nasolacrimal duct obstruction ( nldo ) is a common congenital abnormality that occurs in 30% of neonates ( range 6 to 84%).1 only 2 to 4% of these children become symptomatic , and most cases of nldo resolve spontaneously in the first year of life.1 
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  dacryocystocele or congenital mucocele of nasolacrimal duct is a relatively rare variant of nldo , representing 0.1% of children with congenital obstruction , and results from the coexistence of a distal and a proximal obstruction.1 
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  nasolacrimal duct mucocele typically presents as a bulging in the lower medial canthus of the eye , associated with epiphora . , we report a case of congenital nasolacrimal duct mucocele , which recurred after surgery and was treated with endoscopic approach , followed by a literature review . the patient was a 30-year - old man with a history of bilateral congenital cyst of nasolacrimal duct diagnosed by the presence of a bulge in both lacrimal sac topographies since birth , without associated symptoms . he underwent surgery on the left side at 9 years of age and on the right side at 21 years of age , but the tumor recurred on the right side , without tearing , pain , discharge , or other symptoms . in subsequent evaluation with an ophthalmologist , a lack of upper and lower right lacrimal ducts was identified and indicated reconstruction surgery lacrimal spot , which was done in december 2007 . however , he developed ipsilateral epiphora later , requiring another two procedures  dacryocystectomy in july 2011 and august 2011but without success , leading to recurrent local infections . after the last procedure , computed tomography ( ct ) showed a cystic expansion in the right lacrimal sac topography and dilatation of the bony canal of the nasolacrimal duct ( figs . 1 and 2 ) . computed tomography of the paranasal sinuses , axial section , in bone window , showing hypodense cystic lesion in the right nasolacrimal duct topography . 
 computed tomography of the paranasal sinuses , coronal section , in bone window , showing hypodense cystic lesion in the right nasolacrimal duct topography . the patient was then referred for evaluation by the rhinology group of hospital universitrio professor edgard santos ( salvador , brazil ) ; nasal endoscopy showed no alterations . he had endoscopic dacryocystorhinostomy in december 2011 , with confection of mucosal flap and osteotomy of nasolacrimal bone , noting that the lacrimal sac was already opened with drainage of thick purulent secretion . the patient remains asymptomatic and without clinical signs 1  year and 8 months after surgery . the nasolacrimal duct is formed by canalization of the caudal extremity of an epithelial cord derived from the ectoderm in the naso - optic fissure , which is often not completed at birth . nldo at birth is common and usually asymptomatic or presents with epiphora in neonates and infants , which resolves spontaneously in most cases.2 generally , it results in blockage in the distal end of the nasolacrimal system , at the hasner valve level , although the blockage can also occur at the lacrimal spot.2 
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  nasolacrimal mucocele , on the other hand , occurs in a small proportion of children with nldo , when there is a distal obstruction ( distal membrane perforation failure ) associated with a proximal obstruction , which can be functional or mechanical.2 
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 5 it is characterized by a cystic mass at the medial canthus with dilation of the nasolacrimal duct that can , rarely , extend into nasal cavity.2 
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 6 patients with dacryocystoceles may present with local infection or difficult breathing or breast - feeding in the breast ipsilateral to the mucocele.5 
  although dacryocystoceles are rare in adults , recurrent chronic keratitis of bacterial etiology ( chlamydia trachomatis ) has been reported in patients with trachoma , which , due to repeated infections , can lead scarring of the conjunctiva and even to lacrimal obstruction.7 
  it is believed that a mixture of mesodermal cells , mucus , amniotic fluid , tears , and colonizing bacteria compose the contents of the lacrimal sac , causing distention of the lacrimal system seen in dacryocystocele.7 
  encephalocele , hemangioma , dermoid cysts , and nasal gliomas may present similarly and must be considered in the differential diagnosis.5 
  dacryoceles appear as rounded , well - circumscribed lesions centered in the region of lacrimal sac in ct and magnetic resonance imaging ( mri ) . in ct , if infected , it may show a peripheral contrast uptake.8 
  conservative treatment of dacryocystocele is based on a short course of topical antibiotics , warm compresses , and local massage three times a day , with a reported resolution rate of 76% . dacryocystitis may occur within a few days or weeks and requires intravenous antibiotics to prevent sepsis . most ophthalmologists recommend early surgical intervention in cases of respiratory compromise , dacryocystitis , cellulitis , large dacryocystoceles inducing astigmatism , or recurrent dacryocystoceles and in cases of failed conservative strategies.1 
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 10 in cases of infection or respiratory compromise , drainage is required 24 to 48 hours after the start of antibioticoterapia.6 
  dacryocystorhinostomy is a surgery commonly performed , in which a fistula is created between the lacrimal sac and the nasal cavity to relieve the epiphora caused by nldo . the success rates vary from 75 to 95% in external access and 60 to 90% in endoscopic approach . the most common cause of failure in endoscopic surgery is obstruction of the new ostium by granulation or scar tissue.11 
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  however , recent studies have shown better results with endoscopic dacryocystorhinostomy with confection mucosal flap in front of the middle turbinate and subsequent lateral wall osteotomy , with similar rates compared with the external access . the endoscopic technique has advantages such as no scars , less surgical trauma , less bleeding , a quicker return to work , and preservation of the medial canthus structure , providing sustainability of lacrimal pump mechanism.11 
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  the success of surgery depends on creating a large bony ostium and preventing closure of this stoma . use of mucosal flaps after wide resection of bone surrounding the sac is one technique used to prevent granulation tissue and narrowing of the canal , with good results according to the literature.11 
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  the main advantage of external dacryocystorhinostomy ( dcr ) is visualization of the anatomy that facilitates the precise removal of bone in the lacrimal fossa and enables the exact anastomosis of the nasal mucosa and lacrimal sac . nevertheless , an intranasal component that is not recognized prior to the external access increases the chance of treatment failure if the catheter does not pass over the wall of the cyst.5 
 11 nasolacrimal duct mucocele is a rare occurrence ; however , it carries a risk of major complications ( local infection , cellulitis , respiratory distress , etc . ) . surgery ( dacryocystorhinostomy ) is considered as the definitive treatment , and external access is still the most widespread and commonly used approach by ophthalmologists . however , the interest in an endoscopic nasal approach has increasingly grown as recent studies have shown good results with this technique , with similar success rates between the two types of procedures .
introduction  mucoceles are benign expansive cystic formations , composed of a mucus - secreting epithelium ( respiratory or pseudostratified epithelium ) . 
 nasolacrimal mucocele occurs in a small proportion of children with nasolacrimal duct obstruction and is characterized by a cystic mass in the medial canthus with dilation of the nasolacrimal duct ; although dacryocystoceles are rare in adults , they have been reported in patients with trachoma . 
 objective  discuss clinical aspects , diagnosis , and therapeutic management of mucocele of nasolacrimal duct based on literature review . 
 resumed report  the authors report a case of bilateral congenital nasolacrimal duct cysts in a 30-year - old man , identified as a tumor in the topography of both lacrimal sacs since birth without associated symptoms . 
 the patient underwent successive surgical treatments , leading to recurrence of the tumor at the right side and recurrent local infections . 
 conclusion  endoscopic dacryocystorhinostomy has been increasingly used with good results and success rates similar to the external access .