Mr. C is a 35-year-old man who comes to your outpatient office complaining of 1 day of diarrhea.
|What is the differential diagnosis of diarrhea? How would you frame the differential?|
Although the presence of diarrhea is actually defined by stool weight, it is more useful to define acute diarrhea clinically. Diarrhea can be thought of as bowel movements of a looser consistency than usual that occur more than 3 times a day. Acute diarrhea develops over a period of 1–2 days and lasts for less than 4 weeks. (This chapter will not address chronic or intermittent diarrhea.) The differential diagnosis below uses the pivotal point of presenting symptoms to organize diagnoses into three categories: noninfectious, gastroenteritis, and infectious colitis. This structure is easy to remember, focuses history taking, allows prognosticating, and is also a good framework on which to consider therapy See Fig. 12–1.
Diagnostic approach: diarrhea.
Noninfectious diarrhea is recognized by the lack of constitutional symptoms. Infectious diarrhea that presents with large volume (often watery) stool, constitutional symptoms, nausea and vomiting, and often abdominal cramps can be categorized as gastroenteritis. Infectious colitis presents with fever, tenesmus, and dysentery (stools with blood and mucus). Many organisms can cause both gastroenteritis and inflammatory diarrhea.
Medications and other ingestible substances (some with osmotic effect)
Sorbitol (gum, mints, pill fillers)
Fructose (fruits, soft drinks)
Fiber (bran, fruits, vegetables)
Medications causing diarrhea through nonosmotic means
Selective serotonin reuptake inhibitor antidepressants
Infectious diarrhea: gastroenteritis
Viral (most common)
Caliciviruses (Norovirus, formally Norwalk virus)
Bacterial (commonly food-borne)
Infectious diarrhea: inflammatory colitis
The first symptom the patient noted was a poor appetite while eating breakfast. He was unable to finish his usual cup of coffee and a bowl of cereal. During his 20-minute drive to work he developed nausea and diaphoresis. Upon arriving at work he developed low-grade fever, abdominal cramping, and vomiting. Over the next 12 hours, diarrhea developed. He describes the stool being watery and brown without any blood.
|At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis? Given this differential diagnosis, what tests should be ordered?|
Mr. C seeks medical attention within about 24 hours of the onset of diarrhea. The pivotal points in his history are acute onset of symptoms over about 60 minutes, early predominance of nausea, and watery brown stool. This presentation certainly speaks for an infectious cause. The low-grade fever and absence of dysentery make it likely that the diagnosis is in the category of gastroenteritis. Table 12–1 lists the differential diagnosis.
Mr. C is otherwise in good health. He reports no recent illnesses or antibiotic exposures. There have been no recent changes in his diet, and he has eaten only food prepared at home for the last week. He lives with his wife and reports no known sick contacts. He works as a bus driver.
He has not traveled from New York City, where he lives and works.
The physical exam is notable for temperature, 38.2°C; BP is 110/80 mm Hg and pulse is 100 bpm while lying down; BP is 90/72 mm Hg and pulse is 126 bpm while standing; RR, 12 breaths per minute. Sclera and conjunctiva are normal. The abdomen is soft and diffusely tender with hyperactive bowel sounds. The rectal exam shows brown, heme-negative stool.
|Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?|
Table 12–1. Diagnostic Hypotheses for MR. C.
| Save Table
Table 12–1. Diagnostic Hypotheses for MR. C.
|Diagnostic Hypotheses||Clinical Clues||Important Tests|
|Norovirus virus||Hyperacute onset Vomiting usually present||Resolution in 24-48 hours|
|Toxin-mediated gastroenteritis, such as Staphylococcus aureus|
Common food poisoning
Onset 1-8 hours after exposure
Vomiting is predominant
|Rapid resolution, within 12 hours|
|Bacterial gastroenteritis, such as Salmonella infection|
Fairly specific clinical syndromes
High fevers possible
|Stool cultures can be diagnostic|
Contact with children
Vomiting common and constitutional signs present
|Resolution in 24-72 hours|
Leading Hypothesis: Norovirus
Acute vomiting is usually the presenting symptom. Mild diarrhea begins after the vomiting. Mild abdominal cramping is common. Low-grade fever and dehydration are usually present. All symptoms resolve completely by 3 days.
Calciviruses, of which Norovirus and closely related viruses such as Sapovirus are the most common, account for about 80% of adult nonbacterial gastroenteritis.
Most commonly occurs in winter.
Transmission may be person-to-person or may be food-borne. Norovirus is the most common cause of food-borne infection.
High attack rate (up to 50% of exposed individuals)
Incubation period is 1–2 days.
There are no diagnostic tests available for routine clinical use.
Diagnosis is made by clinical presentation.
Most patients with acute diarrhea require only supportive care. Supportive care is meant to provide rehydration and symptom relief.
Oral rehydration is the most important means of rehydration.
For patients with mild diarrhea and little volume depletion, any oral fluids (such as the commonly prescribed Gatorade, pedialyte, chicken soup) are appropriate rehydration.
For patients with ...
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