Abstract
To assess the use of Multi-detector computed tomography instillation dacryocystography (MDCT-DCG) and its role in the diagnosis of lacrimal drainage system (LDS) blocks. It is a prospective evaluation of Twenty-five cases presenting with symptoms with NLDO (nasolacrimal duct obstruction) assessed by MDCT-DCG. The study was conducted in LN medical college and JK hospital Bhopal (M.P) territory centre between January 2016 and January 2017. Various levels of LDS obstruction were detected, Lower canaliculus 12% common canaliculus in 20% patients, lacrimal sac in 12% junction between lacrimal sac and NLD in 40% and NLD obstruction in 16% patients. The most common CTDCG findings were dilated opacified lacrimal sac with no opacification of the nasolacrimal duct (NLD) in 40% patients. CTDCG is a non-invasive, quick, patient friendly, indispensable in the assessment of NLDO procedure that adds benefit in documentation and preoperative planning.
Keywords: Multi-detector computed tomography, Dacryocystography, Lacrimal drainage system, Nasolacrimal duct
Introduction
The main indication for the evaluation of the lacrimal pathways is epiphora which is the excessive tearing of any etiology. It may due to excessive tear production, resulting in inadequate evaporation and drainage due to the large volume of tears. other even more common situation is epiphora caused by Anatomical obstruction may occur at any point along the lacrimal drainage pathway and may be congenital or acquired [1]. Clinical examination and probing are often sufficient to diagnose and plan treatment [2]. Other causes are diverticula, fistulas, medial canthal tumors, mid-face trauma and obstruction secondary to surgical intervention [3].
Nasolacrimal drainage obstruction (NLDO) is mainly classified as congenital obstruction or acquired obstruction. Acquired obstruction is further divided into primary or secondary. Primary acquired nasolacrimal duct obstruction (PANDO) describes obstruction caused by inflammation or fibrosis without any precipitating cause [4]. Secondary acquired lacrimal drainage obstruction (SALDO) include as infectious, inflammatory, neoplastic, traumatic and mechanical [5, 6]
Imaging study of the lacrimal system in patients with epiphora allows the diagnosis of lacrimal obstructions and their possible complications and, from the therapeutic point of view it provides safer information for indicating the surgery and the type of procedure to be performed [7]. The first contrast-enhanced radiographs of the lacrimal pathways were performed by Ewing in 1909utilizing a bismuth subnitrate solution, aiming at demonstrating a lacrimal abscess [8].
Currently, the lacrimal pathways study is mainly divided into functional and anatomical evaluations. The functional evaluation is mainly performed by means of staining tests, scintigraphy. The anatomical evaluation is performed by conventional dacryocystography (DCG), computed tomography (CT) and magnetic resonance imaging (MRI) each with its own advantages and limitations [9]. Conventional DCG is capable of demonstrating the patency as well as intrinsic pathology of lacrimal drainage system. However, it is limited in its ability to demonstrate information extrinsic to the nasolacrimal drainage system and provides limited soft tissue detail [10]. Dacryoscintigraphy, using Technetium-99 m pertechnetate solution, is a physiological study of the lacrimal drainage system, it is limited by suboptimal resolution and lack of easy availability [10].MRI scan show the lacrimal sac as clearly as CT scan, but it does not show the canaliculi and has the same limitations as a standard CT scan in viewing canalicular pathology. Injection gadolinium is needed to visualize the canaliculi [10]. Although it can be performed without exposure to ionizing radiation or contrast by using saline for filling the lacrimal system, the test is expensive, gives poor bony details, has a long acquisition time with image degradation in case of patient movement and is not recommended as a routine examination [9, 10]. Plain or intravenous (IV) enhanced CT does not image the superior, inferior and the common canaliculi. They are identified by placement of topical contrast medium either into the conjunctival sac or by cannulation of the punctum. High- resolution thin sections CT (HRCT) imaging in the axial and/ or coronal plane is helpful in assessing those structures intimately associated with the nasolacrimal drainage system [10]. By combining CT with DCG (CTDCG), the relationship between the nasolacrimal drainage system and the surrounding soft tissue and bony structures can be clearly demonstrated. It defines the lacrimal system anatomy and facilitates preoperative planning and intraoperative decision making [11].
