Diarrhoea can take the form of anything from a semi-loose to a completely liquid stool and may result in having to go to the toilet more frequently and urgently. Other symptoms which can accompany diarrhoea include stomach pains, nausea, vomiting, loss of appetite and fever.

Causes

Diarrhoea is common in HIV disease, especially in people with low CD4 counts. Studies suggest that at the time of their death, 80% of people with AIDS have had diarrhoea for at least a month.

Infections are a common cause of diarrhoea, including Cryptosporidium, Microsporidium, CMV, MAI, giardiasis, Salmonella and Shigella. Data from the Swiss HIV Cohort Study suggests that less that half the cases of chronic diarrhoea (46%) are caused by an infection.

Another common cause of diarrhoea in people with HIV is drug treatment. Diarrhoea can also be a side-effect of treatment with antibiotics as the normal bacteria which live in the gut and help to digest food are disrupted. Sometimes this may result in a secondary infection with the bacterium Clostridium difficile which can result in severe and persistent diarrhoea. Other drugs which may cause diarrhoea include the class of anti-HIV agents known as protease inhibitors (e.g. nelfinavir) and other anti-HIV drugs such as AZT and ddI. See When diarrhoea is a drug side effect below.

It is now relatively uncommon for a specific cause not to be found. In such cases mild diarrhoea can usually be attributed to the direct effect of HIV on the gut. In rare instances this may be accompanied by weight loss (wasting syndrome). However, one of the commonest causes of diarrhoea in people who have no gut infection is the irritable bowel syndrome, in which diarrhoea often alternates with constipation and is associated with bloating and excessive wind; this may be increased by stress.

What to do

Diarrhoea will usually settle in a few days but if it is severe or becomes persistent then it is important to see your doctor for investigation and treatment. To look for infections, your doctor will want to analyse a sample of stool, and may also take a rectal biopsy as some organisms can be found in the tissue even when the stool does not show the organism.

As diarrhoea may result in excessive loss of salts and water from the body, it is important to drink plenty of fluid or alternatively special oral rehydration drinks (e.g. Dioralyte or sports drinks like Gatorade). You will lose a lot of potassium when you have severe diarrhoea, but you can replace this by eating foods like bananas, potatoes, chicken and fish, which contain high levels of potassium.

Diarrhoea that is due to the direct effects of HIV on the gut can be treated with anti-HIV drugs. Combination therapy has been associated with fewer symptoms, reduced HIV viral load and increased CD4 cells in gastrointestinal tissue.

If specific microbes that can cause diarrhoea are found, such as Shigella, specific anti-microbial drugs may be prescribed. For more information on these, look up the specific infection in the index.

Anti-diarrhoeal agents such as imodium and codeine may be of help with chronic diarrhoea. As weight loss may accompany diarrhoea improving your diet and getting advice on nutrition is important. Glutamine has also been shown to improve diarrhoea.

Probiotic Lactobacillus preparation does not appear to reduce the amount of diarrhoea with non-infectious causes.

Severe diarrhoea can cause soreness around the anus and other practical problems which the district nurse or those at the clinic or hospital will be able to advise you on how to cope with. Bed linen and clothes may need to be washed more frequently and help may be provided through local social services or AIDS charities.

People with irritable bowel syndrome may be helped by changing the fibre content of their diet either upwards or downwards, and also by the use of anti-spasmodic therapy such as Colofac.

Also see Weight loss in Symptoms and illnesses: A to Z of symptoms and Wasting syndrome - overview in Symptoms and illnesses: A to Z of illnesses.

When diarrhoea is a drug side effect

Diarrhoea has been reported as a side effect of all the protease inhibitors, with ddI and abacavir from the NRTI class, and with co-trimoxazole and some other antibiotics.

With some drugs, diarrhoea may be an early side effect which gradually goes away. With other drugs it may be a permanent feature of living with that drug.

The severity of the diarrhoea also varies. Severe diarrhoea - many trips to the toilet each day, large and uncontrollable liquid bowel movements and feelings of weakness or dizziness as a result of the loss of fluid and electrolytes - is experienced by around 25% of people starting nelfinavir treatment and nearly 20% of people starting saquinavir. Similar levels have been seen with amprenavir, lopinavir, ritonavir and indinavir. Less serious problems - loose bowel movements or transient bursts of diarrhoea - may be experienced by a larger proportion of people starting protease inhibitor treatment. Serious diarrhoea may also persist: in a 72 weeks study of lopinavir/ritonavir, around 10% of participants were still experiencing serious diarrhoea after 18 months on treatment.

Changes to diet seem to have a relatively small effect on drug-related diarrhoea.

Different treatments have been tested to control diarrhoea that is caused by medication:

• Imodium (loperamide) is the most commonly prescribed anti-diarrhoea drug. You can also buy loperamide tablets over the counter in the pharmacy if you suddenly begin to experience diarrhoea after starting a new drug. Loperamide is a relatively weak anti-diarrhoea treatment, and if the recommended dose is not keeping it under control, you may need to try other medications such as lomotil or octreotide.

• Calcium supplements of 500mg twice a day have been shown to reduce the diarrhoea associated with nelfinavir treatment.

• Glutamine has been shown to improve the diarrhoea associated with nelfinavir treatment.

• Oat bran tablets have also been shown to improve the diarrhoea associated with nelfinavir; these work by absorbing fluid, making stools larger, and slowing the movement of stools through the intestines.

A combination of nutritional counselling, psyllium (a form of soluble fibre), calcium carbonate and loperamide can reduce the severity of nelfinavir-related diarrhoea, and improve quality of life.

See Nelfinavir - key research in Drugs used by people with HIV: protease inhibitors for further information about these studies.