CONSTIPATION

Constipation is a relative term as frequency of defecation varies significantly in different children. For practical purpose, passage of hard stools every third day or even at Iesserfrequency may be termed constipation.

Defecation is largely a reflex activity in infants, before gradual development of voluntary control. Reflex is initiated by the distension of rectum by faeces sending afferent stimuli to spinal defecation centers at S₂_₄ followed by efferent parasympathetic impulses to relax anal sphincter.

Voluntary control by higher centres generally develops by 18 months, when defecation may be initiated or inhibited using abdominal and diaphragmatic musculature to alter abdominal pressure and anal tone. Etiology: Constipation may be functional or organic (Table 14.6). Organic constipation may arise from: (a)

TABLE 14.6: Causes of constipation

Non-organic

• Habitual (functional): Faulty toilet training

• Low fecal load: Under-feeding, low fiber diet

• Dehydration: Top feeding, poor water intake

Organic

• Dehydration: Fever, polyuria (Diabetes mellitus/insipidus)

• Mechanical: IHPS, AIO, anorectal anomalies

• Poor evacuation reflex: Hirschsprung disease

• Painful defecation: Anal fissure, hemorrhoids

• Hypotonia

- General—hypothyroidism, floppy child, C. palsy

- Local—spinal lesions, paralytic ileus, hypokalemia

• Drugs: Iron, laxative abuse, antihistaminics

IHPS: Infantile hypertrophic pyloric stenosis, AIO: Acute intestinal obstruction.

filling, (e.g. starvation, ileus) or evacuation, (e.g. anal fissures) defects in rectum, (b) impaired defecation reflex (Hirschsprung disease, spinal lesions), or (c) lack of effective contraction due to hypotonia of voluntary muscles.

Anal fissures, Hirschsprung disease and hypo­thyroidism are three most common causes of organic constipation, except in early infancy when mild ano­rectal malformations have to be excluded.

Constipation tends to be self-perpetuating, with hardening of stools due to excessive retention in colon, making act of defecation further painful with voluntary retention. Eventually, watery colonic contents may percolate around hard-retained stools (fecoliths) and leak through anal sphincter, leading to encopresis.

Functional constipation is defined as persistence of constipation for gt;4 weeks with any two or more of following features: (a) stool frequency #8804;2 per week, (b) hard, painful bowel movements, (c) excessive retention of stools, (d) large diameter stool obstructing the Indian pots, (e) faecal incontinence, (f) faecal mass or fecoliths on abdomen/rectum examination (IAP 2018).

Faulty and coercive toilet training, changes in the diet, acute illness or lack of clean toilet are important causes of functional constipation in children.

Diagnostic evaluation of constipation involves:

• Age of onset: Functional constipation often begins after 2 years of life

• Clinical evaluation for possible organic cause, as indicated by presence of intermittent diarrhea, significant abdominal distension and failure to thrive.

• Stool examination: Hard pellet or ribbon-like stools indicate Hirschsprung disease.

• Per-rectal examination to assess for anal position (anorectal malformations), fissures, anal tone (lax in spinal lesions), rectal findings (empty in Hirschsprung disease, fecoliths in functional constipation) and gush of fecal matter after withdrawal of finger (Hirschsprung disease).

• Exclusion ofhypothyroidism by bone age estimation and serum TSH levels.

• Anorectal manometry for suspected Hirschsprung disease.

Treatment of organic constipation depends on the cause, while functional cases are treated with: (a) Regular toilet training, (b) high-fiber diet (0.5 g/kg/day) with adequate water intake, (c) faecal disimpaction, and (d) oral laxatives. Anal fissures, if there, must be treated.

Faecal disimpaction is indicated in acute severe cases with PO polyethylene glycol (25 ml/kg/hr for 4-6 hours) or per-rectal enema (sodium phosphate enema 2.5 ml/ kg gt; 2 years). Saline enema is used in young infants.

Oral laxatives are indicated in sub-acute or chronic cases after excluding an obstructive pathology. Polyethylene glycol (0.5-1 gm/kg/day q12-24hr) is the preferred laxative of choice in children, though other osmotic laxatives, e.g. lactulose (1-3 ml/kg/day q12-24 hr) or Lactilol (200-400 mg/kg/day q12-24 hr) may also be used. Laxative therapy should be continued for many weeks before slow tapering.

Oral stimulant laxatives, e.g. Sodium picosulfate (10-20 mg/day q24 hr) or Bisacodyl (5 mg/day gt; 3 yr of age) may be used as rescue therapy for 2-3 days in patients on osmotic laxatives with intermittent exacerbations.

14.4.5