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Gastroenteritis
Gastroenteritis
Acute gastroenteritis is defined as diarrheal disease of rapid onset, often with nausea, vomiting, fever, or abdominal pain. It occurs an average of 1.3-2.3 times per year between the ages of 0 and 5 years. Rates among children in child care centers are three times higher. Most episodes of acute gastroenteritis will resolve within 3 to 7 days.


Pathophysiology
Gastroenteritis in children is caused by viral, bacterial, and parasitic organisms, although the vast majority of cases are viral or bacterial in origin. Twenty five percent of cases may be reported as having "no pathogen," depending on the quality of the laboratory techniques used.
Oral ingestion is the primary route of infection, although rotavirus is transmitted by respiratory or mucous membrane contact as well.


Viral Gastroenteritis

All of the viruses produce watery diarrhea often accompanied by vomiting and fever, usually not associated with blood or leukocytes in the stool or with prominent cramping.


Rotavirus is the predominant viral cause of dehydrating diarrhea. Rotaviral infections tend to produce severe diarrhea, causing up to 70% of episodes in children under 2 years of age who require hospitalization. Rotavirus infection tends to occur in the fall in the southwest of the US, then sweeping progressively eastward, reaching the northeast by late winter and spring.
Norwalk viruses are the major cause of large epidemics of acute nonbacterial gastroenteritis. In schools, camps, nursing homes, cruise ships, and restaurants.
Enteric adenovirus is the third most common organism isolated in infantile diarrhea.
Bacterial Gastroenteritis
The bacterial diarrheas work through the elaboration of toxin (enterotoxigenic pathogens) or through invasion and inflammation of the mucosa (invasive pathogens).
Secretory diarrheas are modulated through an enterotoxin, and the patient does not have systemic symptoms (fever, myalgias) or signs of local irritation of the bowel (tenesmus), or evidence of gut inflammation in the stool (white or red blood cells). The diarrhea is watery, often is large in volume, and often associated with nausea and vomiting.
Invasive diarrhea is caused by bacterial enteropathogens, and is accompanied by systemic signs, such as fever, myalgias, arthralgias, irritability, and loss of appetite. Cramps and abdominal pain are prominent. The diarrhea consists of the frequent passing of small amounts of "mucousy" stool. Stool examination reveals leukocytes, red blood cells, and often gross blood.
The same organisms that typically cause an invasive or inflammatory pattern of illness also may cause a secretory or viral pattern.
Acute Diarrhea Patterns and Associated Pathogens
Secretory/enterotoxigenic
Inflammatory
Characterized by watery diarrhea and absence of fecal leukocytes
Characterized by dysentery (ie, symptoms and bloody stools), fecal leukocytes, and erythrocytes
Food poisoning (toxigenic)
Staphylococcus aureus
Bacillus cereus
Clostridium perfringens
Shigella
Invasive E coli
Salmonella
Campylobacter
Enterotoxigenic
Escherichia coli
Vibrio cholera
Giardia lamblia
Cryptosporidium
Rotavirus
Norwalk-like virus
C difficile
Entameba histolytica


General Approach to the Patient with Gastroenteritis
Rapidly determining and managing the fluid losses, dehydration and electrolyte abnormalities is significantly more important than ascertaining the specific microbiologic cause.
History should include questions regarding recent antibiotic use, underlying diseases, other illnesses in the family, travel, untreated water, raw shellfish, attendance at a child care center, and foods eaten recently.


