Paediatric Clinical Chemistry

Question 1

What are the features of necrotising enterocolitis on abdominal x-ray?

Answer 1

Multiple dilated bowel loops
Bowel wall oedema
Intramural air
May have subdiaphragmatic air if perforated

Question 2

Why are neonates predisposed to acidosis?

Answer 2

Because reabsorption (in general) is less effective than in adults because they have a short proximal tubule in the nephron

Question 3

How does the distal tubule in babies react to aldosterone?

Answer 3

It is relatively unresponsive. This leads to a persistent loss of sodium and reduced potassium excretion. Thus the upper limit of normal for potassium is higher in neonates than in adults (6.0 mmol/L).

Question 4

What is the main difference with regards to the Loops of Henle and distal collecting ducts in neonates?

Answer 4

Loop of Henle and distal collecting ducts are short and juxtaglomerular so they have reduced concentrating ability

Question 5

What causes redistribution of extracellular fluid after birth?

Answer 5

Pulmonary resistance drops causing release ANP

Question 6

Below what % of weight loss is normal in the first week of life?

Answer 6

10%

Question 7

List the fluid requirements for neonates on days 1-5 of life.

Answer 7

mL/kg/day
60
90
120
150
180

Question 8

What is the most common cause of hyponatraemia in a baby?

Answer 8

Congenital adrenal hyperplasia
Most commonly caused by deficiency of 21-hydroxylase

Results in reduced cortisol and aldosterone - salt loss

Build up of 17-OH-progesterone and 17-OH-pregnenolone. These go on to produce high levels of androgens.

Question 9

List the clinical features of congenital adrenal hyperplasia.

Answer 9

Hyponatraemia + hyperkalaemia with volume depletion
Hypoglycaemia
Ambiguous genitalia in female neonates
Growth acceleration

Question 10

What is the term for bilirubin encephalopathy?

Answer 10

Kernicterus

Question 11

Why is the threshold for treatment for jaundice lower in premature babies?

Answer 11

They have less albumin and the BBB is leakier.

Question 12

What is the most common cause of conjugated hyperbilirubinaemia?

Answer 12

Biliary atresia

Question 13

What other abnormalities are associated with biliary atresia?

Answer 13

Cardiac malformations
Polysplenia
Situs inversus

Question 14

What happens to calcium after birth?

Answer 14

It will fall

Question 15

When are calcium and phosphate mostly laid down in pregnancy?

Answer 15

3rd trimester