Chapter 41: Constipation

Constipation is the difficult passage of small hard stools. The Rome III criteria define it has having two or more of the following, for at least 12 weeks:

• infrequent passage of stools <3/week

• passage of lumpy or hard stools at least 25% of time

• straining >25% of time

• sensation of incomplete evacuation >25% of time

• use of manual manoeuvres >25% of time

• sensation of anorectal obstruction/blockage >25% of time

Accordingly it affects more than 1 in 5 in the population.¹

However, the emphasis should be on the consistency of the stool rather than on the frequency of defecation; for example, a person passing a hard stool with difficulty once or twice a day is regarded as constipated, but the person who passes a soft stool comfortably every two or three days is not constipated. Various causes of chronic constipation are summarised in FIGURE 41.1.

Using the diagnostic strategy model (see TABLE 41.1), the five self-posed questions can be answered as follows.

Probability diagnosis

The commonest is ‘idiopathic’ constipation where there is no structural or systemic disease. This is also referred to as ‘functional’ constipation.

Probably the most frequent single factor causing constipation in Western society is deficiency in dietary fibre, including fruit, green leafy vegetables and wholemeal products. The amount of fibre in our diet is directly related to stool weight and to colonic transit time. The average colonic transit time in the large bowel for Westerners is 60 hours; for a rural African on a very high-fibre diet it is 30 hours. Other compounding factors are dehydration, lack of physical activity and inappropriate bowel habits. Constipation is also a common problem in pregnancy.

Serious disorders not to be missed

Neoplasia

It is obvious that colonic or anorectal neoplasms must not be missed in a patient, especially middle-aged or elderly, presenting with constipation or other change in bowel habit. Most cases present with either complete or incomplete bowel obstruction.

Extrinsic malignancy, such as lymphoma or ovarian cancer, compressing or invading the rectum, also has to be considered. Cancer of the large bowel is most prevalent in our society and appropriate screening examinations, including rectal examination, sigmoidoscopy and colonoscopy, must be considered where appropriate.

Megacolon

In children it is important to detect the presence of megacolon, for example megacolon secondary to Hirschsprung disorder. Symptoms dating from birth suggest Hirschsprung disorder, which occasionally may present for the first time in adult life.

Neurological disorders

Constipation, often with faecal impaction, is a common accompaniment to paraplegia, multiple sclerosis, cerebral palsy and autonomic neuropathy.

Pitfalls

The pitfalls can be summarised as follows:

• impacted faeces

• depressive illness

• purgative abuse

• local anal lesions

• drugs

Although patients with impacted faeces usually present with spurious diarrhoea, it is a form of idiopathic constipation and is very commonly encountered in general practice, especially in bedridden elderly people.

Anal pain or stenosis, such as fissure-in-ano, thrombosed haemorrhoids, perianal haematoma or ischiorectal abscess, leads to constipation when the patient is hesitant to defecate.

General pitfalls and tips

• Ensure the patient is truly constipated, and not having unreal expectations of regularity.

• Ensure that the anthraquinone group of laxatives, including ‘Ford pills’, is never used long term because they cause melanosis coli and associated megacolon.

• Be very wary of alternating constipation and diarrhoea (e.g. colon cancer).

• In a busy practice be careful not to let ‘familiarity breed contempt’ (e.g. onset of hyperparathyroidism, cancer).

• Avoid relying solely on the rectal examination to exclude cancer.

Seven masquerades checklist

Three of the primary masquerades (see TABLE 41.1) are important causes of constipation, namely drugs, depression and hypothyroidism. Many drugs (see TABLE 41.2) may be associated with constipation, especially codeine and its derivatives, antidepressants, aluminium and calcium antacids. A careful drug history is thus mandatory. Fortunately the constipation is usually relieved once the drug is withdrawn. Constipation can be a significant symptom in all types of depressive illness and may be aggravated by treatment with antidepressants.

