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Unit 1 - The Epidemiology and Etiology of Diarrhoea
Unit 2 - Pathopysiology of Watery Diarrhoea: Dehydration and Rehydration
Unit 3 - Assessing the Diarrhoea Patient
Unit 4 - Treatment of Diarrhoea at Home
Unit 5 - Treatment of Dehydrated Patients
Unit 6 - Dysentery, Persistent Diarrhoea, and Diarrhoea Associated with Other Illnesses
Unit 7 - Diarrhoea and Nutrition
Unit 8 - Prevention of Diarrhoea

Unit 6 - Dysentery, Persistent Diarrhoea, and Diarrhoea Associated with Other Illnesses
Medical Education: Teaching Medical Students about Diarrhoeal Diseases

World Health Organization 1992

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Definition, etiology, and importance
Clinical features and diagnosis
Antibiotic therapy
Definition, etiology, and importance
Risk factors
Nutritional impact
History and examination
Laboratory examination
Fluid and electrolyte replacement
Nutritional therapy
Measles-associated diarrhoea
Pneumonia and diarrhoea
Fever and diarrhoea EXERCISES



Some children with diarrhoea are not adequately treated by the combination of rehydration and diet therapy described in Treatment Plan A (see Unit 4). This applies in particular to children with dysentery or persistent diarrhoea, or whose illness is complicated by severe undernutrition or an infection outside the intestinal tract. While such patients may need rehydration, they may also require special approaches to feeding, antimicrobial therapy, or other treatment. This unit describes the management of children with dysentery, persistent diarrhoea, or other infections that may accompany or predispose to diarrhoea. The management of children with diarrhoea and severe undernutrition is considered in Unit 7.


Definition, etiology, and importance

Dysentery is defined as diarrhoea with visible blood in the stools. The most important and most frequent cause of acute dysentery is Shigella, especially S. flexneri and S. dysenteriae type 1. Other causes include Campylobacter jejuni, especially in infants, and, less frequently, Salmonella; dysentery caused by the latter agents is usually not severe. Enteroinvasive Escherichia coli are closely related to Shigella and may cause severe dysentery. However, infection with this agent is uncommon. Entamoeba histolytica cause dysentery in older children and adults, but rarely in children under 5 years of age.

Dysentery is an important cause of morbidity and mortality associated with diarrhoea. About 15% of all diarrhoeal episodes in children under 5 years are dysenteric, but these cause up to 25% of all diarrhoeal deaths. Dysentery is especially severe in infants and in children who are undernourished, develop clinically evident dehydration during their illness, or are not breast-fed. It also has a more harmful effect on nutritional status than acute watery diarrhoea. Dysentery occurs with increased frequency and severity in children who have measles or have had measles in the preceding month, and diarrhoeal episodes that begin with dysentery are more likely to become persistent than those that start with watery stools.

Clinical features and diagnosis

The clinical diagnosis of dysentery is based solely on the presence of visible blood in the diarrhoeal stool. The stool will also contain numerous pus cells (polymorphonuclear leukocytes) which are visible with a microscope, and it may have abundant mucus; these latter features suggest infection with a bacterial agent that invades the intestinal mucosa (such as C. jejuni or Shigella), but alone are not sufficient to diagnose dysentery. In some episodes of shigellosis, the stool is initially watery, becoming bloody after one or two days. This watery diarrhoea is sometimes severe and may cause dehydration. Usually, however, numerous small bloody stools are passed and dehydration does not occur. Patients with dysentery frequently have fever, but sometimes the temperature is abnormally low, especially in the most serious cases. Cramping abdominal pain and pain in the rectum during defecation, or attempted defecation (tenesmus) are common; however, young children are unable to describe these complaints.

