01OverviewDefinition, clinical context and the essential points that orientate the chapter.
The exocrine pancreas supplies lipase, proteases, amylase and bicarbonate. Lipid digestion is usually affected most visibly, producing pale, oily, difficult-to-flush stool, but patients may not volunteer this description. Malabsorption contributes to sarcopenia, osteoporosis and deficiencies of vitamins A, D, E and K, while the underlying pancreatic disease also reduces intake through pain, nausea or cancer cachexia. Diabetes from pancreatic endocrine failure can coexist and requires care that accounts for inconsistent absorption and impaired glucagon response.
Faecal elastase is measured from a formed stool and reflects pancreatic secretion. A clearly low result supports PEI, whereas an intermediate result requires clinical review and often repetition; dilution from watery diarrhoea can produce a false low value. Cross-sectional pancreatic imaging is required to establish chronic pancreatitis, obstructing tumour, duct disease or postoperative anatomy but cannot quantify digestion alone. PERT supplies enteric-coated porcine enzymes. UK consensus recommends a substantial starting lipase dose with meals and snacks, then titration to symptoms and nutritional response. Acid suppression can be considered when adequate, correctly timed PERT remains ineffective, while other malabsorptive causes are assessed.
Key points
- Pancreatic exocrine insufficiency is inadequate delivery or activity of digestive enzymes and bicarbonate, causing maldigestion, weight loss and micronutrient consequences.
- Common settings include chronic pancreatitis, pancreatic cancer, pancreatic resection, cystic fibrosis and severe or necrotising acute pancreatitis; always identify the underlying pancreatic disease.
- Steatorrhoea is a late and variably recognised sign; bloating, abdominal discomfort, diarrhoea, excess wind, difficulty maintaining weight and fat-soluble vitamin deficiency may appear earlier.
- Faecal elastase-1 is the practical first-line test when diagnosis is uncertain, but watery stool can dilute the sample and a low result does not reveal the cause.
- In a high-probability setting such as pancreatic cancer or major pancreatic resection, do not withhold enzyme treatment while waiting for an imperfect faecal test.
- Pancreatic enzyme replacement therapy must be taken with every fat- or protein-containing meal, snack and nutritional supplement, spread through eating to mix with chyme.
- Do not routinely prescribe a low-fat diet because it can worsen energy deficiency; optimise enzymes and use a pancreatic specialist dietitian instead.
- If response is incomplete, check timing, dose, supply, adherence and gastric acidity, then investigate alternative or additional causes rather than escalating indefinitely.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Chronic pancreatitis
Progressive acinar destruction, duct obstruction and reduced bicarbonate delivery make chronic pancreatitis a common cause of pancreatic maldigestion.
Cancer and pancreatic surgery
Tumour, pancreatic resection and altered postoperative mixing reduce enzyme output or prevent enzymes meeting food at the correct intestinal site.
Cystic fibrosis and severe acute injury
Inherited thick secretions, pancreatic necrosis and other diffuse pancreatic disease can substantially reduce functioning exocrine tissue.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Insufficient enzyme delivery
Too little lipase, protease and amylase reaches the duodenum, or delivery is poorly synchronised with a meal.
- 2Maldigestion
Fat and other macronutrients remain in forms that cannot be absorbed efficiently, with fat digestion usually affected earliest and most visibly.
- 3Nutrient and energy depletion
Unabsorbed fat is lost in stool, while chronic calorie, protein and vitamin deficits drive weight loss and systemic consequences.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Bulky pale oily stool, droplets in the pan, floating or difficult flushing, offensive wind and urgency suggest fat malabsorption but may be absent until enzyme output is markedly reduced.
Unintentional weight loss, reduced muscle, fatigue, low albumin from combined disease, easy bruising or low-trauma fracture can reveal prolonged inadequately treated PEI.
Chronic calcific pancreatitis, pancreatic head cancer, duct obstruction, total or substantial resection and necrotising pancreatitis create a high pre-test probability even before classic stool symptoms.
Persistent loose stool or weight loss may reflect underdosing, taking capsules before or after rather than through food, missed snacks, supply interruption, acid inactivation or another diagnosis.
New hyperglycaemia alongside pancreatic structural disease and maldigestion suggests combined endocrine and exocrine damage; hypoglycaemia risk can be unpredictable after extensive loss.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Faecal elastase-1First step - Why
- Estimate pancreatic exocrine secretion using a practical non-invasive stool test.