The metabolic causes of constipation include hypothyroidism, hypercalcaemia and porphyria. We occasionally encounter the patient with hypercalcaemia, for example, hyperparathyroidism, but thyroid dysfunction is relatively common in general practice.

Diabetes rarely can be associated with constipation when an autonomic neuropathy can lead to alternating bouts of constipation and diarrhoea.

Psychogenic considerations

Constipation may be a manifestation of an underlying functional problem and psychiatric disorder, such as depression, anorexia nervosa, schizophrenia or drug abuse. Drug abuse must always be considered, keeping in mind that narcotics and laxatives present with rebound constipation. More commonly, it may reflect the inactive lifestyle of the patient and provide a good opportunity for appropriate counselling.

History

It is important to ask patients to define exactly what they mean by constipation. Some people believe that just as the earth rotates on its axis once a day, so should their bowels open daily to ensure good health. As always, a careful history is appropriate, including stool consistency, frequency, ease of evacuation, pain on defecation and the presence of blood or mucus. A dietary history is very relevant in the context of constipation.

Key questions

• How often do you go to the toilet?

• What are your bowel motions like?

• Are they bulky, hard, like rabbit pellets or soft?

• Is there pain on opening your bowels?

• Have you noticed any blood?

• Have you noticed any lumps?

• Do you have any soiling on your underwear?

• How do you feel in yourself?

• What medications are you taking?

Diary

Ask the patient to keep a 10-day diary recording frequency and nature of stools, and whether any difficulty was experienced when passing stool.

Examination

The important aspects are abdominal palpation and rectal examination. Palpation may reveal the craggy mass of a neoplasm, faecal retention (especially in the thin patient) or a tender spastic colon. The perianal region should be examined for localised disease. The patient should be asked to bear down to demonstrate perianal descent, haemorrhoids or mucosal prolapse. Perianal sensation and the anal reflex should be tested. Digital rectal examination is mandatory, and may reveal a rectal tumour and faecal impaction, as well as testing for rectal size and tone. If there is a history from infancy, a normal or narrow rectum suggests congenital megacolon (Hirschsprung disorder) but, if dilated, acquired megacolon.

General signs that may be significant in the diagnosis of constipation are summarised in FIGURE 41.2.

Rectal examination

The most important first step is to do the examination.

• Explain to the patient what will happen.

• After inspection with the patient in the left lateral position and with knees drawn up, a lubricated gloved index finger is placed over the anus.

• Part the buttocks.

• Ask the patient to concentrate on slow deep breathing.

• With gentle backwards pressure the finger is then inserted slowly into the anal canal and then into the rectum (it helps patient comfort if they push down or squeeze to accommodate the finger).

• Rotate the finger anteriorly to feel the prostate in males and the cervix in females.

• The finger will reach to about 7–8 cm with gentle thrusting into the perineum.

• Gently withdraw the finger and examine the whole circumference of the rectum by sweeping the finger from posterior on both sides.

• Any pain: fissure, proctitis, excoriation from diarrhoea (a rectal examination will not be possible in the presence of a fissure)

• Induration from a chronic fissure or fistula in the anal canal

• The sphincter tone

• The nature of the faeces (? impaction)

• The rectal wall: cancer is usually indurated, elevated and ulcerated; a villous adenoma has a soft velvety feel

• Posteriorly: the sacrum and coccyx

• Laterally: the side walls of the pelvis

• Anteriorly: cervix and pouch of Douglas in the female; prostate and rectovesical pouch in the male

• It feels larger if the patient has a full bladder.

• The normal prostate is a firm smooth rubbery bilobed structure (with a central sulcus) about 3 cm in diameter.

• A craggy hard mass suggests cancer.

• An enlarged smooth mass suggests benign hypertrophy.

• A tender, nodular or boggy mass suggests prostatitis.

In the female, the cervix or a vaginal tampon can be mistaken for a mobile extrarectal tumour.

