What could be causing left abdominal pain in an adult that worsens after eating?

Left Abdominal Pain Triggered by Eating

The most likely diagnosis is functional dyspepsia, but you must first exclude high-risk surgical causes—particularly chronic mesenteric ischemia, intestinal obstruction, and splenic flexure pathology—using CT abdomen/pelvis with IV contrast as your initial imaging study. 1, 2

Immediate Risk Stratification

Check for alarm features that mandate urgent imaging:

• Age ≥55 years with weight loss requires 2-week wait endoscopy to exclude gastro-oesophageal malignancy 3
• Age ≥60 years with abdominal pain and weight loss requires urgent CT scan 3
• Postprandial pain with vomiting, especially bilious or fecaloid vomiting, indicates possible intestinal obstruction or mesenteric ischemia and requires immediate CT with IV contrast 1
• Tachycardia, hypotension, fever, or signs of peritonitis require immediate surgical consultation without delay 1
• Classic triad of postprandial pain 30-60 minutes after eating, weight loss, and food avoidance strongly suggests chronic mesenteric ischemia and requires CT angiography 1

Diagnostic Imaging Strategy

Order CT abdomen/pelvis with IV contrast as your first-line imaging study for left-sided abdominal pain triggered by eating, as recommended by the American College of Radiology with a rating of 8/9 (usually appropriate). 2 This single study evaluates:

• Mesenteric ischemia (acute or chronic) 1
• Intestinal obstruction with transition points 1
• Splenic pathology, pancreatic disease, and gastric abnormalities 2
• Splenic flexure diverticulitis or colitis 2
• Unexpected findings that alter diagnosis in nearly 50% of cases 2

Do not rely on plain radiography—it has very limited diagnostic value for left upper quadrant pain. 2

Essential Laboratory Workup

Obtain the following baseline investigations:

• Full blood count in patients aged ≥25 years 3
• H. pylori breath or stool testing—all patients with dyspepsia should be tested 3
• Coeliac serology if there are overlapping IBS-type symptoms 3
• Serum lipase and liver function tests to evaluate pancreatic or hepatobiliary pathology 1
• Complete metabolic panel and serum lactate if intestinal ischemia is suspected 1

Differential Diagnosis Framework

High-Risk Surgical Causes (Must Exclude First)

• Chronic mesenteric ischemia: Postprandial pain 30-60 minutes after eating with weight loss and atherosclerotic risk factors requires CT angiography 1
• Intestinal obstruction: Previous abdominal surgery has 85% sensitivity for adhesive obstruction; bilious vomiting is diagnostic 1
• Splenic flexure pathology: Diverticulitis or colitis can present as left upper quadrant pain 2
• Acute pancreatitis: Confirmed by lipase >2× upper limit of normal 2

Functional Dyspepsia (Diagnosis of Exclusion)

Functional dyspepsia is the most common cause when imaging and endoscopy are normal, characterized by: 3

• Postprandial fullness, early satiety, or epigastric pain/burning for >8 weeks 3
• Pain precipitated or exacerbated by meal ingestion 3
• Pain unrelated to defecation (unlike IBS) 3
• Up to 50% overlap with IBS symptoms 3

Management Algorithm

If Imaging and Labs Are Normal:

1. Test and treat H. pylori: If positive, provide antibiotic eradication therapy and reassess symptoms 3

2. First-line pharmacotherapy:

   • Proton pump inhibitor (e.g., omeprazole 20 mg once daily before meals) for 4-8 weeks 1
   • This works even if H. pylori is negative 3

3. Second-line options if PPI fails:

   • Tricyclic antidepressants (TCAs) to modulate gut-brain axis pain perception 2
   • Consider prokinetic agents if early satiety predominates 3

4. Lifestyle modifications:

   • Avoid trigger foods (including coffee if it worsens symptoms) 4
   • Regular exercise may help some patients 3
   • Do not recommend restrictive diets—they can lead to malnutrition 3

5. Refractory symptoms:

   • Refer to gastroenterology for consideration of endoscopy, behavioral interventions, or combination therapy 2
   • Psychological therapies (cognitive behavioral therapy) may be beneficial 3

If Age >40 Years or Family History of GI Cancer:

Consider non-urgent endoscopy even without other alarm features, particularly if symptoms are treatment-resistant. 3

Critical Pitfalls to Avoid

• Do not delay CT imaging while "observing" a patient with postprandial pain and vomiting—serious pathology cannot be excluded by examination alone 1
• Do not assume functional dyspepsia without first excluding organic causes with imaging, especially in patients over 40 years 1
• Do not dismiss left-sided pain as benign without imaging when clinical suspicion exists—CT alters diagnosis in nearly half of cases 2
• Do not overlook chronic mesenteric ischemia in patients with atherosclerotic risk factors and the classic triad of symptoms 1
• Reassess patients with severe pain every 4-6 hours if initial workup is negative to detect evolving peritonitis or ischemia 1