Transtail Artery Hepatic Artery Catheterization In Rats Under Direct Vision: A Radiation-Free Method For Establishing Animal Models

Summary

This protocol describes a reproducible open-abdominal trans-caudal-artery chemoembolization technique in rats, enabling precise intra-arterial drug delivery, controlled liver embolization, and standardized assessment of therapeutic and biological responses in liver cancer models.

Abstract

Rat liver tumor models are indispensable for studying trans-arterial chemoembolization (TACE), drug delivery, and tumor biology. However, conventional techniques utilizing fluoroscopy-guided carotid or femoral access are often constrained by high equipment costs, technical complexity, and cumulative radiation risks to operators. This protocol presents a radiation-free alternative using open-laparotomy-guided transtail artery catheterization. We provide a comprehensive, step-by-step description of the procedure, beginning with standardized anesthesia and exposure of the ventral caudal artery (VCA). The core of the technique involves performing a midline laparotomy to enable direct visualization of the hepatoduodenal anatomy, allowing for the precise advancement of a 1.6 Fr microcatheter into the common hepatic artery (CHA) or proper hepatic artery (PHA) using a 0.014-inch microguidewire. Our validation study in 32 rats demonstrates that this method achieves a high technical success rate of 96.9% (31/32) with a mean procedure time of 22.5 ± 2.3 min. This technique provides an accessible, reproducible, and transparent platform for laboratories focusing on localized therapeutic evaluation and embolic biology. This method effectively lowers the barrier for establishing high-quality interventional models in preclinical research environments where advanced imaging is unavailable.

Introduction

Trans-arterial delivery techniques are widely used in preclinical liver cancer research, particularly for modeling trans-arterial chemoembolization (TACE), localized drug delivery, and intra-arterial immunotherapy. However, conventional vascular access routes in rats—including femoral or carotid artery cannulation—are limited by anatomical constraints, vessel fragility, and great technical difficulty, resulting in variability in success rate and reproducibility^1,2,3,4.

The transtail artery approach has emerged as a superior method for establishing TACE models due to its minimal invasiveness and high reproducibility. Studies by Kumagai et al. demonstrated that transtail artery access allows selective catheterization with an average procedure time of approximately 9.5 min, emphasizing its feasibility and steep learning curve, even for operators with limited microsurgical experience⁵. Similarly, Hong et al. reported a shorter catheterization time of 6.9 ± 1.4 min, highlighting the efficiency of this technique. Advantages include reduced complications such as cerebral ischemia or limb ischemia associated with carotid or femoral approaches, owing to the dual blood supply of the tail via collateral vessels⁶.

However, the use of digital subtraction angiography (DSA) guidance for catheterization introduces notable inconvenience. First, radiation exposure poses risks to both operators and animals during fluoroscopic procedures, which is particularly concerning in long-term experiments⁷. Second, the technical complexity of DSA-guided catheterization, including the need for specialized equipment and expertise, increases procedure difficulty and time.

In contrast, open laparotomy for catheterization offers distinct advantages, primarily by eliminating the requirement for specialized DSA equipment. Furthermore, this method ensures a radiation-free procedural environment, effectively protecting both the operator and the animal from ionizing radiation during the catheterization phase. This method provides a practical solution for studies prioritizing rapid implementation and safety, particularly in environments where advanced imaging is unavailable. Thus, exploring open laparotomy-based TACE models could complement existing techniques, facilitating broader applications in liver cancer research.

Protocol

Perform all animal procedures in accordance with the institutional guidelines for the care and use of laboratory animals. Ensure that all surgical and interventional steps comply with approved animal protocols.

1. Anesthesia and preoperative preparation

1. Induce and maintain anesthesia.
   1. Induce anesthesia with 3–5% inhaled isoflurane in an induction chamber.
   2. Administer a maintenance dose of intraperitoneal 1% pentobarbital sodium at 40 mg/kg.
   3. Apply a thin layer of ophthalmic ointment to both eyes to prevent corneal desiccation throughout the surgical procedure.
2. Position the animal.
   1. Place the rat in the supine position on the surgical platform.
   2. Maintain body temperature at 37 °C using a heating pad.

2. Exposure of the ventral caudal artery (VCA)

1. Create the tail incision.
   1. Identify a point approximately 5 cm distal to the tail base.
   2. Make a 1.5 cm longitudinal midline incision on the ventral surface of the tail using a scalpel.
2. Expose the artery.
   1. Perform sharp dissection through the superficial fascia to expose the VCA, located approximately 1 mm beneath the skin.
   2. Dissect and separate small accompanying veins to fully expose the artery.
      NOTE: Avoid injury to the transverse branches arising from the VCA.

3. Vessel conditioning

1. Reduce arterial spasm.
   1. Apply lidocaine gel to the exposed VCA.
2. Place a distal tie.
   1. Loop a 4-0 suture around the distal segment of the VCA without tightening to facilitate vessel elevation in subsequent steps. Apply a vascular clamp to the proximal VCA to prevent bleeding during incision of the vessel (Figure 1).

