33rd Annual Scientific Meeting proceedings

Biliary mucoceles can be challenging clinical cases, not often because of the surgery itself but due to the multiple complex co-morbidities that can affect outcomes in these cases resulting in mortality rates in up to 40% as reported in the veterinary literature. Recent work has improved our understanding of factors affecting morbidity and mortality of these patients and these factors can be divided into perioperative, intraoperative, and postoperative causes.

Perioperative morbidity
The first question to consider is whether surgery is required for all our cases, as medical management would eliminate perioperative morbidity. What we do know is that once a biliary mucocele is established it is likely to progress and progression leads to further cholestasis, necrosis of the gall bladder wall and likely eventual rupture. Cases of gall bladder rupture are considered urgent and non-elective. There is also evidence to suggest that performing surgery early rather than later and performing elective surgery rather than non-elective surgery reduces morbidity. Studies have reported mortality rates when comparing elective versus non elective of 6% versus 22% and 2% versus 20%. The harder question to answer is whether biliary sludge rather than mucoceles can be managed medically. There is a growing body of evidence that suggests that biliary sludge is a pre-cursor to mucocele formation and that these cases progress (in one study 13% eventually became established mucoceles). These therefore may not be as “incidental” as we think and these cases, at the very least, should be monitored closely for progression.

Other perioperative factors to consider are the co-morbidities these patients often have, notably endocrine disorders. Hyperadrenocorticism is associated with biliary mucoceles and cases that are diagnosed with HAC are twice as likely to die following cholecystectomy. Furthermore, we also have data to suggest that 8% of cases die due to thrombotic events and this is likely an underestimation due to the difficulties in confirming this aetiology. Therefore, a thorough preoperative evaluation for endocrine diseases and haemostatic disorders are likely to be beneficial in driving down morbidity and mortality rates.

Intraoperative morbidity
Causes of intraoperative morbidity are multifactorial but can be briefly summarized as: hypotension, pain, anaesthesia related, surgical related and the presence of septic inflammation. Surgical morbidity relates mainly to additional procedures such as flushing the common bile duct, and this will be discussed in the following lecture. Hypotension can be caused by the usual general factors identified in critical patients (SIRS, sepsis, drugs, fluid imbalance) but specifically in these patients there seems to be a degree of “unexplained” hypotension related to the disease itself. In humans a condition is seen where obstructive cholestasis causes acute renal failure and there is strong evidence that the bile constituents themselves have profound effects on myocardial function, peripheral vascular resistance, and diuresis and this likewise may explain the unpredictable hypotension we observe in our patients. Pain is also hard to control (in all phases of morbidity) and for both these reasons the use of epidural anaesthesia / analgesia and instillation of epidural catheters appears to have favourable results in terms of anaesthetic and analgesic management as well as postoperative food intake.

There is varying literature on the relevance of positive bacterial cultures, but one large scale study showed a threefold increase in mortality rates within 14 days of surgery in cases with positive bacterial cultures. The incidence of positive bacterial cultures in the literature is low (10-22%) but many cases have had pre-treatment with antibiotics at the time of culture so identifying bacteria is hard in these cases. It would be prudent to obtain a pre-operative cystocentesis to inform antibiotic choice but in the absence of this, if infection is suspected, then drugs effective against Gram negative aerobes and anaerobic organisms would be indicated.

Postoperative morbidity
There are a host of postoperative complications reported but most commonly we see pancreatitis, pain, hypotension, inappetence, nausea, regurgitation, and ileus. Unfortunately, many of these problems contribute to the other so the effects are amplified but equally if we can address pain, inappetence and hypotension often the other effects are more easily managed. There are a multitude of anti-emetic, prokinetic and analgesic drugs that are useful in postoperative management, however it is crucial that nutrition is not neglected. Enteral feeding not only ensures maintenance of the enterocytes, but also promotes motility and secretion of the hormone cholecystokinin, both important factors in ensuring free flow of bile. Feeding tubes therefore should be seriously considered in these cases, with either gastrostomy tubes or oesophagostomy tubes appropriate choices.

References

1. Malek S, Sinclair, E, Hosgood G, et al. Clinical findings and prognostic factors for dogs undergoing cholecystectomy for gallbladder mucocele, Vet Surg 42: 418-426, 2013
2. Jaffey JA, Graham A, VanFerde E, et al. Gallbladder mucocele: variables associated with outcome and the utility of ultrasonography to identify gallbladder ruptures in 219 dogs (2007-2016), Vet Intern Med 32: 195-200, 2018
3. Hattersley R, Downing F, Gibson S, et al. Impact of intra-oeprative hypotension on mortality rates and post-operative complications in dogs undergoing cholecystectomy, JSAP (2020) 61, 624-629
4. Friesen S.L., Upchurch D.A., Hollenback D.L. et al. Clinical findings for dogs undergoing elective and nonelective cholecystectomies for gall bladder mucoceles, JSAP (2021) 62, 547-553
5. Butler T., Bexfield N., Dor C., et al. A multicenter retrospective study assessing progression of biliary sludge in dogs using ultrasonography, Vet Intern Med 2022; 36: 976-985
6. Sambugaro B., De Gennaro C., Hattersley R.D. and Vettorato E. Extradural anaesthesia-analgesia in dogs undergoing cholecystectomy: A single centre retrospective study. Front. Vet. Sci Sep 9;9:966183, 2022