The cervix sign of pyloric stenosis describes the indentation of the pylorus into the fluid-filled antrum, seen in pyloric stenosis on ultrasound examination.
2. Westra S J, C J de Groot, N J Smits and C R Staalman. “Hypertrophic pyloric stenosis: use of the pyloric volume measurement in early US diagnosis..” Radiology 172, no. 3 (1989): 615-619. doi:VL - 172.