For reasons unknown, gallbladder mucocele is an increasingly common cause of acute abdomen requiring emergency surgery in dogs. Because we are diagnosing and treating more of these cases, clinical experience and research on the disease is progressing, elucidating more answers to some of the questions about this condition.
What causes a mucocele to form? A mucocele is formed by excessive secretion of mucus by the gallbladder wall. Histologically it has been described as cystic mucosal hyperplasia. The thick mucus congeals with the bile and causes distension of the gallbladder and sometimes the common bile duct and extrahepatic ducts. Eventually pressure necrosis of the gallbladder wall can occur, resulting in bile peritonitis.
Which patients are at risk for a mucocele? While there does not appear to be a specific breed association, our clinical impression is that smaller breed dogs are overrepresented. Clinical studies have shown that patients with hyperadrenocorticism or hypothyroidism may be at increased risk.
What are the most common clinical signs? Vomiting, lethargy, cranial abdominal pain and sometimes icterus are seen in patients with a gallbladder mucocele. Laboratory abnormalities often include dehydration, elevated WBC count, and elevation in liver enzymes and bilirubin.
What modalities are best for diagnosis? While radiographs can demonstrate loss of detail in the cranial abdomen and sometimes faint mineralization in the soft tissues in the area of the gallbladder, ultrasound is far more useful in making the diagnosis. The gallbladder is enlarged, with stationary echogenic contents often in a stellate pattern. Often the cranial abdominal mesentery/fat surrounding the gallbladder is hyperechoic and free fluid may be present. The extrahepatic ducts and proximal aspect of the common bile duct can be distended as well.
Is medical treatment possible? Medical treatment has been successful in a limited number of cases. Treatment includes symptomatic treatment of pain and nausea, along with ursodiol, S-adenosyl-l-methionine, and famotidine. Due to the potentially fatal complication of gallbladder rupture and bile peritonitis, this modality should be reserved for early cases where the patient/client has significant clinical or financial contraindications for surgery and anesthesia.
How is surgical treatment performed? Emergency abdominal exploratory is performed as soon as the patient is stable enough to undergo anesthesia. Alternately, in early cases where there is no evidence of distension of the extrahepatic ducts or common bile ducts, laparoscopic cholecystectomy could be considered. With an open approach, a cranial midline incision is performed and the falciform fat excised to improve visibility in the cranial abdomen. The stomach can be decompressed with an orogastric tube and intestines packed off outside the abdomen to further improve exposure of the liver and gallbladder. The area is isolated with moistened lap pads to control contamination. The gallbladder is gently dissected from the hepatic fossa so that the gallbladder neck and cystic duct are accessible. The cystic artery is ligated and right angle clamps used to occlude the gallbladder neck and cystic duct. The duct is severed between the clamps and the gallbladder and its contents removed. A stay suture can be placed in the cystic duct, the clamp released and the cystic and common bile duct flushed normograde with a red rubber catheter and saline to ensure patency. If needed, this catheter can also be redirected proximally into the distal extrahepatic ducts to flush out any gelatinous debris. Alternately, the duodenal papilla can be accessed through an enterotomy and the duct flushed retrograde, but this still must be done after the gallbladder has been removed due to maximal distention already from the mucus. Adding an enterotomy to the procedure also increases surgical time and introduces the potential for complications from the enterotomy site. After flushing, the duct is double ligated. Biopsy of the gallbladder wall and hepatic parenchyma is recommended as well as a bile culture.
What does the post-operative management entail? Patients are usually hospitalized for 24-48 hours post-operatively, if no major complications occur. Patients are sent home on exercise restriction, pain management and a 2-4 week course of broad spectrum antibiotics which is tailored to match sensitivity results from the culture taken at surgery. Potential complications include ileus, chemical peritonitis, infection, anemia, hypoproteinemia, overwhelming inflammatory responses (SIRS), and other system dysfunctions such as disseminated intravascular coagulation and multiorgan failure.
What is the prognosis? Prognosis after surgical management of gallbladder mucocele is favorable with survival rates reported between 68 and 79 percent. At our hospital, results have been similar with approximately 80 percent of dogs treated over the past 24 months surviving beyond discharge from the hospital.
Suggested reading: Mayhew, PD, Weisse, C. Liver and biliary system. In Tobias, KM, Johnston, SA, Eds. Veterinary Small Animal Surgery Volume 2 pp 1601-1621.