DiarrhoeaDiarrhoea is defi ned as the passing of increased amounts of loose stools (more than 300 g in 24 hours in adults). There are several causes, but the condition is usually short-lived and symptoms can be treated with over-the-counter medication.
Causes
Acute diarrhoea (infective diarrhoea, gastroenteritis)
Acute diarrhoea is caused by bacterial or viral infection, usually from contaminated food.
Damage to cells in the intestinal mucosa causes infl ammation and prevents absorption of water from the intestine into the blood stream, and the fl uid is evacuated in watery stools.
The condition is self-limiting and normally resolves within 72 hours.
Traveller’s diarrhoea
This is the term given to diarrhoea experienced by travellers or holidaymakers.
Causes, and the severity of symptoms, vary with location.
Attacks are normally short-lived, lasting up to 4–7 days, and begin early in a trip, although they can occur at any time.
Some infections can cause persistent or recurrent diarrhoea and systemic complications.
More serious microbial infections, such as typhoid and cholera, and parasitic infections, such as giardiasis and amoebic dysentery, may be contracted in tropical and subtropical areas.
Up to 15% of patients with traveller’s diarrhoea have dysentery (bloody diarrhoea).
Chronic diarrhoea
Recurrent or persistent: there are several causes and chronic diarrhoea requires medical investigation.
Causes include:
– irritable-bowel syndrome (IBS) – a common functional bowel disorder of unknown aetiology, of which diarrhoea is a common symptom (see Chapter 14)
– infl ammatory bowel disease (for example, Crohn’s disease, ulcerative colitis)
– malabsorption syndromes (such as coeliac disease)
– bowel tumour
– metabolic disease (diabetes, hyperthyroidism)
– side-effects of drugs
– laxative abuse.
Epidemiology
Acute diarrhoea
The exact incidence is unknown, but it is very common and everybody is thought to have a bout at least once in their life.
Traveller’s diarrhoea
Between 30 and 80% of all travellers are estimated to suffer.
In up to about 60% of cases no pathogenic cause is found. Of the rest, the causative organisms are:
– enterotoxigenic Escherichia coli – responsible for 40–75% of traveller’s diarrhoea from an infectious cause; most common in Africa and Central America
– enterohaemorrhagic E. coli and Shigella species – up to 15%, most common in Africa and Central America
– Salmonella species – up to 10%
– Campylobacter jejuni – up to 10%, more common in travellers in Asia
– viruses (for example, rotavirus, Norwalk virus), protozoa and helminths – up to 10%
– Giardia lamblia (especially occurs in travellers in Eastern Europe)
– Entamoeba histolytica – up to 3%.
Signs and symptoms
Acute diarrhoea
rapid onset
watery stools, passed frequently
resolves spontaneously within 72 hours
there may be:
– abdominal cramps and fl atulence
– nausea and vomiting
– weakness and malaise
– fever
– in babies and young children, diarrhoea may be associated with respiratory symptoms.
Traveller’s diarrhoea
early onset, usually within fi rst 3 days of trip
normally of short duration: mean 4 days, maximum 7 days
bloody diarrhoea in about 15% of cases
other symptoms as for acute diarrhoea.
Symptoms and circumstances for referral
duration:
– more than 72 hours in older children and adults
– more than 48 hours in children under 3 years and elderly patients
– more than 24 hours in people with diabetes
– more than 24 hours in babies under 1 year
– babies under 3 months: refer immediately.
diarrhoea associated with severe vomiting and fever
history of change in bowel habit
recurrent diarrhoea
presence of blood or mucus in stools
suspected adverse drug reaction
alternating constipation and diarrhoea in elderly patients – may indicate faecal impaction
signs of dehydration in babies: dry skin, sunken eyes and fontanelle, dry tongue, drowsiness, less urine than normal.
Treatment
Oral rehydration therapy
The first line of treatment for acute diarrhoea is fluid and electrolyte replacement by oral rehydration therapy (ORT).
Normal faeces contain 60–85% water, and the body loses between 70 and 200 ml of water per day through defecation. In diarrhoea, water loss of up to four times
this volume per loose stool occurs, and sodium and potassium alkaline salts are excreted along with it, leading to a fall in plasma pH (acidosis). This can have serious metabolic consequences, particularly in the very young and the elderly.
Fluid and electrolyte losses are increased if vomiting also occurs.
Oral rehydration salts are not intended to relieve symptoms but are designed to replace water and electrolytes lost through diarrhoea and vomiting.
They contain sodium and potassium to replace these essential ions and citrate and/or bicarbonate to correct acidosis.
Glucose is also an important ingredient as it acts as a carrier for the transport of sodium ions, and hence water, across the mucosa of the small intestine, as well as providing the energy necessary for that process.
