In a 53‑year‑old woman with three days of periumbilical abdominal pain and watery diarrhea, no fever, vomiting, or urinary symptoms, and urinalysis showing moderate leukocytosis and microscopic hematuria (likely stool contamination), what is the most likely diagnosis and initial management?

Acute Gastroenteritis with Likely Stool-Contaminated Urinalysis

This patient most likely has acute infectious gastroenteritis, and the urinalysis findings represent stool contamination rather than true urinary tract infection; initial management should focus on oral rehydration and supportive care without empiric antibiotics.

Clinical Reasoning

The clinical picture strongly suggests acute gastroenteritis rather than a urinary or other intra-abdominal pathology:

• The absence of urinary symptoms (dysuria, frequency, urgency) combined with prominent gastrointestinal symptoms makes UTI highly unlikely despite the abnormal UA. 1
• Leukocyturia without urinary symptoms in the setting of diarrhea typically indicates specimen contamination from perianal stool rather than true infection. 1
• The periumbilical location of pain with watery diarrhea for 3 days is classic for non-inflammatory gastroenteritis or early inflammatory enteritis. 2

Diagnostic Approach

Determine if This is Inflammatory vs Non-Inflammatory Diarrhea

• The absence of fever, visible blood in stool, and severe systemic symptoms suggests non-inflammatory (watery) diarrhea, which is most commonly viral and self-limited. 3
• Periumbilical pain with diarrhea lasting >3 days can suggest inflammatory infection, but the lack of fever makes bacterial causes less likely. 3

When to Obtain Stool Studies

• Stool culture for Salmonella, Shigella, Campylobacter, and Yersinia is indicated only when fever AND bloody/mucoid stools are present. 4, 5
• In this case, without fever or bloody stools, stool cultures are NOT indicated at this time. 3
• If symptoms persist beyond 7 days or worsen with development of fever or bloody stools, then obtain stool studies including bacterial culture and C. difficile testing. 4

Initial Management Strategy

Rehydration is the Cornerstone

• Oral rehydration solution (ORS) with sodium 90 mM, potassium 20 mM, chloride 80 mM, bicarbonate 30 mM, and glucose 111 mM is first-line therapy for mild-to-moderate dehydration. 3, 4
• Assess for volume depletion signs: dry mucous membranes, decreased skin turgor, tachycardia, orthostatic hypotension, decreased urination, or lethargy. 4, 5
• If the patient can tolerate oral intake, ORS is superior to IV fluids; reserve IV crystalloids for severe dehydration or inability to maintain oral hydration. 4

Empiric Antibiotics Are NOT Indicated

• In most people with acute watery diarrhea without recent international travel, empiric antimicrobial therapy is not recommended (strong recommendation). 3
• The modest benefit of empiric antibiotics (shortening illness by approximately 1 day) is outweighed by risks of antimicrobial resistance, C. difficile superinfection, and prolonged pathogen shedding. 3, 4

Exceptions That Would Require Antibiotics (None Apply Here)

• Sepsis or severe systemic illness 4
• Bacillary dysentery (frequent bloody stools, high fever, severe cramps, tenesmus) 4
• Immunocompromised status with severe illness 3, 4
• Infants <3 months old 4, 5
• Recent international travel with fever ≥38.5°C 4

Red Flags Requiring Escalation

When to Obtain Further Testing

• Development of fever ≥38.5°C warrants stool culture for bacterial pathogens. 4, 5
• Appearance of bloody or mucoid stools requires stool culture and testing for Shiga toxin-producing E. coli (STEC). 6, 4
• Severe abdominal pain with minimal fever should raise suspicion for STEC; obtain both culture for O157:H7 and Shiga-toxin assays before any antibiotics. 6, 4
• If ≥6 bowel movements above baseline (grade 3 severity), obtain urgent gastroenterology consultation and consider CT abdomen/pelvis. 4

When to Consider Hospital Admission

• Inability to maintain oral hydration 4
• Hemodynamic instability (tachycardia, hypotension) 4
• Severe or worsening abdominal pain suggesting complications 4
• Development of peritoneal signs 4

Critical Pitfalls to Avoid

• Do NOT treat the abnormal urinalysis as a UTI in the absence of urinary symptoms; this represents stool contamination. 1
• Do NOT prescribe antimotility agents (loperamide, opiates) if fever or bloody stools develop, as they increase toxic megacolon risk. 4
• Do NOT start empiric antibiotics for uncomplicated watery diarrhea, as this provides minimal benefit and increases harm. 3, 4
• Do NOT assume this is simply viral gastroenteritis if symptoms persist >7 days or if fever/bloody stools develop; reassess and obtain stool studies. 3, 4

Disposition and Follow-Up

• Advise the patient to return immediately if fever, bloody stools, severe abdominal pain, signs of dehydration, or inability to tolerate oral fluids develop. 4
• If symptoms persist beyond 7 days without improvement, obtain stool studies and consider alternative diagnoses including parasitic infection or inflammatory bowel disease. 3
• Reassure the patient that most acute watery diarrhea is self-limited and resolves within 3-7 days with supportive care alone. 3