Feline Cholecystitis (Bacterial and Necrotizing)

Feline cholecystitis refers to inflammation of the gallbladder in cats, encompassing both bacterial (suppurative) and necrotizing forms. The bacterial form results from infection of the gallbladder wall, most commonly secondary to ascending enteric organisms from the duodenum or via hematogenous spread. Necrotizing cholecystitis represents the most severe end of the spectrum, characterized by ischemic necrosis of the gallbladder wall, which carries a high risk of gallbladder rupture, bile peritonitis, and sepsis. Both forms are closely associated with the feline hepatobiliary triad—a concurrent presentation of cholangitis, pancreatitis, and inflammatory bowel disease—making the condition clinically complex and potentially life-threatening.

Bacterial Cholecystitis: The gallbladder is normally sterile in healthy cats. Bacterial colonization most often occurs via ascending infection from the duodenum through the common bile duct, particularly when normal duodenal motility is impaired or the sphincter of Oddi is incompetent. Hematogenous seeding via the portal circulation is another recognized pathway. The most commonly implicated organisms are gram-negative enteric bacteria—Escherichia coli, Enterococcus spp., Streptococcus spp., Clostridium spp., and Bacteroides spp. In cats specifically, Helicobacter and Salmonella species have also been implicated in biliary infections. Once bacteria colonize the gallbladder mucosa, an acute inflammatory response ensues: neutrophil infiltration, mucosal edema, and mural thickening. Bacterial toxins and endotoxins exacerbate local tissue injury and trigger systemic inflammatory response syndrome (SIRS) in severe cases.

Necrotizing Cholecystitis: Necrotizing cholecystitis arises when ischemia of the gallbladder wall is superimposed on or leads to bacterial infection. Ischemia may result from sustained gallbladder distension (secondary to cholelithiasis, biliary sludge, or obstruction), thrombosis of cystic artery branches, or severe transmural inflammation with vascular compromise. The combination of ischemia and bacterial toxin-mediated damage leads to full-thickness mural necrosis. The structurally weakened gallbladder wall is highly susceptible to perforation, releasing infected bile into the peritoneal cavity and causing septic bile peritonitis—a life-threatening emergency. Cats with concurrent pancreatitis, inflammatory bowel disease, cholelithiasis, common bile duct obstruction, or biliary sludge syndrome face an elevated risk of progressing to necrotizing disease. Immunosuppression (e.g., feline immunodeficiency virus infection, prolonged corticosteroid use) further predisposes cats to severe bacterial biliary disease.

History and Physical Examination: A thorough history (anorexia, vomiting, lethargy, previous hepatobiliary disease) combined with cranial abdominal pain on palpation, icterus, and fever should raise strong suspicion. Cats with necrotizing disease or gallbladder rupture may present collapsed or in septic shock.

Laboratory Evaluation:

• ·Complete Blood Count (CBC): Leukocytosis with neutrophilia and a left shift (immature band neutrophils) is typical of bacterial infection. A degenerative left shift, neutropenia, or toxic neutrophils suggests sepsis. Anemia (low HCT) may be present in chronic cases or following rupture. Thrombocytopenia (low PLT) can occur in sepsis-associated disseminated intravascular coagulation (DIC).
• ·Serum Chemistry Panel:
  • ·ALT (Alanine Aminotransferase): Markedly elevated, reflecting hepatocellular injury due to biliary backpressure and ascending cholangitis
  • ·ALP (Alkaline Phosphatase): Elevated, indicating cholestasis (note: ALP is less diagnostically sensitive in cats than in dogs due to shorter enzyme half-life, so even mild elevations are significant)
  • ·TBIL (Total Bilirubin): Elevated, confirming cholestasis; values >50 µmol/L are common in obstructive or severe cholecystitis
  • ·GGT (Gamma-Glutamyl Transferase): Often elevated, a useful marker of biliary disease in cats
  • ·ALB (Albumin): May be low (hypoalbuminemia) in chronic disease due to hepatic synthetic failure or protein-losing enteropathy from concurrent IBD
  • ·GLOB (Globulins): May be elevated reflecting chronic inflammation or infection
  • ·BUN and CREA: Generally within reference range unless concurrent renal disease or pre-renal azotemia from dehydration/sepsis is present
  • ·Blood Glucose: Hypoglycemia possible in septic patients; hyperglycemia may reflect stress response
  • ·Electrolytes: Hypokalemia and hyponatremia may result from anorexia and vomiting
• ·Coagulation Profile: PT/aPTT prolongation possible if hepatic production of clotting factors is impaired; critical to assess before surgical intervention

Urinalysis: Bilirubinuria may be present; bacterial culture of urine may occasionally reveal concurrent urinary tract infection.

Diagnostic Imaging:

• ·Abdominal Ultrasound (gold standard for biliary evaluation): Reveals gallbladder wall thickening (>1 mm is abnormal in cats), mural irregularity or hyperechogenicity, pericholecystic fluid, intraluminal sludge, cholelithiasis, biliary duct dilation, and loss of normal wall layering in necrotizing disease. Free peritoneal fluid or echogenic peritoneal fat suggests rupture and bile peritonitis.
• ·Radiography: May identify radiopaque choleliths and free abdominal gas (rare, associated with emphysematous cholecystitis from gas-producing organisms); generally less informative than ultrasound

Bile and Culture: Ultrasound-guided cholecystocentesis (performed carefully, with coagulation assessment and operator experience) can yield bile for cytology and aerobic/anaerobic bacterial culture and sensitivity—critical for guiding antimicrobial therapy. Cytology showing degenerate neutrophils and intracellular bacteria is diagnostic of septic bile.

Abdominocentesis: If free abdominal fluid is present, fluid sampling for cytology, bilirubin concentration (compared to serum), and bacterial culture is essential to confirm or exclude bile peritonitis.