ORT can be recommended for patients of any age, even when referral to a doctor is considered necessary.
There are no contraindications unless the patient is vomiting frequently and unable to keep the solution down, in which case intravenous fl uid and electrolyte replacement may be necessary.
Fluid overload from excessive administration of ORT is highly unlikely, but possible if it is continued in babies and young children for more than 48 hours. Fluid overload is recognised by the eyelids becoming puffy, and is rapidly corrected by withholding ORT and other liquids.
Antimotility agents
Non-prescription medicines are available containing the opioid drugs loperamide, morphine and diphenoxylate.
One of the effects of opioid drugs is to cause constipation by increasing tone of both the small and large bowel and reducing intestinal motility.
They also increase sphincter tone and decrease secretory activity along the gastrointestinal tract. Decreased motility enhances fluid and electrolyte reabsorption and decreases the volume of intestinal contents.
Loperamide
Loperamide has a high affinity for, and exerts a direct action on, opiate receptors in the gut wall.
It also has a high first-pass metabolism so little reaches the systemic circulation, and at the restricted dosage permitted for non-prescription use it is unlikely to cause any of the side-effects associated with opiates.
It is not licensed for non-prescription use in children under 12 years.
Morphine
Morphine acts promptly on the intestine (within 1 hour of administration), because of its direct action on intestinal smooth muscle and quick absorption from the gastrointestinal tract.
Its action peaks within 2–3 hours and lasts about 4 hours.
Morphine is not well absorbed orally and its availability may be reduced in combination products because of its adsorption on to other constituents.
The morphine content of diarrhoea preparations may also be subtherapeutic.
Morphine, particularly in Kaolin and Morphine Mixture, is subject to abuse and many pharmacists severely restrict its sale.
Diphenoxylate
Diphenoxylate is a synthetic derivative of pethidine.
It has little or no central action but acts selectively on gastrointestinal smooth muscle. It takes longer to act than loperamide.
Diphenoxylate is combined with atropine as co-phenotrope. Atropine is included at a subtherapeutic dose to discourage abuse, on the premise that unpleasant antimuscarinic effects will be experienced if higher than recommended doses are taken.
Co-phenotrope is not licensed for non-prescription use in children under 16 years.
Adsorbents
The rationale behind the use of adsorbents is that they are capable of adsorbing microbial toxins and microorganisms onto their surfaces. Because these substances are not absorbed from the gastrointestinal tract, the toxins and microorganisms are thereby excreted in the stool.
This lack of absorption also means that adsorbents are relatively harmless and safe to use, but there is little evidence that they are effective.
Adsorption is a non-specific process and, as well as adsorbing toxins, bacteria and water, the drugs may interfere with the absorption of other drugs from the intestine. This should be borne in mind if recommending adsorbent antidiarrhoeals to patients taking other medicines.
The adsorbents used in antidiarrhoeals are kaolin, attapulgite and bismuth salicylate.
Bismuth subsalicylate is claimed to possess adsorbent properties, and some studies have shown it to be effective in treating diarrhoea. Large doses are required and salicylate absorption may occur. It should be avoided by individuals sensitive to aspirin.
Additional adviceFor patients suffering from diarrhoea
Drink plenty of clear fl uids, such as water and diluted fruit squash.
Avoid drinks high in sugar as these can prolong diarrhoea.
Avoid milk and milky drinks, as a temporary lactose intolerance occurs due to damage done by infecting organisms to the cells lining the intestine, making diarrhoea worse.
Many people with acute diarrhoea do not feel like eating, but those who do will probably benefi t from eating light, easily digested food.
Babies should continue to be fed as normal, whether by breast or bottle. Formula feeds should be diluted to quarter-strength, and built back up to normal over 3 days. During this period, babies should be fed more frequently than normal and feeds should be supplemented with ORT. To avoid traveller’s diarrhoea in areas of risk
Always wash the hands thoroughly with soap and dry in the air or with a clean towel before using them to put anything in the mouth. Carry antiseptic wipes or hand-cleaning gel in case washing facilities are not available.
Avoid the local drinking water, even for cleaning teeth; drink only bottled mineral water. Avoid ice cubes, dairy products, ice cream and home-distilled drinks.
Eat only fresh foods that have been directly and suffi ciently heat-treated.
Avoid unpeeled fruit and vegetables and uncooked meat.
Do not eat salads that have been washed in the local drinking water.
Avoid shellfi sh and fi sh unless you are sure they are fresh and have not been living in water near to a sewage outlet.
Avoid food from street stalls unless you can be sure this is fresh and cooked instantly.
Try to eat only in establishments that are clean and hygienically run. Try to look inside the kitchen to ensure that there are no fl ies and no left-over food in pots, and that the staff have no visible sores or boils.
Generally follow the dictum: cook it, boil it, peel it – or leave it
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