What is the likely diagnosis for a patient experiencing Left Upper Quadrant (LUQ) pain triggered by eating fried and fatty foods, with the pain wrapping around the rib cage and accompanied by sticky stools?

Likely Diagnosis: Chronic Pancreatitis

The clinical presentation of left upper quadrant pain triggered by fatty foods, wrapping around to the back/rib cage, accompanied by sticky stools (steatorrhea) is most consistent with chronic pancreatitis with exocrine pancreatic insufficiency.

Key Diagnostic Features Supporting This Diagnosis

Pain Pattern Analysis

• LUQ pain radiating to the back is the hallmark presentation of pancreatic pathology, distinctly different from biliary disease which typically causes right upper quadrant pain 1
• The "wrapping around rib cage" distribution matches the classic pancreatic pain radiation pattern that follows the retroperitoneal location of the pancreas 2
• Fatty food precipitation occurs in both biliary and pancreatic disease, but when combined with LUQ location (not RUQ), pancreatic etiology becomes more likely 2

Steatorrhea as the Critical Distinguishing Feature

• Sticky stools (steatorrhea) indicate malabsorption of fats due to pancreatic exocrine insufficiency—this does NOT occur with biliary disease alone
• Steatorrhea develops when >90% of pancreatic function is lost, representing advanced chronic pancreatitis
• The combination of postprandial pain AND steatorrhea is pathognomonic for chronic pancreatitis with exocrine insufficiency

Why This is NOT Biliary Disease

Anatomic Location Excludes Typical Biliary Pathology

• Biliary colic and cholecystitis cause right upper quadrant pain, not left 1, 3
• The ACR Appropriateness Criteria specifically address RUQ pain for biliary evaluation, not LUQ 1
• While fatty foods trigger biliary pain (40% of biliary disease patients), biliary disease does not cause steatorrhea 2

Steatorrhea Rules Out Isolated Biliary Disease

• Gallbladder dysfunction (biliary dyskinesia or hyperkinesia) causes pain but never causes steatorrhea 4, 5
• Bile is necessary for fat emulsification, but pancreatic lipase is required for fat digestion—steatorrhea indicates pancreatic insufficiency, not biliary obstruction

Alternative Diagnosis to Consider: Painful Rib Syndrome

When to Suspect Musculoskeletal Etiology

• Painful rib syndrome presents with lower chest/upper abdominal pain with a tender spot on the costal margin that reproduces pain on palpation 6, 7
• This accounts for 3% of general gastroenterology referrals and is often misdiagnosed, leading to unnecessary cholecystectomies 6
• However, painful rib syndrome is movement and posture-dependent and does NOT cause steatorrhea 7

Critical Distinguishing Features

• Examine for focal tenderness at the costal margin, particularly at the end of the lowest floating rib 6, 7
• If pain is reproduced by pressing the tender spot and there is no steatorrhea, painful rib syndrome becomes the diagnosis 6
• The presence of steatorrhea in this patient effectively excludes painful rib syndrome as the sole diagnosis

Recommended Diagnostic Workup

Initial Laboratory Studies

• Fecal elastase-1 to confirm pancreatic exocrine insufficiency (most specific non-invasive test)
• Lipase and amylase (may be normal in chronic pancreatitis)
• Liver function tests to exclude biliary obstruction mimicking pancreatic disease

Imaging Algorithm

• CT abdomen with IV contrast is the preferred initial imaging for suspected chronic pancreatitis, evaluating for pancreatic calcifications, ductal dilatation, and atrophy
• MRI with MRCP provides superior visualization of pancreatic ducts and can identify early chronic pancreatitis when CT is negative 1
• Ultrasound has limited utility for pancreatic evaluation due to bowel gas interference, unlike its 9/9 rating for RUQ/biliary assessment 3, 8

Advanced Functional Testing if Imaging is Equivocal

• Endoscopic ultrasound (EUS) with pancreatic function testing provides the highest sensitivity for early chronic pancreatitis
• Secretin-stimulated MRCP can assess pancreatic duct compliance and secretory function

Critical Pitfalls to Avoid

• Do not assume LUQ pain is biliary disease—the gallbladder is in the RUQ, and biliary pain does not typically present on the left side 1, 3
• Do not ignore steatorrhea—this finding mandates evaluation for pancreatic insufficiency and cannot be explained by biliary dyskinesia or musculoskeletal causes 6, 4
• Do not order HIDA scan for LUQ pain—this test evaluates gallbladder function for RUQ pain and is inappropriate for left-sided symptoms 8, 5
• Do not miss painful rib syndrome by failing to palpate the costal margin, but recognize that steatorrhea indicates additional pathology beyond musculoskeletal causes 6, 7