A newborns failure to pass meconium within 24 hours after birth may indicate which of the following

Introduction

99% of healthy full-term infants pass their first stool or meconium within 24 hours of birth and all healthy term neonates should do so by 48 hours.

No neonate should be discharged before passing meconium, and failure of a full-term infant to pass meconium in the first day of life should raise suspicion of intestinal obstruction.

Of note, up to a third of preterm infants will not pass meconium in the first 48 hours of life, and may take as long as 9 days for their first stooling.

Neonatal intestinal obstruction occurs in 1/1500 live births. This will classically present as failure to pass meconium, progressive abdominal distention and anorexia, culminating in bilious emesis and/or intestinal perforation. 

Etiologies are from intrinsic developmental defects, abnormalities of peristalsis or intestinal contents, or from insults in utero after the formation of normal bowel. 

Failure to recognize and address neonatal bowel obstruction can result in aspiration of vomit, sepsis, mid-gut infarction, bowel perforation or enterocolitis.

Differential diagnoses for presentations of intestinal obstruction in the neonate:

Failure to pass meconium with bilious vomiting

• Malrotation and volvulus
• Duodenal atresia distal to ampulla of Vater
• Jejunoileal atresia
• Meconium ileus
• Meconium plug syndrome
• Hirschprung’s disease
• Small left colon syndrome
• Imperforate anus

Failure to pass meconium with non-bilious vomiting

• Duodenal atresia proximal to ampulla of Vater
• Annular pancreas

Initial passage of meconium with subsequent obstruction and non-bilious emesis with each feed suggests pyloric stenosis

Evaluation of Bilious Emesis

Bilious emesis in the neonate should be treated as a life-threatening emergency because it is often a presenting symptom of volvulus.

Evaluation of clinically stable neonates begins with cessation of PO feeds, nasogastric tube decompression, IV fluids, and blood gasses to assess acid-base status

If infant has signs of systemic decompensation (eg hematemesis, peritonitis, shock), patient should immediately be taken for emergent surgical exploration for assumed malrotation and volvulus

Stabilized patients should have appropriate imaging. Most likely, patient will have abdominal plain film as first step, with a variety of possible etiologic clues

• Free air—suggestive of pneumoperitoneum and intestinal perforation, this patient needs emergent surgical intervention
•  Double bubble sign—Duodenal atresia
•  Pneumatosis intestinalis—NEC
•  Dilated bowel—this patient has a distal obstruction, diagnosis should be further clarified with barium enema
•   If none of the above signs on x-ray, move to barium swallow study to assess for malrotation/volvulus:  If there is a strong index of suspicion for malrotation/ volvulus, barium swallow study should be chosen as first imaging modality. Volvulus will appear with corkscrew pattern on study.
• Contrast enema can help diagnose causes of distal obstruction
• Microcolon is most suggestive of jejunoileal atresia or meconium ileus
• Rectosigmoid transition zone—Hirschsprung’s disease

Meconium Plug Syndrome

• Most common form of functional bowel obstruction in the newborn, with an incidence of 1/500
•  It is a transient form of distal colon or rectal obstruction caused by inspissated and dehydrated meconium, the etiology for which is unknown
• Diagnosis is made through barium enema revealing the outline of meconium plug. Barium enema can also be therapeutic along with rectal stimulation in inducing passage of the meconium
• Generally, infants with meconium plug syndrome have normal bowel function after passing the meconium plug

Meconium ileus

• Differentiated from meconium plug syndrome by location of the stool in ileum or proximal colon, rather than distal colon
• Barium enema will reveal microcolon in meconium ileus, in contrast to meconium plug syndrome, which will demonstrate normal, or even dilated colon, with areas of clearing which represent the plugs
• 90%-95% of patients with meconium ileus have cystic fibrosis (CF), therefore all patients with meconium ileus without a diagnosis of CF should undergo sweat testing
• 15-20% of patients with CF will have meconium ileus, there is no correlation with severity of CF and presence of obstruction
• Half of infants with meconium ileus also have comorbid associated anomalies such as volvulus, jejunoileal atresia, or bowel perforation

