Infectious gastroenteritis (subacute) (pediatrics): Clinical sciences

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Introduction 0:00–0:27

Subacute infectious gastroenteritis refers to an infection of the stomach and intestines that lasts longer than 2 weeks.
Gastrointestinal infections typically present with diarrhea after fecal-oral contact or ingestion of contaminated food or water.
Most cases of subacute infectious gastroenteritis are caused by either bacteria or parasites. Now, if a pediatric patient presents with a chief concern suggesting subacute infectious gastroenteritis, first perform an ABCDE assessment to determine if they’re unstable or stable.

Unstable Patient 0:27–0:55

If unstable, stabilize their airway, breathing, and circulation. Next, obtain IV access, start IV fluids, and put your patient on continuous vital sign monitoring.
Finally, provide supplemental oxygen if needed, and consider starting antibiotics. Now, let’s return to the ABCDE assessment and take a look at stable patients.

Stable Patient 0:55–2:07

Start by obtaining a focused history and physical examination. History will reveal more than 14 days of diarrhea, possibly in combination with fever, malaise, anorexia, vomiting, and abdominal cramps.
The patient might also report a known sick contact or recent travel, and some patients may report weight loss. Finally, the exam may reveal abdominal tenderness.
This clinical picture is highly suggestive of subacute infectious gastroenteritis. To look for the causative pathogen, collect a stool sample and order labs.
Depending on the suspected pathogen, you may want to order a stool culture to identify bacterial pathogens; and a stool glutamate dehydrogenase, C.
diff toxins A and B, and an nucleic acid amplification test, or NAAT, to look for Clostridioides difficile or C. diff.
Additionally, send stool ova and parasites, Giardia and Cryptosporidium antigens, and a Cyclospora examination, to look for parasitic pathogens.
First, let’s take a look at findings you’d expect to see in bacterial infection. In this case, the stool culture might be positive; or C.

Bacterial Infection 2:07–2:38

diff tests like the stool glutamate dehydrogenase antigen test, C. diff toxins A and B, and the NAAT could be positive.
Any one of these findings confirms bacterial infection. Let’s look at some common causes, starting with enteroaggregative Escherichia coli, or EAEC for short.
Patients with EAEC infection have watery diarrhea that may contain mucus, or in rare cases, blood. Some patients report recent travel to a developing country.

EAEC 2:38–3:47

If the stool culture grows EAEC, you can confirm the diagnosis. Although EAEC infections are usually self-limited, antibiotics can shorten the duration of illness and are indicated for immunocompromised patients or those experiencing prolonged or severe disease.
If you decide to treat with antibiotics, choose azithromycin or fluoroquinolone. Here’s a clinical pearl!
For some types of subacute bacterial gastroenteritis, you should avoid antibiotics, since they increase the risk of complications.
For example, antibiotics increase the risk of hemolytic uremic syndrome in Shiga-toxin producing E. coli infection; and they can prolong the patient’s carrier state in Salmonella gastroenteritis, keeping them contagious for longer.
Additionally, whether or not your patient gets antibiotics, be sure to recommend an oral rehydration solution as needed, and have them continue a normal diet.
Next, let’s take a look at Clostridioides difficile, or C. diff.

Clostridioides difficile 3:47–5:03

Affected patients typically experience fever, bloating, abdominal pain, and occasionally, bloody stools; often after recent antibiotic or PPI use or a hospitalization.
The glutamate dehydrogenase antigen test and C. diff toxins A and B will usually be positive, but if results are inconclusive, the NAAT can confirm C.
diff infection. Once you’ve made the diagnosis, discontinue any current antibiotics that might have triggered the infection, and begin treatment with oral vancomycin or oral or intravenous metronidazole.
Here’s a clinical pearl! Antibiotic use can alter the intestinal flora without affecting C.
diff, which allows it to multiply and produce toxins that attack the colon wall. This causes severe inflammation with plaque or “pseudomembrane” formation at the site of mucosal injury, which is called pseudomembranous colitis.
Lastly, be sure to recommend an oral rehydration solution as needed, and have them continue a normal diet. Alright, let’s switch gears and discuss parasitic infection, which is usually caused by Giardia, Cryptosporidium, Cyclospora, or Entamoeba species.

