In order to establish an accurate diagnosis of the respective etiology and potential complications, detailed information must be obtained on the following topics: a comprehensive clinical history extending as far back as the onset of the diarrheal illness; prior dietary history; breastfeeding history; socioeconomic status and living conditions; and prior medical history, including prior infectious diseases and family history. History and physical examination can provide an outline of the profile of a patient’s nutritional status and other consequences of the diarrheal illness. The laboratory investigation should include a stool culture and a search for ova and parasites in fresh stool specimens, a detection of fecal pH and reducing substances search in the stools, a search for leukocytes and occult blood in the stools, and a determination of fecal α1 anti-trypsin and steatocrit.
Considering the high prevalence of carbohydrate intolerance in the diet reported in PD patients as a perpetuating factor of diarrhea, the approach should include overload tests with the various carbohydrates commonly used in the diet, such as lactose, glucose, and fructose. The lactulose load test should also be carried out in order to detect a possible bacterial overgrowth in the small intestine. All these tests should preferably be carried out by the technique of the H2 breath test, because this is a noninvasive method with high sensitivity and specificity .
If possible, the determination of fecal electrolytes should also be done, which will distinguish osmotic from secretory diarrhea . In many cases, a small bowel biopsy should be performed to evaluate the mucosal architecture and the inflammatory infiltrate in the lamina propria, to investigate specific causes, and to demonstrate the extent of intestinal damage . The knowledge of the intensity and extension of morphological damage enables the appropriate dietary management approach. When concurrent rectal bleeding occurs, it may be necessary to perform a rectal biopsy to evaluate the degree and type of inflammation .
The importance of proper rehydration and dietary management during the acute diarrheic episode for preventing the progression to PD is well-known . Antibiotic treatment is recommended only for prolonged infection caused by Salmonella, Giardia, Cyclospora, and EAEC (the latter especially if the infant is less than 3 months old or malnourished, immunodeppressed, or shows signs of systemic disease)  and in the presence of bloody diarrhea when Shigella is isolated in the stools . The decision to prescribe antibiotics is limited to laboratory evidence of the enteropathogen and type of microbial resistance [54, 55].
Although ready-to-use therapeutic food (RUTF) has greatly improved the capacity for rapid catch-up growth in both the hospital and community, it is necessary to focus more on the initial diets of unwell children with nutritional aggravation, due to the persistence of diarrhea and malabsorption of the nutrients. Fasting is clearly deleterious for such children, as the practice of resuscitation on children’s wards with IV fluids, minerals, vitamins, and antibiotics (without milk or equivalent) has shown. Small, frequent feeding is crucial, but volumes may need to be individualized, which makes it very difficult for pediatric wards with a scarcity of nursing resources, especially during evening and night shifts. WHO guidelines recommend the use of F75 formula, following research done >30 years ago . But now there is a clearer concept of the gut in malnutrition due to the persistence of diarrhea, so better diets are available in the market. Osmolality, in particular, may be important. F75 has an osmolality of 333 mOsmol/L, while there are commercial lactose-free formulas with 160 mOsmol/L .
The use of an extensive hydrolyzed protein formula or even a mixture of amino acids based formula is indicated in the following clinical circumstances: (1) acute diarrhea in infants under 6 months or less than 1 year of age with severe malnutrition, associated with dehydration and/or metabolic disorders; (2) PD with aggravation of the nutritional status or frequent recurrence of dehydration and/or metabolic acidosis .
The prescription of zinc and vitamin A seems to have a positive impact over the cellular immune system, helping in the treatment of acute and persistent diarrhea [59–61]. It is necessary to prescribe a daily supplementation of zinc at a dose of 10 mg/day for a period of 2–3 months after the diarrhea episode has ceased.
In conclusion, UNICEF and WHO propose seven strategic measures to be implemented around the world for diarrheal disease control: (1) fluid replacement to prevent dehydration; (2) zinc treatments, which decrease the severity and duration of the attack; (3) immunization against rotavirus and measles; (4) early and exclusive breastfeeding and vitamin A supplementation; (5) hand washing with soap; (6) improved water supply quantity and quality, including safe storage of water in homes; and (7) promoting community-wide sanitation . Other proposals for reducing the incidence of PD include prolonged and exclusive breastfeeding and strategies to ensure a safe food supply for adequate weight and height development, considering that protein-energy malnutrition is a risk factor for this syndrome . Gut infections lead to malnutrition, and malnutrition increases the risk for further intestinal infections. Ending the vicious cycle of diarrhea–malnutrition should be assigned priority as a goal for pediatricians concerned with the safe development of children .
Compliance with Ethics Guidelines
Conflict of Interest Ulysses Fagundes-Neto declares that he has no conflict of interest.
Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by the author.
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