Table I.

Summary of the Studies of Gastrointestinal pH and Transit Time in Pediatric Populations (focused on Neonates)^a

Gastrointestinal parameters	Ingested material	Populationb	Postnatal age	Gestational age	Results	Method	Reference
Gastric pH	Fastedc	10 Preterm neonates	7–15 days	33.5 (31–37) weeks	Mean 2.6	In situ pH electrode	(9)
	Fastedc	13 Preterm neonates	2–6 days	34.0 (32–38) weeks	Mean 4.6	In situ pH electrode	(9)
	Fastedd	2 Preterm neonates	16–17 days	24–25 weeks	1.6–1.9	In situ pH electrode	(10)
	Fastedd	10 Preterm neonates	16–17 days	26–27 weeks	1.4–2.3	In situ pH electrode	(10)
	Fastedd	10 Preterm neonates	16–17 days	28–29 weeks	1.3–2.3	In situ pH electrode	(10)
	Fastedd	10 Preterm neonates	15–21 days	24–31 weeks	1.5–2.3	In situ pH electrode	(11)
	Fastede	9 Preterm neonates	14 ± 3 daysf	33.1 ± 0.4 weeksf	Mean 1.8	pH meter on gastric aspirates	(12)
	Fastedg	15 Preterm neonates and infants	N/A	36 (35–38) weeksh	Mean 1.9, 1.8, and 3.1i	In situ pH electrode	(13)
	Fedj	9 Preterm neonates	14 ± 3 daysf	33.1 ± 0.4 weeksf	Mean pH around 6	pH meter on gastric aspirates	(12)
	Fedj	8 Preterm neonates	19 ± 5 daysf	31.1 ± 0.9 weeksf	Mean pH around 6	pH meter on gastric aspirates	(12)
	Fedj	9 Preterm neonates and infants	25 ± 5 daysf	30.0 ± 1.1 weeksf	Mean pH around 6	pH meter on gastric aspirates	(12)
	Fedk	15 Preterm neonates and infants	N/A	36 (35–38) weeksh	Mean 6.9, 6.0, and 5.7i	In situ pH electrode	(13)
Luminal pH of small intestine	Fastedl	12 Healthy children	8–14 years	N/A	Mean duodenal: 6.4	Radiotransmitting pH-sensitive capsule	(14)
					Mean proximal: 6.6
					Mean middle: 7.0
					Mean distal: 7.4
	N/Am	7 Neonates and infantsn	2 weeks to 3 months	N/A	Duodenal: 6.4 ± 0.5 (5.8–6.9)o	pH meter on enteric aspirates	(16)
					Jejunal: 6.6 ± 0.4 (6.0–7.0)o
					Ileal: 6.9 ± 0.7 (6.2–8.0)o
	N/Am	8 Neonates and infantsp	2 weeks to 3 months	N/A	Duodenal: 6.3 ± 0.9 (5.0–7.4)o	pH meter on enteric aspirates	(16)
					Jejunal: 6.0 ± 0.5 (5.2–6.4)o
					Ileal: 6.3 ± 0.8 (5.4–7.5)o
Gastric emptying time	Calorie-containing liquidr	8 Preterm neonates	17 ± 7 (15, 6–26)s days	29.5 ± 2.4 (28, 27–32)s weeks	62 ± 33 (54, 30–120)s min	Scintigraphy	(22)
	Calorie-containing liquid	Neonates	N/A	N/A	75 mint	Meta-analysisu	(24,25)
	Calorie-free liquid	Neonates	N/A	N/A	10 mint	Meta-analysisu	(24,25)
	Total diet (fed)	Neonates	N/A	N/A	75 mint	Meta-analysisu	(24,25)
Small intestinal transit time	General materialv	Neonates	N/A	N/A	4 ht	Meta-analysisu	(24,25)

N/A not applicable

^aData are expressed as mean ± SD, minimum-maximum, or mean ± SD (minimum-maximum)

^bAll these neonates, infants, and children were free from any gastrointestinal problems

^cAt least 3-h fast before measuring

^dAll neonates were totally supported with parenteral nutrition throughout the period of the study

^eMeasured at 3 h after a formula milk feed

^fData are expressed as mean ± SE

^gMeasured in 3–4 h after a breast milk or infant formula feed

^hPostmenstrual age

ⁱData represent intragastric pH at 3, 6, and 9 cm below the lower oesophageal sphincter, respectively

^jMeasured immediately after a formula milk feed

^kMeasured in 0–1 h after a breast milk or infant formula feed

^lAt least 8-h fast before measuring

^mThe neonates and infants were maintained on the same feeding regimen throughout the period of the study; however, the feeding regimen was not mentioned in this report

ⁿThe neonates and infants were fed exclusively with breast milk

^oIndividual data were captured by computer digitization, and subsequently summarized by descriptive statistics

^pThe neonates and infants were fed exclusively with cow’s milk

^rA mixture of ^99mTc (0.2–0.4 MBq, 0.5 mL) and expressed breast milk

^sGastric emptying half-time. Data are expressed as Mean ± SD (median, minimum-maximum)

^tReference value

^uInformation on transit time through gastrointestinal tract published by the International Commission on Radiological Protection (ICRP) is a comprehensive meta-analysis of data derived from various techniques

^vThe reference value of small intestinal transit time is applied to all material, according to the ICRP report