33.5.1  Diagnosis of diarrhoeal diseases

Accurate diagnosis of a specific type of diarrhoeal disease is only possible with laboratory identification of the infectious agents, mainly from stool samples. This can be essential in determining the type of treatment if antibiotics are required, and can also help to target prevention and control measures most effectively. However, laboratory diagnosis of the infectious agent takes time and is not needed for the treatment of most cases of acute watery diarrhoea among children. You can begin treating most children immediately on the basis of your clinical diagnosis, i.e. your knowledge of the characteristic symptoms and signs of acute watery diarrhoea described earlier in this study session, without the need for identifying the specific infectious agent.

Laboratory diagnosis is required for:

• children with dysentery (which could be bacillary or amoebic)
• all adults with severe diarrhoea, however caused.

Even in cases where laboratory diagnosis is required, you should not wait for the results of the investigation before starting rehydration as described below (Section 34.4.2) and referring the patient to the nearest health centre or hospital. Explain to the adult patient or caregiver (if the patient is a child) that referral is needed for further diagnosis, because treatment varies depending on the specific cause of the disease. Ensure that the patient seeks treatment urgently, as the disease could worsen rapidly and lead to serious outcomes.

Although you can’t be sure of the diagnosis yourself, if you suspect dysentery or cholera, ask whether anyone else in the patient’s household, or their neighbours, have a similar illness. This helps you to identify and report suspected cases, which is essential to prevent an epidemic from spreading.