A number of severe and potentially fatal complications can occur during dysentery, especially when the cause is Shigella; they include: intestinal perforation, toxic megacolon, rectal prolapse, convulsions (with or without a high fever), septicemia, haemolytic-uraemic syndrome, and prolonged hyponatraemia. A major complication of dysentery is weight loss and rapid worsening of nutritional status. This is caused by anorexia, which may be marked, the body's increased need for nutrients to fight infection and repair damaged tissue, and the loss of serum protein from the damaged intestine (i.e., protein-losing enteropathy). Death from dysentery is usually caused by extensive damage to the ileum and colon, complications of sepsis, secondary infection (e.g., pneumonia), or severe undernutrition. Children convalescing from dysentery are also at increased risk of death from other infections, owing perhaps to their poor nutritional state or impaired immunity.

The cause of an episode of dysentery usually goes undetermined. Stool culture, to detect pathogenic bacteria, is rarely possible. Moreover, at least two days are required before results of a culture are available, whereas a decision on antimicrobial therapy must be made immediately. Stool microscopy to detect protozoa may also be unavailable or unreliable. Amoebiasis can only be diagnosed with certainty when trophozoites of E. histolytica containing red blood cells are seen in fresh stools or in mucus from rectal ulcerations (obtained during proctoscopy). The detection of cysts alone is not sufficient for a diagnosis of amoebiasis. Amoebiasis should be suspected when a child with dysentery does not improve following appropriate antibiotic therapy for shigellosis.


Children with dysentery should be presumed to have shigellosis and treated accordingly. This is because Shigella cause about 60% of dysentery cases seen at health facilities and nearly all cases of severe, life-threatening disease. If microscopic examination of the stool is performed and trophozoites of E. histolytica containing erythrocytes are seen, antiamoebic therapy should also be given (see below). The four key components of the treatment of dysentery (see Figure 6.1) are:

  • antibiotics
  • fluids
  • feeding
  • follow-up

Antibiotic therapy

Early treatment of shigellosis with an appropriate antibiotic shortens the duration of the illness and reduces the risk of serious complications and death; however, such treatment is effective only when the Shigella are sensitive to the antibiotic that is given. If treatment is delayed or an antibiotic is given to which the Shigella are not sensitive, the bacteria may cause extensive damage to the bowel and enter the general circulation causing septicaemia, prostration, and sometimes septic shock. These complications occur more frequently in children who are undernourished or in infants, and may be fatal.

As the antibiotic sensitivity of the infecting strain of Shigella is not known for each case, it is important to use an oral antibiotic to which most Shigella in the area are known to be sensitive. Co-trimoxazole is the usual choice, but ampicillin is effective in some areas (see Annex 7). Although treatment is recommended for five days, there should be a substantial improvement after two days, i.e., less fever, pain, faecal blood, and loose motions. If this does not occur, the antibiotic should be stopped and a different one used; in many areas this would be nalidixic acid. Although other bacteria, such as C. jejuni and Salmonella, can cause dysentery, the disease is usually relatively mild and self-limited.
Young children with dysentery should not be treated routinely for amoebiasis. Treatment should only be given when E. histolytica trophozoites containing red blood cells are identified in faeces or when bloody stools persist after consecutive treatment with two antibiotics that are usually effective for Shigella. The preferred treatment for amoebic dysentery is metronidazole (see Annex 7). If dysentery is caused by E. histolytica an improvement will occur within 2-3 days of starting treatment.


Children with dysentery should be evaluated for signs of dehydration and treated accordingly (see Units 3-5). All patients with dysentery should be offered water and other drinks during their illness, especially if they have fever.


Children with dysentery should continue to eat, so that nutritional damage during the disease can be prevented or minimized. Feeding may be difficult, however, because of anorexia. The general feeding guidelines in Treatment Plan A (Units 4 and 7) should be followed: continue breast-feeding; give frequent small meals at least six times a day; encourage the child to eat; choose energy and nutrient-rich foods that the child prefers; and give one extra meal a day using the same foods for at least two weeks after diarrhoea stops.


Most patients with dysentery show substantial improvement within two days after beginning treatment with an effective antibiotic. These patients should complete the five-day treatment, and do not require special follow-up. Other patients should be followed closely, particularly children who do not show a clear improvement within two days, and children known to be at high risk of death or other complications. High-risk children (i.e. infants, the undernourished, those not breast-fed, and any who have been dehydrated) should be monitored frequently as outpatients or admitted to hospital. Dysentery patients with severe undernutrition should be hospitalized routinely. Children showing no improvement after the first two days of antibiotic treatment should be given a different antibiotic, as described above.


