A 13‐year‐old 4.65 kg male castrated domestic shorthair cat was presented for further evaluation of biliary obstruction secondary to a previously diagnosed biliary carcinoma.

The patient had undergone a computed tomography (CT) scan and exploratory laparotomy, which identified a non‐resectable mass involving the entire CBD and extending to the liver hilus, with subsequent diffuse intrahepatic biliary duct dilatation. Biopsy of the mass was consistent with carcinoma. There also was concern for a soft tissue structure in the right caudal lung lobe and sternal lymphadenopathy on imaging. Incidental findings included left coxofemoral subluxation and a chronic pubic fracture associated with previous trauma. Previous treatment included placement of an esophagostomy tube; a single dose of carboplatin at 180 mg/m² IV; hospitalization for IV fluid therapy, ampicillin/sulbactam, vitamin B complex, vitamin K1, maropitant, cyproheptadine, pantoprazole, and gabapentin; as well as prior administration of robenacoxib, mirtazapine, gabapentin, and a supplement containing silymarin, N‐acetyl cysteine, zinc, and vitamin E.

At presentation 8 days after exploratory laparotomy, test results indicated markedly increased liver enzyme activities and hyperbilirubinemia (Table S1) as well as neutrophilia with a left shift, increased symmetric dimethylarginine (SDMA), hypokalemia, and hypoalbuminemia. Abdominal ultrasonography identified a hyperechoic liver with generalized intrahepatic duct distension without clinically relevant gallbladder dilatation, with a hypoechoic nodule (approximately 0.6 cm) at the level of the distal CBD. Bilateral chronic kidney disease and a small volume of peritoneal effusion also were noted.

Biliary stenting was recommended and carried out. The patient was pretreated with vitamin K1 (0.5 mg/kg SC q 12 h) and deamino‐D‐arginine vasopressin (DDAVP; 1.0 u/kg SC 15 min before surgery) to minimize bleeding risk. Exploratory laparotomy confirmed biliary obstruction secondary to diffuse tumor burden. Gallbladder puncture using an 18‐Ga IV catheter was performed in an attempt to gain biliary access because the entire CBD was filled with tumor, but was unsuccessful because of occlusion of the cystic duct by tumor. Biliary access then was obtained using intra‐operative ultrasound‐guided puncture of a dilated intrahepatic bile duct of the left lateral lobe using a 22‐Ga IV catheter. An antegrade cholangiogram confirmed obstruction from the intrahepatic ducts at the level of the hilus and throughout the entire CBD (Figure 1A). A 0.018″ hydrophilic guidewire (Weasel Wire, angled 0.018″ by 150 cm, Infiniti Medical, Palo Alto, Cali) was passed through the catheter and into the intrahepatic biliary system. The 22‐Ga catheter was exchanged for a 4 French micropuncture system (Micropuncture Access Set, 4Fr by 10 cm, Cook Medical, Bloomington Ill) and the guidewire was exchanged for a 0.035″ stiffened angle‐tipped hydrophilic guidewire (Weasel Wire, stiff angled 0.035″ by 150 cm, Infiniti Medical, Palo Alto, Cali). Under fluoroscopic guidance the guidewire was navigated through the tumor and CBD (Figure 1B) and into the duodenum. A small puncture was made into the descending duodenum to gain through‐and‐through guidewire access. A 6 mm × 60 mm non‐covered self‐expanding metallic stent (SEMS) then was advanced in a retrograde manner over the guidewire from the duodenum up the CBD and into the left intrahepatic biliary duct (Figure 1C). The stent was deployed across the CBD and into the duodenum (Figure 1D) allowing for decompression of the left side of the liver. A locking loop nephrostomy catheter (Locking Loop Catheter with Stiffening Cannula, 6.5F by 20 cm, Norfolk Vet Products, Skokie Ill) was fed over the guidewire from the liver side and coiled into the left biliary duct for potential future intraparenchymal chemotherapy. A dacron cuff was glued into place on the liver capsule to prevent biliary leakage, and the distal end of the catheter was passed through the body wall using blunt dissection and connected to a SC access port (Medium titanium vascular access port, Norfolk Vet Products, Skokie, Ill) for future access. Total procedure time was 97 min. Bile collected during biliary puncture was submitted for aerobic and anaerobic culture, and all cultures were negative.

