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 
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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 . 