CTDCG are better in displaying the smaller components of the lacrimal system, the superior, inferior and common canaliculi, than MRDCG [12]. It is more sensitive than MRDCG in distinguishing high-grade stenosis from total obstruction of the nasolacrimal drainage system. The increasing capabilities of thin-slice helical CT, with two- dimensional (2D) and three-dimensional (3D) reconstruction and shorter acquisition time offers excellent imaging resolution and patient compliance. CTDCG technique was first described in detail in 2002 by Freitag et al. [9]. Since then, only limited reports of this technique have been described.
Multidetector CT (MDCT) is the recent advancement in CT technology. in helical CT single-row detector array used but in MDCT multiple row detector array is used. This allows shorter breath-hold time and faster scan times, with. It reduces motion artifacts which in turn, produces more diagnostic images. In it increased volume coverage combined with thinner slice thickness obtains better quality, volume data sets, for workstation analysis, either in multiplanar reformation (MPR), curved planner (CP) reformation or 3-D imaging. Moreover, by using MDCT, different image thickness can be obtained from the same acquisition data set [13]
In this study we use comfortable instillation dacryocystography with MDCT. The aims of the present study are to demonstrate multi-detector CTDCG for assessment of the lacrimal pathway’s obstruction.
Materials and Methods
Prospective analysis of 25 (20 females and 5 males) patients who underwent CTDCG during the period January 2016 to January 2017 at LN medical college and JK hospital Bhopal (M. P) tertiary referral centre was done. All patients with primary epiphora were clinically evaluated in Ophthalmology Department for LDS obstruction. Their ages ranged from 10 to 70 years. Detailed history including history of previous lacrimal surgery, trauma or sinus disease was elicited. Lacrimal system evaluation, including position and appearance of the punctum and lid, presence or absence of medial canthal mass, regurgitation on pressure on the sac or canaliculus, and syringing, was performed. The study protocol was approved by the review board of institution, and informed written consent was taken from patients. Each patient was questioned about the relative discomfort of contrast material and any side effects of contrast material.
The patients were recommended for CT-DCG after a risk–benefit analysis to assure that the amount of benefit outweighs the amount of risk. CTDCG was performed in patients in whom there was uncertainty as to the cause of epiphora on clinical examination or in the presence of medial canthal mass. Patients with known allergy to iodine or contrast media was exclude from undergoing the study. The patients were clinically examined by the ophthalmologist All patients were referred to the Radiology Department at the same location and underwent CTDCG examination. Contrast media used was iohexol (Omnipaque, 300 mg iodine /ml). It is a low-osmolar, water-soluble, non-ionic, iodinated contrast. Two drops of contrast medium were instilled into the conjunctival cull de sac of the diseased site every minute for total of 5 min, followed by instillation of 2 drops when the patient placed supine on the scanner table. Simultaneous MDCT scanning of the facial structures was performed. At the end of examination, a few drops of saline were instilled to assist the elimination of the contrast. The CT-DCG examination was performed on GE Lightspeed4 scanner and Siemens Emotion6 MDCT. Scanning parameters included volumetric high-spatial-frequency kernel algorithm. Slice thickness was 1.25 mm. Table speed for volumetric CT to enable the least cycles of breath-holds as possible. Tube rotation was 0.6–0.9 s (0.75 s). Detector Collimation 1 mm. Helical mode (volumetric CT). Matrix: 512 · 512.FOV: 150–180. kVp and mAs per slice: 120 kVp and approximately 150 mAs. The thin slice was sent to the workstation, where they were available for viewing in axial, sagittal and coronal planes. Coronal oblique view was valuable in viewing the contrast column in the nasolacrimal duct. The nasolacrimal systems of the all patients were scanned in the prone position for direct coronal imaging and to allow for retention and gravitational flow of the instilled contrast media through the nasolacrimal ducts.
Analysed data was included:
Clinical level of obstruction.
The level of obstruction was compared with the final clinical reports.
