Stenting of a Partially Obstructed Nasolacrimal Duct Using A Steerable Angle-Tipped Hydrophilic Guide Wire in a Cat

Abstract

A 2-year-old neutered male American domestic shorthair cat was referred to the Purdue University Veterinary Hospital (PUVH) for chronic epiphora suspected secondary to nasolacrimal (NL) system obstruction. At the first visit, the cat had epiphora OD and facial dermatitis but no other abnormalities on physical and ophthalmic examinations. Computed tomography (CT)-dacryocystorhinography revealed partial obstruction of the NL duct secondary to stenosis near the distal root of the right maxillary third premolar (107). A digital three-dimensional (3D) model of the right maxilla and NL duct was created for inspection and virtual cannulation of the NL. The model was 3D printed and cannulation of the NL duct was rehearsed with various stent materials. Retrograde NL stenting with the guidance of a steerable angle-tipped hydrophilic guidewire was conducted following a paranasal incision. A urethral catheter was cannulated over the guidewire and maintained for 44 days. The epiphora resolved immediately after stenting. At 21 days post-stenting, the cat developed acute bullous keratopathy secondary to self-trauma which was treated with a third eyelid flap. On the final follow-up communication with the owner at 210 days post-stenting, no epiphora or any other concerns were reported. To the authors’ knowledge, this is the first report of successful NL stenting and resolution of epiphora in a cat with a partial NL system obstruction.

Introduction

The nasolacrimal (NL) duct is a drainage system that drains conducts tears from the ocular surface to the nasal cavity. The nasolacrimal drainage system consists of the superior and inferior puncta, superior and inferior canaliculi, lacrimal sac, NL duct, and nasal puncta.¹ Various congenital and acquired diseases of the nasolacrimal duct system have been described in dogs,^2,3 rabbits,⁴ cats,⁵ horses,^6,7 and cattle.⁸ The most common consequence of disorders of the NL duct is obstruction which results in epiphora and secondary facial dermatitis and tear staining.

Normo- or retrograde cannulation of the NL duct with a silastic tube has been a standard treatment in dogs with intramural NL duct obstruction since the technique was described in the 1970s³. Alternative methods including the use of lacrimoscopy and fluoroscopy-guided stenting have also been proposed for cases in which cannulation is challenging.⁹ When cannulation of the NL duct fails, other surgical methods such as rerouting the duct to the nasal cavity (conjunctival rhinostomy) or the maxillary sinus (conjunctival maxillary sinustomy) can be considered.^10,11 These procedures, however, involve drilling through bone and highly vascular tissues and are thus more invasive and at greater risk for complications.

Although the anatomy of the NL system in cats is similar to that of other species,¹ the comparatively small sizes of the skull and the NL system itself can make cannulation of the NL duct challenging. The narrow nasal passages and small nostrils of cats make locating and approaching the nasal punctum difficult. Although the computed tomographic appearance of the normal feline NL system has been reported,¹ comprehensive evaluation of the NL duct remains challenging to for clinicians. Recently, three-dimensional (3D) modeling and printing have been embraced in veterinary medicine for virtual inspection of anatomy as well as surgical planning in challenging cases with complex anatomy.^12,13 To the best of the authors’ knowledge, cannulation of the NL duct in cats to resolve obstruction has not been reported. This case report describes the successful correction of partial obstruction of the NL duct in a cat by means of a modified retrograde NL duct cannulation using a steerable angle-tipped hydrophilic guidewire (AH guidewire) following a paranasal incision. This report also describes the three-dimensional anatomy of the obstructed NL duct as determined from 3D virtual modeling and printing.

