What is Gastroenteritis (Diarrhea/Vomiting)?
Gastroenteritis is inflammation of the stomach and intestinal lining, with common symptoms including diarrhea, vomiting, abdominal pain, and fever. The causes are diverse, ranging from viruses, bacteria, parasites, medications, and stress, and it is categorized into “acute” and “chronic” forms.
Most cases are benign and resolve spontaneously within a few days, but dehydration can progress rapidly, posing a risk of severe complications, especially in the elderly, infants, and immunocompromised individuals. Additionally, with food poisoning and infectious enteritis, preventing the spread of infection within the household and workplace is crucial.
Dehydration progresses faster than you might think.
Diarrhea and vomiting can lead to a significant loss of fluids and electrolytes, sometimes causing dehydration to advance within hours. If you cannot drink fluids, feel lethargic, or are not urinating, do not hesitate to seek medical attention promptly.
Main Causes of Gastroenteritis
Viral Gastroenteritis (Most Common)
| Virus | Peak Season | Characteristics |
|---|---|---|
| Norovirus | Winter (Nov–Mar) | Sudden vomiting/diarrhea, mild fever, highly contagious |
| Rotavirus | Winter–Spring (Feb–May) | Common in infants/young children, white stools, vaccine preventable |
| Adenovirus | Year-round | Mainly diarrhea, sometimes accompanied by fever/sore throat |
| Sapovirus | Winter | Similar to norovirus, milder symptoms |
Bacterial Gastroenteritis (Food Poisoning)
| Bacteria | Cause Food | Characteristics |
|---|---|---|
| Salmonella | Chicken eggs, poultry, pets (reptiles) | Fever, abdominal pain, diarrhea, incubation 12–48 hours |
| Campylobacter | Chicken (raw/undercooked) | Bloody stools, abdominal pain, incubation 2–5 days, can lead to Guillain-Barré syndrome |
| Enterohemorrhagic E. coli (O157, etc.) | Beef, raw liver, contaminated vegetables | Bloody stools, risk of Hemolytic Uremic Syndrome (HUS), requires caution |
| Staphylococcus aureus | Rice balls, bento boxes (contamination from hands) | Severe vomiting 1–6 hours after eating |
| Vibrio parahaemolyticus | Sashimi, seafood | Common in summer, severe abdominal pain/diarrhea |
| Clostridium perfringens | Leftover stews, curries | Diarrhea/abdominal pain 6–24 hours after eating |
| Bacillus cereus | Fried rice, yakisoba | Vomiting-type, diarrheal-type |
Other Gastroenteritis
- Parasitic: Anisakiasis (sashimi), Giardia, Entamoeba histolytica
- Drug-induced: Antibiotics, NSAIDs, anticancer drugs
- Antibiotic-associated colitis: Clostridioides difficile (C. diff colitis)
- Chronic gastroenteritis: Inflammatory bowel disease (Ulcerative colitis, Crohn's disease), Irritable bowel syndrome (IBS)
- Ischemic colitis: Sudden severe pain + diarrhea/bloody stools in the elderly
Symptoms and Severity Guidelines
Mild
- Diarrhea several times a day, mild vomiting
- Able to drink fluids
- Overall condition relatively good
- Fever below 38°C
Moderate
- Diarrhea 10+ times a day
- Repeated vomiting
- Difficulty with fluid intake
- Fever 38°C or higher
- Signs of mild dehydration
Severe (Seek immediate medical attention)
- Bloody stools/mucus and bloody stools
- Persistent severe abdominal pain
- Significantly reduced urine output (none for over half a day)
- Drowsiness/severe fatigue
- Decreased skin elasticity/sunken eyes
- Persistent high fever of 39°C or higher
- Uncontrollable vomiting, unable to drink fluids
- Elderly, infants, pregnant women, immunocompromised individuals
- Diarrhea after overseas travel
Signs of Dehydration (Important)
Special attention for children and the elderly
Dehydration can progress rapidly without clear self-awareness. If any of the following signs are present, seek medical attention.
| Dehydration Stage | Signs |
|---|---|
| Mild (3–5%) | Dry mouth, reduced urine output, mild fatigue |
| Moderate (6–9%) | Dry lips/oral cavity, decreased skin elasticity, dizziness upon standing, rapid pulse |
| Severe (10%+) | Altered consciousness, shock, anuria, cold extremities |
Signs of Dehydration in Children
- No tears when crying
- Diaper not wet (for over 6 hours)
- Lethargic and lacking energy
- Sunken fontanelle (infants)
- Dry mouth
Examination and Tests at Our Clinic
Key Points for Medical Interview
- Onset and course of symptoms
- Recent food intake (raw food, leftovers)
- Symptoms in others who ate the same food
- History of overseas travel
- Nature of diarrhea (watery, mucous/bloody, white), frequency
- Content and frequency of vomiting
- Severity of fever/abdominal pain
- Fluid intake/urine output
- Past medical history/medications (antibiotics, NSAIDs, etc.)