Endoscopy

Sigmoidoscopy—in particular, flexible sigmoidoscopy with examination of the rectosigmoid—is important in excluding local disease; search for abnormalities such as blood, mucus or neoplasia. The insufflation of air sometimes reproduces the pain of the irritable bowel syndrome.

It is worth noting that 60% of polyps and cancers will occur in the first 60 cm of the bowel⁴ and diverticular disorder should be evident with the flexible sigmoidoscope.

The presence of melanosis coli is an important sign—it may give a pointer to the duration of the constipation and the consequent chronic intake (perhaps denied) of anthraquinone laxatives.

Investigations

These can be summarised as follows:

• Haematological:

  • – haemoglobin

  • – ESR

• Stools for occult blood

• Biochemistry (where suspected):

  • – thyroid function tests

  • – serum calcium

  • – serum potassium

  • – carcinoembryonic antigen (a tumour marker)

• Radiological:

  • – CT colonography (virtual colonography)

  • – double contrast barium enema (especially for primary colonic disease, e.g. megacolon)

  • – bowel transit studies, using radio-opaque shapes taken orally and checking progress by abdominal X-ray or stool collection

• Physiological tests:

  • – anal manometry—test anal tone

  • – rectal sensation and compliance, using an inflatable rectal balloon

  • – dynamic proctography, to determine disorders of defecation

  • – Rectal biopsy, to determine aganglionia

Idiopathic constipation

It is best to classify idiopathic constipation into three subgroups:

1. simple constipation

2. slow transit constipation

3. normal transit constipation (irritable bowel syndrome)

Of these, the commonest is simple constipation, which is essentially related to a faulty diet and bad habit. Avery Jones,⁷ who defined the disorder, describes it as being due to one or more of the following causes:

• faulty diet—inadequate dietary fibre

• neglect of the call to stool

• unfavourable living and working conditions

• lack of exercise

• travel

Dyschezia, or lazy bowel, is the term used to describe a rectum that has become unresponsive to faecal content, and this usually follows repeated ignoring of calls to defecate.

Slow transit constipation occurs primarily in women with an apparently normal colon, despite a high-fibre intake and lack of the other causes described by Avery Jones. Many are young, with a history dating from early childhood or, more commonly, adolescence. Constipation may follow childbirth, uncomplicated abdominal surgery or a period of severe dieting. However, in the majority no precipitating cause is evident.

A defecatory disorder is where there is a paradoxical contraction rather than normal relaxation of the anal sphincter and associated muscles responsible for evacuation. Also known as dyssynergic dysfunction.

Management

Most patients have simple constipation and require reassurance and education once an organic cause has been excluded. Encourage modification of lifestyle.

• Adequate exercise, especially walking, is important.

• Develop good habit: answer the call to defecate as soon as possible. Develop the ‘after breakfast habit’. Allow time for a good relaxed breakfast and then sit on the toilet. Don’t miss meals—food stimulates motility.

• Avoid laxatives and codeine compounds (tablets or mixture).

• Take plenty of fluids, especially water and fruit juices (e.g. prune juice).

• Eat an optimal bulk diet. Eat foods that provide bulk and roughage, such as vegetables and salads, cereals (especially wheat fibre), fresh and dried fruits, and wholemeal bread. Enough fibre should be taken to convert stools that sink to stools that float.

Examples of food with good bulk properties are presented in TABLE 41.3.⁸ Fruit has good fibre, especially in the skin, and some have natural laxatives (e.g. prunes, figs, rhubarb, apricots).

Treatment (pharmaceutical preparations)

Some patients may not tolerate unprocessed bran but tolerate pharmaceutical preparations better (see TABLE 41.4). An appropriate choice would be one of the hydrophilic bulk-forming agents such as ispaghula or psyllium. Avoid stimulant laxatives except for short sharp treatments.

