Ans. b (Ultrasonography) (Ref. Bailey and Love 25th/pg. 79)CONGENITAL HYPERTROPHIC PYLORIC STENOSIS (CHPS/IHPS)# 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 choice)The 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, double/triple track sign, diamond sign/twining recess, pyloric teat/teat sign, beak sign/antral beaking, umbrella/kirklin/mushroom sign and caterpillar sign may be seen.# Treatment:- Ramsted's 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