Classification

Morphological classification of these lesions allows different surgeons and centers to compare outcomes and is also of therapeutic and prognostic value. The most commonly accepted system is that proposed by Louw13 and modified by Grosfeld et al.14 Whether the lesion is classified as ileal or jejunal is determined by the most proximal affected segment (Figure 2.5).

Stenosis is a localized narrowing of the lumen without any break in the continuity or mesenteric defect. The intestinal wall may be thickened and rigid at the stenotic site and there is a small, often minute, lumen. The overall intestinal length is not shortened. Type 1 atresia is the result of a membranous web occluding the lumen with no mesenteric defect and no intestinal shortening. The lumen is usually completely occluded and the proximal bowel is therefore dilated but remaining in continuity with the collapsed distal segment. Type 2

Apple Peel AtresiaIleal Atresia Apple Peel

Figure 2.5 Variants of ileal atresia. (a) Type 1 due to an internal web (not shown) with no mesenteric defect; (b) type 2 atresia with blind ends joined by a fibrous cord; (c) type 3(a) - blind ends separated with a mesenteric defect; (d) type 3(b), in which the ileum is coiled like an 'apple peel' around a single vessel and completely separated from the proximal dilated duodenum; (e) type 4 or multiple atresias.

Figure 2.5 Variants of ileal atresia. (a) Type 1 due to an internal web (not shown) with no mesenteric defect; (b) type 2 atresia with blind ends joined by a fibrous cord; (c) type 3(a) - blind ends separated with a mesenteric defect; (d) type 3(b), in which the ileum is coiled like an 'apple peel' around a single vessel and completely separated from the proximal dilated duodenum; (e) type 4 or multiple atresias.

atresia arises from a complete obliteration of the intestinal segment into a fibrous cord, which joins two blind ends and runs in the free edge of the mesentery. There is no mesenteric defect and once again the total bowel length is usually normal. In both type 3(a) and type 3(b) atresia the intestine is likely to be shortened and this may have significant clinical consequences. Type 3(a) atresia consists of blind-ending proximal and distal bowel with no connection and an often large mesenteric defect. The blind ends are often physiologically abnormal with decreased or absent peristaltic activity, which may give rise to torsion, distension or perforation. Type 3(b) atresia, also known as apple peel atresia because of its gross morphology, may involve massive intestinal loss. It consists of intestinal atresia near the ligament of Treitz, oblit eration of the superior mesenteric artery (SMA) beyond the origin of the middle colic branch and absence of the dorsal mesentery. The remaining intestine is coiled helically (like an apple peel) around a single perfusing vessel, often has impaired vascularity and is almost inevitably short. Furthermore, there may be additional segments of type 1 or 2 atresia within the apple peel segment. Such a configuration probably arises from occlusion of the SMA due to thrombus, embolus or strangulation as part of a midgut volvulus. In type 4 atresia there are multiple atretic segments and the intestine may resemble a string of sausages. Overall bowel length is usually shortened and the intestine grossly dilated. It has been proposed that the etiology of type 4 atresia may be due to failure of recanalization of solid epithelial-

ization throughout the length of the intestine rather than from multiple single vascular events.

Whilst it is generally accepted that stenosis and atresia of types 1, 2 and 3(b) are the result of intrauterine vascular accidents, a genetic component has been suggested in types 3(b) and 4.

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Responses

  • michael
    Which type of intestinal atresia is appropriately paired with its correct classification?
    4 years ago

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