Clinical Evaluation and Treatment of Acute Diarrhea


Step One--Assess child for degree of dehydration
No dehydration
Continue oral hydration and feeding
Some/severe dehydration--------->
Initiate rehydration by oral route (intravenous for severely dehydrated patients)
Step Two--Assess Clinical History for Etiologic Clues
Etiologic Clue
Etiology Suggested
Fever, crampy abdominal pain, tenesmus
Inflammatory colitis or ileitis
History of bloody stool
Shigella, enteroinvasive EC, amebiasis, other bacterial causes
Fever and abdominal pain and like appendicitis
Yersinia enterocolitis
Current or previous antibiotic use
Antibiotic-associated enteritis or pseudomembranous colitis
Multiple cases and common food source
Incubation <6 hours: Staphylococcus aureus, Bacillus cereus
Incubation >6 hours: Clostridium perfringens
Ingestion of inadequately cooked seafood
Vibrio sp
Recent measles, severe malnutrition, AIDS, other causes of immunosuppression
Bacterial (Salmonella), viral (rotavirus), or parasitic (isosporiasis, Cryptosporidium)
Step Three--Examine Stool:
Indicated for:
Finding:
Etiology Suggested:
Visual examination of specimen
All patients
Gross blood
Dysentery, colitis, invasive organism
Microscopic
examination for
white/red blood cells
Patients who have had diarrhea >3 days, fever, blood in stool, weight loss beyond fluid deficit
Red cells and leukocytes
Red cells without leukocytes
Shigella, enterohemorrhagic EC, enteroinvasive EC, Campylobacter, Clostridium, E histolytica
Parasitic examination (wet mount, acid-fast staining, or concentration)
Diarrhea >10 days
Positive
Giardia, Amoeba, Cryptosporidium, Isospora, Strongyloides
Clostridium difficile toxin
Especially patients taking antibiotics
Positive
C difficile colitis

Assessment of Diarrheal Dehydration
Clinical Finding
Mild
(10-40 mL/ kg)
Moderate
(50-90 mL/kg)
Severe
(100-130 mL/ kg)
Affect/sensorium
Normal
Irritability
Lethargy
Stupor
Eyes
Normal
Sunken
Deeply sunken
Mucous membrane
Normal
Dry
Very dry
Tears when crying
Yes
No
No
Thirst
Normal
50
0
+++
++++ or unresponsive
Skin turgor (capillary refill)
Normal
Reduced (<1 sec)
Very reduced (2-3 sec)
Fontanelle
Normal
Depressed
Severely depressed
Pulse
Full
Full
Weak
Feeble or absent
Pulse rate
Normal
Elevated
Very rapid
Blood pressure
Normal
Normal
Low or absent
Fluid Therapy
Mild-to-moderate dehydration
Oral rehydration therapy (ORT) is the preferred method. ORT is a glucose-electrolyte solution.
Mildly or moderately dehydrated children should receive ORT at 50 mL/kg (mild dehydration) or 100 mL/kg (moderate dehydration) over a 4-hour period. Replacement of stool losses (at 10 mL/kg for each stool) and of emesis (estimated volume) will require adding appropriate amounts of solution to the total.
If all but sips of fluid are vomited, oral hydration can be achieved by administering a teaspoonful of solution every 2 to 5 minutes.
Use of cola, fruit juice and sports beverages are not recommended; their electrolyte content is inappropriate, and they contain too much carbohydrate.
Prevention of Dehydration. Children who have diarrhea, but not dehydrated, may be given glucose-electrolyte solution in addition to their regular diets to replace stool losses; however, special solutions are not necessary as long as the well-hydrated child can consume an age-appropriate diet and is encouraged to drink more than the usual amounts of the normal fluids in his diet.
Severely dehydrated children who are in a state of shock must receive immediate and aggressive intravenous (IV) therapy. When the patient is stable, hydration may be continued orally.
Intravenous Rehydration
When intravenous rehydration is required, it should begin with an isotonic solution (normal saline, lactated Ringer). Severe dehydration clinically is associated with a loss of 10-12% of body weight in fluids and electrolytes (100 to 120 mL/kg); therefore, this amount plus whatever additional losses occur should be infused in no more than 6 hours in infants, and even more rapidly in children older than 1 year.
Infusion rates of up to 100 mL/min are appropriate in older children. Infusion rates of 40 mL/kg are given over the first 30 minutes, with the remainder of the deficit (70 mL/kg) over the next 2.5 hours, accompanied by clinical observation until a strong radial pulse is restored and the calculated fluid loss replenished.
For infants, correction should be slower, with infusion rates no more than 30 mL/kg over the first hour and the remaining 70 mL/kg over 5 hours to avoid rapid extracellular to intracellular shifts of fluid and electrolytes and subsequent convulsions.
Subsequent maintenance fluids should be given orally. Oral fluids should be initiated as soon as the patient can drink. They should be given simultaneously with intravenous fluids until the total fluids administered have replenished the calculated deficit, after which the intravenous line can be discontinued.
Antibiotic Therapy
The effectiveness of antimicrobial therapy is well established in shigellosis. Shigella is the classic cause of bacterial dysentery and is the second most commonly identified bacterial pathogen in diarrhea between the ages of 6 months and 10 years in the US.
It causes an initial brief period (1 to 2 days) of watery diarrhea and then it invades the colonic epithelium, causing frequent bowel movements with mucus and gross blood. Treatment usually consists of ceftriaxone or cefixime.
Refeeding
Children who have diarrhea and are not dehydrated should continue to be fed age-appropriate diets. Children who require rehydration should be fed age-appropriate diets as soon as they have been rehydrated. Early feeding of a regular diet reduces the duration of diarrhea.
Fatty foods and foods high in simple sugars, such as sweetened tea, juices, and soft drinks should be avoided. Well-tolerated foods include complex carbohydrates (rice, wheat, potatoes, bread, and cereals), lean meats, yogurt, fruits, and vegetables. The BRAT diet (bananas, rice, applesauce, toast) does not supply optimal nutrition.
Introducing the child's regular form of milk early in the course of therapy is recommended. Although diarrhea often is associated with a reduction in intestinal lactase, this change is not significant in 80% of pediatric patients. If lactose intolerance becomes apparent, a lactose-free preparation may be substituted.

