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Outcomes of Endoscopic Dacryocystorhinostomy: Enhancing the Patency of the Rhinostomy
Dacryocystorhinostomy (DCR) is the definitive treatment for epiphora caused by nasolacrimal duct obstruction (NLDO). The procedure creates a functioning passageway for tears from the lacrimal sac into the nasal cavity by bypassing the obstructed nasolacrimal duct. The cause of NLDO can be idiopathic, as in primary acquired NLDO, or it can be secondary to other disease entities. Secondary causes include infectious, inflammatory, neoplastic, traumatic, and mechanical processes.
A common cause of DCR failure is mucosal scarring around or over the ostium. Many techniques for preventing or limiting fibrosis and scarring around the surgical ostium have been described. These include various surgical techniques, placement of postoperative stents, and application of anti-inflammatory or antiproliferative mediations. As surgical techniques have been described in the previous chapters, this section reviews the adjunct procedures and medications that have been used to optimize outcomes.
Outcomes of Endoscopic Dacryocystorhinostomy
Endoscopic DCR has been compared to external DCR in various studies. Advocates for the endonasal approach offer the benefits of addressing comorbid sinonasal disease and septal deviation as well as the avoidance of an external scar. A Cochrane review published in 2017 reports no difference in anatomic success between the two groups when mechanical endonasal DCR was compared to the external approach (90% both groups; relative risk 1.00; 95% confidence interval 0.81 to 1.23; 40 participants); however, the endonasal group did not achieve patency as often when the laser-assisted technique was used (63% vs. 91%; relative risk 0.69; 95% confidence interval 0.52 to 0.92; 64 participants).
Two recent retrospective case series report data from 624 and 120 cases of endoscopic, endonasal DCRs. Coumou et al. reported an anatomic success rate in 90.1% and a functional success rate in 90.1% of adults with the use of silicone stenting, removed 3 months after surgery. They had a 3.2% complication rate and average follow-up time between 3 and 21 months. Ciger et al. reported an anatomic success rate of 92.5% and functional success rate of 92.5% without the use of silicone stenting with mean follow-up of 46.5 months. Similarly, they had a 3.3% complication rate. Both of these studies discuss postoperative scarring (fibrosis, granulation, and synechiae) at the rhinostomy site as the primary cause for failure. Further, Ciger et al. reported that the scarring was identified in the 3- to 4-month postoperative time frame.
Outcome data for patients who undergo revision DCR for either failed external or endoscopic DCR are also available. Ali, Psaltis, and Wormald report 91.3% anatomic and 86.9% functional success rates after revision endoscopic DCR with a mean follow-up of 26.4 months. Moreover, they report the causes of primary failure, including cicatricial ostium closure (55%), scarred internal common opening (27%), and organized granuloma over the common canaliculus (16.7%). In addition, 39% of patients underwent adjunctive septoplasty and 5.5% had endoscopic sinus surgery at the time of revision.
The published rate of success for patency in endoscopic DCR ranges from 78% to 100% and is approximately 90% in the studies reviewed previously. These rates are comparable to those of the open approach, but both approaches continue to leave an approximate 10% risk of failure, primarily from the formation of scar tissue. This provides an opportunity for the discovery of an adjunctive therapy or procedure to improve the overall outcome of this procedure.
Nasolacrimal Stent Type
Since the development of nasolacrimal stents, a number of different materials have been used, including organic materials, metals, and synthetic materials. Stents are designed to promote longer retention and prevent inflammation. Stenting materials should be inert, pliable, smooth, and readily available. Silicone and polyethylene meet many of these qualifications and are the material of choice for most modern stents.
The decision regarding whether or not to insert a stent is made, by some, based on the tightness of the common canaliculus. This can be assessed by passing a Bowman probe (Integra LifeSciences, Cincinnati, OH) through the canaliculus, and if significant resistance is met, a stent is placed. Bicanalicular stents, which traverse the superior and inferior canaliculi and meet in the common canaliculus, are the most common type used for DCR. Silicone material is used most often, but alternative stent materials have also been used, including small red rubber catheters and C-flex lacrimal catheters (Consolidated Polymer Technologies, Clearwater, FL). A study by Woog, Metson, and Puliafito et al. used traditional silicone tubing, 10-Fr red rubber urinary catheters, and C-flex catheters for stenting purposes. A segment of either red rubber catheter or C-flex catheter was used at the stoma site to aid with patency. They demonstrated success in all 10 cases when the red rubber catheter was used, with no need for revision. The use of this catheter was abandoned later in the study, however, as placement and securement of this catheter type were found to be tedious. They instead opted for a C-flex catheter made of highly biocompatible thermoplastic for the remainder of the study. This catheter was easier to place, as the silicone stent could be placed through the center of the C-flex catheter rather than next to it, as was done with the red rubber catheter. Patency was maintained in all five cases stented with the C-flex stent, but follow-up in this group was shorter. In comparison, only a 68% success rate was found when the silicone stent was used alone. The authors endorse that the earlier cases, which used silicone stenting alone, may have been subjected to increased failure rates related to the learning curve for using the device.
Studies have reported that the silicone stent itself may cause tissue granulation, predisposing the site to postoperative infection, adhesions, and punctal lacerations, resulting in surgical failure and complications. A meta-analysis by Kang et al. found no significant difference in the surgical success rate between endoscopic DCR with silicone intubation and that without stenting. Complications of DCR without stenting can also include synechiae formation and granulation tissue surrounding the stoma.
Modifications to stent materials have also been proposed to improve the success rate in DCR. Applications of antimicrobial substances can, in theory, prevent biofilm formation and prevent stent occlusion. However, these substances create irregularities on the stent surface, which allows for easier adherence and colonization by disruptive bacteria. Uncoated devices have been found to develop similar surface irregularities after exposure to normal living conditions for 3 months. This may suggest a negligible change in risk of biofilm development owing to the physical characteristics of coating materials. Nevertheless, no effective method to prevent formation of biofilms on nasolacrimal stents has been identified. Future endeavors should seek to design materials with nonstick properties and material coatings that can prevent formation of polysaccharide biofilms.
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