Anorectal Malformation

• The incidence is 1/4000 live births, including anal stenosis, imperforate anus, and fistula
• Malformations are caused by a defect in embryonal development where the urorectal septum, lateral mesoderm and ectodermal structures combine to form the normal rectum and lower urinary tract
• 70% of infants with anorectal malformation have associated anomalies. The mnemonic VACTERL is used to describe the combination of Vertebral defects, Anal atresia, Cardiac defects, Tracheoesophageal fistula, Renal defects and Limb anomalies. As such, patients should receive further workup with echocardiogram (preferably before surgery), CXR for vertebral anomalies, renal ultrasonography
• Anal stenosis accounts for 20% of anorectal anomalies and treatment is with dilatation

Malrotation and volvulus

• Caused by a failure of normal bowel rotation. The mid-gut does not complete its normal 290° counterclockwise rotation during embryologic development, resulting in abnormal placement and fixation of the small bowel
• Volvulus occurs when the small intestine rotates around the superior mesenteric artery, leading to vascular compromise and possible infarction/necrosis of the small bowel. Volvulus usually occurs within the first week of life
• Radiographs may show a “gasless” abdomen, may show signs of intestinal dilation, or may be completely normal. Barium swallow study may show corkscrew pattern.

• Treatment is with the Ladd’s procedure involving counterclockwise reduction of the volvulus, release of adhesive bands (Ladd’s bands) to mobilize the duodenum, and appendectomy
•  Recurrence of mid-gut volvulus after the Ladd’s procedure can occur in up to 10% of cases.
• Patients shown on workup to have malrotation without volvulus will also undergo a (less emergent) Ladd procedure to reduce risk of future volvulus
• For further information: https://pedclerk.bsd.uchicago.edu/page/malrotation

Duodenal atresia

• Caused by failure to recanalize the lumen after the solid phase of intestinal development. This occurs between the 4th and 5th week of gestation
•  Diagnosis can be made in utero if polyhydramnios is present
• Plain films can reveal the “double bubble sign”, and an upper GI series might be necessary to distinguish between malrotation and duodenal atresia

• 40% of the patients with duodenal atresia have Down Syndrome
• VACTERL syndrome is also associated with duodenal atresia, patients need workup for associated anomalies
• If patient also has Down Syndrome, perform rectal biopsy or other evaluation for Hirschprung’s disease

Pyloric Stenosis

• Rate of 3 in 1,000 live births, more commonly in males (4-6:1)
• A condition of hypertrophy of the pylorus, with elongation and thickening of tissue that progresses to near-complete obstruction of the gastric outlet
• Typically arises at 3-6 weeks of life, but it can present even in the first few months
• An "olive-like" mass is very often described as being palpated in the right upper quadrant of the abdomen, but may not be present
• The diagnosis is confirmed by ultrasound examination of the abdomen, which will display a thickening of the pyloric sphincter where the mass is palpated
• Patients should be observed for complications of dehydration and vomiting, such as hypochloremic hypokalemic metabolic alkalosis
• Fluid resuscitation and surgery are the standard for treatment

Hirschsprung’s disease

• Occurs in 1/5000 infants with a male to female predominance of 4:1.
• The pathogenesis of the disease is failure of migration of the neural crest cells that form the colonic ganglion cells. Without parasympathetic innervation, the colon cannot relax or undergo peristalsis, resulting in a functional obstruction
• The aganglionic segment is limited to the rectosigmoid in the majority of patients. 10% have full colonic involvement and in 10% more, there is lack of ganglion cells into the small bowel
• Diagnosis of Hirchsprung’s disease can be made with barium enema, revealing a transition zone between the constricted aganglionic segment and the proximal, normally dilated segment.
• Confirmation of the diagnosis can be made with rectal suction biopsy, which will demonstrate absent ganglion cells, hypertrophied nerve fibers, and elevated acetylcholinesterase activity
• The treatment is through surgical resection of the aganglionic bowel and approximation of normal, ganglionic tissue near the anus
• Major complications of the disease, even after surgical resection, are bowel obstruction and enterocolitis, though most patients go on to normal or near-normal bowel function
• Given association with wide variety of chromosomal and monogenetic abnormalities, further evaluation should include referral to genetic counselor

