Diarrhea is a condition where the patient has frequent watery bowel movement. To illustrate, a diarrheal condition results from an abnormal functioning of metabolic processes in the small and large intestine. In fact, these processes are responsible for the absorption of different ions, other substances, and therefore water in the stools. Diarrhea can be acute featuring minimum three rounds per day for a maximum of 14 days, and originates from an infection. On the other hand, diarrhea that lasts longer than 14 days is referred as chronic or persistent diarrhea, and noninfectious causes are behind it.

Causes of diarrhea:

It's important to diagnose and manage diarrhea by determining the underlying cause. In general, several causes such as inflammatory bowel disease (IBD), malabsorption, or drug side effects are prevalent. Notably, consistency, color, frequency, and volume of stools, as well as the presence or absence of intestinal symptoms such as nausea or vomiting, abdominal pain, and fever vary among different causes.

Etiologies are:

• Rotavirus, calcivirus, astrovirus, shigella, giardia, campylobacter and cryptosporidium species are commonly found in children's daycares.
• Consumption of food containing bacteria; for example, raw or contaminated food.
• Travel history to regions having specific pathogens such as enterotoxigenic Escherichia coli.
• Swimming in pools, camping, or sea exposure.
• Use of antibiotics or immunosuppressants.
• Hospitalization.
• Contact with young dogs/cats or turtles causing campylobacter and salmonella respectively 

Symptoms of diarrhea:

Symptoms based on osmotic or secretory diarrhea forms:

• Secretory: where bacterial or viral infection causes watery or loose stool, fever, nausea or vomiting. 
• Osmotic: First, fatty diarrhea (malabsorption) such as in celiac disease and chronic pancreatitis leading to upper abdominal pain, bloating, bulky and foul-smelling stool. Second, watery diarrhea such as lactose intolerance causing bloating or flatulence.

Are acute diarrhea and acute gastroenteritis the same?

It is wrong to consider these two as synonyms. Indeed, gastric and small intestinal involvement are both included under the term gastroenteritis. However, gastric involvement in acute diarrhea is rarely seen even if it's caused by infection. Add to that, the presence of enteritis is also not always evident during acute diarrhea such as the case of shigellosis and cholera.

Diagnosis:

For acute diarrhea:

• Stool culture in case of illness or blood containing stool.
• Lactoferrin or Shiga toxin test in case of bloody stool.
• Clostridium difficile test in case the patient was lately hospitalized or used antibiotics.
• CT scan if peritoneal symptoms are present.

For chronic diarrhea:

• Blood count
• Stool analysis
• Erythrocyte sedimentation rate (ESR)
• Basic metabolic panel
• Liver panel
• Stimulating thyroid hormone
• Colonoscopy or endoscopy

In case of rotavirus:

•  Rotavirus antigen test using enzyme immunoassays and latex agglutination tests

Adenovirus:

• Enzyme immunoassay

Parasites:

• Stool examination every 3 days

In case or colitis or inflammation:

• Culture for Salmonella, Shigella, Campylobacter, Clostridium Difficile, and Yersinia enterocolitica

Treatment:

Medication becomes the only hope if diarrhea persists for long even after you trying to fix it at home.

1. Rehydration: Fluid and electrolyte replenishment is a key component of diarrhea management. Therefore, patients must drink diluted fruit juice, Pedialyte, or Gatorade. Intravenous fluids may be required for severe diarrhea.
2. Foods: In addition to foods low in fiber, eating bland 'BRAT' foods such as toast, oatmeal, bananas, soup, white rice, and applesauce can assist with improving symptoms.
3. Anti-diarrheal treatment: anti-motility and anti-secretory agents lowers diarrhea frequency, but they are not advised for bloody feces or fever cases.
4. Antibiotics: to treat bacterial etiologies. Patients with severe symptoms may benefit from empiric antibiotic therapy with an oral fluoroquinolone.
5. Probiotic supplementations: In patients with acute diarrhea, this is a mean to lessen the symptoms severity and duration.

Ways to prevent diarrhea:

• Wash hands before and after handling food especially meat, and do not cut vegetables with the same knife you used to cut meat.
• Use sanitizers such as alcohol sanitizers if you don’t have access to water at the moment. Also, make sure you sanitize things you used as well while being exposed to germs.
• Rubbing hands with soap lather shouldn’t go less than 20 seconds while washing.

Ways to prevent traveler’s diarrhea:

Living in a developed country means sanitization and fresh food is prevalent. You should keep in mind that this isn’t the case in the less developed countries, and your body won’t handle the changes well. Thus, you should:

• Never drink tap water! Drink water or other drinks from sealed water bottles, never drink tap water
• Brush your teeth using bottled water
• Avoid water entering your system while you shower
• Never eat raw meat!
• Wash fruits and vegetable well before you eat them
• Keep antibiotics in your bag if you experience a lot of illness due to immune conditions
• Check the traveler’s health website made by The Centers for Disease Control and Prevention

Vaccination prevents rotavirus:

Rotavirus is the most common cause of diarrhea disease in children and infants worldwide. However, there's two approved vaccines against rotavirus than can protect your child against this unpleasant viral infection. Actually, parents are to check with the pediatric to monitor and vaccinate the baby.

Dehydration as a complication:

Obviously, diarrhea causes dehydration since water is continuously leaving the body. Unfortunately, ignoring or leaving diarrhea without treatment is life threatening. As a matter of fact, signs of dehydration are dry mucous membranes, dry mouth, low urine output, dark yellow urine, thirst, fatigue, dizziness, decreased tear film, and sunken eyes.

References:

Nemeth V, Pfleghaar N. Diarrhea. [Updated 2021 Nov 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK448082/