<prompt> In a child of one month age with history of nonbilious vomiting and no weight gain with palpable epigastric lump, first investigation to be done isBarium studyUltrasonographyEndoscopyCT scan  <response>: Ans. b Ultrasonography Ref. Bailey and Love 25thpg. 79CONGENITAL HYPERTROPHIC PYLORIC STENOSIS CHPSIHPS Increased incidence in firstborn male child with M:F ratio 4:1. Incidence of hypertrophic pyloric stenosis is approximately 2-5 per 1,000 births per year. Most commonly affects boys aged 2-8 weeks Characterised by projectile vomiting after feeds Gastric peristalsis can be seen and a lump felt Inherited as dominant polygenic trait. Ultrasound investigation of choiceThe diagnosis can be confirmed by an ultrasound scan, which shows the thickened pyloric muscle. Pyloric muscle wall thickness 2.5-3 mm Pyloric volume 1.4 cm3 Pyloric length 1.2 cm Pyloric transverse diameter 13-16 mm with pyloric channel closed.- Target Sign: Hypoechoic ring and hypertrophied pyloric muscle around echogenic mucosa centrally transverse scan.- Cervix sign and antral-nipple sign: indentation of muscle mass on fluid-filled antrum longitudinal scan.Normal values: Pyloric canal length: 15 mm Muscle wall thickness: 3 mm Pyloric width: 7 mm Contrast radiology Barium study is now not necessary. Upper Gl Imaging barium study -features- Elongation and narrowing of pyloric canal 2-4 cm length with string sign, doubletriple track sign, diamond signtwining recess, pyloric teatteat sign, beak signantral beaking, umbrellakirklinmushroom sign and caterpillar sign may be seen. Treatment:- Ramsteds Pyloromyotomy splits the hypertrophied muscle leaving the mucosa intact.Additional Educational points:ULTRASOUND is investigation of choice for diagnosing: Initial test of choice Screening for blunt trauma abdomen Focused Assessment by Sonography for Trauma, focal liver lesions, obstructive jaundice or acute abdomen. Hydrocephalus in infants, Neonatal cerebral hemorrhage To differentiate cystic and solid nodule in thyroid Screening of rotator cuff injury Pleural effusion Gallstones, CHPS, ascitis Minimal, Pelvic abscess Developmental dysplasia of hip DDH CDH Scrotal lesions 