Case Summary

History and Ophthalmic Examinations

A 2-year-old neutered male American domestic shorthair cat weighing 4.4 kg was referred to the Purdue University Veterinary Hospital (PUVH) for the evaluation of epiphora in the right eye (OD) and NL system obstruction. The owners noticed excessive tearing OD since they found the cat as an approximately 1-month-old stray kitten. The cat was seen previously by a veterinary ophthalmologist at another clinic and was diagnosed with chronic epiphora OD and associated periocular facial dermatitis secondary to distal NL duct obstruction. The ophthalmologist cannulated the NL duct under sedation, flushed it, and was able to establish patency to the passage of fluid but was unable to fully pass a silastic catheter. The epiphora continued following this procedure as well as a subsequent attempt to flush the NL system under general anesthesia. At the first visit to the PUVH, complete physical and ophthalmic examinations were performed including neuro-ophthalmic evaluations, Schirmer tear test (Schirmer tear test strips, Schering-Plough Animal health, Kenilworth, NJ, USA), fluorescein staining (Ful-Glo fluorescein sodium ophthalmic strips, AkornLake Forest, IL, USA), tonometry (icare Tonovet, Vantaa, Finland), slit-lamp biomicroscopy (Kowa SL-17 portable slit lamp, Tokyo, Japan), and binocular indirect ophthalmoscopy (Heine binocular indirect ophthalmoscope, Herrsching, Germany; Volk 20D, Mentor, OH, USA). These examinations revealed severe epiphora OD that caused almost the entire right side of the face to be wet. Alopecia, erythema, and scabs were present on the periocular skin (Fig. 1). The cat became agitated with gentle palpation of the affected skin. After applying topical anesthetic OD (Proparacaine Hydrochloride Ophthalmic Solution, Akorn, Fort Worth, Texas,USA), the superior and inferior puncta were cannulated using a 23G lacrimal cannula and normograde nasolacrimal flushing was attempted but patency could not be established. The nasal punctum was not visible precluding attempts at retrograde cannulation. There were no other ocular or systemic abnormalities noted.

Figure 1.

Image of the right side of the face of a 2-year-old neutered male American domestic shorthair cat with epiphora and facial dermatitis. Note the periocular alopecia, erythema, wetness, and scab formation secondary to chronic epiphora as a sequela to partial obstruction of the nasolacrimal duct OD.

Computed Tomography – Dacryocystorhinography and 3D Modeling

On the following day, computed tomography (CT)-dacryocystorhinography was performed under general anesthesia. The cat was pre-medicated with dexmedetomidine (5 μg/kg IM, Dextomitor, Zoetis Inc., Kalamazoo, MI, USA) and butorphanol (0.2 mg/kg IM, Torbugesic, Zoetis INC., Kalamazoo, MI, USA). General anesthesia was induced with propofol (3 mg/kg IV, PropoFlo, Zoetis, Parsippany-Troy Hills, NJ, USA) and maintained with isoflurane (Isoflurane solution, Covertus, Portland, ME, USA) in oxygen. A CT of the head was performed using a 64-slice MDCT (GE LightSpeed VCT, GE Healthcare, Milwaukee, WI, USA) with the following image acquisition parameters: helical scan mode, 100 kVp, 200 mA, slice thickness = 0.625 mm, tube rotation time = 1 s, pitch = 0.5, matrix = 512 × 512, and detail algorithm. Post-contrast images were acquired at 10, 30, and 90 seconds following the start of intravenous administration of non-ionic iodinated contrast agent (2 mL/kg, iohexol, Omnipaque^™ 240, GE Healthcare, Marlborough, MA, USA). Injection rate was adjusted such that the total volume of contrast was delivered over 20 seconds. The superior and inferior puncta were cannulated with a 23G lacrimal cannula one at a time. After occluding the non-cannulated punctum with digital pressure, NL duct flushing was attempted by applying moderate pressure using a 6 mL syringe containing 0.9% normal saline but this failed to establish patency. Subsequently, approximately 1 mL of non-diluted iodinated contrast agent (iohexol, Omnipaque^™ 240) was injected through the lacrimal cannula in the inferior punctum. The CT revealed that the right fossa for the lacrimal sac, lacrimal canal, and lacrimal sulcus were enlarged (approximately twice the diameter of the left) and filled by heterogeneous, mixed fluid and soft tissue attenuating, marginally contrast enhancing material. Following dacryocystorhinography, contrast filled the lacrimal sac and descending portion of the NL duct. However, the lumen of the NL duct tapered markedly from the level of the distal root of the right maxillary third premolar (107; at the junction of the descending and horizontal parts of the NL duct) to the level of the right maxillary second premolar (106). The diameter of the NL duct from this location to its opening into the ventral nasal vestibule at the level of the alar fold was very small, measuring less than or equal to 0.5 mm. Additionally, the walls of the portion of the NL duct within the lacrimal canal and lacrimal sulcus were mildly thickened. These findings indicated chronic dacryocystitis with stenosis of the distal portion of the NL duct resulting in partial duct obstruction, proximal duct dilation, and pressure resorption of the maxillary bone. The area of partial obstruction was within the distal NL duct, approximately 14.3 mm from the right nasal punctum. Following CT-dacryocystorhinography, normograde cannulation with varying sizes of nylon suture (Ethilon 2–0, 3–0, and 4–0, Ethicon, Raritan, NJ, USA) and red rubber urethral catheters (3.5 and 5 Fr, Kendall, Mansfield, MA, USA) was attempted but unsuccessful. Retrograde cannulation was subsequently attempted but also unsuccessful as the nasal punctum could not be identified.

