Pancreatic exocrine insufficiency (PEI) results from reduced pancreatic enzyme secretion, leading to malabsorption, malnutrition, and impaired quality of life. Although pancreatic enzyme replacement therapy (PERT) is the standard treatment, some patients remain symptomatic despite apparently adequate therapy. Possible causes include suboptimal dosing or concomitant conditions such as small intestinal bacterial overgrowth (SIBO). This study aims to determine the prevalence of SIBO in symptomatic PEI patients despite adequate PERT and to identify treatable causes of persistent symptoms using non-invasive diagnostic tests, with the goal of improving nutritional status and quality of life.

Pancreatic exocrine insufficiency (PEI) is defined as a reduction in pancreatic exocrine secretion below the level required for normal digestion of nutrients, leading to malabsorption, malnutrition, reduced quality of life, and increased morbidity. Chronic pancreatitis represents the most common cause of PEI, although the condition may also develop after pancreaticoduodenectomy.

Pancreatic enzyme replacement therapy (PERT) with pancrelipase is the standard treatment and is effective in most patients. However, a proportion of individuals continue to experience gastrointestinal symptoms and weight loss despite apparently adequate therapy, possibly due to suboptimal dosing or concomitant conditions such as small intestinal bacterial overgrowth (SIBO). The mixed triglyceride breath test may help evaluate the adequacy of enzyme replacement therapy, while non-invasive breath tests using glucose or lactulose represent practical diagnostic alternatives for SIBO.

This study aims to determine the prevalence of SIBO in patients with PEI who remain symptomatic despite adequate PERT and to identify treatable causes of persistent gastrointestinal symptoms and malnutrition through non-invasive diagnostic tests, with the ultimate goal of improving patients' nutritional status and quality of life.

Inclusion Criteria:

• Age ≥ 18 years
• Ability and willingness to participate in the study and to comply with study procedures
• Diagnosis of chronic pancreatitis with pancreatic exocrine insufficiency (defined as fecal elastase < 200 µg/g of stool)
• Ongoing pancreatic enzyme replacement therapy (PERT) with persistent gastrointestinal symptoms (including abdominal pain, dyspepsia, bloating, excessive flatulence, diarrhea, or steatorrhea) or unintentional weight loss ≥ 10% within the previous 6 months despite adequate PERT dosing (≥ 40,000 IU per main meal and half dose for snacks)
• Patients with ampullary or pancreatic tumors who underwent partial pancreatectomy and subsequently developed pancreatic exocrine insufficiency with persistent gastrointestinal symptoms
• Indication to undergo glucose, lactulose, and mixed triglyceride breath tests as part of routine clinical practice
• Signed written informed consent

Exclusion Criteria:

• Age < 18 years or > 75 years
• Pancreatic adenocarcinoma or bile duct tumors under active or previous adjuvant therapy
• Moderate to severe liver disease
• Severe chronic kidney disease (eGFR < 30 mL/min/1.73 m²)
• History of major gastrointestinal surgery, including total pancreatectomy
• Presence of other active organic gastrointestinal diseases
• Diabetic gastroparesis
• Known celiac disease
• Obstructive jaundice
• Liver cirrhosis Child-Pugh class C
• Recent or ongoing infections
• Severe chronic obstructive pulmonary disease (COPD)
• Symptomatic thyroid disorders
• Use of antibiotics, laxatives, probiotics, or prokinetic agents within 4 weeks prior to breath testing
• Inability or refusal to undergo study procedures
• Inability or refusal to provide informed consent

The study population consists of adult patients (≥18 years) with pancreatic exocrine insufficiency (PEI) attending a tertiary referral center. Eligible participants include:

1. patients with chronic pancreatitis and documented PEI, and
2. patients who underwent partial pancreatectomy for ampullary or pancreatic tumors and subsequently developed PEI.

All participants present with persistent gastrointestinal symptoms and are undergoing evaluation with glucose, lactulose, and mixed triglyceride breath tests as part of routine clinical practice to investigate pancreatic exocrine function and the presence of small intestinal bacterial overgrowth (SIBO).