What are the potential differential diagnoses (DDx) for a patient with stomach burning, nausea, and pain with any food or fluid intake, denying indigestion or reflux, identifying the left upper quadrant as the area of discomfort, with symptoms occurring over the past 12-18 hours?

Differential Diagnoses for Acute Left Upper Quadrant Pain with Nausea and Food Intolerance

Given the acute onset (12-18 hours), left upper quadrant localization, burning pain, nausea, and inability to tolerate oral intake, the most critical immediate considerations are acute pancreatitis, gastritis/peptic ulcer disease, splenic pathology, and less commonly, myocardial infarction or gastric volvulus.

Life-Threatening Conditions to Exclude First

Cardiac Causes

• Myocardial infarction can present with epigastric or left upper quadrant pain, particularly inferior wall MI 1
• Look specifically for: radiation to jaw/arm/back, diaphoresis, dyspnea, exertional component, cardiac risk factors 1
• This must be ruled out immediately in any patient with upper abdominal pain, especially with associated nausea 1

Acute Pancreatitis

• Classic presentation: severe epigastric/left upper quadrant pain radiating to the back, nausea, vomiting, inability to tolerate oral intake 1
• The 12-18 hour timeframe and severity with any food/fluid intake strongly suggests this diagnosis 1
• Check serum lipase (>3x upper limit of normal is diagnostic) and assess for risk factors: alcohol use, gallstones, hypertriglyceridemia 1, 2

Gastrointestinal Causes (Most Likely Given Presentation)

Gastritis and Peptic Ulcer Disease

• Burning pain with food intake is highly characteristic of gastritis or peptic ulcer disease 1
• Left upper quadrant localization suggests gastric body/fundus involvement 1
• CT findings may show gastric wall thickening (>5mm), mucosal hyperenhancement, or focal outpouching from ulceration 1
• Risk factors to assess: NSAID use, H. pylori infection, alcohol, stress 1

Gastroparesis

• Nausea, vomiting, and postprandial symptoms with inability to tolerate food are cardinal features 1, 3
• However, the acute 12-18 hour onset makes this less likely as gastroparesis typically presents with chronic or subacute symptoms 1, 4
• Consider if patient has diabetes, prior gastric surgery, or opioid use 4, 5

Gastric Outlet Obstruction

• Presents with nausea, vomiting, and inability to tolerate oral intake 1
• Physical exam may reveal a succussion splash (fluid splashing sound with abdominal palpation) 1
• Requires imaging or endoscopy to diagnose 4

Splenic and Adjacent Organ Pathology

Splenic Infarction or Rupture

• Left upper quadrant pain with acute onset warrants consideration of splenic pathology 1, 2
• Assess for: trauma history, hematologic disorders, embolic sources, left shoulder pain (Kehr sign) 2

Left-Sided Diverticulitis

• Can present with left upper quadrant pain, though left lower quadrant is more typical 1, 2
• Associated with fever, altered bowel habits, localized tenderness 2

Metabolic and Systemic Causes

Diabetic Ketoacidosis

• Presents with nausea, vomiting, abdominal pain (can be diffuse or localized) 6, 7
• Check glucose, ketones, anion gap if patient has diabetes or appears systemically ill 2

Medication/Toxin Effects

• Critical to assess: opioids, GLP-1 agonists, NSAIDs, antibiotics, chemotherapy 3, 5, 6
• These can cause acute gastric symptoms mimicking organic disease 7, 8

Less Common but Important Considerations

Gastric Volvulus

• Acute onset, severe pain, inability to tolerate oral intake, retching without productive vomiting 1
• Requires urgent surgical evaluation if suspected 1

Mesenteric Ischemia

• Severe pain out of proportion to examination findings, particularly in elderly with vascular disease 1, 2
• The acute onset and severity warrant consideration, though left upper quadrant localization is atypical 2

Hereditary Angioedema

• Can present with acute, severe abdominal pain and gastrointestinal symptoms without cutaneous findings 9
• Consider if patient has recurrent unexplained episodes or family history 9

Critical Pitfalls to Avoid

• Do not dismiss cardiac causes based solely on left upper quadrant localization—obtain ECG and troponin 1
• Do not assume GERD/reflux when patient explicitly denies these symptoms; the denial should redirect you toward other causes 1
• Acute onset (12-18 hours) argues against chronic conditions like gastroparesis or functional dyspepsia unless there's an acute exacerbation 1, 4
• Pain with ANY food or fluid intake suggests either severe mucosal inflammation (gastritis/PUD), obstruction, or pancreatitis rather than functional disorders 1

Recommended Initial Workup

• Laboratory: Complete blood count, comprehensive metabolic panel, lipase, liver function tests, troponin, urinalysis, pregnancy test if applicable 1, 2
• Imaging: CT abdomen/pelvis with IV contrast is the most comprehensive initial study for acute nonlocalized or left upper quadrant pain 1, 2
• ECG: Mandatory to exclude cardiac ischemia 1
• Upper endoscopy: Consider if gastritis/PUD is strongly suspected and patient is stable, though CT may be performed first in acute presentations 1, 4