Antidiarrheal Compounds (eg, loperamide, diphenoxylate, bismuth compounds, Kaopectate) should not be used to treat acute diarrhea.
Laboratory Examinations
Most noninflammatory diarrheal illnesses respond in 3 to 5 days to simple rehydration therapy and dietary management alone, obviating the need for initial laboratory evaluations. The presence of blood in the stool, fever, or persistence of the diarrhea for more than 3 days may trigger a laboratory pursuit of an etiologic agent.
Microscopic Stool Examination. If erythrocytes and white blood cells are present, particularly in the setting of fever, a bacterial pathogen (Campylobacter, Yersinia, Salmonella, Shigella) should be suspected. Many red blood cells in the absence of white blood cells suggests the presence of Entamoeba.
Stool culture should be reserved for individuals whose diarrhea has not responded to fluid and feeding and for those who have signs of inflammatory disease (fever, myalgias) and the presence of leukocytes or red blood cells in the stool.
Clinical Evaluation and Treatment of Persistent Diarrhea-lasting longer than 14 Days
Step--One
Assess child for degree of dehydration ------------> Appropriate rehydration
Step–Two. Assess Etiologic Clues
Etiologic Clue
Etiology Suggested
Bloody stool
Invasive organism, particularly Shigella and Entameba histolytica
Malnutrition (inadequate weight for age)
Inadequate diet, decreased resistance
Dietary changes, especially addition of milk or formula
Possible milk or protein hypersensitivity
Problems following milk ingestion
Lactose malabsorption
Antibiotic treatment
Antibiotic-associated enterocolitis or resistant organism
Step–Three. Stool Examination
Test
Finding
Etiology Suggested
Visual examination
Bloody stool
Invasive organism
Microscopic stool exam, including search for ova, parasites, and Cryptosporidium
Red and white blood cells
E histolytica cysts
Giardia, E histolytica trophozoites
Shigella, other invasive organism
Etiologic role unclear
Etiologic role more likely; specific treatment indicated
Stool pH, reducing substances
pH <5.5 and ++ reducing substances
Lactose or other carbohydrate malabsorption.
Stool culture and sensitivity
Pathogens present
Etiology and antibiotic treatment
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