The microorganisms that cause dysentery are spread by faecally-contaminated hands, food, and water. The spread of shigellosis by hands is very efficient because the number of Shigella required to cause disease is very small (as few as 10-100 organisms). Important measures to prevent shigellosis are described in greater detail in Unit 8.


Definition, etiology, and importance

Persistent diarrhoea is a diarrhoeal episode that lasts for 14 days or longer (see Unit 1). Up to 20% of acute diarrhoeal episodes become persistent. Persistent diarrhoea often causes nutritional status to deteriorate and is associated with increased mortality. In some areas, it causes 30-50% of all diarrhoea-associated deaths, and as many as 15% of episodes of persistent diarrhoea result in death. There is no single microbial cause, although enteroadherent E. coli may play a greater role than other agents; Cryptosporidium may also be important in severely undernourished or immunodeficient persons. A number of other pathogenic bacteria and protozoa are found with nearly equal frequency in cases of acute and persistent diarrhoea, but their role in causing this problem is unclear. Irrespective of its cause, persistent diarrhoea is associated with extensive changes in the bowel mucosa, especially flattening of the villi and reduced production of disaccharidase enzymes; these cause reduced absorption of nutrients and may perpetuate the illness after the original infectious cause has been eliminated.

Risk factors

A number of risk factors for persistent diarrhoea have been identified:

  • Undernutrition - this may delay the repair of damaged intestinal epithelium, causing diarrhoea to be prolonged.
  • Recent introduction of animal milk or formula (or soya-based milk) - this could reflect lactose intolerance, hypersensitivity to milk (or soya) protein, bacterial contamination of the milk, or some other mechanism. Animal milk appears to be an important factor in 30-40% of episodes of persistent diarrhoea.
  • Young age - most episodes occur in children under 18 months of age.
  • Immunological impairment - this is seen in undernourished children, during or following measles or some other viral infections, and in patients with the acquired immunodeficiency syndrome (AIDS).
  • Recent diarrhoea - this includes children who have experienced a recent episode of acute diarrhoea or a previous episode of persistent diarrhoea.
  • Knowledge of these risk factors helps to identify children who are most likely to develop persistent diarrhoea and, in some instances, to guide treatment.

    Nutritional impact

    Persistent diarrhoea is largely a nutritional disease. It occurs more frequently in children who are already undernourished and is itself an important cause of undernutrition. A single episode of persistent diarrhoea can last 3-4 weeks or longer and cause dramatic weight loss, sometimes leading rapidly to severe undernutrition, i.e. marasmus.

    Weight loss during persistent diarrhoea is caused by reduced absorption of all nutrients, but especially of fat and, in some children, lactose. Other contributing factors include poor food intake, owing to anorexia or withholding of food, or substituting dilute, low-energy foods. Patients are also likely to be deficient in various vitamins and minerals: those of special importance because of their role in the renewal and repair of the intestinal mucosa and/or their role in normal immunological responses include folate, vitamin B12, vitamin A, zinc, and iron.


    The initial management of children with persistent diarrhoea is summarized in Figure 6.1 and discussed below.

    History and examination

    These should cover the same areas as in cases of acute diarrhoea, but with special attention to the following questions:

  • How many days has this episode of diarrhoea lasted?
  • What is the child being fed, breast milk or animal milk? If over 4-6 months of age, is the type and amount of weaning food adequate? Is the food given in small frequent servings? How is the child's appetite?
  • Was animal milk or formula (or soya formula) introduced recently? Does the diarrhoea seem to be worse soon after animal milk or formula is given?
  • Has an antibiotic been given? If so, which one?
  • If this is a repeat visit, has the mother noted: any change since the last visit in frequency of diarrhoea, blood in the stool, fever, or feeding problems? Could she follow the last treatment advice given?
  • Is the child dehydrated?
  • What is the child's nutritional status? Has it declined during this illness? (Measure and plot weight and height, if possible.)
  • Has the stool been bloody? Is it bloody now?
  • Laboratory examination

    For all patients, it is important to observe whether the stool is bloody. The use of other laboratory examinations will depend upon their availability. Some of the most useful ones are summarized in Table 6.1.

