tracheal agenesis is a rare and lethal congenital anomaly , where a complete interruption or absence of the trachea is present .
since it was initially described in 1900 , few cases have been published worldwide ( 1 ) .
the prevalence of tracheal agenesis is less than 1:50,000 with a male to female ratio of 2:1 . in general ,
52% of cases are associated with premature delivery and approximately half of the cases are associated with polyhydramnios ( 2 ) .
type i is characterized by agenesis of the proximal trachea and by the presence of a distal tracheoesophageal fistula , whereas type ii is defined by a complete absence of the trachea and by the presence of normal bifurcating bronchi . in type iii ,
isolated type ii tracheal agenesis with fistula is rare , and up to 94% of cases are associated with other congenital abnormalities .
newborns with type ii tracheal agenesis usually present with polyhydramnios , respiratory distress , aphonia , cyanosis , and an inability to undergo endotracheal intubation . currently , type ii tracheal agenesis accounts for approximately 50 - 60% of all cases . at present
, the etiology of type ii tracheal agenesis is unknown and no significant karyotype exists ( 4 ) . in general , prenatal diagnoses
this case report depicts an unusual situation where type ii tracheal agenesis with esophageal fistula was diagnosed independently of any other congenital anomalies .
our patient was born to a 31-year - old g2p1a0 mother and a non - consanguineous father .
prenatal ultrasound at 25 , 29 , and 32 weeks showed polyhydramnios and suspected esophageal atresia .
amniocentesis reductions were performed three times during the pregnancy to reduce the volume of amniotic fluid . aside from these findings ,
the patient was delivered at 35 1/7 weeks gestation by caesarean section owing to fetal bradycardia and the suspected diagnosis of esophageal atresia .
its birth weight was 1850gm , indicative of intrauterine growth restriction ( iugr ) . respiratory distress developed immediately following birth and attempts at intubation with a 2.5 mm endo - tracheal tube ( ett ) failed due to the blockage below the vocal folds .
examination showed a hypoxic newborn with a po2 of 63 , with a blood ph of 6.8 and a pco2 of 135 .
mask ventilation was also difficult , but an o2 saturation of 95% was achieved following administration of 75% fio2 .
once stabilized , the perinatal patient was immediately transferred to the operating room of a tertiary pediatric medical center . a second intubation using a 2.5 mm ett failed due to subglottic obstruction .
rigid bronchoscopy was performed and revealed a blind pouch below the vocal folds ( fig .
1 ) . notice the scope in the subglottic segment demonstrating 
 absent cervical and thoracic trachea .
tracheostomy was attempted but was unsuccessful as no cervical trachea was palpable below the cricoid cartilage .
intraoperative fluoroscopy of the trachea also confirmed the subglottic stenosis and absence of the lower cervical and thoracic trachea .
the presence of a bronchoesophageal fistula was identified with both bronchi originating from a flattened carina .
the bronchi and carina exhibited unusual horizontal orientation and the carina demonstrated a straight continuous roof with no tracheal remnants ( fig .
2 ) . note the unusual horizontal orientation of r / l main 
 bronchi and carina ( with contrast in the esophagus and bronchial 
 tree ) visualized using fluoroscopy .
based on these imaging studies , isolated type ii tracheal agenesis with bronchioesophageal fistula was diagnosed .
a post - mortem ct scan revealed a 7 mm remnant segment of cervical trachea ( with no lumen ) running in the craniocaudal plane and confirmed the complete absence of the lower cervical and thoracic trachea .
the carina originated from the esophagus and joined to the right and left main bronchi .
floyd et al . defined type ii tracheal agenesis as complete absence of the trachea with the presence of normal bifurcating main bronchi ( 3 ) .
94% of cases are associated with other congenital defects including congenital cardiac , genitourinary , gastro - intestinal , pulmonary , cns , and musculoskeletal anomalies ( 3,6,7 ) .
while the embryological mechanisms behind type ii tracheal agenesis remain controversial , it has been suggested that tracheal agenesis is a result of the abortion of the lung bud outgrowth and delayed formation of the bronchi and lungs via remnant primordial mesenchyme which often attaches to the esophagus ( 7 ) .
also , while no significant genetic karyotype has been found to correlate with tracheal agenesis , homozygous shhnull mutant mice show foregut defects similar to those seen in tracheal agenesis ( 8) .
tracheal agenesis should be included in the differential diagnosis when the following clinical signs are manifested : neonate with a history of polyhydramnios , absence of an audible cry at birth , failure to intubate beyond the vocal folds , and respiratory distress ( 9 ) . in patients with tracheal agenesis ,
surgical correction has been proposed as a corrective measure ( 6 ) . to date , only one patient with type ii tracheal agenesis has survived beyond the neonatal period . however , that surviving patient had a proximal tracheoesophageal fistula in addition to a bronchoesophageal fistula , which allowed the successful establishment of a permanent airway by performing a tracheotomy and inserting a long t tube to create a patent airway ( 10 ) . while temporary management can include the insertion of an esophageal tube , depending on the extent of the fistula , infants with a complete absence of the trachea tend to die within hours of birth , as a permanent airway can not be created .
however , there is no established medical protocol for life conservation in isolated type ii complete tracheal agenesis .
currently , this anomaly is incompatible with life and future hopes for survival will depend on surgical developments .
 in this report we describe a newborn with a rare case of type ii tracheal 
 agenesis and bronchoesophageal fistula . 
 polyhydramnios and suspected esophageal 
 atresia were identified during routine pre - natal ultrasound screening . upon 
 delivery , rigid bronchoscopy , esophagoscopy , and intraoperative fluoroscopy 
 were 
 performed , where both bronchi and the carina showed unusual horizontal orientation 
 making it difficult to identify the fistula . however , 
 a post mortem ct confirmed 
 the diagnosis of an isolated type ii tracheal agenesis with bronchoesophageal fistula . 
INTRODUCTION
CASE REPORT
DISCUSSION