Infectious gastroenteritis (acute) (pediatrics): Clinical sciences

Acute infectious gastroenteritis refers to an infection of the stomach and intestines that has a rapid onset and lasts 2 weeks or less. Gastrointestinal infections typically present with vomiting and diarrhea after fecal-oral contact or ingestion of contaminated food or water. Most cases of acute infectious gastroenteritis are caused by either viral or bacterial pathogens.

Now, if a pediatric patient presents with a chief concern suggesting acute infectious gastroenteritis, first perform an ABCDE assessment to determine if they are unstable or stable.

If unstable, stabilize their airway, breathing, and circulation. Obtain IV access, start IV fluids, and consider administering a fluid bolus. Next, begin continuous vital sign monitoring, including heart rate, respiratory rate, blood pressure, and pulse oximetry; provide supplemental oxygen if needed; and consider starting antibiotics.

Now that we’ve discussed unstable patients, let’s return to the ABCDE assessment and take a look at stable patients.

Start by obtaining a focused history and physical examination.

History typically includes the acute onset of diarrhea, vomiting, anorexia, and abdominal cramps lasting 2 weeks or less. Some patients also report a fever or a sick contact.

Physical exam may demonstrate abdominal tenderness and hyperactive bowel sounds, but in more severe cases, you might see signs of dehydration, like decreased skin turgor, sunken eyes, and dry mucous membranes.

These findings are highly suggestive of acute infectious gastroenteritis.

Next, assess whether there are indications for obtaining a stool culture. These include outbreaks in a childcare setting or school; exposure to animals or contaminated food; blood or mucus in the stool; or recent foreign travel. Additionally, any young or immunocompromised patient with a high fever should have stool sent for culture.

Now, if there’s no indication for a stool culture, you should suspect viral gastroenteritis, which is commonly caused by rotavirus, norovirus, or adenovirus.

Let’s start with rotavirus infection. Affected patients are typically under 18 months of age and unvaccinated, with most infections occurring in the winter months. Caregivers typically report a sudden onset of fever and vomiting, followed by watery diarrhea one or two days later. With these findings, suspect rotavirus infection.

This is usually a clinical diagnosis, but if needed, you can obtain a stool rotavirus antigen test. A positive test confirms a diagnosis of rotavirus infection.

Now let’s take a look at norovirus infection. History usually reveals a sudden onset of vomiting, followed by watery diarrhea and abdominal cramps. Your patient may also report fever, myalgia, fatigue, and headache. At this point, suspect norovirus infection, which is often a clinical diagnosis.

However, norovirus often causes gastroenteritis outbreaks in closed environments, so if your patient attends a school or daycare, consider further testing, like a PCR stool test. A positive PCR confirms a diagnosis of norovirus infection.

Finally, let’s discuss adenovirus infection. History commonly reveals low-grade fever and respiratory symptoms, like congestion, runny nose, sore throat, and cough. Patients often have watery diarrhea lasting 1 or 2 weeks, along with vomiting and abdominal pain.

The exam might reveal conjunctivitis. With these findings, suspect an adenovirus infection, which doesn’t usually require laboratory confirmation, but if the diagnosis is unclear, consider obtaining a PCR stool test. A positive PCR confirms a diagnosis of adenovirus infection.

Viral gastroenteritis is usually self-limited, and management consists of supportive care, including oral rehydration solution, possibly in combination with antiemetics.

Alright, let’s switch gears and take a look at patients with one or more indications for a stool culture, starting with noninflammatory diarrhea.

In this case, suspect bacterial gastroenteritis. To identify the pathogen, obtain a stool culture with a microscopic exam, and assess the stool for fecal leukocytes.

Now, if fecal leukocytes are absent, your patient has noninflammatory diarrhea. In this case, illness is often caused by toxin-producing bacteria such as Bacillus cereus, Staphylococcus aureus, or enterohemorrhagic E. coli.

Let’s start with Bacillus cereus infection. The history typically reveals profuse watery diarrhea with abdominal pain, cramps, and less than 24 hours of nausea and vomiting. Patients might report eating leftover rice that’s been left at room temperature for more than a couple of hours, which is a well-known source of this bacterium. If the stool culture grows Bacillus cereus, you can confirm the diagnosis.

Moving on to Staphylococcus aureus infection. Patients often report a sudden onset of vomiting, abdominal cramps, and diarrhea. Ingestion of mayonnaise-containing food like potato salad is often the source of Staph. aureus infection, especially if it was left in a warm environment, such as an outdoor picnic. A positive stool culture confirms the diagnosis of Staphylococcus aureus infection.

Finally, let’s focus on enterohemorrhagic E. coli, or EHEC for short. The history typically reveals watery diarrhea and abdominal cramps and followed by bloody stools and vomiting. Symptoms may have started after your patient ate an undercooked hamburger. If the stool culture is positive for enterohemorrhagic E. coli, diagnose EHEC infection.

Here’s a clinical pearl! E. coli O157:H7 is a Shiga toxin-producing E. coli, or STEC for short, that’s associated with hemolytic uremic syndrome.

Shiga toxin injures the intestinal epithelium and underlying blood vessels causing inflammation and leading to the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. A standard culture won’t identify this strain, so ask the lab to test for it specifically!

Now, regardless of its cause, noninflammatory diarrhea is usually self-limited and doesn’t require antibiotics, so supportive care is the mainstay of treatment. This includes oral rehydration solution, possibly in combination with antiemetics.

Alright, let’s switch gears and discuss cases in which fecal leukocytes are present, then starting with diarrhea that contains blood or mucus.