Use a general bulking agent e.g. psyllium or ispaghula granules 1–2 teaspoonsful (o) once or twice daily, or Benefiber^® 2 teaspoonsful (o) twice daily.

• Use an osmotic laxative or a fibre-based stimulant preparation e.g. macrogol 3350 + 1–2 sachets, each dissolved in 125 mL water once daily

• or

• lactulose syrup, 15–30 mL (o) daily until response, then 10–20 mL daily

• or

• dried fruits with senna leaf (Nu-Lax) 10 g nocte

• or

• docusate + senna (50–80 mg), 1–2 tabs nocte

(Recheck cause.)

• Magnesium sulphate 1–2 teaspoons (15 g) in water once or twice daily (if normal kidney function)

• or

• as capsules (Colocap Balance) 15 caps over 15 minutes

• or

• combined bulking/stimulating agent (e.g. frangula/sterculia [Normacol plus])

• or

• glycerin suppository (retain for 15–20 minutes)

• or

• sodium citrate or phosphate enema (e.g. Fleet Enema)

• or

• Microlax enema

Constipation in children

Constipation is quite common in children but no cause has been discovered in up to 95%. The most common factor is diet. Constipation often begins after weaning or with the introduction of cow’s milk. It is rare with breastfeeding. Low fibre intake and a family history of constipation may be associated factors.⁵ Most children develop normal bowel control by 4 years of age (excluding any physical abnormality). It is normal to have a bowel movement every 2–3 days, providing it is of normal consistency and is not painful.

It is important to differentiate between encopresis and constipation:

Constipation usually appears between 2 and 4 years of age, and up to a third of primary school-aged children will report constipation over a 12-month period. In toddlers, the gender distribution is equal, but by age 5, boys are more likely to get constipation than girls, with the frequency of faecal incontinence three times higher in boys.

Constipation in children is defined as having two or more of the following over the previous 2 months:

• <3 bowel motions per week

• >1 episode of faecal incontinence per week (previously referred to as encopresis)

• large stools in rectum or palpable on abdominal examination

• retentive posturing (e.g. ‘stiff as a board’ standing/lying, tip toes, crossed legs, braces against furniture) and withholding behaviour (e.g. refuses, hides, requests nappy, denies need to go)

• painful defecation

Faecal incontinence, which is a consequence of chronic constipation, is the passage of stool in an inappropriate place in children who have been toilet trained. It can present as soiling, due to faecal retention with overflow of liquid faeces (spurious diarrhoea) aka encopresis.

Constipation is nearly always functional (>95%),⁶ though the GP should check for any red flags for a pathological cause (see below). The key feature in functional constipation is chronic faecal retention leading to rectal dilatation and insensitivity to the normal defecation reflex.

Normally the rectum is empty just prior to defecation; with faecal retention, the rectum is stretched, weak and numb and it can leak.

Other important conditions

Hirschsprung disorder:

• consider if delay in passing first meconium stool and subsequent constipation

Anal fissure in infants:

• consider if stool hard and associated with pain or bleeding

• the mainstay of treatment is dietary manipulation

Principles of treatment of functional constipation^5,6

• Encourage relaxed child–parent interaction with toilet training, such as appropriate encouragement, ‘after breakfast habit’ training, regular toileting (where possible), three times/day for 3–5 minutes, reinforce desired behaviour with stickers on an age-appropriate chart.

• Introduce psychotherapy or behaviour modification program, especially where ‘fear of the toilet’ exists.

• Establish an empty bowel: remove any severely impacted faeces with microenemas (e.g. Microlax), and even disimpaction under anaesthesia if necessary. A good guide if faecal ‘rocks’ are visible on X-ray.

• Advice for parents of children over 18 months:

  • – Drink ample non-milk fluids each day—several glasses of water, unsweetened fruit juice (be cautious of cow’s milk).

  • – Use prune juice, which contains sorbitol.

  • – Get regular exercise—walking, running, outside games or sport.

