The abdominal mass in pyloric stenosis in a new born child can be best palpated:
Ref. Sabiston Textbook of Surgery. Pg. 1869
 
Background

Hypertrophy of the pyloric sphincter causes narrowing of the gastric outlet
Most common cause of gastric obstruction in patients 2-12 weeks old
Risk factors include male (4:1); firstborn (2:1); white/caucasian; term infants; bottle-fed babies

Presentation

Usually present around 3-6 weeks with a history of progressively worsening non-billious vomiting (may be projectile)
Associated with poor weight gain, decreased urine output (fewer wet nappies) and stools, excessive hunger, dry mucous membranes and depressed fontanelle
Examination of the abdomen may reveal an epigastric ‘olive-shaped’ mass

Management

Fluid resuscitation- correct any electrolyte disturbance (particularly hypokalaemia) prior to surgery
Nil by mouth and nasogastric drainage or suction prior to surgery and between feeds
Surgery – Pyloromyotomy
During feeding
In the umbilical area
In the epigastric area
In the right hypochondriac quadrant