    Fluid and electrolyte replacement

    The child's hydration status should be assessed as described in Unit 3. ORS is satisfactory for replacing losses of water and salts in most children with persistent diarrhoea; a few patients have severe glucose malabsorption (see Unit 5) and require intravenous fluid therapy. Some patients with persistent diarrhoea develop dehydration and continue to lose stool rapidly after rehydration; they should be hospitalized and may require treatment with intravenous fluids until the rate of purging declines.

    Nutritional therapy

    Proper feeding is the most important aspect of treatment for most children with persistent diarrhoea. Many can be treated on an ambulatory basis with food available in the home; however, some require specialized care in hospital. The goals of nutritional therapy are to:

  • temporarily reduce the amount of animal milk (or lactose) in the diet;
  • provide a sufficient intake of energy, protein, vitamins, and minerals to facilitate the repair process in the damaged gut mucosa and improve nutritional status;
  • avoid giving foods or drinks that may aggravate the diarrhoea; and
  • ensure that the child's food intake during convalescence is adequate to correct any undernutrition and prevent its recurrence.
  • The general guidelines for feeding during and after diarrhoea given in Treatment Plan A (see Unit 4) should be followed. Some especially important or additional guidelines are shown in Figure 6.1 and given below:
  • Children under 6 months of age or with evidence of dehydration should be rehydrated and referred to hospital for further management. They may require special efforts to maintain hydration, replacement of animal milk with lactose-free or artificial milk formula, laboratory studies to identify pathogenic bacteria or protozoa in their faeces, or other specialized procedures.
  • For older children, the mother should be instructed to:
  • continue breast-feeding;
  • dilute any animal milk given to the child with an equal amount of water or replace it with a fermented milk product, such as yoghurt. This reduces by half the amount of lactose in the child's diet. In many cases, this step will cause the diarrhoea to subside rapidly;
  • ensure a full energy intake for the child (i.e., about 110 kcal/kg/day) by giving thick cereal with added vegetable oil; mix this with other foods, such as well-cooked and mashed pulses, vegetables, and if possible, meat or fish. Avoid low energy foods that are dilute or bulky. At least half of the child's energy intake should come from foods other than milk or milk products;
  • avoid foods that are hyperosmolar (these are usually foods or drinks made very sweet by the addition of sucrose, such as soft drinks or commercial fruit drinks); these can make the diarrhoea worse;
  • give food in frequent small meals, at least six times a day; and
  • provide supplementary vitamins and minerals, in particular folate, vitamin B12, vitamin A, zinc and iron, if possible.
  • Tell the mother to follow these instructions for five days and then bring the child back to be checked:
  • if the diarrhoea has not stopped, refer the child to hospital for specialized care, as described above;
  • if the diarrhoea has stopped, tell the mother to:
  • continue to give the same foods for the child's regular diet;
  • after one more week, gradually reintroduce the usual animal milk or formula (if the child normally takes it) over several days; and
  • given an extra meal each day for at least one month. If the child is undernourished, this regimen should be continued until the deficit of weight for height is corrected. The child should also be seen at monthly intervals to monitor growth (see Annex 3) and ensure that the feeding guidelines are being followed.
  • Drug therapy

    Persistent diarrhoea patients with bloody stool or a stool culture positive for Shigella should receive an antibiotic for shigellosis. If stool culture yields another bacterial pathogen, e.g. enteropathogenic E. coli, an oral antibiotic to which that agent is sensitive should be given. If Giardia cysts, or trophozoites of either Giardia or E. histolytica are seen in the faeces, a course of appropriate antiprotozoal therapy should be given (see Annex 7). However, "blind" therapy with antibiotics or antiprotozoal agents is not rewarding and should not be given. Similarly, no "antidiarrhoeal" drug (including antimotility drugs, antisecretory drugs and adsorbents) has any proven value in patients with persistent diarrhoea; such drugs should not be given (see also Unit 4).


