No. 16, October 1994
About 10% of diarrhoeal episodes in children under 5 years of age have visible blood in the stool and these cause about 15% of diarrhoea-associated deaths in this age group. Compared with watery diarrhoea, bloody diarrhoea generally lasts longer, is associated with more complications, is more likely to adversely affect a child's growth, and has a higher risk of death.
Bloody diarrhoea in a young child is usually a sign of a serious invasive bacterial infection of the bowel. Pathogens that cause bloody diarrhoea may also cause diarrhoea without visible blood, but such episodes are less severe, generally resembling diarrhoeal disease caused by non-invasive pathogens. The presence of visible blood is, thus, a convenient and reliable indicator of severity.
The correct treatment of bloody diarrhoea includes: (i) giving an antimicrobial that is effective against Shigella, (ii) giving oral rehydration salts (ORS) solution or other fluids to prevent or treat dehydration, (iii) continuing to feed the child, and (iv) providing follow-up, especially for children at increased risk of serious morbidity or death. When these steps are followed, most episodes of bloody diarrhoea resolve rapidly and many serious consequences are avoided.
Dysentery has the same meaning as bloody diarrhoea. Although sometimes used to describe bloody diarrhoea that is associated with fever, abdominal cramps, rectal pain and mucoid stools, these features do not always accompany bloody diarrhoea, nor does their presence or absence necessarily define its etiology or determine how it should be treated.
Shigella are the most important cause of bloody diarrhoea among yÿÿng children in developing countries. Shigella cause 50% or more of all episodes of bloody diarrhoea, a much higher proportion of episodes that are clinically severe, and most of the estimated 370 000 deaths from bloody diarrhoea that occur worldwide each year in children younger than five years.
Episodes of bloody diarrhoea caused by other bacterial pathogens occur less frequently than shigellosis, are usually less serious, and their cause is often difficult to determine except in research laboratories. These bacteria include: Campylobacter jejuni, enteroinvasive Escherichia coli, entero-haemorrhagic E. coli and non-typhoid serotypes of Salmonella.
Amoebiasis is an uncommon cause of bloody diarrhoea in young children. A study done in China, India, Mexico, Myanmar and Pakistan involving 3640 children under three years of age with acute diarrhoea yielded only 10 cases of probable invasive amoebiasis (1.5% of all episodes of bloody diarrhoea), but 400 cases of all episodes of bloody diarrhoea). In Bangladesh, a study of 101 children with bloody diarrhoea (mean age 21 months) revealed none with E. histolytica trophozoites in their stool.
Culturing the stool is of little value because many invasive bacteria require special culture media, unusual growth conditions, or diagnostic antisera that are often unavailable. Also, attempts to isolate Shigella may fail unless the specimen is inoculated immediately and properly transported to the laboratory. Moreover, the results of culture are available only after two or three days, whereas treatment must be decided upon when the child is first seen.
The diagnosis of invasive amoebiasis requires that typical trophozoites of E. histolytica containing red blood cells be seen in the stool by a reliable technician. However, even experienced tech-nicians frequently mistake non-pathogenic protozoa, white blood cells, macrophages con-taining red blood cells or partially digested vegetable matter for amoebic trophozoites. Where the skill of technicians is not confirmed by regular quality control procedures, amoebiasis is routinely over-diagnosed and laboratory reports are of little value. The detection only of amoebic cysts is not evidence of invasive amoebiasis.
The antimicrobial susceptibility of local Shigella strains should be monitored regularly and the results used to develop, or modify, national treatment guidelines. Unfortunately, resistance to ampicillin is now widespread and resistance to cotrimoxazole is increasing. Nalidixic acid, formerly used as a "backup" drug to treat resistant shigellosis, is now the drug of choice in some areas, but resistance to it is also appearing. Health facilities should try to stock more than one locally effective antimicrobial for Shigella.
Antimicrobials that are not effective for shigellosis are listed in Table 2. These include: (i) agents to which Shigella are usually resistant, and (ii) those to which Shigella are sensitive in vitro, but which penetrate poorly the intestinal mucosa where invasive Shigella must be killed. Treatment of shigellosis with any of these agents, or an antimicrobial to which resistance has developed, is ineffective.
Resistant organisms:Most S. dysenteriae type 1; many other Shigella species
Dose:25 mg/kg 4 times a day for 5 days
Drug: Trimethoprim-Sulfamethoxazole (TMP-SMX;also called cotrimoxazole)
Resistant organisms:Many S. dysenteriae type 1; variable among other Shigella species
Dose:TMP 5 mg/kg and SMX 25 mg/kg; twice a day for 5 days
Drug: Nalidixic acid
Resistant organisms: Increasing among S. dysenteriae type 1;uncommon among other Shigella species for 5 days
Dose:15 mg/kg 4 times a day
Resistant organisms: Rare among all Shigella species
Dose:20 mg/kg 4 times a day for 5 days
Resistant organisms: Rare among all Shigella species
Dose:20 mg/kg twice a day for 5 days
For further information, contact:
The Director, Division of Diarrhoeal and Acute Respiratory Disease Control
World Health Organization, 1211 Geneva 27, Switzerland
Tel: +41 22 791-2632, Fax: +41 22 791-4853,