and gastroprotectants (omeprazole, ranitidine, sucrulphate) if vomiting and anorexia are unrelenting. Ursodiol is administered to improve the bile acid profile, to protect hepatocytes and biliary epithelium against the injurious effects of bile stasis and to promote choleresis. Some evidence also exists that ursodiol upregulates canalicular transporters and thus may be beneficial in dogs with transporter gene defects (Hottinger 2014). Other agents with antioxidant properties such as SAMe have also been postulated to have some benefit in medical management of GB MCs. Investigation into the presence of underlying endocrinopathies (DM, Cushing's, hypothyroidism) and treatment of those conditions as well as cessation of exogenous steroid therapy is also important in these cases. Medical management is often life-long and requires good pet owner compliance and dedication. Regular examinations (at least 6 weekly), which should include serial ultrasonographic examination of the GB and serum liver enzyme activity analyses, are imperative. Frequent communication with pet owners on their perception of the status of their dog's clinical condition is also important. Progression of the disease in any fashion on serial examinations should warrant immediate surgical intervention. Euthanasia may unfortunately need to be considered in cases where medical management is unsuccessful in controlling the animal's clinical signs to an acceptable level and cost constraints prohibit surgery.