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Determining the cause of diarrhoea

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VOL: 98, ISSUE: 23, PAGE NO: 47

Debbie King, RGN, BSc, DPSN, is infection control nurse, Birmingham Public Health Laboratory, Birmingham Heartlands Hospital

An increase in the number of patients with diarrhoea may be an indicator of an outbreak of gastrointestinal infection. While prompt collection of faecal samples for microbiological investigation is vital in determining the cause of such an occurrence, accurate history-taking with reference to interpreting patients' symptoms plays an equally important role in managing potential outbreaks at ward level.

An increase in the number of patients with diarrhoea may be an indicator of an outbreak of gastrointestinal infection. While prompt collection of faecal samples for microbiological investigation is vital in determining the cause of such an occurrence, accurate history-taking with reference to interpreting patients' symptoms plays an equally important role in managing potential outbreaks at ward level.

Determining the cause
Diarrhoea is a term frequently used by both health care professionals and patients alike. It is defined as an abnormal faecal discharge characterised by frequent and/or watery stool. However, diarrhoea is purely a multifactoral symptom of gastrointestinal disturbance that may be chronic or acute.

Chronic diarrhoea is usually associated with an underlying pathology, such as ulcerative colitis or Crohn's disease. Patients may be undergoing investigation for prolonged altered bowel habit. Having insight into the patient's medical history and reason for admission will help determine if this is a likely cause for the presenting symptoms.

Acute diarrhoea can be due to a wider range of causes. One study indicated that it occurs in 40-60% of critically ill patients and 20% of general medical/surgical patients who receive enteral nutrition (Rombeau et al, 1989). Other mechanical causes for acute diarrhoea may be a result of constipation, with a liquid stool bypassing the faecal mass, which may then be mistaken for diarrhoea. Over-use of laxative treatment in constipated patients may result in an equally misleading symptom.

Aside from these mechanical reasons, acute diarrhoea may also be attributable to infective agents. It is important for controlling cross infection that the potential for such infective agents is established quickly. This is done through assessment to rule out any possible mechanical cause so that the appropriate infection control measures can be taken.

Infective diarrhoea
Unexpected, unexplained diarrhoea thought to be infective may be due to a number of possible agents - viral, bacterial, antibiotic-related infection and travel-associated.

Viral diarrhoea can present as a sporadic or epidemic illness and can be attributable to a number of different viruses, including rotavirus (commonly seen in babies and small children) and small round structured virus, such as Norwalk agent. Such gastrointestinal infections are usually associated with vomiting.

Bacterial diarrhoea can be caused by a number of organisms, including salmonella, shigella, campylobacter and toxin-producing strains of Escherichia coli, such as E.coli 0157. Acquisition of these organisms is generally associated with food. However, with the exception of campylobacter (Skirrow, 1990), cross infection can occur.

For many years antibiotic-related diarrhoea was considered to be a non-infective accepted side-effect of such treatment. However, it is now recognised that the use of antibiotics disrupts the normal gut flora and, in some instances, can predispose to infection with Clostridium difficile. This spore-bearing organism can survive in the environment and be a potential reservoir of infection and cause of outbreaks (Hall, 1993; Verity et al, 2001). With this particular infection clusters of cases may occur, where a number of patients may be identified as being positive for the organism, but these may be different strains or not linked and therefore not considered an outbreak.

Patients with travel-associated diarrhoea may present in hospital and be a potential risk factor for cross infection. Examples of such infections might include cryptosporidial infection, giardiasis, or other protozoa or parasites.

Determining an outbreak
A sudden rise in the number of patients with unexpected, unexplained diarrhoea may indicate an outbreak of gastrointestinal infection. It is important that the infection control team (ICT) is notified of such an event at an early stage. It is generally accepted that two or more patients with diarrhoea within a 24-hour period should alert staff to the possibility of an outbreak.

The ICT will advise on patient management and precautions to be taken. Prompt implementation of infection control measures will reduce the risk of spread among staff and patients. Obtaining specimens for bacteriological and virological examination is of fundamental importance in determining the cause of an outbreak, but it is vital that infection control precautions are implemented according to the symptoms and not delayed until a result is available.

Accurate assessment is essential
When an ICT is investigating and advising in an outbreak it will take account of the ward or environment as a whole. It is important that ward staff have information about the patients with symptoms and those who are at risk to hand, that management are informed of the outbreak, and that the ward staff and ICT work collaboratively.

This information about patients that should be collected can be summarised as follows:

- Symptoms - this information includes the frequency, colour, odour and consistency of the stool. Odour can also play a part in the interpretation of symptoms (Clostridium difficile is said to have a characteristic 'barnyard' smell). It is also important to identify whether the patient has any other associated symptomology, including vomiting, fever, myalgia or abdominal cramps.

- The patient - assessment of a patient's bowel habit forms part of a systems model of nursing (Roper et al, 1982). Therefore it is possible to begin to identify a potential cause, should the current situation differ from the patient's norm. As discussed earlier, this could be due to the patient's condition, underlying medical history or treatment. The length of time the patient has been on the ward is important, as the incubation periods of the different infections vary, and it may be the case that the patient was incubating an infection on admission. This is particularly important when considering potential food-associated outbreaks.

Implementing controls
Patients with unexpected, unexplained diarrhoea should be nursed in single rooms using enteric precautions - disposable gloves and aprons for handling faeces. Where side-room facilities are unavailable the ICT will advise on cohorting symptomatic patients.

Hands are a primary means of transmission of micro-organisms, and effective hand-washing is, therefore, an essential intervention. Alcohol hand rubs can be used in addition to soap and water or as an alternative for physically clean hands.

The environment is an important reservoir of infective organisms, and therefore cleaning should be increased to reduce the potential environmental bio-load. Particular attention should be paid to 'touch points', such as door handles, toilet flushes, hand washbasin taps and grab rails, and to commodes and bedpan holders. Cleaning with detergent and water should be followed by disinfection with a solution of hypochlorite (Rao, 1995; Viral Gastroenteritis Sub-Committee of the Public Health Laboratory Service Virology Committee, 1998). In Clostridium difficile infection, spores are considered to be resistant to conventional cleaning, and thorough cleaning followed by disinfection with sodium hypochlorite 1,000ppm is recommended (Wilcox and Spencer, 1995).

Evaluating the outcome
As with all nursing interventions, evaluating the effectiveness is an integral part of managing an outbreak. It is vital that ward staff and infection control personnel keep accurate records of both the individual patient's bowel habit and the advice given by the ICT regarding the ward as a whole, in accordance with UKCC guidance on record-keeping. This will assist in individual management of patient symptoms and aid the ICT to assess whether the outbreak is over. Daily review of the ward during an outbreak may result in movement of patients who have recovered to allow isolation of those with continuing symptoms.

Collaboration of ward and infection control staff is vital in managing an outbreak. For this to be carried out effectively, the provision of accurate information regarding the patient's symptoms and medical history is imperative. This will enable prompt interventions to reduce the risk of the outbreak spreading.

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