Parasitic Infection 5:03–5:27

Here, labs will demonstrate positive ova and parasites, a positive Giardia or Cryptosporidium antigen test, or a positive Cyclospora examination.
Any of these results confirms parasitic infection. First, let’s talk about Giardia lamblia, also called Giardia intestinalis or Giardia duodenalis.

Giardia 5:27–6:35

Infected patients typically experience flatulence and intermittent large-volume, foul-smelling, greasy stools. If history reveals that your patient attends daycare or has been drinking from a stream, and yields a positive Giardia antigen test, confirm giardiasis.
You can treat this with tinidazole, nitazoxanide, or metronidazole. In addition, be sure to recommend an oral rehydration solution as needed, and have your patient continue a normal diet.
Here’s a clinical pearl! You might see Giardia under a microscope during the ova and parasite examination, but you’ll often need to look at more than one stool sample to find it.
Because the Giardia antigen test is more sensitive, it’s the preferred diagnostic test. If you do find Giardia on microscopy, you’ll see two nuclei with four pairs of flagella; and when stained, it looks just like a smiling face!
Next up is Cryptosporidium. The patient’s history typically reveals profuse, watery diarrhea; crampy abdominal pain; anorexia; nausea; and vomiting.

Cryptosporidium 6:35–7:11

These symptoms often wax and wane in a cyclical fashion. Patients might also mention recent travel, daycare attendance, or swimming in a public pool.
Now, if Cryptosporidium antigen is positive, you can confirm the diagnosis of a Cryptosporidium infection. Begin treatment with nitazoxanide, recommend an oral rehydration solution as needed, and have your patient continue a normal diet.
Now, let’s take a look at Cyclospora. Affected patients typically have explosive, watery diarrhea.

Cyclospora 7:11–7:52

Some also describe nonspecific symptoms, like fatigue, low-grade fever, body aches, and headache; in addition to abdominal bloating, cramping, and anorexia.
Some patients report recent travel to a subtropical or tropical area. If staining reveals Cyclospora oocysts on microscopic examination, you can diagnose Cyclospora infection and begin treatment with trimethoprim-sulfamethoxazole.
Additionally, remember to recommend an oral rehydration solution as needed, and have your patient continue a normal diet.
Last up is Entamoeba histolytica. Patients usually experience a gradual onset of symptoms like abdominal pain and increased stool frequency, which can be bloody.

Entamoeba7:52–9:14

Many patients also report tenesmus, or the frequent urge to stool, even when the bowel is empty. Unlike some other causes of infectious diarrhea, Entamoeba usually does not cause constitutional symptoms like fever.
Many patients also report recent travel to a tropical area. On top of that, the ova and parasite examination will be positive for Entamoeba.
Then, consider an Entamoeba histolytica infection, and order antigen testing for confirmation. If it’s positive, diagnose Entamoeba histolytica infection.
Treat with metronidazole, followed by paromomycin. Finally, be sure to recommend an oral rehydration solution as needed, and have your patient continue a normal diet.
Let’s wrap this up with a high-yield fact! Entamoeba histolytica infection can be complicated by extraintestinal manifestations, such as amebic liver abscess, which contains necrotic debris that resembles “anchovy paste”.
These patients usually have fever, as well as hepatomegaly and abdominal pain, distention, and tenderness. Alright, as a quick recap… If a patient presents with subacute infectious gastroenteritis, collect a stool sample and order labs.

Review 9:14–10:03

A stool culture can identify bacterial pathogens such as EAEC, while a stool glutamate dehydrogenase antigen test, C. diff toxins A and B, or NAAT can identify Clostridioides difficile.
On the other hand, a stool ova and parasite test, Giardia and Cryptosporidium antigens, and Cyclospora examination can identify parasitic pathogens such as Giardia, Cryptosporidium, Cyclospora, and Entamoeba histolytica.
. treat your patient with appropriate antimicrobials if indicated provide oral rehydration solution as needed and encourage your patient to