Chapter 6: Elimination
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Source: Adapted from NICE ([172]).
Constipation
Definition
Constipation results when there is a delayed movement of intestinal content through the bowel. It has been described as persistently difficult, infrequent or incomplete defaecation, which may or may not be accompanied by hard, dry stools (Konradsen et al. [112]). Constipation is a subjective disorder, being perceived differently by different people owing to the wide variety of bowel habits among healthy people (Woodward [256]). Consequently, there is a lack of consensus among both healthcare professionals and the general public as to what actually constitutes constipation (Kyle [119], Perdue [198]).
Anatomy and physiology
The rectum is very sensitive to rises in pressure, even of 2–3 mmHg, and distension will cause a perianal sensation with a subsequent desire to defaecate. A co‐ordinated reflex empties the bowel from the mid‐transverse colon to the anus. During this phase, the diaphragm, abdominal muscles and levator ani muscles contract and the glottis closes. Waves of peristalsis occur in the distal colon and the anal sphincter relaxes, allowing the evacuation of faeces (Tortora and Derrickson [237]). The stimulus to defaecate varies in individuals according to habit, and, if a decision is made to delay defaecation, the stimulus disappears and a process of retroperistalsis occurs whereby the faeces move back into the sigmoid colon (Naish and Court [153]). If these natural reflexes are inhibited on a regular basis, they are eventually suppressed and reflex defaecation is inhibited, resulting in such individuals becoming severely constipated.
Related theory
It has been estimated that up to 27% of a given population experience constipation (Dutcher et al. [69]), with an average prevalence of 20% across the general population (Roque and Bouras [216]). Constipation occurs when there is either a failure of colonic propulsion (slow colonic transit) or a failure to evacuate the rectum (rectal outlet delay), or a combination of these problems (Woodward [256]).
The management of constipation depends on the cause. There are numerous possible causes, with many patients being affected by more than one causative factor (Figure 6.23). While constipation in itself is not life threatening, it can lead to bowel perforation, aspiration of vomit or faecal impaction, any of which can be life threatening (Nazarko [158]). Particularly, constipation can be associated with abdominal pain or cramps, feelings of general malaise or fatigue, and feelings of bloatedness. Nausea, anorexia, headaches, confusion, restlessness, retention of urine, faecal incontinence and halitosis may also be present in some cases (Fritz and Pitlick [83], Kyle [119]).
Figure 6.23 Classification of constipation. Source: Reproduced with permission of The Royal Marsden.
The effective treatment of constipation relies on the cause being identified by thorough assessment, to prevent polypharmacy, which can exacerbate the problem (Wald and Talley [239]). Constipation can be categorized as primary, secondary or functional (RCN [206]). Primary constipation has no pathological cause (RCN [206]). Factors that lead to the development of primary, or idiopathic, constipation are extrinsic (or lifestyle related) and include:
- an inadequate diet (low fibre)
- poor fluid intake
- a lifestyle change
- ignoring the urge to defaecate.
Secondary constipation is attributed to another disorder; whether this be metabolic, neurological or psychological, there is an identifiable cause of the constipation (RCN [206]). Examples of disease processes that may result in secondary constipation include anal fissures, colonic tumours, irritable bowel syndrome and conditions such as Parkinson's disease. Constipation may also result as a side‐effect of certain medications, such as opioid analgesics (RCN [206], Woodward [256]).
Functional constipation can result from pelvic floor dysfunction or inadequate relaxation of these muscles during defaecation (dyssynergic defecation) and/or inadequate propulsive forces. Treatment of these will depend on the cause and resulting symptoms. Patients who have not responded to the usual constipation treatments should go on to have their functional ability tested (Skadoon et al. [227]).
Bowel obstruction and ileus
Bowel obstruction occurs when the passage of contents through the bowel lumen is inhibited, either by mechanical (anatomical) or non‐mechanical causes. The alternative term ‘ileus’ is sometimes used to describe the failure of passage of intestinal contents in the absence of any mechanical obstruction (Morton and Fontaine [151]).
