Pathologies located within the nasal cavity are a cause of external DCR failure. Although a preoperative CT scan is useful in the assessment of nasolacrimal drainage and adjacent anatomical structures, it is not routinely performed before DCR.[4–10]The present study evaluates abnormal findings in CT scans of patients with NLDO and its effect on changing treatment approaches.
The majority of patients (n = 162) enrolled in this study were female (63.6% female vs 36.4% male) Which was consistent with previous studies.[11, 12] Dimensions of the bony nasolacrimal canal, middle nasolacrimal duct, and lower nasolacrimal fossa were smaller in females. In addition, acute angle between the bony canal and the nasal floor in females predisposes them to chronic inflammation of the nasolacrimal drainage system and consequent NLDO. All these anatomical differences can justify the greater prevalence of NLDO among females.[13–17] Furthermore, the results of the present study showed that turbinate deformity was more common in females, which might be another reason for the higher prevalence of NLDO in females.
In this study, abnormal CT scan finding on the same side of NLDO was detected in 71% of the participants which was similar to the results of the study conducted by Yazici et al. (70%). This rate was lower than that obtained in the studies performed by Kallman et al. (87%) and Habesoglu et al. (95.1%).[18, 19] However, a lower rate (57.3%) of abnormal CT scan findings has been reported by Choi et al. which may be due to racial and anatomical variations in different countries.
It should be noted that the most common abnormal finding in this study was nasal septal deviation (37%) followed by turbinate deformity (35.8%) and periocular inflammation (23.5%). In a study carried out by Choi et al., soft tissue opacity in NLDO was reported as the most common (85.9%) abnormal CT finding, which could be attributed to the upright position of patients during CT scans since a high percentage of patients without NLDO (81.7%) showed this abnormality.[10] Loftus et al. and Czyz et al. reported NLD opacity in approximately 70% of the normal population. Czyz et al. showed that air was present more fully in the upright rather than supine position.[16, 17] In the present study, all CT scans were performed in a supine position which can justify the lower percentage of soft tissue opacity in NLD (6.8%).
Nasal septal deviation as the most common CT scan finding in this study was observed in 37% of the cases which was comparable to that in studies conducted by Kallman et al. (39%),[18, 19]though less than that in the studies performed by Habesoglu et al., Sefi et al. and Yazici et al. (64.6%, 65%, and 70% respectively).[19, 20] On the other hand, the rate of patients with nasal septal deviation in Choi et al. and Kaplama et al. studies was lower than that in the current study (11.9% and 27.4% respectively).[10, 21] The nasal septal deviation was the first and second abnormal CT scan findings in the studies carried out by Kaplama et al. and Habesoglu et al, respectively.[19, 20] These differences can be explained by racial and anatomical differences, different imaging indications, and different criteria for the interpretation of abnormal CT scan findings.
In this study, septum deviation and turbinate deformity caused 3.6-fold, and 3.9-fold changes in the surgical approach, respectively. Habesoglu et al. and Kallman et al. reported a higher prevalence of sinonasal pathologies in patients with NLDO compared to those in the control group. Moreover, they reported a higher rate of nasal septal deviation in these patients compared to those in the control group.[18, 19] In the study performed by Habesoglu et al, it has been reported that the incidence of inferior turbinate hypertrophy and maxillary sinusitis was higher in patients with NLDO than in the control group, which was in line with the results obtained in the study conducted by Sefi et al study.[19] The results of the studies conducted by Yazici et al., Lee et al., and Taban et al. were indicative of the correlation between the side of the septal deviation with the side of NLDO.[20, 22–23] On the other hand, based on the results of the previous studies, DCR failure may be due to the untreated existing sinonasal pathologies, such as nasal septum and concha bullosa pathologies.[19, 21] The high percentage of nasal and sinus pathologies in the present study and the role of these conditions in the development of NLDO and the rate of recurrence following DCR could be the reason for changing the surgical approach in a significant number of patients.
In the present study, chronic sinusitis did not lead to a change in the surgical approach. The reason for this difference might be the presence of sinusitis in sinuses not adjacent to the nasolacrimal duct or the resolution of sinusitis by medical treatment. Habesoglu et al. showed that maxillary sinusitis was more common in patients with NLDO; however, they did not find any relationship between the presence of ethmoidal sinusitis and NLDO.[19] The sinuses were not evaluated separately in this study, therefore, no association was found in this regard.
Abnormal CT scan finding was detected in 71% of patients in the present study. The percentage of endonasal DCR was almost 30% higher in cases with an abnormal nasal cavity on CT scan than those without these problems (59.6% vs. 30.2%) which highlights the importance of performing CT scans for surgical planning. Numerous studies supported the performance of CT scans before surgery in all cases of acquired nasolacrimal obstruction. However, some arguments oppose this. Moreover, a CT scan can recognize bony anatomy surrounding the lacrimal outflow system, anatomical variants, factors contributing to nasolacrimal obstruction (such as septal deviation, turbinate malposition, and sinusitis), and malignancies or other mucosal abnormalities.[9,10.21] However, there are some limitations regarding the application of CT scans. Intrinsic tumors of the lacrimal outflow tract may not be evident on a CT scan. The positive predictive value of the test is low for neoplasia as the cause of lacrimal outflow obstruction. Radiation exposure and cost are other concerns in this regard.[24, 25] It is worth mentioning that there are several ideas about the importance of imaging in a patient with nasolacrimal duct obstruction.
Regarding the limitations of the present study, one can refer to the limited number of patients. Moreover, the effect of sinonasal surgery was not evaluated on the surgical outcome, which should be considered in future studies.