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Gastroenteritis is a general term referring to inflammation or infection of the gastrointestinal tract, primarily the stomach and intestines.[1] It can be caused by infection with bacteria, viruses, or other parasites, or less commonly reactions to new foods or medications. It often involves stomach pain (sometimes to the point of crippling), diarrhea and/or vomiting, with noninflammatory infection of the upper small bowel, or inflammatory infections of the colon.[2][3][4][5]
It usually is of acute onset, normally lasting fewer than 10 days and self-limiting. Sometimes it is referred to simply as 'gastro'. It is often called the stomach flu or gastric flu even though it is not related to influenza.[6]
If inflammation is limited to the stomach, the term gastritis is used, and if the small bowel alone is affected it is enteritis.
Globally, gastroenteritis caused 4.6 million deaths in children in 1980 alone, most of these in the developing world.[3] Harrison's Principles of Internal Medicine estimates the current total figure to be 2.4 to 2.9 million per year.[4] This number has now come down significantly to approximately 1.5 million deaths annually, largely due to global introduction of proper oral rehydration therapy.[7]
The incidence in the developed countries is as high as 1-2.5 cases per child per year and a major cause of hospitalisation in this age group.
Age, living conditions, hygiene and cultural habits are important factors. Another factor is the location. Aetiological agents vary depending on the climate. Furthermore, most cases of gastroenteritis are seen during the winter in temperate climates and during summer in the tropics.[3]
The main contributing factors include poor feeding in infants. Diarrhea is common, and may be (but not always) followed by vomiting. Viral diarrhea usually causes frequent watery stools, whereas blood stained diarrhea may be indicative of bacterial colitis. In some cases, even when the stomach is empty, bile can be vomited up.
A child with gastroenteritis may be lethargic, suffer lack of sleep, or run a low fever and have signs of dehydration, which include dry mucous membranes, tachycardia, reduced skin turgor, skin color discoloration, sunken fontanelles and sunken eyeballs and darkened eye circles, poor perfusion and ultimately shock.
It is important to consider infectious gastroenteritis as a diagnosis per exclusionem. A few loose stools and vomiting may be the result of systemic infection such as pneumonia, septicaemia, urinary tract infection and even meningitis. Surgical conditions like appendicitis, intussusception and, rarely, even Hirschsprung's disease may mislead the clinician.
Non-infectious causes to consider are poisoning with heavy metals (i.e. arsenic, cadmium), seafood (i.e. ciguatera, scombroid, toxic encephalopathic shellfish poisoning) or mushrooms (i.e. Amanita phalloides). Secretory tumours (i.e. carcinoid, medullary tumour of the thyroid, vasoactive intestinal peptide-secreting adenomas) and endocrine disorders (i.e. thyrotoxicosis and Addison's disease) are disorders that can cause diarrhea. Also, pancreatic insufficiency, short-gut syndrome, Whipple's disease, coeliac disease, and laxative abuse should be excluded as possibilities.[5]
The principal treatment of diarrheal illness in both children and adults is rehydration, i.e. replenishment of water lost in the stools. Depending on the degree of dehydration, this can be done orally with oral rehydration solutions (ORS), commercial (See Ceralyte[8] [9]) or home-made rehydration fluids, or through intravenous delivery. Symptoms may exhibit themselves for up to 6 days. Bowel movements will return to normal within a week after that.
Because of the stomach's fragility due to the illness, rehydration through the drinking of fluids must be slow and spaced out as to not overwhelm the stomach and cause further nausea and vomiting. Doctors recommend that one take slow sips every few minutes, and if vomiting still occurs, it is best to refrain from any drinking or eating for the next half hour.
When the symptoms are severe one usually starts empirical antimicrobial therapy, i.e. fluoroquinolone.[2] Pseudomembranous colitis is treated by discontinuing the causative agent and starting with metronidazole.[2][3][4][5]
Loperamide is an opioid analogue commonly used for symptomatic treatment of diarrhea. It slows down gut motility, but does not cross the mature blood-brain barrier[2] to cause the central nervous effect of other opioids. In too high doses, loperamide may cause constipation and significant slowing down of passage of feces, but an appropriate single dose will not slow down the duration of the disease.[10] Although antimotility agents have the risk of exacerbating the condition, this fear is not supported by clinical experience according to Sleisenger & Fordtran's Gastrointestinal and Liver Disease and the Oxford Textbook of Medicine.[2][5] Nevertheless, Harrison's Principles of Internal Medicine discourages the use of antiperistaltic agents and opiates in febrile dysentery, since they may mask, or exacerbate the symptoms.[4] All these textbooks agree that in severe colitis antimotility drugs should not be used.
Loperamide prevents the body from flushing toxins from the gut, and should not be used when an active fever is present or there is a suspicion that the diarrhea is associated with organisms that can penetrate the intestinal walls, such as E. coli O157:H7 or salmonella.
Loperamide is also not recommended in children, especially in children younger than 2 years of age, as it may cause systemic toxicity due to an immature blood brain barrier, and oral rehydration therapy remains the main stay treatment for children.
Bismuth subsalicylate (BSS), an insoluble complex of trivalent bismuth and salicylate, is another drug that can be used in mild-moderate cases.[2][5]
Combining an antimicrobial drug and an antimotility drug, seems to be effective more rapidly.[2][5]
Dehydration is the most serious complication of the diarrhea caused by gastroenteritis and needs prompt rectification by a clinician if severe.
Febrile convulsions are not uncommon in children, especially with rotavirus infections.
Sugar malabsorption is the most common complication, especially in infants. This may result in the reappearance of diarrhea after milk, and hence the sugar lactose, is reintroduced into the diet.