Results
Twenty-five patients were enrolled 20/25 (80%) females and 5/25 (20%) males, age ranged from 10 to 70 years. All patients presented with one-sided primary epiphora. 18 patients (72%) had left sided epiphora and 7 (28%) patients had right sided epiphora. Epiphora and inner canthus swelling were the presenting complaints in 3 patients (12%). Twenty-two (88%) presented with epiphora with no inner canthal swelling (Table 1). There were twenty-three patients (92%) with infective aetiology, one with failed DCR (4%), one with posttraumatic obstruction (4%) (Table 2). NLDOs were occur at different levels. It starts as high as the punctum; to as low as the inferior nasolacrimal meatus at the inferior nasal turbinate. In this study from a clinical point of view; a broader classification was proposed which classifying high obstruction as those in the common canaliculus, mid-level obstructions as those in the region from the lacrimal sac (LS) neck to the lower third of the bony canal, and low-level obstructions as those at the lower end of the nasolacrimal duct (NLD). CTDCG showed obstructions at various levels of the lacrimal outflow system 3/25 (12%) at the level of lower canaliculus (idiopathic PANDO related to canalicular mucus plugs with mucocele), 5/25 (20%) at level of the common canaliculus (1 patient failed dacryocystorhinostomy), 3/225 (125%) at LS, 10/25 (40%) at the junction between the lacrimal sac and duct (= proximal NLD), and 4/25 (16%) along the tract of the lacrimal duct (= distal NLD), distal NLD block include 1 patients with posttraumatic obstruction. Clinical testing of the LDS system showed same levels of obstruction with the exception of NLD level where the clinical testes did not differentiate proximal form distal NLD obstruction (Table 3).CTDCG showed anatomically tight bony canals and a small proximal mucocele 3/25 (12%), opacification of the canaliculi with no opacification of the LS and NLD in 5/25 (20%) patients, incomplete contrast filling of the LS with no pacification of the NLD in 3/25 (12%), dilated opacified sac and no opacification of the NLD in 10/25 (40%), partial distal NLD obstruction with delayed faint opacification in post-traumatic patient 1/25(4%), and complete NLD obstruction in 4/25 (16% (Table 4).
Table 1.
Distribution of patients according to clinical presentation
| Clinical presentation | No. of patients | % |
|---|---|---|
| Epiphora without swelling | 22 | 88 |
| Epiphora with swelling | 3 | 12 |
Table 2.
Distribution of patients according to final diagnosis
| Final diagnosis | No. of patients | % |
|---|---|---|
| infective aetiology | 23 | 92 |
| failed DCR | 1 | 4 |
| posttraumatic obstruction | 1 | 4 |
Table 3.
Level of lacrimal drainage obstruction as detected by CTDCG and clinical tests
| Level of obstruction | *Clinical testes (%) | CTDCG (%) |
|---|---|---|
| Lower canaliculus | 12 | 12 |
| Common canaliculus | 20 | 20 |
| Lacrimal sac | 12 | 12 |
| Lacrimal sac to NLD junction | 56 | |
| proximal NLD obstruction | 40 | |
| Distal NLD | 16 |
*Clinical testing including: inspection of punctum, palpation of the lacrimal sac, regurgitation test, syringing (irrigation), and diagnostic probing
Table 4.
CTDCG findings in patients
| CTDCG findings | No. of patients |
|---|---|
| anatomically tight bony canals and a small proximal mucocele | 3/25 (12%) |
| Opacification of the canaliculi with no opacification of the LS and NLD | 5/25 (20%) |
| Incomplete contrast filling of the LS, with no opacification of the NLD | 3/25 (12%) |
| Dilated opacified sac and no opacification of the NLD | 10/25 (40%) |
| Complete NLD obstruction | 4/25 (16%) |
| Partial distal NLD obstruction with delayed faint opacification | 1/25(4%) |
Discussion
The lacrimal drainage apparatus is susceptible to a multiple pathologic finding, including obstruction, infection, inflammation, and neoplasms. The diagnosis of these processes is aided by the use of radiologic studies. But these techniques have their drawbacks [9]. Dacryoscintigraphy is a physiological study of the lacrimal drainage system but it is limited by suboptimal resolution and lack of easy availability. Conventional cannulation dacryocystography is invasive and requires administration of local anaesthesia, cannulation, dilatation of the lacrimal punctum, and injection of contrast material. Thus, it requires patient cooperation and may be difficult in paediatric patients and there is also the risk of iatrogenic trauma or scarring of the lacrimal apparatus; and also, it offers minimal information extrinsic to the nasolacrimal drainage system and provides limited soft tissue detail [14]. MRI scanning is useful in imaging the lacrimal sac, but it is expensive, gives poor bony details, and has a long acquisition time with image degradation in case of patient movement; so, it is not recommended as a routine examination[15].our technique is non-invasive, rapid, easily performed and does not require topical anaesthesia, cannulation, nor dilatation of the lacrimal punctum Compared