4. Laparotomy and exposure of the hepatic artery (Figure 2 and Figure 3)

1. Perform midline laparotomy.
   1. Make a 5 cm midline incision inferior to the xiphoid process using straight scissors.
   2. Open the abdominal cavity and gently elevate the liver cranially using a moist cotton swab.
2. Expose the hepatoduodenal region.
   1. Retract the intestines toward the left abdominal cavity.
   2. Expose the hepatic hilum and identify major vascular structures (Figure 2A).
3. Dissect the arterial anatomy.
   1. Dissect the abdominal aorta and the common hepatic artery (CHA) bifurcation (Figure 3).
   2. Use micro-forceps to gently dissect the perivascular sheath, avoiding any direct traction on the vessel. Adequate exposure of the junction between the abdominal aorta and the CHA facilitates rapid catheter placement in subsequent steps (Figure 2B).
      CAUTION: Thoroughly loosening the perivascular connective tissue on the surface of the CHA increases its upward angle, thereby facilitating the subsequent smooth advancement of the guidewire and catheter into the vessel.

5. Arteriotomy and catheter insertion

1. Control proximal blood flow.
   1. Apply a vascular clamp on the proximal VCA to prevent bleeding.
2. Perform arteriotomy.
   1. Use micro-scissors to make a small transverse incision on the VCA.
3. Insert the guidewire and microcatheter.
   1. Elevate the distal VCA using the pre-placed 4-0 silk suture (Figure 1A).
   2. Insert the 0.014-inch microguidewire into the VCA. Gently advance the 1.6 Fr microcatheter over the guidewire. Facilitate advancement by applying gentle traction on the distal VCA suture to straighten the vessel. Advance the catheter approximately 15 cm to reach the celiac axis (Figure 1B).

6. Selective cannulation and drug/embolic delivery

1. Advance the catheter to the hepatic artery.
   1. Advance the guidewire–catheter assembly under direct visualization toward the bifurcation between the abdominal aorta and the CHA.
   2. Place curved forceps beneath the abdominal aorta and gently elevate it. Adjust the tip of the guidewire–catheter assembly to the bifurcation between the abdominal aorta and the CHA. Advance and withdraw the assembly while coordinating with the curved forceps to facilitate rapid entry of the guidewire into the CHA (Figure 3A,B).
2. Confirm position and prepare for infusion.
   1. Continue advancing the guidewire–catheter assembly until the catheter tip is visualized within the PHA at the hepatic hilum (Figure 4).
   2. Withdraw the guidewire and confirm free blood backflow through the catheter to ensure intraluminal placement.
3. Deliver agents.
   1. Connect a three-way stopcock and syringe to the catheter hub.
   2. Inject the planned agent, contrast medium, or embolic suspension.
      CAUTION: Use appropriate shielding and PPE when handling chemotherapeutic drugs or embolic agents.

7. Catheter removal and wound closure

1. Remove the catheter.
   1. Remove the catheter carefully after completing the infusion.
2. Ligate the vessel.
   1. Tie off the proximal VCA using 4-0 silk suture to prevent bleeding.
3. Close surgical incisions.
   1. Close the abdominal incision in two layers (muscle and skin) using interrupted 4-0 silk sutures.
   2. Close the tail incision with interrupted 4-0 sutures.

8. Re-intervention (Optional)

1. Perform repeat access.
   1. If repeat TACE is required, create a new incision closer to the tail base (approximately 3 cm).
   2. Repeat steps 2 through 7.
      NOTE: Additional interventions should be spaced according to the study design and animal welfare guidelines.

Results

The technical efficacy and safety of the radiation-free transtail artery catheterization protocol were evaluated in a validation cohort of 32 rats, with key performance metrics summarized in Table 1. Technical success, defined as stable microcatheter placement in the common hepatic artery (CHA) followed by the unobstructed delivery of embolic materials, was achieved in 31 out of 32 animals (96.9%). The mean procedure time, measured from the initial exposure of the ventral caudal artery (VCA) to final cat...

Discussion

The rat open-abdomen, trans-tail-artery catheterization method presented here provides a practical and reproducible alternative to traditional TACE models that require fluoroscopic guidance. Several prior studies have established small-animal TACE via the tail artery approaches, typically using DSA to guide catheterization and confirm vascular access^1,2,3,4,5....

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Blunt-tip microforceps (0.4 mm)	Suzhou Shiqiang	11001-12
Curved forceps	Shanghai Medical Instruments (Jinzhong)	S110-3
Heparinized saline injection	Jiangsu Wanbang Biochemical Pharmaceutical Group Co., Ltd.	H32020612
Iodixanol injection	Jiangsu Hengrui Pharmaceuticals Co., Ltd.	H20103675
Isoflurane	RWD Life Science	R510-22
Lidocaine gel	Shandong Fangming Pharmaceutical Group	20180322
Micro-scissors	Shanghai Medical Instruments (Jinzhong)	S320-1
Microcatheter (1.6 Fr)	Cardiolink Science	SS-40-1.6F
Microguidewire (0.014 inch)	Cardiolink Science	PGW14-150A
Needle holder	Shanghai Medical Instruments (Jinzhong)	S201-1
PVA microspheres	Cardiolink Science	VM-20110
Scalpel blade	Shanghai Medical Instruments (Jinzhong)	B102-11
Sodium pentobarbital solution (1%)	Shanghai Pharmaceuticals Holding Co., Ltd.	https://www.sphchina.com/
Straight forceps	Shanghai Medical Instruments (Jinzhong)	S110-1
Straight scissors	Shanghai Medical Instruments (Jinzhong)	S310-1
Suture (4-0) with 3/8-circle needle	Shanghai Jinhuan Medical	J-40-45
Disposable Sterile Syringe (1 mL, 2 mL, 5 mL)	Jiangsu Zhiyu Medical Instrument Co., Ltd.	Z-1022
Toothed forceps	Shanghai Medical Instruments (Jinzhong)	S112-2
Vascular clips	Roboz Surgical Instrument	RS-5420