Causes of Neonatal Constipation
Constipation in neonates is primarily caused by intestinal dysmotility, but several specific conditions can lead to this problem, including Hirschsprung's disease, hypothyroidism, and anatomical abnormalities.
Common Causes of Neonatal Constipation
Functional Causes
- Intestinal dysmotility: Most common cause in neonates 1
- Feeding-related factors:
- Formula feeding (compared to breastfed infants who typically have more frequent stools) 2
- Transition from breast milk to formula (changes stool consistency and frequency)
- Inadequate fluid intake
Congenital and Anatomical Causes
- Hirschsprung's disease (congenital aganglionic megacolon):
- Anal stenosis or malformations
- Intestinal malrotation
- Functional megacolon
- Imperforate anus 1
Metabolic and Endocrine Causes
- Hypothyroidism: Can cause decreased intestinal motility 1
- Hypercalcemia: Affects smooth muscle function in the intestine
- Hypokalemia: Disrupts normal intestinal motility 1
Neurological Causes
- Hypotonia: Affects abdominal muscle strength needed for defecation 1
- Spinal cord abnormalities: Can affect innervation of the bowel
Red Flags for Organic Causes
- Delayed passage of meconium beyond 48 hours of life
- Failure to thrive and gross abdominal distention (suggesting Hirschsprung's disease)
- Empty and tight rectum on examination (characteristic of Hirschsprung's disease)
- Associated symptoms of intestinal obstruction
- Developmental delays 5
Diagnostic Approach
History: Focus on timing of first meconium passage, stool pattern, and feeding method
Physical examination:
- Abdominal examination for distention
- Rectal examination (distended rectum full of stool suggests functional constipation; empty tight rectum suggests Hirschsprung's disease) 3
- Neurological assessment for tone and reflexes
Consider laboratory tests for suspected metabolic/endocrine causes:
- Thyroid function tests
- Electrolytes (particularly calcium and potassium)
Common Pitfalls in Diagnosis
- Misdiagnosing normal stool patterns: Breastfed infants may normally have infrequent stools (as low as once every few days) without being constipated 2
- Overlooking serious underlying conditions: Constipation present from birth or beginning in the neonatal period is more likely to have an organic cause 3
- Unnecessary treatment: Formula-fed infants who defecate less than once per day should not automatically be diagnosed with constipation requiring treatment 2
Management Considerations
- Treatment should be directed at the underlying cause
- For functional constipation, dietary modifications and ensuring adequate hydration are first-line approaches
- Severe cases may require disimpaction and maintenance therapy
- Surgical intervention may be necessary for anatomical causes or Hirschsprung's disease 4
Remember that constipation that begins in the neonatal period, especially if associated with failure to pass meconium within 48 hours of birth, requires prompt evaluation to rule out serious organic causes.