  • – Provide high-fibre foods—high-fibre cereals, wholegrain bread, brown rice, wholemeal pasta, fresh fruit with skins left on where possible, dried fruits such as sultanas, apricots or prunes, fresh vegetables.

• Advice on correct posture and position—‘how to do a poo’:⁵

  • – Feet supported (e.g. with a foot stool)

  • – Knees higher than bottom and apart

  • – Leaning forward with elbows on knees

  • – Encourage child to push out stomach

  • – Ensure privacy (including at preschool/school)

• Laxatives—if constipation has been brief in duration, treat for 3 months, but for chronic constipation, treat for 6 months minimum.

• Can use macrogol 3350 (Movicol), paraffin oil or lactulose.

• For acute faecal impaction, high-dose laxatives can be used until liquid stools are achieved, and then revert back to maintenance treatment. Enemas are suitable only for children with acute severe rectal pain or distress and are rarely required.

• Use a pharmaceutical preparation as a last resort to achieve regularity.

First line:⁶

• paraffin oil (e.g. Parachoc): RCT evidence indicates suitable and better than stimulant laxative

  • or

  • osmotic laxative (e.g. lactulose): 1–3 mg/kg

    • – 1–5 years: 10 mL per day

    • – >5 years: 15 mL per day

  • or

  • macrogol 3350 with electrolytes:

    • – 2–12 years: 1 sachet Movicol-Half in 60 mL water once daily

    • – >12 years: 1 sachet Movicol (or 2 Movicol-Half) daily

Severe constipation/faecal impaction:

• consider admission to hospital

• abdominal X-ray

• macrogol 3350 with electrolytes (double above doses and water)

• Microlax enema

If unsuccessful, add ColonLYTELY via nasogastric tube or sodium phosphate enema (Fleet Enema) (not <2 years).

Constipation in the elderly

Constipation is a common problem in the elderly, with a tendency for idiopathic constipation to increase with age. In addition, the chances of organic disease increase with age, especially colorectal cancer, so this problem requires attention in the older patient. Faecal impaction is a special problem in the aged confined largely to bed. Constipation is often associated with Parkinson disease. In the elderly, an osmotic laxative such as sorbitol or lactulose may be required for long-standing refractory constipation, but stimulant and other non-osmotic laxatives should be avoided.

Faecal impaction

This is a difficult problem, especially in the older person who may not be aware of the problem especially if they have spurious diarrhoea. Symptoms include malaise, anorexia and nausea, confusion, headache, abdominal discomfort ± colic and bloating, a sense of inadequate defecation and frequent amounts of small stool. Complications include spurious diarrhoea, faecal incontinence, bowel obstruction, urinary incontinence or retention. It often follows opioid medication. Confirm with rectal examination ± plain X-ray of abdomen. Treat with oral or osmotic laxatives (e.g. 8 sachets of macrogol 3350 for 3 days with or without rectal suppositories) or enema, e.g. Fleet Enema, Microlax.

Manual disimpaction

If manual disimpaction should be necessary, the unpleasant procedure can be rendered virtually odourless if the products are ‘milked’ or scooped directly into a container of water. A large plastic cover helps restrict the permeation of the smell.

Discomfort and embarrassment are reduced by this method and by adequate premedication (e.g. IV midazolam and IV fentanyl) if large faecaliths are present.

Colorectal cancer

General features

• Commonest GIT malignancy

• Second most common cause of death from cancer in Western society

• Generally men over 50 years (90% of all cases)

• Mortality rate about 60%

• Good prognosis if diagnosed early

• Two-thirds in descending colon and rectum

Refer to section on genetics of colorectal cancer (see CHAPTER 18).

Predisposing factors

• Ulcerative colitis (long-standing)

• Familial: familial adenomatous polyposis (FAP), hereditary non-polyposis colorectal cancer

• Colonic adenomata

• Decreased dietary fibre

• Age >50 years

This is determined by the family history (see TABLE 41.5).