Stabilization (Emergency/Critical Patients): Cats with suspected necrotizing cholecystitis, gallbladder rupture, bile peritonitis, or septic shock require immediate aggressive stabilization: intravenous fluid resuscitation (isotonic crystalloids ± colloids), correction of electrolyte abnormalities (especially hypokalemia), nutritional support via feeding tube if anorexic, and broad-spectrum intravenous antimicrobials initiated before culture results are available.

Antimicrobial Therapy: Empirical antibiotic selection should provide coverage against gram-negative enteric pathogens and anaerobes pending culture and sensitivity results. Common protocols include:

• ·Ampicillin-sulbactam intravenously (broad spectrum, good biliary penetration)
• ·Enrofloxacin (gram-negative coverage; use with caution in cats due to risk of retinal toxicity at high doses) combined with metronidazole (anaerobic and anti-inflammatory)
• ·Ticarcillin-clavulanate or piperacillin-tazobactam for polymicrobial or resistant infections
• ·Antibiotic therapy should be adjusted based on culture/sensitivity results and continued for a minimum of 4–6 weeks in bacterial cholecystitis/cholangitis

Surgical Management:

• ·Cholecystectomy (surgical removal of the gallbladder) is the definitive treatment for necrotizing cholecystitis, emphysematous cholecystitis, gallbladder rupture, bile peritonitis, or failed medical management. Surgery should not be delayed once gallbladder integrity is compromised.
• ·Bile duct exploration and flushing may be performed concurrently if biliary obstruction or choledocholithiasis is identified
• ·Abdominal lavage is performed intraoperatively when bile peritonitis is confirmed
• ·Intraoperative bile and gallbladder wall samples should be submitted for culture and histopathology

Supportive Care:

• ·Ursodeoxycholic acid (ursodiol): Hepatoprotective and choleretic agent; promotes bile flow and reduces biliary sludge; commonly used at 10–15 mg/kg/day orally in stable patients
• ·S-adenosylmethionine (SAMe) and milk thistle (silymarin): Hepatoprotective antioxidants to support hepatocyte integrity
• ·Vitamin K1 supplementation: If coagulopathy is present due to fat-soluble vitamin malabsorption secondary to cholestasis
• ·Antiemetics: Maropitant or ondansetron to control nausea and vomiting
• ·Nutritional support: Assisted enteral feeding (esophagostomy or nasogastric tube) for anorexic cats to prevent hepatic lipidosis
• ·Pain management: Buprenorphine or other opioid analgesics for abdominal discomfort
• ·Treatment of concurrent disease: IBD, pancreatitis, and cholangitis should be managed concurrently for best outcomes

The prognosis for feline cholecystitis varies substantially by disease form and severity at presentation. Data on long-term prognosis is limited in current veterinary literature; no peer-reviewed survival statistics specific to feline bacterial and necrotizing cholecystitis were identified in the references cited above. However, based on general veterinary clinical knowledge:

Bacterial (non-necrotizing) cholecystitis: Cats diagnosed early and managed aggressively with appropriate antibiotics, supportive care, and treatment of concurrent hepatobiliary disease generally carry a guarded to fair prognosis. Many cats can achieve clinical remission, though recurrence is possible, particularly if underlying risk factors (biliary sludge, IBD, immunosuppression) are not controlled.

Necrotizing cholecystitis and gallbladder rupture: These carry a guarded to grave prognosis. Bile peritonitis secondary to gallbladder rupture is a surgical emergency with high mortality if untreated. Even with prompt surgical intervention and intensive care, perioperative mortality is significant in critically ill cats. Factors worsening prognosis include:

• ·Presence of septic shock at admission
• ·Severe hypoalbuminemia (ALB <15 g/L)
• ·Thrombocytopenia (PLT <50 × 10³/µL) suggesting DIC
• ·Markedly elevated bilirubin (TBIL >100 µmol/L) reflecting severe cholestasis
• ·Concurrent hepatic failure (prolonged coagulation times, hypoglycemia)
• ·Advanced age or significant comorbidities

Postoperative monitoring of liver enzymes (ALT, ALP, GGT), bilirubin, albumin, and complete blood count is essential to gauge recovery trajectory. Long-term antibiotic therapy and hepatoprotective supplementation improve outcomes in surviving cats.

• ·Regular veterinary wellness examinations with abdominal palpation and periodic biochemical screening (liver enzymes, bilirubin) allow early detection of biliary abnormalities before progression to cholecystitis
• ·Abdominal ultrasound monitoring in cats with known biliary sludge, cholelithiasis, or previous cholangitis helps identify early mural changes warranting intervention
• ·Management of predisposing conditions: Early and sustained treatment of inflammatory bowel disease, chronic pancreatitis, and cholangitis reduces risk of ascending biliary infection
• ·Ursodeoxycholic acid as a long-term cholekinetic agent in cats with biliary sludge syndrome may reduce risk of biliary stasis and secondary infection
• ·Dietary management: High-quality, easily digestible, moisture-rich diets support gastrointestinal motility and reduce biliary stasis; avoiding prolonged anorexia prevents biliary sludge formation
• ·Vaccination and parasite control: While no specific vaccine exists for cholecystitis, maintaining up-to-date vaccination protocols and controlling enteric parasites and infections (including Salmonella and Clostridium exposure through raw food diets) reduces enteric bacterial burden and ascending infection risk
• ·Antimicrobial stewardship: Prompt and appropriate treatment of enteric infections, urinary tract infections, and other bacterial diseases prevents hematogenous spread to the biliary system
• ·Avoiding immunosuppression when possible: Careful monitoring of cats on long-term corticosteroids or other immunosuppressive agents, with regular hepatobiliary screening