The cat recovered well and was hospitalized for the next 3 days on IV fluid therapy, ampicillin/sulbactam (30 mg/kg IV q8h), enrofloxacin (5 mg/kg IV q24h), Vitamin K1 (0.5 mg/kg SC q12h), ondansetron (0.5 mg/kg IV q12h), pantoprazole (1 mg/kg IV q12h), ursodiol (13.5 mg/kg via feeding tube [FTUBE] q24h), methadone (0.2 mg/kg IV q6h), vitamin B complex, and metoclopramide (2 mg/kg/day IV).

Hyperbilirubinemia improved by 1 day post‐operatively, with initial progression of increased hepatocellular enzyme activities, followed by gradual decreases on subsequent follow‐up (Table S1).

Post‐operative radiographs confirmed appropriate placement of the stent and the biliary drainage catheter (Figure 2). Abdominal ultrasonography showed asymmetric biliary tract decompression, with persistent right‐sided intrahepatic biliary tract dilatation (Figure 3A) and resolved left intrahepatic biliary tract dilatation (Figure 3B). The stent was visualized extending from the duodenal lumen through the CBD and into the left lateral liver lobe within the biliary tract (Figure 3C). A large volume of echogenic peritoneal effusion also was observed with hyperechoic mesenteric fat. Fluid analysis was consistent with mild mixed inflammation; no bacteria were seen; aerobic and anaerobic cultures were negative.

The cat was discharged 3 days post‐operatively and transitioned to enteral medications, including amoxicillin/clavulanic acid (13.5 mg/kg PO q12h), enrofloxacin (4.9 mg/kg PO q24h), ondansetron (0.4 mg/kg PO q12h), ursodiol (13.5 mg/kg PO q24h), and cyproheptadine (0.4 mg/kg PO q12h).

There was initial improvement in clinical signs, alongside improvements in laboratory test results. However, the cat was evaluated for anorexia and regurgitation 15 days post‐operatively. Liver enzyme activities and serum bilirubin concentration had continued to improve (Table S1). Abdominal ultrasonography identified an appropriately placed biliary stent with persistent right intrahepatic duct dilatation, resolution of left hepatic duct dilatation, and mild peritoneal effusion. Gastric distension and the presence of hypochloremic metabolic alkalosis were concerning for ileus without evidence of mechanical obstruction. The patient was hospitalized on IV fluids, potassium supplementation, ampicillin/sulbactam (30 mg/kg IV q8h), enrofloxacin (5 mg/kg IV q24h), doxycycline (5 mg/kg IV q12h), maropitant (1 mg/kg SC q24h), buprenorphine (0.015 mg/kg IV q8h), gabapentin (6 mg/kg FTUBE q12h), pantoprazole (1 mg/kg IV q12h), ondansetron (0.5 mg/kg FTUBE q12h), metoclopramide (2 mg/kg/day IV constant rate infusion [CRI]), cisapride (0.6 mg/kg FTUBE q12h), and thiamine (12.5 mg/kg IM q12h). Regurgitation persisted, and repeat abdominal ultrasonography indicated progressive gastric distension and peritoneal effusion with suspicion of functional ileus or the biliary tumor causing mechanical outflow tract obstruction to the proximal duodenum. The biliary stent was not seen to be obstructing the duodenal lumen. The cat became recumbent, developed refractory hypotension, and was euthanized 19 days post‐operatively. A necropsy was not performed.

An 8‐year‐old 3.95 kg male castrated domestic shorthair cat was presented for further evaluation of BDO secondary to a previously diagnosed bile duct adenocarcinoma.

