This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stomach & Duodenum, Subject name: Surgery
True about hyperophic pyloric stenosis is all except: 
Select and explain. 
A. Typical electrolyte abnormality is Hypochloremic, hypokalemic, metabolic alkalosis with paradoxical aciduria ., B. First born male is commonly affected, C. Ramstedt operation is done, D. Visible peristalsis is always seen
D: Visible peristalsis is always seen
Answer: D: Visible peristalsis is always seen 
Explanation: Clinical presentation: Infants is normal at bih, symptomatic between the ages of 3-6 weeksQ . Infants with HPS typically present with projectile non bilious vomitingQ. Visible gastric peristalsis may be seen (not always)as a wave of contraction from the left upper quadrant to the epigastriumQ. Typical electrolyte abnormality: Hypochloremic, hypokalemic, metabolic alkalosis with paradoxical aciduriaQ. First born male commonly affected. Ramsted operation commonly done.