What is the best course of treatment for a patient presenting with acute abdominal pain, specifically stabbing pain in the upper quadrant, intermittent chills, and abdominal tenderness, after consuming oyster soup, with no nausea, vomiting, diarrhea, or constipation, and who is not eating or drinking?

Acute Upper Abdominal Pain After Oyster Consumption: Immediate Management

This patient requires immediate CT abdomen/pelvis with IV contrast, broad-spectrum IV antibiotics, aggressive IV hydration with bowel rest (NPO status), and urgent surgical consultation—do not delay imaging or antibiotics while awaiting diagnostic results. 1

Immediate Diagnostic Workup

Obtain CT abdomen/pelvis with IV contrast immediately as the mandatory first-line imaging study—do not rely on ultrasound or plain films alone in this acute setting with upper quadrant tenderness and systemic symptoms. 1 The CT must specifically evaluate for:

• Bowel wall thickening suggesting infectious enterocolitis 1
• Free air indicating perforation 1
• Fluid collections or abscesses 1
• Signs of bowel ischemia (critical given the "stabbing pain" quality and chills) 2
• Signs of acute cholecystitis or appendicitis 3

Draw laboratory studies immediately:

• C-reactive protein (CRP) and procalcitonin—these have superior diagnostic accuracy compared to WBC count alone for identifying serious infectious complications 1
• At least two sets of blood cultures if fever develops, as chills suggest possible bacteremia 1
• Serum electrolytes, creatinine, and lactate to assess for dehydration and bowel ischemia (lactate >2 mmol/L indicates irreversible intestinal ischemia with hazard ratio 4.1) 2
• Complete blood count with differential 1

Obtain stool studies:

• Clostridium difficile toxin using two-step approach (enzyme immunoassay for glutamate dehydrogenase plus toxin detection or nucleic acid amplification test) 1
• Stool culture for bacterial pathogens, though diagnostic yield may be low 1

Empiric Antibiotic Therapy

Start broad-spectrum IV antibiotics immediately while awaiting diagnostic results—do not withhold antibiotics pending culture results if the patient appears systemically ill. 1 First-line options include:

• Piperacillin-tazobactam OR 1
• Carbapenem with anti-pseudomonal activity 1

The oyster consumption history raises concern for Vibrio species (particularly V. parahaemolyticus or V. vulnificus), which can cause severe gastroenteritis with systemic symptoms. The above regimens provide appropriate coverage. 1

Supportive Management

Institute aggressive supportive care immediately:

• Strict NPO status (bowel rest) until clinical improvement—the patient is already not eating or drinking, which is appropriate 1
• Aggressive IV hydration to correct third-space fluid losses and dehydration 3, 1
• Correct electrolyte abnormalities aggressively 1
• Hold all antimotility agents (loperamide, opiates) until infectious causes are excluded 1
• Serial abdominal examinations every 4-6 hours to detect clinical deterioration 1

Urgent Surgical Consultation

Obtain early surgical consultation immediately—mortality increases dramatically if surgical disease is missed in this population. 1 The combination of stabbing upper quadrant pain, intermittent chills, abdominal tenderness, and inability to tolerate oral intake raises concern for:

• Acute cholecystitis (laparoscopic cholecystectomy is treatment of choice if confirmed) 3
• Perforated peptic ulcer (sudden severe epigastric pain with progression to septic shock has 67.8% mortality) 2
• Acute mesenteric ischemia (severe pain out of proportion to physical findings is the hallmark) 2
• Complicated appendicitis with abscess 3

Immediate surgical exploration is required if any of the following develop:

• Signs of perforation or peritonitis 1
• Bowel ischemia on imaging 1
• Clinical deterioration despite 24-48 hours of appropriate medical therapy 1
• Hemodynamic instability 1

Critical Differential Diagnoses

Acute cholecystitis is highly likely given upper quadrant tenderness after fatty meal (oyster soup). Early laparoscopic cholecystectomy is superior to delayed surgery if confirmed on CT. 3

Vibrio gastroenteritis from contaminated oysters typically presents with acute abdominal pain, vomiting, and diarrhea within 24 hours of consumption—however, this patient lacks diarrhea, making invasive Vibrio infection or another etiology more concerning. 1

Acute mesenteric ischemia must be excluded urgently—the stabbing pain quality and progression to systemic symptoms (chills) fits the typical timeline of arterial occlusion. Every 6 hours of delay doubles mortality. 2

Perforated peptic ulcer presents with sudden severe upper abdominal pain and can progress to septic shock when peritoneal contamination leads to overwhelming sepsis. 2

Common Pitfalls to Avoid

Do not assume normal vital signs exclude serious pathology—fever and peritoneal signs may be absent or subtle, especially early in disease course. 1 The presence of intermittent chills despite potentially normal temperature indicates systemic inflammatory response. 1

Do not delay CT imaging—delaying CT can lead to missed life-threatening complications such as perforation, abscess, or bowel ischemia. 1

Do not rely on stool cultures alone—diagnostic yield is <5% in many settings, and C. difficile testing is more critical. 1

Do not miss acute mesenteric ischemia—severe abdominal pain out of proportion to physical findings is the hallmark, and CT angiography should be performed without delay if suspected. 2

Reassessment and Follow-up

Repeat imaging to evaluate for complications if no improvement within 48 hours of appropriate therapy. 1

Broaden antimicrobial coverage if not already done and no clinical improvement occurs. 1

Consider non-infectious etiologies (inflammatory bowel disease, ischemic colitis) if no improvement within 48 hours of appropriate therapy. 1

Escalate to surgical intervention if indicated by clinical deterioration or imaging findings. 1