Diagnostic value of the acute angle between the prestenotic and poststenotic duodenum in neonatal annular pancreas.

ABSTRACT

OBJECTIVES: To analyze the ability of upper gastrointestinal (GI) saline-contrast ultrasound (US) to detect neonatal annular pancreas. METHODS: Sixty-two neonates, who presented duodenal obstruction and were examined by upper GI saline-contrast US before treatment, were retrospectively analyzed and categorized into four groups according to their final diagnosis group A, annular pancreas (n = 28); group B, duodenal atresia (n = 2); group C, descending duodenal septum (n = 25); and group D, normal (n = 7). The ultrasonic characteristics were analyzed that especially focused on whether the angle between the prestenotic and poststenotic descending duodenum (at or below a derived cutoff) could identify neonatal annular pancreas. RESULTS: To detect annular pancreas using the concave contour of the distal prestenotic duodenum, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined at 71.4%, 100%, 100%, and 80.9%, respectively. When using the hyperechogenic band around the constricted duodenum, the sensitivity, specificity, PPV, and NPV were determined at 82.1%, 94.1%, 92%, and 86.5%, respectively. For using the 40.7° acute angle cutoff between prestenotic and poststenotic descending duodenum, the values of sensitivity, specificity, PPV, and NPV were determined at 100%, 97.1%, 96.6%, and 100%, respectively, of which the area under the receiver operating characteristic curve was 0.979. CONCLUSIONS: Upper GI saline-contrast US has a lower possibility for misdiagnosis of neonatal annular pancreas when considering the acute angle between the prestenotic and poststenotic descending duodenum. KEY POINTS • This study includes the largest series of neonates with annular pancreas of which the characteristics were analyzed using the upper GI saline-contrast US. • Neonatal annular pancreas may be diagnosed by the characteristics-concave contour of the distal prestenotic duodenum; acute angle cutoff of 40.7° between the prestenotic and poststenotic duodenum; the "S" shape formed by the pylorus, the duodenal bulb, and the prestenotic and poststenotic descending duodenum. • The acute angle with the highest diagnostic value can be used to quantitatively diagnose neonatal annular pancreas and avoid potential misdiagnosis caused by sonographers' subjectivity.