ANSWER 23
This patient has diarrhoea and weight loss due to giardiasis. It is important to take a care-
ful history in a patient with diarrhoea. An acute infective diarrhoea develops soon after
ingestion of the offending food. The commonest infective causes of infective gastroenteritis
in the UK are viruses such as rotaviruses, or the bacteria Campylobacter jejuniorSalmonella
enteritidis. Staphylococcal food poisoning occurs within a few hours and typically presents
abruptly and may be severe but short-lived. Campylobacter,SalmonellaandShigellacause
more severe symptoms than viral gastroenteritis. The incubation period for giardiasis is typ-
ically about 2 weeks, but varies from 3 days to 6 weeks. Giardia lambliainfects the small
intestine and causes a watery, yellow, foul-smelling diarrhoea. Loss of appetite, nausea and
weight loss are common. Symptoms usually improve after 2–3 weeks, but can persist, in
some cases causing lactose intolerance.
The history should try to distinguish between the small- and large-bowel origin of the diar-
rhoea. Large-bowel diarrhoea tends to be maximal in the morning, pain is relieved by defae-
cation, and blood and mucus may be present. By contrast diarrhoea of small-bowel origin does
not occur at any particular time, and pain is not helped by defaecation. Typically a pale fatty
stool without blood or mucus occurs in small-bowel disease. Other pathogens which cause
small-bowel diarrhoea include Campylobacter, rotavirus, CryptosporidiaandStrongyloides. If
small-bowel-type diarrhoea persists, other non-infective causes of malabsorption should be
considered such as tropical sprue, coeliac disease, and chronic pancreatitis.
Giardia lambliaoccurs worldwide especially in the tropics but also is endemic in Russia,
and infection occurs commonly in visitors to St Petersburg. Poor sanitation and untreated
water supplies are important factors in transmission. Outbreaks can occur in residents of
nursing homes, and giardiasis is a common cause of diarrhoea in homosexuals.
Diagnosis is made by finding cysts of the parasite in stool samples. If stool samples are
negative, cysts can be found on jejunal biopsy or by sampling duodenal fluid by asking
the patient to swallow the Enterotest capsule. Treatment is with a course of metronidazole.
Ideally a stool sample should be examined 6 weeks after treatment to ensure the parasite
has been eradicated. Alcohol, dairy products and spices should be avoided during the
recovery period.
If no infective cause had been found for this man’s diarrhoea and weight loss, further inves-
tigations would have been necessary to exclude causes such as malignancy or thyrotoxicosis.
- Stool samples should be sent in a patient returning from abroad with diarrhoea.
- Always take an accurate history of recent foreign travel in a patient with diarrhoea.
- Attempt to distinguish clinically between small- and large-bowel origin of the diarrhoea.
- Giardiasis is a common cause of traveller’s diarrhoea.