Chapter 297 Normal Digestive Tract Phenomena
Gastrointestinal function varies with maturity; what is a physiologic event in a newborn or infant might be a pathologic symptom at an older age. A fetus can swallow amniotic fluid as early as 12 wk of gestation, but nutritive sucking in neonates 1st develops at about 34 wk of gestation. The coordinated oral and pharyngeal movements necessary for swallowing solids develop within the 1st few months of life. Before this time, the tongue thrust is upward and outward to express milk from the nipple, instead of a backward motion, which propels solids toward the esophageal inlet. By 1 mo of age, infants appear to show preferences for sweet and salty foods. Infants’ interest in solids increases at about 4 mo of age. The recommendation to begin solids at 6 mo of age is based on nutritional and cultural concepts rather than maturation of the swallowing process (Chapter 42). Infants swallow air during feeding, and burping is encouraged to prevent gaseous distention of the stomach.
A number of normal anatomic variations may be noted in the mouth. A short lingual frenulum (“tongue-tie”) may be worrisome to parents but only rarely interferes with eating or speech, generally requiring no treatment. Surface furrowing of the tongue (a geographic or scrotal tongue) is usually a normal finding. A bifid uvula may be normal or associated with a submucous cleft of the soft palate.
Regurgitation, the result of gastroesophageal reflux, occurs commonly in the 1st year of life. Effortless regurgitation can dribble out of an infant’s mouth but also may be forceful. In an otherwise healthy infant with regurgitation, volumes of emesis are commonly ∼15-30 mL but occasionally are larger. Most often, the infant remains happy, although possibly hungry, after an episode of regurgitation. Episodes can occur from <1 to several times per day. Regurgitation gradually resolves in 80% of infants by 6 mo of age and in 90% by 12 mo. If complications develop or regurgitation persists, gastroesophageal reflux is considered pathologic rather than merely developmental and deserves further evaluation and treatment. Complications of gastroesophageal reflux include failure to thrive, pulmonary disease (apnea or aspiration pneumonitis), and esophagitis with its sequelae (Chapters 315 and 316).
Infants and young children may be erratic eaters; this may be a worry to parents. A toddler might eat insatiably or refuse to consume food during a meal. Toddlers and young children also tend to eat only a limited variety of foods. Parents should be encouraged to view nutritional intake over several days and not be overly concerned about individual meals. Infancy and adolescence are periods of rapid growth; high nutrient requirements for growth may be associated with voracious appetites. The reduced appetite of toddlers and preschool children is often a worry to parents who are used to the relatively greater dietary intake during infancy. Demonstration of age-appropriate growth on a growth curve is reassuring.
The number, color, and consistency of stools can vary greatly in the same infant and between infants of similar age without apparent explanation. The earliest stools after birth consist of meconium, a dark, viscous material that is normally passed within the 1st 48 hr of life. With the onset of feeding, meconium is replaced by green-brown transition stools, often containing curds, and, after 4-5 days, by yellow-brown milk stools. Stool frequency is extremely variable in normal infants and can vary from none to 7 per day. Breast-fed infants can have frequent small, loose stools early (transition stools), and then after 2-3 wk can have very infrequent soft stools. Some nursing infants might not pass any stool for 1-2 wk and then have a normal soft bowel movement. The color of stool has little significance except for the presence of blood or absence of bilirubin products (white-gray rather than yellow-brown). The presence of vegetable matter, such as peas or corn, in the stool of an older infant or toddler ingesting solids is normal and suggests poor chewing and not malabsorption. A pattern of intermittent loose stools, known as toddler’s diarrhea, occurs commonly between 1 and 3 yr of age. These otherwise healthy growing children often drink excessive carbohydrate-containing beverages. The stools typically occur during the day and not overnight. The volume of fluid intake is often excessive; limiting sugar-containing beverages and increasing fat in the diet often leads to resolution of the pattern of loose stools.
A protuberant abdomen is often noted in infants and toddlers, especially after large feedings. This can result from the combination of weak abdominal musculature, relatively large abdominal organs, and lordotic stance. In the 1st yr of life, it is common to palpate the liver 1-2 cm below the right costal margin. The normal liver is soft in consistency and percusses to normal size for age. A Riedel lobe is a thin projection of the right lobe of the liver that may be palpated low in the right lateral abdomen. A soft spleen tip might also be palpable as a normal finding. In thin young children, the vertebral column is easily palpable, and an overlying structure may be mistaken for a mass. Pulsation of the aorta can be appreciated. Normal stool can often be palpated in the left lower quadrant in the descending or sigmoid colon.
Blood loss from the gastrointestinal tract is never normal, but swallowed blood may be misinterpreted as gastrointestinal bleeding. Maternal blood may be ingested at the time of birth or later by a nursing infant if there is bleeding near the mother’s nipple. Nasal or oropharyngeal bleeding is occasionally mistaken for gastrointestinal bleeding (Chapter 97.4). Red dyes in foods or drinks can turn the stool red but do not produce a positive test result for occult blood.
Jaundice is common in neonates, especially among premature infants, and usually results from the inability of an immature liver to conjugate bilirubin, leading to an elevated indirect component (Chapter 96.3). Persistent elevation of indirect bilirubin levels in nursing infants may be a result of breast milk jaundice, which is usually a benign entity in full-term infants. An elevated direct bilirubin is not normal and suggests liver disease, although in infants it may be a result of extrahepatic infection (urinary tract infection). The direct bilirubin fraction should account for no more than 15-20% of the total serum bilirubin. Elevations in direct bilirubin levels can follow indirect hyperbilirubinemia as the liver converts excessive indirect to direct bilirubin and the rate-limiting step in bilirubin excretion shifts from the glucuronidation of bilirubin to excretion of direct bilirubin into the bile canaliculus. Indirect hyperbilirubinemia, which occurs commonly in normal newborns, tends to tint the sclerae and skin golden yellow, whereas direct hyperbilirubinemia produces a greenish yellow hue.
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