to conventional cannulation dacryocystography and dacryoscintigraphy, and compared with MRI our technique was very short, well tolerated, less costly and gives good bony details. Moran et al., Karen et al., and Waite et al. reported that CT dacryocystography with instillation technique had many potential advantages including, no cannulation with no risk of iatrogenic injury and better physiologic evaluation of the patient’s disease than the nonphysiologic distension of the LDS by cannulation dacryocystography [12, 16, 17]. In our study we used MDCT because images are superior to that of helical CT as it provides higher contrast resolution. key advantage of multi-detector CT over the helical CT is that it was no longer necessary to try to position patients for coronal images. Plain or intravenous enhanced CT does not image the superior, inferior and the common canaliculi; which can be identified by CT–DCG [18, 19]. In current study we performed unilateral CT dacryocystography in all patients, with no instillation in the normal side to shorten the procedure time and improve patient satisfaction. This was in line with Udhay et al. also advised against bilateral CT dacryocystography [15]. In our study We used water-soluble non-ionic contrast medium in the conjunctival cul de sac. it is a physiologic method to evaluate lacrimal obstruction using and the same method is used by Zinreich et al. [19]. Karen et al. reported that addition of topical saline caused less discomfort than topical contrast material alone and we also added of topical saline solution at the end of the examination to improve patient satisfaction [12]. CT dacryostography method was safe and it was performed rapidly allowing examination of paediatric or less cooperative patients without the need for sedation. It is superior to clinical evaluation particularly of the lower lacrimal drainage system as it can identify the exact level of obstruction which cannot be determined by irrigation method (syringing). this technique needed no manipulation of the lacrimal system as compared to probing or cannulation which may be traumatizing or associated with false passage. In current study, CTDCG showed obstruction at various levels of the lacrimal outflow system, the most common level was the junction between the lacrimal sac and duct (= proximal NLD) and Followed by obstruction at the level of the common canaliculi which seen as filling of the superior and inferior canaliculi with no filling of the lacrimal sac and NLD. one of our patients showed partial NLD obstruction with delayed faint opacification, it was associated fascial trauma. Clinical testing of the LDS system showed same levels of obstruction with the exception at the NLD level where the clinical testes did not differentiate proximal form distal NLD obstruction. NLDO is more common in Females than males which may be attributed to the relatively smaller size of the nasolacrimal canal in females. It is possibly related to the smaller diameter of the bony canal and the fluctuating hormone levels affecting mucous membranes in females [20–22] CT-DCG can identify the site and cause of obstruction in post-traumatic lacrimal obstruction. frequently Mid-facial fractures involve the bones about the lacrimal sac fossa, and/or nasolacrimal ducts, leading to nasolacrimal obstruction. Bony fractures may also initiate a cicatrizing reaction that may result in nasolacrimal duct obstructions [22].to evaluate probing and DCR failures MDCT-DCG is a valuable where small size and inappropriate position of osteotomy are frequent causes of DCR failure [23].
For the above-mentioned reasons, we believe that CTDCG imaging technique of evaluation is highly reproductive and objective and it is indispensable in the management of NLDO to assess the nasolacrimal drainage system and the adjacent facial skeleton, thus improving therapeutic planning.
Limitation of this study was that it did not included patients with complex lacrimal pathology, non-availability of several nasolacrimal pathologies and different patterns of the encountered diseases. still, we believe that CTDCG is indispensable in the management of NLDO to assess the nasolacrimal drainage system and the adjacent facial skeleton, thus improving therapeutic planning.
Conclusion
MDCT -DCG improve visualization of the lacrimal drainage system in fine detail with high contrast resolution that adds benefit in documentation and preoperative planning and also it improves patient comfort and short acquisition time makes this technique suitable for children and uncooperative patients.
Funding
This study is not funded by any source and conducted in ENT department of LN medical college, Bhopal MP.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical Approval
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed Consent
Informed consent was obtained from all individual participants included in the study.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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