A digital 3D surface model of the right hemimaxilla and NL duct was segmented from postcontrast CT scan images using 3D modeling software (3D Slicer 4.11., http://slicer.org) and the centerline of the duct was extracted using the vascular modeling toolkit (VMTK, http://www.vmtk.org) (Fig. 2). The geometry of the NL duct (such as length and angle) was calculated using control points of the centerline. The total length of the NL duct was 30.1 mm, and partial obstruction occurred over 1.8 mm at 14.3 mm from the nasal punctum. An approximately 110-degree curvature was present in the NL duct caudal to the obstruction at the junction of the descending and horizontal parts of the NL duct, similar to that described previously.¹ The curvature started at 5.9 mm from the superior punctum. The obstruction of the NL duct was virtually unblocked using the 3D modeling software. The hemimaxilla with the virtually unblocked NL duct was 3D printed out of clear resin using a stereolithography 3D printer (Form 3, Formlabs, Somerville, MA) with a resolution of 25 μm × 25 μm × 50 μm (Fig. 2). A variety of stent materials and sizes were tested on the 3D printed model.

Figure 2.

Sagittal (A) and dorsal (B) views of digital 3D models of the right hemimaxilla with the turbinates removed and an image of modified 3D printed model (C). The NL duct (blue) was segmented and the central line (red) with control points was established. The NL duct was partially obstructed between points 9 and 10. The NL duct was angled (110°) between points 11 and 13 in the sagittal plane (A) followed by another notable angle change between points 8 and 11 next to tooth roots in the transverse plane (B). Points 1 and 18 indicate the nasal and the superior puncta, respectively. Normograde stenting with 4–0 nylon (red arrow) failed caudal to the canine tooth root in the 3D printed model (C). c – caudal; r – rostral; ct – canine tooth; d – dorsal; l – lateral; m – medial; r – rostral; v – ventral.

Nasolacrimal Stenting

Stenting the NL duct using the guidance of a steerable AH guide wire was elected with a backup plan of conjunctival maxillary sinustomy in the event the cannulation was not successful. NL duct exploration and stenting using a steerable AH guide wire was practiced in a cadaver cat head prior to the procedure in the patient cat (Fig. 3D). The patient was placed under general anesthesia as described above, with the exception of replacing the butorphanol in the premedication with methadone (0.3 mg/kg, IV, Methadone 10 mg/mL injectable, Akorn, Lake Forest, IL, USA). The cat was placed in sternal recumbency and the right periocular and perinasal region was clipped and prepared aseptically with diluted povidone-iodine solution and sterile saline. A steerable AH guidewire (Weasel Wire, 0.46 mm in diameter, 50 cm in length, Infinity Medical, Menlo Park, CA, USA) and an open-end urethral catheter (3.0 Fr, 70 cm in length, Cook Medical, Bloomington, IN, USA) were immersed in 0.9% saline in a basin (Fig. 3A) and saline was also injected through the plastic tubing over the guidewire using a 3 mL syringe. These steps are necessary to sufficiently hydrate the wire and catheter to ensure that they are advanced smoothly within the NL duct. Normograde NL duct flushing was attempted again as described previously but was unsuccessful, as was normograde NL duct cannulation using the steerable AH guidewire. Retrograde cannulation was subsequently attempted but the right nasal punctum could not be identified, even following retraction using a pair of Joseph skin hooks (Fig. 3B).

Figure 3.

