**4. Classification**

Duodenal obstruction can be either compete (atresia) or partial (stenosis or perforate web). Although intrinsic obstruction can occur at any level in the duodenum, nearly 85% of these patients have obstructions at the junction between the first and second parts of the duodenum. The ampulla of Vater is commonly located proximal to the obstruction, which occurs in 85% of the cases, with the common bile duct often traversing the medial aspect of the obstructing septum, a critical anatomical consideration during surgical repair [6, 11].

Gray and Skandalakis classified duodenal atresia into three types (**Figure 2**) [12]:

Type 1 (over 90% of cases): There is an obstructing septum, web, or diaphragm formed from mucosa and submucosa with an intact mesentery (**Figure 2A**). A variant of this anomaly is a "windsock deformity" where the septum is thin and stretches distally in the duodenum. Therefore, externally, the obstruction appears to be more distal than its true location (**Figure 2B**) [13].

Type 2 (1% of cases): There are proximal dilated and distal collapsed portions of the duodenum, and both are connected by a fibrous cord with an intact mesentery (**Figure 2C**).

Type 3 (7% of cases): There is no connection between the two ends of the duodenum with a V-shaped mesenteric defect (**Figure 2D**).
