Double track sign is seen in -
On upper gastrointestinal fluoroscopy: * delayed gastric emptying * peristaltic waves (caterpillar sign) * elongated pylorus with a narrow lumen (string sign) which may appear duplicated due to puckering of the mucosa (double-track sign) * the pylorus indents the contrast-filled antrum (shoulder sign) or base of the duodenal bulb (mushroom sign) the entrance to the pylorus may be beak-shaped (beak sign)
Duodenal atresia
CHPS
Gastric ulcer
Achalasia
GIT and hepatobiliary system