Infectious gastroenteritis: Clinical sciences

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Introduction0:00–0:28

Gastroenteritis refers to inflammation of the gastrointestinal tract, typically caused by infectious pathogens. These pathogens injure the intestinal lining, leading to fluid shifts and water loss through diarrhea and vomit.
The diagnosis of what’s causing gastroenteritis is made by first evaluating whether the patient’s diarrhea is watery or bloody, as well as identifying common pathogens such as bacteria, viruses, or parasites.
Now, if you suspect gastroenteritis, you should perform an ABCDE assessment to determine if your patient is unstable or stable.

Unstable patient0:28–0:59

If the patient is unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access, start IV fluids, and begin continuous vital sign monitoring including blood pressure, heart rate, and oxygen saturation.
Provide supplemental oxygen if needed, and start broad spectrum antibiotics. Okay, let’s go back to the ABCDE assessment and take a look at stable patients.

Stable patient0:59–2:03

First, start by taking a focused history and physical exam. Your patient may report diarrhea, nausea, vomiting, and abdominal pain.
Other common symptoms include flatulence, fecal urgency, and possibly fever. On the other hand, physical exam findings will reveal abdominal tenderness, and may show signs of dehydration, such as dry skin and mucous membranes, decreased skin turgor, and decreased capillary refill time.
At this point, you should suspect gastroenteritis. Here’s a clinical pearl!
Be sure to always clarify stool frequency and consistency whenever taking a history. Diarrhea is defined as passing of three or more unformed stools in 24 hours.
If your patient is passing formed stools, or has not had multiple episodes per day, they do not have diarrhea. Once you suspect gastroenteritis, determine if the diarrhea is watery or bloody.

Watery diarrhea2:03–6:50

Let’s first talk about watery diarrhea. If your patient has watery diarrhea, first assess the patient’s level of dehydration.
Signs of mild dehydration include mild tachycardia, dry skin and mucous membranes, decreased skin turgor, and slightly delayed capillary refill time.
If your patient has mild dehydration, provide supportive care, which includes oral rehydration therapy, or ORT for short.
Then, assess your patient’s response to treatment in 24 to 48 hours. If the response is adequate, and your patient is able to maintain hydration with ORT, then you can diagnose acute gastroenteritis.
In this case, continue current management until diarrhea resolves. If the response is inadequate, and your patient cannot maintain hydration with ORT, proceed with management for moderate to severe dehydration.
So, let’s go back to the assessment of dehydration. Individuals with moderate to severe dehydration typically present with signs of hypovolemia, such as tachycardia and tachypnea, very dry skin and mucous membranes, decreased skin turgor, and delayed capillary refill time.
Additionally, your patient may present with sunken eyes, decreased urine output, fatigue, weakness, and even altered mental status.
Here’s a clinical pearl! Although lab tests aren’t required for most patients with acute diarrhea, some labs can help assess the level of dehydration, such as ordering a BMP to look for hypokalemia or acute kidney injury.
If your patient presents with moderate to severe dehydration, be sure to start IV fluids for rehydration. Additionally, consider starting empiric antibiotics, and giving bismuth subsalicylate and an antimotility agent like loperamide.
Next, assess travel history. If the patient has recently traveled, you can diagnose traveler’s diarrhea, which is typically caused by Enterotoxigenic Escherichia coli or ETEC for short.
In this case, you should continue the current management with bismuth subsalicylate and an antimotility agent until diarrhea resolves, while antibiotic therapy is reserved for patients with severe diarrhea.
On the other hand, if your patient does not have a history of recent travel, order an enteric pathogen panel and assess the results.
If no pathogen is identified, continue the current management plan and assess the patient’s response to treatment. If the response is inadequate, you should consider an alternative diagnosis.
If the response is adequate, however, you can confirm the diagnosis of acute gastroenteritis and again, continue current management until diarrhea resolves.
Now, let’s go back to the enteric pathogen panel. If a bacterial pathogen is identified, you can diagnose bacterial gastroenteritis.
Common bacterial pathogens that cause watery diarrhea include Staphylococcus aureus, Bacillus cereus, and enteropathogenic E.
Coli or EPEC, as well as Salmonella enterica, which sometimes can also cause bloody diarrhea. Lastly, tailor the antibiotic therapy based on the results of the panel.
Keep in mind that bacterial gastroenteritis is usually self-limiting, so antibiotics are often not necessary unless the patient is severely ill or immunocompromised.
Here’s a high yield fact! Clostridioides difficile infection, or C.
diff for short, often presents with diffuse, foul smelling, watery diarrhea, but keep in mind that it may also present with bloody diarrhea.
Additionally, your patient may have a history of recent antibiotic use, which can alter gastrointestinal microflora and increase the susceptibility to C.
diff infection, so be sure to carefully review the patient's medication list. Now, if the enteric pathogen panel identifies a virus, you can make the diagnosis of viral gastroenteritis.
Common viral pathogens leading to watery diarrhea include norovirus, adenovirus, and enterovirus. If you initially treated your patient with empiric antibiotics, be sure to stop them, since they are not going to shorten the duration of viral gastroenteritis.
Finally, continue supportive care for your patient.And lastly, let’s return to the enteric pathogen panel. If a parasite is identified, you can diagnose parasitic gastroenteritis.
Common parasites causing watery diarrhea include Cryptosporidium and Giardia, so tailor antibiotics based on the results.

