Biliary Tract Abnormalities
World Small Animal Veterinary Association World Congress Proceedings, 2015
Michael Willard1, DVM, MS, DACVIM
1Texas A&M University, College Station, TX, USA

Cholecystitis

Cholecystitis may be much more common than many people realize. Dogs that have evidence of antibiotic responsive hepatobiliary tract disease may have a bacterial cholecystitis. Typically, both the ALT and SAP are increased, and icterus is common. Most dogs with cholecystitis do not have discernable gall stones. Many (maybe most) gall stones found in dogs and cats are clinically insignificant and only serve to confuse veterinarians. Ultrasound findings in dogs with bacterial cholecystitis are nonspecific: finding "sludge" in the gall bladder can also occur in clinically normal dogs. However, aspirating bile via percutaneous puncture with a 22–25 gauge needle may be very helpful. Rarely, such aspiration technique will cause a vagal response that will cause extreme bradycardia; however, if this happens all that is usually needed is an injection of a parasympatholytic such as glycopyrrolate. Finding WBCs and/or bacteria in the bile seems to be very specific, but we are not really sure how sensitive this test is for cholecystitis. Therapy usually involves chronic (i.e., > 6–8 weeks) antibiotic therapy. If I cannot culture bacteria, I prefer to use a combination of amoxicillin and enrofloxacin. If that approach is unsuccessful, then cholecystectomy is usually the next step. Do not do a cholecystotomy or an incisional biopsy of gall bladder wall; dehiscence appears to be a major cause of morbidity and mortality after such surgery. Rather, remove the entire gall bladder and submit it for histopathology and microbiology. Be sure that you do not ligate or transect the common bile duct, or you may kill the dogs. Remember that cholecystectomy may be required to cure a patient with cholecystitis.

Emphysematous cholecystitis is classically associated with diabetes mellitus, but it probably occurs just as often in non-diabetic animals. This is diagnosed radiographically. Treatment with antibiotics that are effective against gas-producing anaerobic bacteria (e.g., penicillin, metronidazole, chloramphenicol, or clindamycin) is usually successful.

Spontaneous rupture of the gall bladder is usually due to a necrotizing cholecystitis associated with bacterial infection or mucocele (see below). Animals with septic cholecystitis and spontaneous rupture are usually icteric and present as having an acute abdomen. Cure requires cholecystectomy and aggressive antibacterial therapy. This disease seems to be uncommon, but can be life-threatening. Ultrasound is one of the best tools to detect this disease. It is important to remember that you should never take biopsies of the gall bladder. If you are going to do anything to the gall bladder, then you either a) squeeze it to see if it empties, b) aspirate it to obtain bile for cytology and culture, or c) remove it. Just make sure that when you remove the gall bladder, you do not ligate or obstruct the common bile duct.

Mucocoele

Sometimes excessive mucus is secreted into the gall bladder and becomes so thick and inspissated that it essentially becomes a solid mass. This is referred to as a biliary mucocoele. When the contents develop the consistency of thick Jell-O and occlude the common bile duct, EHBO occurs. Diagnosis is by ultrasound. You are not looking for gravity-dependent sludge; rather, you are looking for a "stellate" appearance to the gall bladder. Cholecystectomy appears to be the only appropriate therapy. Many of these patients have necrosis of the wall of the gall bladder and will eventually rupture causing peritonitis. Prognosis is good, as long as you do surgery before the gall bladder ruptures there are no post-surgical complications such as pancreatitis. A couple of very controversial points are what constitutes the ultrasonographic diagnosis of an immature biliary mucocoele, and whether gall bladders with non-gravity dependent "sludge" need to be removed or not. Some animals with "immature" mucoceles seemingly resolve if treated with choleretics such as ursodeoxycholic acid.

Gall stones, as mentioned are usually there simply to distract the veterinarian. I am not saying that they never cause disease. I am saying that they are usually innocent of causing disease. If you find gall stones, you should first look elsewhere for the cause of the patient's illness. If you can find nothing else that seems likely to be responsible for causing hepatobiliary tract disease in the patient, only then should you allow yourself to focus on the gall stones. Of course, if there are bacteria in the bile, then the gall stones are likely to be very important and should be removed so as to prevent recrudescence of the infection.

Gall Stones

Gall stones, as mentioned are usually there simply to distract the veterinarian. I am not saying that they never cause disease. I am saying that they are usually innocent of causing disease. If you find gall stones, you should first look elsewhere for the cause of the patient's illness. If you can find nothing else that seems likely to be responsible for causing hepatobiliary tract disease in the patient, only then should you allow yourself to focus on the gall stones. Of course, if there are bacteria in the bile, then the gall stones are likely to be very important and should be removed so as to prevent recrudescence of the infection. Pancreatitis is the most important cause of extrahepatic biliary tract obstruction (EHBO) in the dog. If EHBO is present in a sick dog and appears to be idiopathic, it should generally be assumed to probably be due to pancreatitis until there is evidence to the contrary.

References

1.  Baker SG, Mayhew PD, Mehler SJ, et al. Choledochotomy and primary repair of extrahepatic biliary duct rupture in seven dogs and two cats. J Small Anim Pract. 2011;52:32–37.

2.  Kook PH, Schellengerg S, Grest P, et al. Microbiologic evaluation of gallbladder bile of healthy dogs and dogs with iatrogenic hypercortisolism: a pilot study. J Vet Intern Med. 2010;24:224–228.

3.  Kutsunai M, Kanemoto H, Fukushima K, et al. The association between gall bladder mucoceles and hyperlipidaemia in dogs: a retrospective case control study. Vet J. 2014;199:76–79.

4.  Malek S, Sinclair E, Hosgood G, et al. Clinical findings and prognostic factors for dogs undergoing cholecystectomy for gall bladder mucocele. Vet Surg. 2013;42:418–426.

5.  Willard MD, Fossum T. Extrahepatic biliary disorders. In: Washabau RJ, Day MJ, eds. Canine and Feline Gastroenterology. St. Louis, MO: Elsevier; 2013:933–936.

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Michael Willard, DVM, MS, DACVIM
Texas A&M University
College Station, TX, USA


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