The cat previously had undergone abdominal ultrasonography and exploratory laparotomy, which identified biliary obstruction with marked distension of the gallbladder, hepatic and cystic ducts, and a mass within the CBD causing complete luminal obstruction. The cat was also noted to have pancreatitis and peritonitis. A routine cholecystoduodenostomy was performed. Histopathology of the mass was consistent with bile duct adenocarcinoma. Previous treatment included IV fluid therapy, ampicillin, enrofloxacin, ondansetron, maropitant, famotidine, Denamarin, and vitamins B12 and K1.

Although the patient initially improved after cholecystoduodenostomy with resolution of hyperbilirubinemia, recurrence of the biliary obstruction occurred 16 days later. The cat was presented to the hospital with persistent severe hyperbilirubinemia, increased liver enzyme activities, as well as anemia, reticulocytosis, monocytosis, and an increased plasma fibrinogen concentration.

Surgical intervention to pursue biliary stenting was considered. Vitamin K1 (0.6 mg/kg SC) and DDAVP (1.1 mg/kg SC) were given preoperatively. On abdominal exploratory, the tumor was noted to be obstructing the cystic duct, leading to failure of the cholecystoduodenostomy. A rendezvous procedure utilizing a hybrid approach was performed as described above, with some modifications. Biliary access was accomplished through a dilated intrahepatic bile duct of the left lateral lobe. An antegrade cholangiogram confirmed obstruction (Figure 4A). The guidewire and micropuncture system were utilized, as described in case 1, but because of the choleduodenostomy, the wire was passed through the cystic duct, into the gallbladder, and out into the duodenum (Figure 4B). Additionally, instead of retrograde stent placement, a non‐covered SEMS biliary stent (4 mm × 60 mm) was placed in an antegrade manner from the left intrahepatic biliary duct access point, through the cystic duct, and exiting the cholecystoduodenostomy site within the gallbladder (Figure 4C), which was communicating with the duodenum. A post‐stenting cholangiogram confirmed biliary patency (Figure 4D). A locking loop catheter again was advanced over the guidewire and placed into the left biliary duct, and it was left in place connected to a SC access port for potential intraparenchymal chemotherapy. Total procedure time was 111 min. The bile culture was positive for Enterococcus faecium .

Recovery was uneventful and the cat was treated with IV fluid therapy with supplemental potassium chloride, metoclopramide (2 mg/kg/day IV CRI), maropitant (1 mg/kg IV q24h), ondansetron (0.9 mg/kg IV q12h), ampicillin/sulbactam (30 mg/kg IV q8h), enrofloxacin (5 mg/kg IV q24h), and methadone (0.2 mg/kg IV q6h).

Improvement of hyperbilirubinemia and increased liver enzyme activities was noted post‐operatively (Table S1). Post‐operative radiographs showed an appropriately‐placed stent and biliary drainage tube (see Figure 5). A partial kink of the tubing was seen as it entered the body wall, but it was of no clinical consequence. Ultrasonography showed asymmetrical decompression of the intrahepatic biliary duct tracts, with ongoing right biliary obstruction and left‐sided decompression (Figure 6). Echogenic peritoneal effusion and hyperechogenicity of the cranial mesenteric fat also were noted.

The cat was discharged 1 day post‐operatively for continued hospitalization at the referring veterinarian and transitioned to enteral doxycycline based on culture results. Laboratory testing performed 3 days post‐operatively showed improvement in liver enzyme activities and serum bilirubin concentration (Table S1). Three weeks postoperatively the cat was reported to have normal serum bilirubin concentration and liver enzyme activities. A repeat CT scan before scheduled radiation planning showed pulmonary metastasis, and PO chemotherapy was initiated. On day 63 post‐operatively, the owner reported a mild increase in serum total bilirubin concentration above the reference interval, but it was < 2.0 mg/dL and the cat was doing well without evidence of left‐sided biliary dilatation. After this update the patient was lost to follow‐up.