The large intestine is the part of the bowel where fluid and electrolytes are absorbed, and store stool before defecation.

Normal defecation is controlled by the muscles of the pelvic floor which contributes to the anal sphincters. The internal sphincter is permanently in tonic contraction, while the external sphincter is in relaxation when the rectum is empty of feces. When feces enter the rectal lumen, tension receptors on the wall activate nerve cells, causing the inner sphincter to relax. The stool is promoted to the lower part of the rectum initiating the process of defecation. Valsava manoeuvre increases the intra-abdominal pressure, the external sphincter relaxes and excretion of stool begins. The function of defecation can be intentionally inhibited by contraction of the external sphincter and gluteus muscles resulting in the backward push of the stool in the rectum. If the refusal to defecate is repeated many times this may lead to dilatation and eventually a decrease in muscle tone of the rectum and colon resulting in fecal retention.

Α. IDOPATHIC (Functional)

In the majority of children, chronic constipation is idiopathic, with no underlying problems of the organs involved. Various theories have been developed about the pathogenesis of functional constipation, and it seems that the etiology is multifactorial. A combination of genetic, environmental, psychological and dietary parameters contribute. Diet plays an important role in the occurrence of constipation with reduced intake of fibre increasing the severity of constipation.

Three syndromes of functional constipation have been described.

• The first concerns newborns and infants up to the 10th week of life (grunting baby syndrome). Parents typically describe the young baby as straining and crying loudly 5-10 minutes before defecation. Stools are normal in composition and appearance and bowel movements occur almost daily. This is perceived as constipation by parents and often by the pediatrician, resulting in anxiety that leads to frequent anal irritation with suppositories or thermometers or unnecessary milk changes. This phenomenon is due to the immaturity of some infants of this age to coordinate the increase in intra-abdominal pressure with the relaxation of the pelvic muscular system. This subsides over time.
• Later in infancy and in early childhood, the hardening of the stool may lead to painful defecation, fecal retention, and constipation. This mainly occurs in the transitional stages of changing diet, i.e. from breast milk to infant milk or the start of solid foods.
• Finally, in older children voluntary stool retention is the main mechanism of constipation. This is a response to the fear of painful defecation when the sensation causes voluntary retention of stool when the sensation of stool in the rectum is flet. The age at which this form of functional constipation occurs has two peaks, the period of toilet training and the beginning of school age. Stool retention may lead to anxiety, abdominal pain or distension, irritability and anorexia as well as diarrhea from overfilling and overflow.

Β. SECONDARY (ORGANIC)

Only a small percentage of children with constipation have an underlying organic disorder that contributes to constipation. Nevertheless, these anatomical, neurological and systemic causes must be ruled out for proper treatment. The main organic causes of constipation are:

Anatomical anomalies

• Anorectal malformations
• Anal stenosis
• Congenital or acquired stenosis of the sigmoid or rectum

Neuromuscular pathologies of the intestine

• Hirschsprung’s Disease
• Neuronal intestinal dysplasia
• Visceral myopathy-neuropathy

Neurological causes

• Myelomeningocele or dysraphism
• Spinal cord injury
• Cerebral palsy

Systemic causes

• Hypothyroidism
• Hyperparathyroidism
• Diabetes mellitus
• Dermatomyositis

Other

• Cow’s milk protein allergy
• Celiac disease

Medications

• Antacids
• Iron supplements
• Diuretics
• Opiates

Hirschsprung’s disease is a genetic disorder with a frequency of 1 in 5000 births that preferentially affects males (4/1). It is characterized by a lack of ganglion cells in the myenteric and submucosal plexus of the intestine. The aganglionic segment is usually limited to the rectosigmoid (80% of children) and only 3% affects the entire large intestine. Studies have shown that in 64% of children the diagnosis is made in the first three months of life and in 80% by the end of the first year. However, in a small percentage (8%) the diagnosis can be delayed to much later in life and usually concerns cases of ultra-short segment Hirschsprung’s disease. 

Celiac disease can occasionally manifest as constipation, although it usually presents with insufficient weight intake and chronic diarrhea. In recent years, articles have been published that include chronic constipation as a manifestation of allergy to cow’s milk proteins, mainly in children under 6 years of age. But before starting a restrictive diet, a challenge test needs to be done to confirm and of course rule out other causes.

The examination of a child with chronic constipation can be based, and is in most cases limited to a detailed history and physical examination.

The history should start from birth with information on the perinatal period and the time of first passing meconium. The non-elimination of meconium in the first 24 hours of life and the onset of constipation from birth raise strong suspicions of Hirschsprung’s disease. Constipation beginning at particular transitional stages of development or nutrition provides important information about the possible pathogenetic mechanism. The composition, volume, diameter of stool, and frequency of bowel movements should be recorded, as well as the presence of overflow (diarrhea from overfilling).

TYPES OF STOOL

From the physical examination it is necessary to record the demographic data and to search for signs of systemic or neurological disease. Examination and palpation of the abdomen reveal the presence or absence of dilation or fecal masses. An anal examination is then necessary to look for stretch marks, inflammation, or even an ectopic site. Finally, a digital examination – which is better postponed with the frightened and uncooperative child – may confirm a dilated rectum from hard stool or a narrowed anal opening. 

Laboratory testing is indicated in those cases where the history and clinical examination suspect organic disease or there is no response to treatment.

Blood tests may include thyroid function, calcium and blood electrolyte levels, determination of specific IgE antibodies against cow’s milk protein (RAST) and detection of antigloidin antibodies.

A plain abdominal x-ray is necessary in the child where palpation of the abdomen is difficult – obesity or lack of cooperation – and perhaps when overflow diarrhea is present, in order to confirm faecal retention. In this case, X-rays are best combined with swallowed x-ray markers. This confirms the retention of feces in the rectum and may exclude cases of reduced mobility of the rest of the colon.

Barium enema is not usually indicated in the investigation of function constipation. However, it is indicated in suspected Hirschsprung’s disease, although it can give false positive or negative results. It is also useful in case of congenital stenosis of the colon or after necrotizing enterocolitis.

Rectal manometry provides information on the function of the internal and external sphincter and the physiology of defecation. It is a good screening test for Hirschsprung disease, as well as for the study of the mechanism of biofeedback of constipation in older children and adolescents.

Rectal biopsy is considered necessary in cases where Hirschsprung’s disease is suspected based on history and occasionally in very severe constipation refractory to treatment.

The treatment of idiopathic constipation consists of:

• Stage 1: Information, education and psychological encouragement of the child and family
• Stage 2: Recommendations to increase fluid intake and adopt a high-fiber diet
• Stage 3: Addition of medication with semisynthetic polysaccharides (lactulose, lactitol) paraffin oil, PEG3350, alone or in combination
• Stage 4: In case where large fecal masses are felt in the abdomen; or very hard stools are in the rectum, Stage 3 is preceded by bowel emptying with large doses of laxatives as part of a Disimpaction regimen
• Stage 5: Gradual reduction of medications over a period ranging from 2 to 6 months or more determined on a case by case basis

In some cases, the treatment of severe long-term constipation may require the Bowel Management Program which combines oral medication, alterations in diet, and enemas. In some cases Antegrade Continence Enema (ACE/Malone) surgery has been reported as a successful treatment option when maximal conservative treatment has failed. The treatment of secondary constipation is individualized according to the condition and the patient.

Evaluation and Treatment of Functional Constipation in Infants and Children: Evidence-Based Recommendations From ESPGHAN and NASPGHAN

M.M. Tabbers et al. JPGN 2014;58: 258–274