Acute gastroenteritis can be caused by bacteria, viruses, or parasites that infect the gastrointestinal tract. This leads to increased fluid secretion and decreased absorption in the intestines, causing diarrhea, nausea, and vomiting. The diarrhea can be classified as osmotic, inflammatory, secretory, or motile depending on the mechanism. Infectious agents such as Shigella, Salmonella, E. coli, and Giardia can invade intestinal cells and cause destruction leading to inflammatory diarrhea. Diagnosis involves assessing the patient's history of symptoms and signs of dehydration through physical examination. Treatment focuses on oral rehydration and hospitalization may be required for severe cases or those with risk factors.

1. Acute Gastroenteritis Diarrhea associated with nausea and vomiting is referred to as gastroenteritis

2. Pathophysiology cause diarrhea by adherence, mucosal invasion, enterotoxin production, and/or cytotoxin production result in increased fluid secretion and/or decreased absorption produces an increased luminal fluid content that cannot be adequately reabsorbed leading to dehydration and the loss of electrolytes and nutrients

3. Diarrheal may be classified: Osmotic - increase in the osmotic load in the intestinal lumen, excessive intake/diminished absorption Inflammatory/mucosal - the mucosal lining of the intestine is inflamed Secretory - increased secretory activity occurs Motile, caused by intestinal motility disorders

4. small intestine is the prime absorptive surface Colon: absorbs additional fluid, transforming a liquid fecal stream in the cecum to well-formed solid stool in the rectosigmoid Enterocyte invasion is the preferred method by which microbes such as Shigella and Campylobacter organisms and enteroinvasive E coli cause destruction and inflammatory diarrhea

5. Salmonella & Yersinia species invade cells but do not cause cell death. invade the bloodstream across the lamina propria and cause enteric fever such as typhoid Normally, more than 100,000 E coli are required to cause disease Only 10 Entamoeba or Giardia cysts may suffice to do the same. Some organisms (eg, V cholera, enterotoxigenic E coli ) produce proteins that aid their adherence to the intestinal wall, thereby displacing the normal flora and colonizing the intestinal lumen

6. nausea, a sudden onset of vomiting, moderate diarrhea, headache, fever (~50%), chills, and myalgia and will last 12-60 hours colonic involvement is usually associated with tenesmus and pain in either of the lower quadrants or the lower back, whereas jejunoileal infection may result in periumbilical pain

7. History: should assess the onset, frequency, quantity, and character of vomiting and diarrhea Recent oral intake, including breast milk and other fluids and food; urine output; wt before illness; and associated symptoms, including fever or changes in mental status should be noted

8. physical examination degree of hydration/percentage deficit: <3%, none; 3-6%, mild; 6-9%,moderate; >10%, severe accurate body wt must be obtained, with temperature, heart rate, respiratory rate, and blood pressure

9. Rectal examination may reveal abscesses, fistulae, and fissures, which may indicate inflammatory bowel disease Hydration and nutritional status Diminished skin turgor, weight loss, resting hypotension and tachycardia, dry mucus membranes, decreased frequency of urination, changes in mental status, and orthostasis can be used to gauge dehydration

10. general condition of the patient should be assessed The appearance of the eyes should be noted, the degree to which they are sunken and presence or absence of tears The condition of the lips, mouth, and tongue will yield clues regarding the degree of dehydration Deep respirations can be indicative of metabolic acidosis Faint/absent bowel sounds can indicate hypokalemia

11. Clinical Management in the Hospital : Indicated for children if : caregivers cannot provide adequate care at home; difficulties in administrating ORT: intractable vomiting, ORS refusal, or inadequate ORS intake; worsening diarrhea or dehydration despite adequate volumes; severe dehydration (>9% of body weight) exists; social or logistical concerns young age, unusual irritability or drowsiness, progressive course of symptoms, or uncertainty of diagnosis exist that might indicate a need for close observation.

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