Jejunoileal atresia

• Occurs in 1:3000 live births
• Caused by mesenteric vascular accident
• Causes of the vascular disruption in the human fetus include segmental or midgut volvulus, intussusception, internal hernia, maternal use of vasoconstrictive medications, inherited thrombophilia, gastroschisis
• ·Most cases of intestinal atresia are sporadic, familial cases of apple peel atresia have been reported, suggesting a genetic component
• Presentation with 24 hours of birth, usually with abdominal distension

Necrotizing enterocolitis

• Occurs in 2.4:1000 live births.
• Incidence inversely correlated with gestational age and birth weight, approximately 13% of cases occur in term infants.
• Etiology and pathophysiology poorly understood
• Most commonly presents 10-12 days after birth, often accompanied by bloody stools and abdominal distension
• Pneumatosis interstitialis is pathognomonic

Coronal reformatted MDCT image showing extensive pneumatosis intestinalis in the left upper quadrant small bowel. The pneumatosis is more cystic and nodular in the small bowel in the midline and the right of midline. This patient had a relatively benign presentation without bowel ischemia and was treated conservatively.
https://en.wikipedia.org/wiki/Pneumatosis_intestinalis

• Further evaluation: platelets and coagulation studies due to increased risk of DIC and blood culture due to increased risk of sepsis
• Treatment can be medical (supportive care, antibiotic therapy, and close monitoring) or surgical (primary peritoneal drainage or laparoscopic resection of necrotic bowel segments).
• For further information: http://pedclerk.bsd.uchicago.edu/page/necrotizing-enterocolitis

Annular Pancreas

• Prevalence at autopsy ~10/100,000, ~2/3 of annular pancreases never manifest with symptoms
• Usually, pancreas develops from one dorsal and two ventral buds at around the fifth week of gestation, by approximately the seventh week, the ventral bud rotates with the gut, passing behind the duodenum from the right to left and eventually fusing with the dorsal bud
•  Annular pancreas results from failure of the ventral bud to rotate with the duodenum, causing envelopment of duodenum
•  Annular pancreas may be complete or incomplete, and are classified based on the drainage site of the annular duct
•  May be associated with obstructive jaundice requiring biliary bypass with choledochoenterostomy
• If causing intestinal obstruction, requires surgical intervention with duodenoduodenostomy

References

1. Failure to pass meconium: diagnosing neonatal intestinal obstruction. Loening-Baucke V. Am Fam Physician. Nov 1999; 60(7): 2043-2050.

2. Bilious vomiting in the newborn: rapid diagnosis of intestinal obstruction. Kimura K. Am Fam Physician. May 2000; 61(9): 2791-2798.

3. Imaging of neonatal gastrointestinal obstruction. Hernanz-Schulman M. Radiol Clin North Am. Nov 1999; 37(6):1163-1186.

4. Behrman: Nelson Textbook of Pediatrics, 16th ed (2002). Philadelphia: W.B. Saunders Company.

5. A decade of experience with the primary pull-through for Hirschsprung disease in the newborn period: a multicenter analysis of outcomes. Teitelbaum DH. Ann Surg. Sep 2000; 232(3):372-380.

6. Genetics of Hirschsprung's disease. Parisi MA. Curr Opin Pediatr. Dec 2000; 12(6):610-617.

7. Long-term outcome and quality of life after the Swenson procedure for Hirschsprung's disease. Bai Y, Chen H, Hao J, et al. J Pediatr Surg 2002; 37:639.

8.Ultrasonographic diagnosis criteria using scoring for hypertrophic pyloric stenosis. Ito S, Tamura K, Nagae I, et al. J Pediatr Surg 2000; 35:1714.

9. NEJM. A Newborn Boy with Vomiting, Diarrhea, and Abdominal distention.  Jan 26, 2012

10. Pancreatic development and anatomical variation. Kozu T, Suda K, Toki F. Gastrointest Endosc Clin N Am 1995; 5:1.

11. Diagnostic Accuracy of Radiologic Scoring System for Evaluation of Suspicious Hirschsprung Disease in Children. Alehossein M, Roohi A, Pourgholami A. Iran J Radiol. 2015 April; 12(2): e12451.

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