    Children with diarrhoea may also have other potentially serious illnesses, especially undernutrition or other infections. Two nutritional disorders associated with diarrhoea are considered in Units 3 and 7: vitamin A deficiency and severe undernutrition. The following discussion concerns infections that may be associated with diarrhoea.

    Measles-associated diarrhoea

    The incidence of diarrhoea is increased during measles, during the 4 weeks following illness, and possibly for up to 6 months after the measles episode. Measles-associated diarrhoea is often severe and of longer than usual duration; the risk of death is also substantially higher than with diarrhoea that is not related to measles, and is probably even greater when children are also undernourished. Where the incidence of measles is high, measles-associated diarrhoea can account for one third, or more, of diarrhoea-associated deaths in young children. Measles vaccination is therefore an important measure for preventing both diarrhoeal episodes and diarrhoea-associated deaths, as well as for preventing measles (see Unit 8).

    The mechanisms by which measles predisposes to diarrhoea are not clear but may include: (i) a direct effect of measles virus on the bowel epithelium, and (ii) virus-induced immuno-suppression, which can last for several months after an episode of measles and reduces the child's defenses against a variety of pathogenic bacteria and protozoa. Measles-associated diarrhoea is frequently bloody, suggesting that Shigella is an important causative agent.

    The evaluation of children with diarrhoea should include an enquiry about recent measles. Treatment of measles-associated diarrhoea should include:

    • treatment of dehydration and dysentery, when present;
    • adequate feeding (as described in Treatment Plan A, Figure 4.1);
    • mouth care for patients with stomatitis, so that this does not interfere with eating; and
    • administration of a prophylactic dose of vitamin A (see Unit 7).

    Pneumonia and diarrhoea

    Diarrhoea with severe dehydration causes rapid breathing that may suggest a diagnosis of pneumonia. However, in pneumonia the respiratory rate equals or exceeds 40 per minute (50 per minute for infants aged 2-11 months), the child is coughing, and intercostal retractions may be seen in the lower half of the chest. In children with severe dehydration, the breathing pattern improves rapidly when dehydration is corrected. If pneumonia is confirmed, an appropriate antibiotic should be given.

    Fever and diarrhoea

    Fever is frequent in patients with diarrhoea. It is often present when diarrhoea is caused by rotavirus or an invasive bacterium such as Shigella, C. jejuni or Salmonella. Fever may also accompany dehydration and disappear during rehydration.

    Fever in a patient with diarrhoea may also be a sign of another infection such as pneumonia, otitis media, or malaria. Diarrhoea patients with fever should be examined for other infections and treated appropriately. However, it is not appropriate to give antibiotics to patients with diarrhoea simply because they have fever: a more specific indication is required, such as pneumonia or bloody stools. If one is not found, the patient should be observed, and the search for the cause of the fever continued, if it persists. Children with fever (38 C or above) or a history of fever during the past five days and who live in an area where there is falciparum malaria should be given an antimalarial or managed according to the recommendations of the national malaria control programme (see Figure 6.1).

    A child with a temperature of 39 C or greater should be treated to reduce the temperature. This may be done by giving paracetamol or, when fever is very high, by sponging the head and abdomen with tepid water and fanning.


    1. Ayaz, who is 2 years old, is brought to the health centre because he has had bloody diarrhoea for three days. The health worker assesses Ayaz and finds that he has no signs of dehydration and is neither febrile nor malnourished. What should the health worker do for Ayaz? (There may be more than one correct answer.)