Bloody diarrhea6:50–9:14

Okay, now that we’ve reviewed watery diarrhea, let’s switch our focus to patients with bloody diarrhea. You will want to start by administering IV fluids and considering empiric antibiotics.
In patients with bloody diarrhea, we usually avoid giving antimotility agents, since they can prolong or even worsen the infection.
Now, after treatment, you should obtain an enteric pathogen panel. Then assess the results, If no pathogen is identified, continue current management and assess response to treatment.
If the response to treatment is inadequate, you should consider an alternative diagnosis; while if the response is adequate, you can confirm acute gastroenteritis so continue current management until diarrhea resolves.On the other hand, if you identify bacteria on the enteric pathogen panel, you can confirm the diagnosis of bacterial gastroenteritis.
Common bacterial pathogens that can present with bloody diarrhea include Campylobacter Jejuni, Clostridioides difficile, Shigella dysenteriae, Salmonella enterica, Yersinia enterocolitica, as well as enteroinvasive and enterohemorrhagic Escherichia coli, or EIEC and EHEC for short.
Lastly, tailor the antibiotic therapy based on the panel, keeping in mind that most cases of bacterial gastroenteritis won’t require antibiotics, unless the patient is severely ill or immunocompromised.
Here’s a high yield fact! Enterohemorrhagic Escherichia coli O157:H7 produces Shiga-toxin, which can lead to hemolytic uremic syndrome, or HUS for short.
HUS is a serious condition consisting of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, so in these patients, don’t forget to order a CBC and CMP, and be sure to avoid antibiotics, since they may actually contribute to the development of HUS.Finally, if you identify a parasite on the enteric pathogen panel, you can confirm parasitic gastroenteritis, which is most commonly caused by Entamoeba histolytica.
If this is the case, treat the patient with metronidazole. Alright, as a quick recap… Gastroenteritis is caused by gastrointestinal inflammation, typically caused by infectious pathogens, that leads to diarrhea or vomit.

Review9:14–11:09

First, perform an ABCDE assessment to determine if they’re unstable or stable. If unstable, stabilize airway, breathing, and circulation.
Next, obtain IV access, start IV fluids, and begin continuous vital sign monitoring. Also, if needed, provide supplemental oxygen, and start broad spectrum antibiotics.
On the other hand, if stable, determine the type of diarrhea. If your patient has watery diarrhea, assess their level of dehydration.
If they’re only mildly dehydrated, give ORT. If there’s adequate response, continue current management until diarrhea resolves.
If there’s inadequate response, or moderate to severe dehydration, start IV fluids, and consider adding empiric antibiotics, bismuth subsalicylate, and an antimotility agent.
Next, assess travel history; if positive, diagnose traveler’s diarrhea and continue current management. If there’s no recent travel history, obtain an enteric pathogen panel.
If no pathogen is identified, assess the patient’s response to treatment. If there’s inadequate response, consider an alternative diagnosis.
If there’s adequate response, continue current management. On the other hand, if the enteric panel is positive for a pathogen, tailor therapy accordingly.
Now, if your patient has bloody diarrhea, start IV fluids and consider empiric antibiotics. Then, get an enteric pathogen panel.
If a pathogen is not identified, assess the patient’s response to treatment. If there’s inadequate response, consider an alternative diagnosis; but if there's adequate response, continue current management.
Finally, if the enteric panel is positive for a pathogen,