Retrograde nasolacrimal cannulation with the guidance of a steerable angle-tipped hydrophilic guidewire (steerable AH guidewire) in a 2-year-old neutered male American domestic shorthair cat. (A) A steerable AH guidewire (0.48 mm in diameter) and an open-end urethral catheter (3.0 Fr) were immersed in 0.9% saline. (B) The right nasal punctum was not visualized even with retraction of the margins of the naris. (C) A 1 cm skin incision was made to expose the nasal punctum. The nasal punctum was cannulated with a 24G IV catheter and a steerable AH guidewire was passed through the catheter. (D) A cadaver cat head showing the exposed left nasal punctum cannulated with a 24G IV catheter after a paranasal skin incision. (E) The guidewire was passed successfully and visualized protruding from the inferior lacrimal punctum (red arrow). (F) The 24G IV catheter was removed and a 3.0 Fr urethral catheter was inserted over the guidewire and passed through the nasal punctum until it emerged from the inferior punctum. (G) The nasal mucosa, subcutaneous layer, and skin were closed and the guidewire was removed. (H) Postoperative image of the cat showing each end of the catheter sutured to facial skin.

In order to visualize the nasal punctum, a 1 cm paranasal incision was made using a No. 15 scalpel blade from the lateral commissure of the right naris toward the medial canthus (Fig. 3C). A lone star retractor was placed and the nasal punctum was exposed. The nasal punctum was located on the lateral wall of the nostril approximately 3 mm from the outer surface. It was more dorsal compared to dogs and horses wherein the puncta are located ventrolaterally near the alar fold. In this patient as well as a cadaver cat head used to practice the procedure, the nasal punctum was hidden behind the alar fold and thus was not identified until the paranasal incision was made. The nasal punctum was cannulated using a 24G IV catheter and a steerable AH guidewire was passed through the catheter (Fig. 3C). The wire was gently pushed and steered towards the nasolacrimal sac and the inferior punctum. After a few attempts, the guidewire was passed successfully and protruded from the inferior punctum (Fig. 3E). The 24G IV catheter was removed and a 3.0 Fr urethral catheter was inserted over the guidewire until it emerged from the interior punctum (Fig. 3F).

Prior to removing the wire, the nasal mucosa of the paranasal incision was sutured around the catheter using 6-0 polydioxanone (PDS II, Ethicon, Raritan, NJ, USA) to secure it in place. The subcutaneous layer was closed with tension-relieving sutures of 4-0 poliglecaprone 25 (Monocryl, Ethicon, Raritan, NJ, USA). The skin was apposed using 6-0 polydioxanone in an intradermal pattern followed by the application of a small amount of tissue glue (Vetbond, 3M, Paul, MN, USA; Fig. 3G). The steerable AH guidewire was removed and the catheter was cut at each end to have approximately 2 cm and 3 cm exposed from the interior punctum and naris, respectively. The portion of the catheter protruding from the inferior punctum was angled ventromedially to ensure it would not contact the cornea and that protruding from the naris was positioned along the dorsal midline of the nose. Each exposed end of the catheter was secured onto the facial skin using a piece of butterfly tape and two simple interrupted sutures of 3-0 Nylon surrounding the catheter (Fig. 3H). Prior to recovering the cat, the location of the catheter was evaluated and it was determined that the catheter was not contacting the cornea. The cat recovered from anesthesia uneventfully.

Postoperative Care and Follow-up

The cat was discharged on the same day of the procedure with an Elizabethan collar (E-collar). The cat was medicated as follows: Cefovecin sodium (Convenia, Zoetis, Parsippany, NJ, USA), 8 mg/kg, subcutaneously once; ofloxacin ophthalmic solution 0.3% (Akorn, Lake Forest, IL, USA), 1 drop OD, 3 times daily for 5 days; prednisolone acetate ophthalmic suspension 1% (Sandoz, Princeton, NJ, USA), 1 drop OD, 3 times daily for 5 days; and robenacoxib 6 mg (Onsior, Elanco, Greenfield, IN, USA) orally once daily for 3 days. At the recheck 5 days following initial presentation, the catheter was well-maintained, there was no epiphora, and there were no signs of ocular or periocular inflammation or irritation (Fig. 4A). The owner was advised to keep the E-collar on the cat and continue the ophthalmic ofloxacin and prednisolone acetate at the same frequency until the next recheck in 3 weeks.

Figure 4.

(A) Image of a 2-year-old neutered male American domestic shorthair cat taken 5 days post-nasolacrimal stenting. No complications were observed at this visit. (B and C) At 21 days post-stenting, the cat removed the E-collar and damaged the sutures holding the catheter. An acute bullous keratopathy was observed in the medial cornea OD. (D) A third eyelid flap was placed using 4-0 Nylon.