Intestinal obstructions are caused by a physical narrowing or internal blockage of the gut lumen, extrinsic compression of the bowel, or a disruption or failure in motility. In cancer patients, malignant bowel obstruction can be either partial or complete, with acute or gradual onset of symptoms (Franke et al. [82]). Obstruction can occur at a single site or, in the case of disseminated intra‐abdominal disease, such as intra‐abdominal carcinomatosis, in multiple sites (Franke et al. [82]).
Intestinal obstruction is a potentially devastating complication for patients, with a vast number of possible clinical causes, and is a condition that can rapidly progress to cause life‐threatening problems (Franke et al. [82]). Intestinal obstruction precipitates a cascade of pathophysiological events that lead to complex and unpleasant symptoms. Thoughtful nursing assessment and evaluation, and meticulous symptom control, can make an important contribution to improving the experience of a patient with bowel obstruction. Management of bowel obstruction may be conservative or surgical and the location of the obstruction, patient prognosis and goal of treatment should be considered when formulating a management plan (Obita et al. [182]). Conservative management usually involves placement of a nasogastric tube (see Procedure guideline 6.17: Insertion of a nasogastric drainage tube), keeping the patient nil by mouth, and managing fluid and medication requirements via intravenous or subcutaneous routes (Ozturk et al. [185]).
Evidence‐based approaches
Rationale
Taking a detailed history from the patient is pivotal in establishing the appropriate treatment plan. It is therefore of vital importance that nurses adopt a proactive preventive approach to the assessment and management of constipation. Kyle and colleagues (Kyle [119], Kyle et al. [121]) have developed, refined and tested a constipation risk assessment tool, now known as the Norgine Risk Assessment Tool (NRAT). This assesses a range of risk factors that appear consistently within the relevant literature on the development of constipation, including:
- nutritional intake and recent changes in diet
- fluid intake
- immobility and lack of exercise
- medication, for example analgesics, antacids, iron supplements or tricyclic antidepressants
- toileting facilities, for example having to use shared toilet facilities, commodes or bedpans
- medical conditions, for example inflammatory bowel disease, irritable bowel syndrome, colorectal cancer, diabetes, or neurological conditions such as multiple sclerosis or muscular dystrophy.
In addition to the identification of these risks and contributing factors, it is important to take a careful history of a patient's bowel habits, taking particular note of the following:
- Any changes in the patient's usual bowel activity. How long have these changes been present and have they occurred before?
- Frequency of bowel action.
- Volume, consistency and colour of the stool. Stools can be graded using a scale such as the Bristol Stool Chart (see Figure 6.3), where constipation would be classified as type 1 or type 2 (Longstreth et al. [133]).
- Presence of mucus, blood, undigested food or offensive odour.
- Presence of pain or discomfort on defaecation.
- Use of oral or rectal medication to stimulate defaecation and its effectiveness.
A digital rectal examination can also be performed, providing the nurse has received sufficient training or instruction to perform it competently. This procedure can be used to assess the contents of the rectum and anal sphincter tone and to identify conditions that may cause discomfort such as haemorrhoids, anal fissures or rectal prolapse (Kyle [120], RCN [206]). See Procedure guideline 6.23: Digital rectal examination for further information.
Additional investigations or referral to specialist services may be indicated if there are any ‘red flag’ symptoms (see Box 6.4), if treatment is unsuccessful, faecal incontinence is present, or if there is ongoing pain or bleeding on defaecation (Bardsley [12]).
Box 6.4
Red flag symptoms that may need referral to a specialist
Refer adults using a ‘suspected cancer pathway referral’ (for an appointment within 2 weeks) for colorectal cancer if:
- they are aged 40 or over with unexplained weight loss and abdominal pain or
- they are aged 50 or over with unexplained rectal bleeding or
-
they are aged 60 or over with
- iron‐deficiency anaemia or
- changes in their bowel habit or
- tests show occult blood in their faeces.
Consider a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer in adults aged under 50 with rectal bleeding and any of the following unexplained symptoms or findings:
- abdominal pain
- changes in bowel habit
- weight loss
- iron‐deficiency anaemia.
