This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
A preterm baby was diagnosed having PDA. Which among the following is the LEAST likely finding in this child? 
Select and explain. 
A. CO2 washout, B. Bounding pulses, C. Necrotizing enterocolitis, D. Pulmonary haemorrhages
A: CO2 washout
Answer: A: CO2 washout 
Explanation: In patent ductus aeriosus (PDA), the pulses are bounding, and pulse pressure is widened due to diastolic runoff through the ductus. PDA with left to right shunt is associated with necrotizing enterocolitis (NEC) due to bowel hypoperfusion. It is the most common acquired GI emergency in the newborn and it is most common in preterm infants, with an incidence of 10% in infants less than 1500 g. Pulmonary hemorrhage can occur in PDA from pulmonary over circulation with the pulmonary vascular resistance droping. Ref: Thilo E.H., Rosenberg A.A. (2012). Chapter 2. The Newborn Infant. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds),CURRENT Diagnosis & Treatment: Pediatrics, 21e.