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Embryogenesis of : Is localized vascular accident a factor?

Hemonta K. Dutta, Shree Harsh Department of Pediatric surgery, Assam Medical college, Dibrugarh, Assam, India

Address for correspondence: Dr. Hemonta K. Dutta, Assam Medical College & Hospital, Dibrugarh, Assam-786 002, India. E-mail: [email protected]

ABSTRACT

Several theories on embryogenesis of esophageal atresia have been proposed, none could explain the whole spectrum of this anomaly. We report a new variant of esophageal atresia in which the two blind pouches were joined by an atretic band. Histology of the atretic part showed groups of striated muscle arranged haphazardly without any lumen. The existing theories on etiology of esophageal atresia cannot explain this variant. However, localized vascular accident during intrauterine life resulting in disturbances in regional microcirculation could be a possible factor as demonstrated by Louw and Barnard in relation to jejunoileal atresia. This is contrary to the current understanding that disproportionate growth of the horizontal esophageal folds results in esophageal atresia.

KEY WORDS: Embryogenesis, esophageal atresia

DOI: 10.4103/0971-9261.55158

INTRODUCTION joined by an atretic segment about 24 mm long and two mm thick [Figures 1 and 2]. The segment seemed to have The embryogenesis of esophageal atresia (EA) is a few muscle fibers [Figure 3]. The atretic segment was poorly understood. Theories such as intra embryonic excised, blind ends opened and a primary anastomosis pressure, vascular accidents, failure of recanalization, performed. The patient had an uneventful recovery and disproportionate growth of the lateral epithelial folds was discharged on 12th post operative day. etc. were inadequate to explain the whole spectrum of this malformation. The latest theory based on electron DISCUSSION microscopic studies suggests that overgrowth of a dorsal horizontal fold in the region of the tracheoesophageal The can be identified at three weeks of separation would result in EA and tracheoesophageal gestation. In the subsequent two weeks, elongation fistula (TEF).[1] This theory also proposes that late of the esophagus occurs mainly due to ascent of the ischemia of an already formed esophagus could result larynx. Ventral tracheal primordium develops at this in pure EA. stage. Rosenthal proposed that this process involves apposition of two lateral longitudinal epithelial CASE REPORT folds. [2] Failure of this apposition leads to tracheoesophageal fistula formation while apposition The author observed a new variant in a patient with too posteriorly results in EA. Smith proposed that pure esophageal atresia. A two-day old male baby during the rapid phase of esophageal elongation, over weighing 2.6 kg presented with frothing from mouth, thinning of the esophagus results in EA.[3] Tandler’s high respiratory rate and a flat abdomen. A catheter theory of failure of recanalization resulting in atresia through the mouth did not go beyond 10 cm from the may explain the rare congenital esophageal web, but lower jaw. Water soluble contrast study showed a blind fail to explain the full thickness defect in EA.[4] The upper pouch. A right posterolateral thoracotomy was presence of abnormal branchial vessels seen in some done. It was observed that both the blind ends were cases of EA suggest a coincident rather than causal

73 J Indian Assoc Pediatr Surg / Apr-Jun 2009 / Vol 14 / Issue 2 Dutta, et al.: Report of a new variant of esophageal atresia

Figure 2: Excised band

Figure1: Atretic band are still other variants such as pure esophageal atresia that showed spontaneous recanalization,[12] which could be the subtype II5 of type 2 in Kluth’s atlas of esophageal atresia with 2 blind esophageal ends and a cyst occupying the intervening space.

Sinha et al. reported another variant with a TEF between the lower pouch and trachea, with a cystic dilatation in the midportion.[13] The tracheal end of the fistula was obstructed by a membranous septum at both ends of a cystic dilatation, leading to a diagnosis of pure EA (gasless abdomen). In the present variant, which was not reported in the literature earlier, two blind ends of the esophagus are connected by an atretic band. The band was 24 mm long and histology of the part showed presence of disorganized striated muscle groups without any lumen. This is similar to type II atresia of the small bowel. Etiology of this variant could be explained on the basis of the antenatal vascular accident theory Figure 3: Histology of atretic part shows disorganized striated muscle proposed by Louw in jejunoileal atresia.[14] Through their classic experimental study in 1955, Louw and relationship.[5,6] Based on detailed saggital sections Barnard demonstrated that intrauterine vascular insult and scanning electronic microscopic studies on chick to the developing bowel results in variable degree of embryos, Kluth and Habenicht proposed the theory atresia.[2] This study was further supported by some of esophagotracheal separation by dorsal and ventral other experimental studies.[15-17] Similar observations horizontal folds.[7] Overgrowth of the dorsal fold results noted in humans led to wide acceptance of this in distal fistulas continuity with the trachea. Although theory. [18-20] Jejunoileal atresia, in rare instances, has this theory comes close to explaining many of the been found to be associated with esophageal, gastric, types of EA and TEF, it fails to explain embryogenesis duodenal and colonic atresias,[18-20] which may point to of some variant of EA. Variants of esophageal atresia, a common etiological factor. reported in literature, such as esophageal atresia with distal tracheoantral fistula associated with congenital REFERENCES intrathoracic stomach and situs inversus (SI),[8] esophageal atresia with triple fistula,[9] esophageal 1. Louw JH, Barnard CN. Congenital , Observations atresia with an abnormally long lower segment on its origin. Lancet 1955;269(6899):1065-7 2. Rosenthal AH. Congenital atresia of the esophagus with that entered the trachea in the region of the upper tracheoesophageal fistula, Report of 8 cases. Arch Pathology thoracic aperture, a long atretic proximal portion of 1931;12:756-72. the lower segment, and an additional membrane in 3. Smith IE. The early development of the trachea and esophagus in the lower segment,[10] esophageal atresia associated relation to atresia of the esophagus and tracheoesophageal fistula. Contributions to Embryology 1957;36:41-57. [11] with esophageal heterotopic pancreas etc. could 4. Tandler J. Zur Entwicklungsgeschichte des menschlichen not be explained on the basis of these theories. There duodenums im fruhen Embryonal stadium. Gegenbaurs

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