Tests
| Test | Purpose |
|---|---|
| Physical examination/Vitals | Assessment of dehydration/general condition |
| Blood test | Inflammation (CRP, WBC), dehydration (BUN, Cr, electrolytes) |
| Urine test | Assessment of dehydration/diabetes |
| Stool test/Culture | Bacterial food poisoning (Salmonella, Campylobacter, etc.) |
| Stool virus antigen test | Norovirus, Rotavirus (if necessary) |
| Abdominal X-ray/Ultrasound | Differentiation of intestinal obstruction, appendicitis, gallstones (if necessary) |
Differentiation from Other Diseases
Many diseases present with diarrhea, vomiting, and abdominal pain. We consider the following in addition to simple gastroenteritis:
- Appendicitis
- Intestinal obstruction (ileus)
- Cholecystitis/Pancreatitis
- Mesenteric ischemia/Ischemic colitis
- Gynecological conditions (ovarian torsion, ectopic pregnancy)
- Urinary tract stones
- Diabetic ketoacidosis
- Myocardial infarction (can present as upper abdominal pain)
- First presentation of inflammatory bowel disease (IBD)
Basic Treatment
Oral Rehydration Therapy (ORT) is the first choice
Utilize Oral Rehydration Solutions like OS-1
For mild to moderate dehydration, oral rehydration solutions (such as OS-1, Aqua Solita) are recommended over sports drinks. This is because their sodium and sugar ratios are medically optimized.
Intravenous (IV) Therapy
- If oral intake is impossible or dehydration is severe
- Saline, Ringer's solution, electrolyte replacement
- Antiemetics and electrolyte correction as needed
- Our clinic offers same-day IV treatment
Medication
| Category | Representative Drugs | Usage Scenario |
|---|---|---|
| Probiotics | Biofermin, Miya BM, Racbic | To regulate intestinal flora |
| Antidiarrheal | Loperamide | Generally not used in bacterial cases as it hinders expulsion of causative bacteria from the body |
| Adsorbents | Tannalbin | For mild diarrhea |
| Antiemetics | Metoclopramide, Prochlorperazine | For severe vomiting |
| Antipyretic analgesics | Acetaminophen | For fever/abdominal pain (NSAIDs are not suitable for gastroenteritis) |
| Antibiotics | Fosfomycin, Fluoroquinolones | Limited use for severe bacterial gastroenteritis |
| Herbal medicine (Kampo) | Goreisan (watery diarrhea), Hangeshashinto (diarrhea/epigastric pain) | Supportive |
Caution with Antidiarrheal Use
Using antidiarrheals (especially loperamide) for diarrhea caused by bacterial infection can trap the causative bacteria and toxins in the body, increasing the risk of worsening symptoms and complications (such as HUS). At our clinic, doctors carefully prescribe these after evaluation.
Home Management and Care
Fluid Intake
- Drink oral rehydration solution in small, frequent amounts (5-10ml/time, every 5 minutes)
- Avoid drinking too quickly, as it can induce vomiting
- Sports drinks should be diluted 2-3 times due to high sugar content
- Plain hot water, barley tea, and clear miso soup are also effective
- Avoid caffeine, alcohol, and dairy products
Diet
- No need to force eating (prioritize fluids)
- If able to eat, choose easily digestible foods like rice porridge, udon, or clear soup
- Avoid fatty, spicy, or high-fiber foods
- Gradually return to a normal diet in stages after symptoms improve
- Limit dairy products, citrus fruits, and carbonated drinks until diarrhea subsides
Rest and Condition Management
- Adequate rest
- Keep the room warm and not too dry
- Record body temperature, number of bowel movements, and urine output
- Re-consult a doctor promptly if symptoms worsen
Infection Prevention and Household Measures
Norovirus Countermeasures
Norovirus is resistant to alcohol disinfection.
Norovirus is difficult to inactivate with ethanol. Sodium hypochlorite (diluted household chlorine bleach) is effective. Special care is required when handling vomit and stool.