Over recent years, international criteria (known as the Rome Criteria) have been developed and revised (Simren et al. [224]) that can help to more accurately and consistently define constipation. According to the Rome IV Criteria, an individual who is diagnosed with constipation should report having at least two of the following symptoms within the past 3 months where those symptoms began at least 6 months prior to diagnosis (Simren et al. [224]):
- straining for at least 25% of the time
- lumpy or hard stool for at least 25% of the time
- a sensation of incomplete evacuation for at least 25% of the time
- a sensation of anorectal obstruction or blockage for at least 25% of the time
- manual manoeuvres used to facilitate defaecation at least 25% of the time (e.g. manual evacuation)
- less than three bowel movements a week
- loose stools rarely present without the use of laxatives.
The myth that daily bowel evacuation is essential to health has persisted through the centuries. This has resulted in laxative abuse becoming one of the most common types of drug misuse in the Western world. The annual cost to the NHS of prescribing medications to treat constipation is in the region of £101 million (Coloplast [50]).
Given that there is a wide normal range, it is important to establish the patient's usual bowel habit and the changes that may have occurred. Many people attempt to manage constipation by themselves with over‐the‐counter remedies before seeking advice despite the impact that it has on their quality of life (Harris et al. [96]). Generally, the patient will complain that they either have diarrhoea or are constipated. These should be seen as symptoms of some underlying disease or malfunction and managed accordingly. The nurse's priority is to effectively assess the nature and cause of the problem, to help find appropriate solutions, and to inform and support the patient. This requires sensitive communication skills to dispel embarrassment and ensure a shared understanding of the meanings of the terms used by the patient (RCN [207]).
Pre‐procedural considerations
Pharmacological support
Laxatives
Laxatives work through direct stimulation of the bowel, by softening faecal matter or a combination of both (Candy et al. [44]). A laxative with a mild or gentle effect is also known as an aperient and one with a strong effect is referred to as a cathartic or purgative. Purgatives should be used only in exceptional circumstances – that is, where all other interventions have failed or when they are prescribed for a specific purpose. The aim of laxative treatment is to achieve comfortable rather than frequent defaecation and, wherever possible, the most natural means of bowel evacuation should be employed, with preference given to the use of oral laxatives where appropriate (NICE [174]). The many different laxatives available may be grouped into types according to the action they have (Table 6.10).
Table 6.10 Classification of laxatives
| Type of laxative | How it works | Name of drug | Notes |
|---|---|---|---|
| Bulk forming | These drugs act by holding onto water so the stool remains large and soft and thereby encourages the gut to move. |
Fybogel
Normacol | This is to be avoided if the patient's bowel activity is not normal or their fluid intake is limited. |
| Stimulant | These drugs cause water and electrolytes to accumulate in the bowel and stimulate the bowel to move. |
Senna tablet/liquid
Bisacodyl tablet/suppositories | This group of drugs is to be avoided if the bowel is not moving very well as these drugs can cause abdominal cramps. |
| Mixed stimulant and softener | Two‐in‐one preparations. | Co‐danthramer liquid or capsules | This drug may cause the urine to change colour. It is a mild stimulant. |
| Softener | These drugs attract and retain water in the bowel. |
Milpar (liquid paraffin and magnesium hydroxide)
Docusate
Arachis oil enema | If the patient is allergic to nuts, they must tell the nurse or doctor as an arachis oil enema should be avoided. |
| Osmotic | These drugs act in the bowel by increasing the stimulation of fluid secretion and movement in the bowel. |
Lactulose
Movicol
Laxido
Phosphate enema
Microlax enema | Can cause bloating, excess wind and abdominal discomfort. |
| 5‐HT4 (5‐hydroxy‐tryptamine receptor 4) receptor agonists (prokinetic agents) | These drugs enhance gut motility by mimicking the effects of serotonin on the gut wall. | Prucalopride | This is not a laxative. It causes an increase in gut motility, resulting in an increase in bowel movements. |
| Peripheral opioid receptor antagonists | These drugs bind to peripheral opioid receptors and so reverse opioid‐induced constipation. | Methylnaltrexone bromide | This is a subcutaneous injection that is only given in advanced stages of illness, in consultation with a specialist palliative care team, where oral laxatives can no longer be taken by mouth. |
Bulk‐forming laxatives
Bulk‐forming agents work by increasing the amount of fibre and therefore water retained in the colon, increasing faecal mass and stimulating peristalsis (Woodward [256]). Ispaghula husk (e.g. manufactured under the brand names Isogel and Regulan) and sterculia (e.g. brand name Normacol) both trap water in the intestine by the formation of a highly viscous gel that softens faeces, increases weight and reduces transit time. These agents need plenty of fluid in order to work (2–3 L per day), as faecal impaction can occur if there is not sufficient fluid intake (Schuster et al. [220]). They also take a few days to exert their effect (Woodward [256]) so are not suitable to relieve acute constipation. Furthermore, bulk‐forming laxatives are contraindicated in some patients, including those who have bowel obstruction, faecal impaction, acute abdominal pain and/or reduced muscle tone, or those who have had recent bowel surgery.