The owner contacted the PUVH ophthalmology service 21 days following the procedure to report that the cat had removed the E-collar and damaged the sutures holding the catheter. Upon examination on the same day, the sutures that held the catheter onto the nose were damaged but the catheter was not dislodged from the NL duct (Fig. 4B). No epiphora was observed. The ophthalmic examination showed a well-defined protrusion of the medial cornea OD with severe edema and stromal hemorrhage, consistent with acute bullous keratopathy (Figs. 4B and C). Fluorescein stain was positive in the affected cornea and trace aqueous flare was observed. As the catheter was in contact with the corneal lesion, corneal injury due to contact with the loosened catheter and/or self-trauma was suspected as the inciting cause of acute bullous keratopathy. To treat the keratopathy and prevent further contact with the catheter, the cat was sedated with butorphanol 0.2 mg/kg and dexmedetomidine 8 μg/kg IV and a third eyelid flap was placed using a stent and 4–0 Nylon. The catheter was also re-sutured to the nose with two simple interrupted sutures using 3–0 Nylon. The prednisolone acetate ophthalmic suspension was discontinued but the ofloxacin ophthalmic solution was continued at the same frequency.

Fifteen days after the third eyelid flap was implemented (37 days post-stenting), the third eyelid flap was intact and the cat appeared comfortable with no ocular discharge or epiphora. One week later (44 days post-stenting), the cat was sedated with midazolam (Midazolam 2mg/2ml injectable, Hospita, Lake Forest, IL, USA) 0.2 mg/kg, butorphanol 0.2 mg/kg, and dexmedetomidine 8 μg/kg, IV and the sutures associated with the third eyelid flap and NL catheter were removed. CT-dacryocystorhinography was conducted as described previously with the addition of injection of contrast into the left NL duct as well as the right. The right fossa for the lacrimal sac, lacrimal canal, and lacrimal sulcus remained enlarged but were no longer filled with material and became filled with contrast. Contrast also filled the entirety of the right NL duct and was visualized entering the ventral nasal meatus. These findings indicated that the cannulation was successful in resolving the NL duct stenosis and partial obstruction. As for the left NL duct, a small portion of the lumen at the level of the distal root of the left maxillary canine tooth (204) never filled with contrast. However, the remainder of the duct both rostral and caudal to this location filled normally and contrast flowed freely into the ventral nasal meatus. Given the evident patency of the left NL duct, the focal portion without contrast was interpreted as a normal ductal narrowing.

On ophthalmic examination, the acute bullous keratopathy OD had resolved and there was no fluorescein stain uptake although there was still residual corneal fibrosis and neovascularization from the previous keratopathy. The cat appeared comfortable OU with no signs of epiphora or other ocular abnormalities (Fig. 5A). The owner was instructed to continue administering the ofloxacin ophthalmic solution 3 times daily OD for 5 additional days and then discontinue.

Figure 5.

(A) Image of a 2-year-old neutered male American domestic shorthair cat taken 44 days post-nasolacrimal stenting. The previous acute bullous keratopathy had resolved and there was no sign of epiphora. Note the residual corneal neovascularization medially. (B) Image of the cat taken 340 days post-stenting. Jone’s test is positive OD indicating a patent nasolacrimal duct.

At the most recent recheck (340 days post-stenting and 296 days post-catheter removal), no epiphora was observed and Jones test was positive (Fig. 5B).

Discussion

This case report describes a modified retrograde NL stenting approach with the guidance of a steerable AH guidewire after a paranasal skin incision for the successful treatment of partial NL duct obstruction in a cat. To the authors’ knowledge, this is the first report describing NL stenting in a cat.

This report illustrates several clinically important points. First, it is challenging to locate the nasal puncta in cats. In both the anesthetized patient and the cadaver, the nasal punctum could not be identified without a paranasal incision. The nares are very small in cats making them difficult to retract or illuminate effectively. The punctum is located further dorsally in comparison to dogs and horses¹⁰ and is hidden behind the alar fold. With a paranasal incision and appropriate retraction, the nasal puncta in our patient and the cadaver were easily located and cannulated.

