What is the possible diagnosis for a patient with fever for 2 weeks, diarrhea for 1 week, and diffuse abdominal pain?

Differential Diagnosis: Prolonged Fever with Diarrhea and Abdominal Pain

The most likely diagnoses in a patient with 2 weeks of fever and 1 week of diarrhea with diffuse abdominal pain include enteric fever (typhoid/paratyphoid), invasive bacterial enterocolitis (particularly Salmonella, Yersinia, or Campylobacter), or parasitic infections, with the specific pathogen depending critically on travel history, immune status, and antibiotic exposure. 1

Primary Diagnostic Considerations

Enteric Fever (Typhoid/Paratyphoid)

• Enteric fever should be at the top of your differential given the prolonged fever (2 weeks) preceding diarrhea onset, as diarrhea is actually uncommon in enteric fever but can occur 1
• This presentation is particularly concerning if the patient has traveled to or had contact with travelers from enteric fever-endemic areas 1
• The combination of persistent fever with systemic manifestations and subsequent gastrointestinal symptoms is classic for Salmonella typhi or paratyphi 1

Invasive Bacterial Enterocolitis

Persistent abdominal pain and fever lasting 2 weeks strongly suggests Yersinia enterocolitica or Y. pseudotuberculosis, which characteristically cause prolonged symptoms and can mimic appendicitis 1

Other bacterial pathogens causing fever with abdominal pain include:

• Salmonella (non-typhoidal) 1
• Campylobacter 1
• Shigella 1
• Non-cholera Vibrio species 1
• Clostridium difficile (especially if recent antibiotic exposure within 8-12 weeks) 1

Parasitic Infections

Since diarrhea has persisted for 1 week (approaching the 14-day threshold for "persistent" diarrhea), parasitic causes must be considered, including 1:

• Cryptosporidium species
• Giardia lamblia
• Cyclospora cayetanensis
• Entamoeba histolytica (which can cause high fever) 1

Critical Clinical Context Needed

Travel History

• Recent international travel with fever ≥38.5°C or signs of sepsis warrants immediate empiric antimicrobial therapy while awaiting diagnostic results 1
• Travel to enteric fever-endemic regions makes typhoid/paratyphoid the leading diagnosis 1
• Travel to cholera-endemic regions or exposure to brackish water/raw shellfish suggests Vibrio species 1

Immune Status

• Immunocompromised patients require a much broader differential including opportunistic pathogens like Mycobacterium avium complex, cytomegalovirus, microsporidia, and Cystoisospora 1
• HIV/AIDS patients with persistent diarrhea need additional testing beyond standard bacterial cultures 1

Antibiotic Exposure

• Recent antibiotic use within 8-12 weeks mandates C. difficile testing, as this is the most common cause of healthcare-associated infectious diarrhea 1
• C. difficile can present with fever, abdominal pain, and diarrhea, though bloody stools are not typical 1

Stool Characteristics

• Presence or absence of blood in stool significantly narrows the differential 1
• Bloody stools suggest STEC, Shigella, Salmonella, Campylobacter, Entamoeba histolytica, Yersinia, or non-cholera Vibrio 1
• Note that STEC patients are typically not febrile at presentation, making this less likely with documented fever 1

Recommended Diagnostic Approach

Immediate Testing Required

Blood cultures must be obtained given the prolonged fever, as this presentation suggests possible bacteremia or enteric fever 1

Stool testing should include 1:

• Culture for Salmonella, Shigella, Campylobacter, Yersinia
• Shiga toxin or genomic assays for STEC
• C. difficile toxin testing (if antibiotic exposure)
• Parasitic examination or antigen testing for Giardia, Cryptosporidium, Cyclospora, Entamoeba

If enteric fever is suspected clinically, also culture 1:

• Bone marrow (particularly valuable if antibiotics already given)
• Duodenal fluid
• Urine

Additional Cultures Based on Epidemiology

• Yersinia testing if right lower quadrant pain or exposure to undercooked pork 1
• Vibrio testing if large-volume "rice water" stools or seafood/brackish water exposure 1

Critical Management Pitfalls

Do Not Delay Treatment in High-Risk Scenarios

Patients with clinical features of sepsis suspected of having enteric fever should receive empiric broad-spectrum antimicrobial therapy immediately after cultures are collected, then narrow therapy based on susceptibility results 1

Empiric therapy for suspected bacterial enterocolitis with fever ≥38.5°C and travel history should be either 1:

• Fluoroquinolone (ciprofloxacin) OR
• Azithromycin (depending on local resistance patterns and travel history)

Avoid Antimotility Agents

Never use loperamide or other antimotility drugs in patients with fever and inflammatory diarrhea, as they can precipitate toxic megacolon or worsen outcomes 2

STEC Antibiotic Caution

If STEC is suspected (bloody diarrhea, abdominal pain, minimal fever), avoid antibiotics as they may increase risk of hemolytic uremic syndrome 1

Non-Infectious Considerations

If symptoms persist beyond 14 days with negative infectious workup, consider 1:

• Inflammatory bowel disease (IBD)
• Post-infectious irritable bowel syndrome (IBS)
• Lactose intolerance

The 2-week fever preceding diarrhea makes infectious causes most likely, but IBD can present with prolonged constitutional symptoms 1, 3