Consider referral to a familial cancer clinic for assessment.

Symptoms

• Blood in the stools

• Mucus discharge

• Recent change in bowel habits (constipation more common than diarrhoea)

• Alternating constipation with spurious diarrhoea

• Bowel leakage when flatus passed

• Unsatisfactory defecation (the mass is interpreted as faeces)

• Abdominal pain (colicky) or discomfort (if obstructing)

• Rectal discomfort

• Symptoms of anaemia

• Rectal examination—this is appropriate because many cancers are found in the lowest 12 cm and most can be reached by the examining finger

If obstructing, there is a risk of rupture of the caecum.

Surgery is needed to circumvent the closed loop obstruction.

• Lymphatics → epigastric and para-aortic nodes

• Direct → peritoneum

• Blood → portal circulation

Various forms of presentation of large bowel cancers are shown in FIGURE 41.3.

Investigations

• FOBT: immunochemical tests (e.g. Inform and InSure) do not require dietary or medication restriction

• CT colonography (investigation of choice)

• Serum CEA level is not useful for diagnosis but is useful for monitoring response to treatment

• Sigmoidoscopy, especially flexible sigmoidoscopy

• Double contrast, barium enema may miss tumours and is being superseded by other imaging

• Ultrasonography and CT scanning not useful in primary diagnosis; valuable in detecting spread especially hepatic metastases

• PET scanning (if available) is useful for follow-up

If FOBT is positive—investigate by colonoscopy or by flexible sigmoidoscopy.

Screening¹⁰

An FOBT every 2 years is now recommended for all people from 50 years (see guidelines in CHAPTER 9).

Colonoscopy is recommended as follows:

• Moderate risk: every five years from 50 years or 10 years younger than when a family member presented

• High risk: guided by clinical genetics team but as a rule yearly or 2 yearly commencing at 25 years, and every 12 months from 12–15 years of age if a strong family history of FAP.¹¹

In addition, flexible sigmoidoscopy and rectal biopsy for those with ulcerative colitis. Refer to a bowel cancer specialist to plan appropriate surveillance.

Management

Early surgical excision is the treatment, with the method depending on the site and extent of the cancer. Dukes’ classification gives a guide to prognosis (see TABLE 41.6). The survival rates for Dukes C cancer have improved with more effective chemotherapy.

There are other classifications for staging of colorectal cancer, including the 0, I, II, III, IV and TNM systems.

Follow-up includes:

• CEA antigen

• colonoscopy

• abdominal imaging: ultrasound or CT scan of liver

Congenital megacolon Hirschsprung disorder (aganglionosis)

Clinical features

• Congenital

• Constipation from infancy

• Abdominal distension from infancy

• Possible anorexia and vomiting

• Male to female ratio = 8:1

• Rectal examination—narrow or normal rectum

• Abdominal X-ray/barium enema—distended colon full of faeces to narrow rectum

• Diagnosis, confirmed by full thickness biopsy, shows absence of ganglion cells

• Absent rectoanal reflex on anal manometry

Treatment

Resect narrow segment after preliminary colostomy.

Acquired megacolon

Clinical features

• In older children and adults

• Mainly due to bad habit

• Can be caused by:

  • – chronic laxative abuse

  • – milder form of Hirschsprung disorder

  • – Chagas disease (Latin America)²

  • – hypothyroidism (cretinism)

  • – systemic sclerosis

• Marked abdominal distension

• Rectal examination—dilate loaded rectum, lax sphincter

• Abdominal X-ray/barium enema—distended colon full of faeces but no narrowed segment

Treatment

Re-education of bowel habit is required.

Patients with constipation or change in bowel habit of recent onset without obvious cause need further investigation.

• Patients with chronic symptoms who do not respond to simple measures should be referred.

Hand-out sheets from Murtagh’s Patient Education 7th edition:

• Bowel cancer

• Constipation