Increasing the bulk may produce side‐effects including flatulence and bloating (Woodward [256]). It may also worsen impaction, lead to increased colonic faecal loading or even intestinal obstruction, and in some cases increase the risk of faecal incontinence. Other potentially harmful effects include causing malabsorption of minerals, calcium, iron and fat‐soluble vitamins, and reducing the bioavailability of some drugs.
Stool softeners
Stool‐softening preparations, such as docusate sodium and glycerol (glycerine) suppositories, act by lowering the surface tension of faeces, which allows water to penetrate and soften the stool (BNF [30]). Liquid paraffin acts as a lubricant as well as a stool softener by coating the faeces and allowing easier passage. However, its use should be avoided as there are a number of problems associated with this preparation. It interferes with the absorption of fat‐soluble vitamins and can also cause skin irritation and changes to the bowel mucosa, while accidental inhalation of droplets of liquid paraffin may result in lipoid pneumonia (BNF [30]).
Osmotic laxatives
Osmotic laxatives, such as lactulose or macrogols (polyethylene glycol), increase the amount of water within the large bowel either through osmosis or by retaining the water they are administered with (BNF [30]). Lactulose is a semi‐synthetic disaccharide that draws water into the bowel through osmosis, resulting in a looser stool. However, it can be metabolized by colonic bacteria, which not only reduces the osmotic effect but also produces gas, which can result in abdominal cramps and flatulence, thereby causing discomfort as well as delaying the osmotic effect by as much as 3 days (BNF [30], Woodward [256]). By contrast, polyethylene glycol is an inert polymer that is iso‐osmotic and binds to water molecules, so it acts by retaining the water it is diluted with when administered (BNF [30], Woodward [256]). Both lactulose and polyethylene glycol are commonly used in the treatment of constipation. A Cochrane review in 2010 recommended that polyethylene glycol is used in preference to lactulose (Lee‐Robichaud et al. [128]) as it results in more frequent bowel motions, softer stools and a reduced need for additional laxative products.
Magnesium and phosphate preparations also exert an osmotic effect on the gut. They have a rapid effect, so fluid intake is important as patients may experience diarrhoea and dehydration. These preparations should be avoided in elderly patients and those with renal or hepatic impairment (BNF [30]). These products are often used as bowel cleansers prior to interventional procedures.
Stimulant laxatives
Laxatives including bisacodyl, dantron and senna stimulate the nerve plexi in the gut wall, increasing peristalsis and promoting the secretion of water and electrolytes in the small and large bowel to improve stool consistency (Rogers [215], Woodward [256]). Stimulant laxatives can cause abdominal cramping, particularly if the stool is hard, and so a stool softener or osmotic laxative may be recommended for use in combination with this group of drugs (BNF [30], Connolly and Larkin [52]). Other adverse effects with high doses of stimulant laxatives include electrolyte disturbances in frail older people and loose stools (Rogers [215], Woodward [256]).
Preparations containing dantron (such as co‐danthramer) are restricted to certain groups of patients, such as the terminally ill, as some studies on rodents have indicated a potential carcinogenic risk (BNF [30]). Dantron preparations should be avoided in incontinent patients, especially those with limited mobility, as prolonged skin contact may cause irritation and excoriation (BNF [30]).
5‐HT4 receptor agonists (prokinetic agents)
5‐HT4 (5‐hydroxytryptamine receptor 4) receptor agonists are not laxatives but enhance gut motility by mimicking the effects of serotonin on the gut wall. Serotonin is usually released when the gut mucosa is stimulated following a meal and its attachment to 5‐HT4 receptors triggers a co‐ordinated contraction and relaxation of the gut's smooth muscle known as the peristaltic wave. Prokinetic agents, such as prucalopride, mimic this action, thereby increasing peristalsis and increasing stool frequency (Rogers [215], Woodward [256]).