Cleaning Vomit/Stool
- Wear disposable gloves and a mask
- Gently wipe with paper towels (do not stir up)
- Disinfect with 0.1% sodium hypochlorite (1,000ppm)
- Wash clothes/towels after disinfecting with sodium hypochlorite
- Wash hands thoroughly after cleaning
- Seal disposed items in double plastic bags
Preventing Household Infection
- Thorough handwashing after toilet use and before meals
- Avoid sharing towels
- Disinfect doorknobs and toilets
- Wash laundry separately and at high temperatures
- Avoid cooking or serving food if experiencing symptoms
Return to School/Work
For norovirus, enterohemorrhagic E. coli, etc., viruses/bacteria can still be shed in feces even after symptoms disappear, so caution is needed regarding the timing of return.
| Disease | Guideline for Absence from Work/School |
|---|---|
| Norovirus | Several days after symptoms resolve (physician's approval for food handlers) |
| Rotavirus | Until vomiting/diarrhea resolve and general condition is good |
| Enterohemorrhagic E. coli (O157, etc.) | After symptom resolution + negative stool culture confirmation |
| Salmonella, Campylobacter | Until symptoms resolve; caution for food service workers |
Key Points to Prevent Food Poisoning
Basic Food Hygiene "3 Principles"
- Do not contaminate: Wash hands, use separate cutting boards/knives, disinfect hands after handling raw meat
- Do not multiply bacteria: Store at low temperatures, consume leftovers quickly
- Kill bacteria: Heat to an internal temperature of 75°C or higher for at least 1 minute
Foods Requiring Special Attention
- Chicken (Campylobacter, Salmonella)
- Raw eggs (Salmonella)
- Rare beef/raw liver (O157)
- Sashimi/Oysters (Norovirus, Anisakiasis, Vibrio parahaemolyticus)
- Leftover curry/stew (Clostridium perfringens)
- Bento boxes/rice balls in summer (Staphylococcus aureus)
- Well water/spring water (E. coli, etc.)
- Raw water, ice, raw vegetables in overseas travel destinations
Frequently Asked Questions
Should I go to the hospital for gastroenteritis?
If symptoms are mild and you can stay hydrated, home care is possible. However, if you cannot drink fluids, have bloody stools, severe abdominal pain, high fever, or signs of dehydration, or if you are an infant, elderly, pregnant, or immunocompromised individual, we recommend seeking medical attention early.
How long does gastroenteritis usually last?
Most viral gastroenteritis cases resolve within 2 to 5 days. Bacterial cases, such as Campylobacter, can last over a week. If symptoms persist, consult a doctor again.
Is there a specific cure for norovirus?
There is no specific cure; symptomatic treatment (hydration, probiotics, antiemetics, IV fluids) is the basic approach. Since it's highly contagious, preventing household infection is crucial.
What precautions should be taken for gastroenteritis in children and the elderly?
Dehydration can progress rapidly, so frequent fluid intake and monitoring urine output and overall energy levels are important. If there's no urine for over half a day, they're lethargic, or their consciousness is altered, seek medical attention immediately.
I suspect food poisoning. What should I do?
Record your symptoms and food intake (for the past 2-3 days) and visit a medical institution. If multiple people who ate the same food develop symptoms, it may be reportable to the public health center.
Can I be seen without an appointment?
Yes, same-day appointments without reservation are possible. However, due to the need for infection control for other patients with vomiting/diarrhea, it would be smoother if you call us before coming.
I ate sashimi and am worried about Anisakis.
Severe upper abdominal pain and vomiting can appear a few hours to several days after eating. If suspected, endoscopic removal may be necessary, and you will be referred to a gastroenterology specialist.
I've had diarrhea since taking antibiotics.
This could be antibiotic-associated diarrhea (C. diff colitis). Mild cases often resolve spontaneously after stopping antibiotics, but severe cases require specific treatment (e.g., oral vancomycin). Please come in for an examination.
Is it okay to use over-the-counter antidiarrheals?
Self-use of antidiarrheals is not recommended for infectious gastroenteritis (bacterial). It can worsen symptoms and increase the risk of complications. Focus on probiotics and receive appropriate prescriptions from a medical institution.
I got diarrhea while traveling abroad.
This is likely "traveler's diarrhea," often caused by E. coli or Campylobacter. Focus on fluid intake, and if accompanied by high fever or bloody stools, seek medical attention. If it persists after returning home, further investigation for parasitic infections (e.g., amoebic dysentery) may be considered.
Features of Our Clinic's Gastroenteritis Treatment
- Same-day blood tests, urine tests, and stool tests for severity and cause assessment
- IV fluid treatment for dehydration
- Prescription of probiotics, antiemetics, and herbal medicine (Goreisan, etc.)
- Appropriate antibiotic selection when bacterial infection is suspected
- Infection prevention guidance (household measures) for Norovirus, Rotavirus, etc.
- Referral to gastroenterology specialists if endoscopic examination is required
- Prompt referral to inpatient medical facilities for urgent cases such as O157 and severe infectious enteritis
- No appointment needed, same-day consultation available / Open 9:00 AM to 9:00 PM daily / 1-minute walk from Jujo Station
"Let's wait and see a little longer" can lead to a dangerous situation.
Even mild gastroenteritis can become severe due to dehydration or complications. If you feel "unable to drink fluids" or "lethargic," please do not hesitate to consult us. Early IV treatment often brings quick relief.
