Diagnostic and Management Guidelines for Non‑Bilious Vomiting in Preterm Infants

Epidemiology & Common Causes

Gastroesophageal reflux disease (GERD) is the most frequent cause of recurrent non‑bilious vomiting in infants, especially those born preterm with immature lower esophageal sphincter function 1.
GERD‑related vomiting is typically non‑forceful regurgitation, and infants usually maintain adequate weight gain when GERD is the sole problem (supported by imaging literature) 2.
Hypertrophic pyloric stenosis (HPS) presents with a palpable epigastric “olive” mass in 60–80 % of cases 3.

Examine for abdominal distension, feeding intolerance, lethargy, and temperature instability to rule out necrotizing enterocolitis (NEC) 1.
Assess for fever, hypothermia, lethargy, poor perfusion, and increased oxygen requirements as indicators of late‑onset sepsis 1.
Any bilious (green) vomiting constitutes a surgical emergency until proven otherwise 3.
Abdominal distension with decreased or absent bowel sounds suggests intestinal obstruction or NEC 1.
Blood in stool or vomit signals mucosal injury and raises suspicion for NEC or intussusception 1.
Lethargy, temperature instability, or altered mental status may indicate sepsis or an inborn error of metabolism 1.
Poor weight gain or weight loss helps differentiate pathologic GERD from benign reflux 3.

Hydration status should be assessed by capillary refill, urine output ≥ 4 wet diapers/24 h, and mucous membrane moisture 4.
Confirm that vomiting remains non‑bilious; emergence of green vomitus mandates immediate escalation 3.
When metabolic disorders are considered, look for lethargy, poor feeding, and abnormal neurologic examination 1.

Plain abdominal radiographs (supine and cross‑table lateral or left lateral decubitus) are obtained to identify dilated bowel loops, pneumatosis intestinalis (NEC), or obstruction patterns 2.
If hypertrophic pyloric stenosis is suspected, abdominal ultrasound is the diagnostic modality of choice, with diagnostic criteria of pyloric muscle thickness > 3–4 mm and channel length > 15–17 mm 3.

Electrolyte panels help differentiate metabolic alkalosis (suggestive of HPS) from metabolic acidosis (seen in NEC or sepsis) 3.

If dehydration is present without evidence of obstruction, initiate oral rehydration therapy with small, frequent volumes (≈ 5 mL every minute) 4.
Place the infant nil per os (NPO) when NEC, obstruction, or any surgical pathology is suspected 4.
Nasogastric or orogastric decompression should be considered when abdominal distension is noted or NEC is a concern (clinical judgment; not directly cited).

A 2–4‑week trial of smaller, more frequent feeds combined with upright positioning after feeds is recommended for infants with benign‑appearing examinations 4.
Continue full‑strength formula or breast milk; dilution of feeds is not advised 4.

Malrotation can present at any age with intermittent non‑bilious vomiting and may progress to bilious emesis; it requires prompt surgical evaluation (radiology literature) 2.
Midgut volvulus secondary to malrotation is a surgical emergency, capable of causing intestinal necrosis within hours 3.

Antiemetics are generally contraindicated in preterm infants because they may mask clinical deterioration 4.