    1. Treat Ayaz with metronidazole for possible amoebiasis, since he has no fever.
    2. Refer Ayaz to the nearest hospital for a stool examination and culture.
    3. Teach the mother to continue feeding Ayaz an energy-rich diet.
    4. Treat Ayaz for five days with an antibiotic effective for Shigella in the area.
    5. Advise the mother to bring Ayaz back if blood has not disappeared from the stool after two days of treatment.
    2. Pedro is 9 months old. He was well until three months ago when his mother stopped breast-feeding and began giving him cow's milk with other food. Since then Pedro has had three episodes of diarrhoea, the current one having begun 18 days ago. Pedro still takes cow's milk but his mother has reduced his intake of solid food since the diarrhoea began. There has been no blood in the stool. Pedro weighs 6 kg. What should the health worker do?
    1. Prescribe a special lactose-free formula and have the mother give this in place of the cow's milk.
    2. Give Pedro metronidazole for possible giardiasis.
    3. Advise the mother to dilute Pedro's milk with an equal amount of water and to increase other energy-rich foods in his diet, e.g., by adding some vegetable oil to his cooked cereal.
    4. Tell the mother to give Pedro sweetened fruit drinks or soft drinks, which he likes, so that he receives enough fluid.
    5. Tell the mother to take Pedro to a hospital if he is not improving in two days.
    3. Maria, aged 16 months, began having watery diarrhoea. After two days, her mother noted some blood in the stool and brought her to the health centre. The doctor noted that Maria had a fever (39 C) and saw that the stool contained blood. There was no evidence of undernutrition. The doctor gave Maria co-trimoxazole but the mother came back after two days saying Maria had not improved and the stool was still bloody. What should the doctor do next?
    1. Tell the mother to continue giving co-trimoxazole, since it is supposed to be given for five days and she has given it for only two days.
    2. Send Maria to the hospital for a stool culture.
    3. Treat Maria with metronidazole for possible amoebiasis.
    4. Stop the co-trimoxazole and give another antibiotic to which most Shigella in the area are sensitive, e.g. nalidixic acid.
    5. Give Maria erythromycin to treat a possible infection with C. jejuni.
    4. Alam is 6 months old and takes only formula milk. He has had watery diarrhoea for the past 14 days and during the last 2-3 days his mother noted some blood in the stool. During the illness, Alam has continued to take his formula. He has not had a fever. How should Alam be treated? (There may be more than one correct answer.)
    1. Alam should be given an antibiotic effective for Shigella in the area.
    2. Alam's mother should start diluting his milk with an equal volume of water. He should start to take cooked cereal with oil and other soft foods to ensure an adequate intake of nutrients. If his diarrhoea has not stopped in five days, he should be referred to hospital for further evaluation and treatment.
    3. Alam should be referred to hospital for special dietary care. This may require the use of a lactose-free or soy-based formula.
    4. Alam's stool should be cultured and examined for amoeba and giardia.
    5. Alam should receive an antidiarrhoeal drug to help control his diarrhoea.
    5. Chinta is 14 months old. She has had a fever and watery diarrhoea for three days. Today some blood was seen in the stool. When seen in the health centre, she is well nourished, drinks ORS eagerly, and has reduced skin turgor. Chinta lives in an area where falciparum malaria occurs. Which of the following steps are appropriate? (There may be more than one correct answer.)
    1. Chinta should receive an antimalarial effective for falciparum malaria, if that is recommended by the national malaria programme.
    2. Chinta should receive oral rehydration following Plan B for "some dehydration".
    3. Chinta should receive treatment for shigellosis, using an antibiotic to which Shigella in the area are usually sensitive.
    4. Chinta's mother should continue to give her a normal energy-rich diet, feeding her frequent small meals.
    5. Chinta's mother should bring her back after two days of treatment to be certain she is responding adequately.


    1. C, D, E. Absence of fever is not unusual in children with shigellosis or dysentery caused by other bacteria. Even in this situation, amoebiasis is very unusual.

    2. C. The mother should bring Pedro back to the health centre after five days; if his diarrhoea has not stopped, he should then be referred to hospital.

    3. D.

    4. A, B. Answer D would be correct only if reliable laboratory facilities were readily available, which is not usually the case.

    5. A, B, C, D, E. The reason Chinta should return for follow-up is that she had dysentery and was dehydrated when first seen.

    updated: 7 June, 2017