The second important point is the choice of materials used for NL cannulation. Due to the very small diameter of the NL system in cats (especially the canaliculi and the NL duct near the root of the canine tooth) as well as the abrupt curves in the course of the NL system, cannulating the NL duct with a red rubber urinary catheter or even suture was impossible in our hands. The red rubber catheter (3.5 Fr or 5.0 Fr) was too thick to pass through the canaliculi and the suture was too flimsy to follow the curvature from the canaliculi to the lacrimal sac during normograde cannulation. NL blockage in most cats is described in the literature as difficult, if not impossible, to resolve.¹⁴ In fact, this cat was referred by a veterinary ophthalmologist for advanced imaging and subsequent conjunctival maxillary sinustomy because initial attempts at NL cannulation were unsuccessful. The authors’ elected to try NL cannulation with the guidance of a steerable AH guidewire before considering conjunctival maxillary sinustomy in order to preserve the original NL pathway. The steerable AH guidewire used in this case (0.48 mm in diameter) had an angled tip which made it possible to steer the wire through the nearly orthogonal curvature in the NL duct near the second premolar tooth as well as from the lacrimal sac to the inferior canaliculi. The guidewire is thin but stiff enough to go through partially obstructed areas. These characteristics make such guidewires commonly used instruments for cardiovascular procedures, intrahepatic portosystemic shunt stenting, and the treatment of urethral obstruction in cats. The use of steerable AH guidewires has been reported in dogs with NL system obstruction.⁹

The 3.0 Fr urethral catheter used in the current case report is designed to be used with the 0.48 mm steerable AH guidewire. Its size permitted cannulation over the steerable AH wire from the nasal punctum through to the inferior punctum while still fitting tightly enough within the inferior canaliculi and NL system to likely expand the NL pathway to some degree.

The final important point from this case is the consideration of placing a third eyelid flap when a catheter is to be maintained within the NL system long-term. Due to the tight apposition of the eyelids against the globe of the eye and the close proximity of the inferior punctum to the cornea, there is risk of corneal injury. At the time of NL stenting, the placement of a third eyelid flap was considered but it was uncertain if the cat would tolerate the flap for 4–6 weeks. Furthermore, after carefully evaluating the location of the catheter it was determined that the catheter was not contacting the cornea and therefore a flap was deemed unnecessary. The cat was doing well at its recheck 5 days post-stenting with no evidence of contact between the catheter and the cornea, and it was not until 21 days post-stenting that the acute bullous keratopathy developed after the cat removed the E-collar. It is unclear whether the cat removed the E-collar first and then rubbed the catheter into the eye or whether the catheter had been displaced over time and drifted into the cornea which prompted the cat to remove the E-collar. Fortunately, the acute bullous keratopathy was successfully treated with a third eyelid flap and adjustments to the ophthalmic medications. In retrospect, placement of a third eyelid flap at the time of stenting may have prevented corneal injury altogether; however, recommending the pre-emptive use of a third eyelid flap when stenting feline NL ducts is beyond the scope of this single case report.

NL disorders are uncommon in cats.¹⁴ Reported causes of NL system obstruction in cats include a maxillary canine tooth root abscess⁵, excessive inflammation following maxillary canine tooth extraction,¹⁵ and squamous cell carcinoma involving the NL system.¹⁴ In dogs, NL system obstruction with foreign bodies is not uncommon^9,10,16; however, this has not yet been reported in cats. The etiology of the partial obstruction of the NL duct in this case was unclear. Although the partially obstructed region was near the distal root of the maxillary third premolar tooth, there was no evidence of periodontitis nor foreign body or neoplasia on postcontrast CT or CT-dacryocystorhinography. Considering the very early onset of clinical signs (at 1 month of age or earlier) the NL duct narrowing may have been a congenital anomaly. Primary infection with feline herpes virus-1 and secondary obstruction due to ocular discharge was thought less likely due to the absence of past or current ocular or respiratory signs other than NL system obstruction.

Although CT-dacryocystorhinography provided valuable information pertaining to the anatomy and patency of the NL duct in this case, CT interpretation is not intuitive for clinicians without extensive radiology training. By creating segmented 3D models of the NL duct, the authors were able to further characterize the geometry of the NL duct as well as digitally manipulate the duct via virtual cannulation. Furthermore, rehearsals using the 3D-printed hemimaxilla with the virtually cannulated NL duct assisted the authors in selecting the appropriate stent material and stenting orientation.

To the authors’ knowledge, this is the first report of successful NL stenting in a cat with partial obstruction of the NL system. It provides a detailed description of the methods implemented as well as several clinically important principles to optimize the approach.