Peripheral opioid receptor antagonists
Methylnaltrexone bromide is a parenteral preparation that is usually administered by subcutaneous injection. It is a peripherally acting selective antagonist of opioid binding to the mu‐receptors, thus reversing peripherally mediated opioid‐induced constipation. As this preparation does not cross the blood–brain barrier, it does not interfere with the centrally mediated analgesic effects of opioids (Rauck et al. [204]). The indications for use are opioid‐induced constipation in patients with advanced illness receiving palliative care and who are unable to take oral laxatives. It is necessary to exclude bowel obstruction prior to their use and they should be used under the advice of a palliative care team (Connolly and Larkin [52]).
Non‐pharmacological support
Diet
Dietary manipulation may help to resolve mild constipation, although it is much more likely to help prevent constipation from recurring. Increasing dietary fibre increases stool bulk, which in turn improves peristalsis and stool transit time (Rogers [215]). The current recommended daily intake of dietary fibre for an adult is 30 g (British Nutrition Foundation [36]).
There are two types of fibre: insoluble fibre is contained in foods such as wholegrain bread, brown rice, fruit and vegetables, and soluble fibre is contained in foods such as oats, pulses, beans and lentils. It is recommended that fibre should be taken from a variety of both soluble and insoluble foods and eaten at times spread throughout the day (British Nutrition Foundation [36]). Care should be taken to increase dietary fibre intake gradually as bloating and abdominal discomfort can result from a sudden increase, particularly in older people and those with slow‐transit constipation (Rogers [215]).
Dietary changes need to be made in combination with other lifestyle changes. There is little evidence to support the benefit of increasing fluid intake for constipation, but there is arguably a benefit in encouraging people to drink the recommended daily fluid intake of at least 2 L (Fritz and Pitlick [83], Rogers [215]). There is a need for further studies to examine the role of dietary manipulation in the management of constipation, particularly concerning the functions of dietary fibre and fluid intake.
Positioning
Patients should be advised not to ignore the urge to defaecate and to allow sufficient time for defaecation. It is important that the correct posture for defaecation is adopted: crouching or a ‘crouch‐like’ posture is considered anatomically correct (Denby [65], Woodward [256]) and the use of a footstool by the toilet may enable patients to adopt a better defaecation posture (NICE [171], RCN [206], Woodward [256]) (Figure 6.24). The use of a bedpan should always be avoided if possible as the poor posture adopted while using one can cause extreme straining during defaecation.
Figure 6.24 Correct positioning for opening your bowels. Source: Reproduced with permission of Norgine Pharmaceuticals Ltd.
Exercise
Constipation is known to be associated with immobility (Krogh et al. [115]) and increasing physical activity is one of the primary management techniques offered to patients (Emly and Marriott [74]). This is because colonic transit time is reduced as physical activity stimulates bowel motility in healthy individuals (Krogh et al. [115]). Patients with chronic idiopathic constipation may benefit from an exercise programme consisting of 30–60 minutes of physical activity per day (De Schryver et al. [62]).
Other treatments
Biofeedback is a behaviour modification technique that encourages bracing of the abdominal wall and relaxation of the pelvic floor muscles to achieve effective defaecation. It is reported to be effective in a significant number of cases but further blinded research is required to test its efficacy more fully (Thakur et al. [236]).
Rectal irrigation is increasingly being offered as a treatment for both chronic constipation (particularly where biofeedback has not worked) and faecal incontinence. It involves instilling lukewarm water into the rectum using a rectal catheter with the aim of ensuring the rectum, sigmoid and descending colon are emptied of faeces (Rogers [215], Woodward [256]).
Overall, lifestyle changes and laxatives (see Table 6.10) are the most commonly used treatments for constipation. In general, laxatives should be used as a short‐term measure to help relieve an episode of constipation as long‐term use can perpetuate constipation and create dependence. The development of newer aperients has broadened the treatment options, particularly for those patients with chronic constipation that has not responded to lifestyle modification or traditional laxatives.
