What questions should be asked, and which body parts should be examined?

I’d use the mnemonic â€OLDCARTS.†When did the diarrhoea begin? Is there any recent travel? Describe the signs and symptoms. How frequently does the diarrhea occur? How long have you been suffering from diarrhea? Describe the stool (color, consistency, amount, and odor), and explain what makes it worse or better. What other symptoms are you experiencing? What kinds of treatments have you tried? On a scale of 1 to 10, how severe is it? Do you rely on laxatives? Have you recently used antibiotics? What medications do you use?
Previous medical history: Have you ever had something like this before? What other illnesses do you suffer from?
Is there anyone else in your family who has these symptoms? Is anyone suffering from a stomach virus, IBS, Crohn’s disease, Colitis, gluten sensitivity, or lactose intolerance?
Do you smoke, drink alcohol, consume caffeine, or use recreational drugs?
Nutritional Functional Pattern: What did you eat today, and what did you eat yesterday? Are there any new foods? What’s the state of your appetite? Do you have any skin conditions? Have you slimmed down? Are you dizzy or weak? (Dunphy, 2015)

A thorough GI exam would be required, including inspection, auscultation, percussion, and palpation. A skin examination would be performed to look for a rash, as well as a neurological examination to look for orthostatic hypotension caused by dehydration.
What diagnostic tests are required, and why?
Diagnostic tests can differ depending on the frequency of the diarrhea, the associated symptoms, the length of time it has been going on, the presence of occult blood, and vomiting. Among the tests would be:

BMP for determining electrolyte imbalance
A complete blood count (CBC) is performed to check for anemia or infection.
Stool culture and sensitivity testing for parasites and bacteria, or stool sample testing for giardia
TSH is used to screen for hyperthyroidism.
ESR is used to check for inflammation (Collins-Bride et al., 2017).
How would you deal with unusual findings?
The treatment will be determined by the findings. Fix the underlying problem. This could include dietary, fluid and electrolyte replacement, iron, blood transfusion, antibiotics, antithyroid agents, and anti-inflammatory corticosteroids.

Chinese herbal medicine combined with acupuncture has been shown to be effective for diarrhea in IBS patients (Yan, 2019). 5-HT3 antagonists, for example, could be used to treat IBS (Yue, 2018).

If additional testing is required, a gastroenterologist will be referred.

What will be your differentials list?

Differential diagnoses include the following:

IBS IBD Acute viral gastroenteritis (Dunphy, 2015)
Geraldine M. Collins-Bride. Clinical Guidelines for Advanced Practice Nursing: An Interprofessional Approach. Jones & Bartlett Learning (J&B Learning), 2017.