- Interpretation and limitations
- Collect formed stool where possible; a low result supports PEI but watery dilution can falsely lower it, and the test neither identifies pancreatic anatomy nor excludes mild disease reliably.
- 02
Pancreatic-protocol CT or MRI - Why
- Identify chronic pancreatitis, malignancy, duct obstruction, atrophy and postoperative anatomy.
- Interpretation and limitations
- Structural abnormality supplies the cause and cancer risk context, but normal-looking imaging does not independently prove normal enzyme function.
- 03
Weight, anthropometry and dietetic assessment - Why
- Measure the functional nutritional effect of maldigestion and reduced intake.
- Interpretation and limitations
- Trend weight and muscle alongside intake, symptoms and disease state; body mass can remain high despite sarcopenia and micronutrient deficiency.
- 04
Fat-soluble vitamins and micronutrients - Why
- Detect replacement needs and consequences of chronic malabsorption.
- Interpretation and limitations
- Assess vitamins A, D, E and coagulation or vitamin K context plus calcium, magnesium, zinc, selenium, B12, folate and iron according to risk and local protocol.
- 05
Glycated haemoglobin and capillary glucose - Why
- Screen for pancreatogenic endocrine insufficiency and treatment instability.
- Interpretation and limitations
- Interpret with nutrition, anaemia and pancreatic anatomy; normal HbA1c can miss rapid change, while brittle glucose may reflect both insulin and glucagon loss.
- 06
Bone health assessment - Why
- Identify osteopenia, osteoporosis and fracture risk from malabsorption and chronic pancreatic disease.
- Interpretation and limitations
- Combine vitamin D, calcium, fracture history, smoking, alcohol, body mass and DEXA when indicated; correction requires adequate PERT as well as replacement.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Coeliac disease
Positive serology while eating gluten and compatible villous atrophy indicate mucosal malabsorption rather than primary pancreatic enzyme failure.
Bile-acid diarrhoea or SIBO
Post-ileal anatomy, specialist bile-acid testing or motility-related bacterial overgrowth may cause diarrhoea and weight loss with a normal pancreas.
Functional bowel disorder
Bloating and variable stool without weight loss, deficiency or pancreatic disease may support IBS; a low elastase in watery stool can be misleading.
Additional chapter-specific clues
Coeliac disease, bile-acid diarrhoea, bacterial overgrowth, short bowel and mucosal disease may coexist or produce similar symptoms and must be considered when treatment underperforms.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01DIAGNOSEConfirm PEI without missing the causeFirst stepMaldigestion, nutritional decline or a high-risk pancreatic condition raises suspicion of exocrine failure.+
- 1Clarify stool character, weight, diet, alcohol, smoking, pancreatitis, surgery, cancer symptoms, diabetes and current enzyme timing, then examine nutrition and jaundice.
- 2Use formed-stool faecal elastase when uncertainty remains, while commencing PERT empirically in a high-probability condition where delay would harm nutrition.
- 3Obtain pancreatic imaging or urgent cancer-pathway review appropriate to presentation; enzyme deficiency is never a substitute label for obstructing anatomy.
- 4Measure nutritional, micronutrient, glucose and bone consequences and refer to a pancreatic specialist dietitian.
02REPLACEMix adequate enzymes with every intakePEI is confirmed or clinically very likely and the patient eats or receives oral supplements.+
- 1Start an evidence-based lipase dose with main meals and half that amount with snacks, checking the exact capsule strength and current product availability.
- 2Teach the patient to take enzymes throughout the meal or supplement, not as one remote pre-meal dose, and never crush enteric-coated microspheres.
- 3Maintain an adequate varied diet and avoid routine fat restriction, using dietetic energy, protein and micronutrient support instead.
- 4Review stool, weight and meal-by-meal use early, increasing the dose rationally when larger or fattier meals remain inadequately covered.
03NON-RESPONSETroubleshoot persistent maldigestionSteatorrhoea, diarrhoea, bloating or nutritional decline persists despite prescribed PERT.+
- 1Reconstruct actual food and enzyme timing, including snacks, milky drinks, supplements, capsule strength, prescription supply and whether capsules are being chewed.
- 2Optimise dose and distribution, then consider a proton pump inhibitor through the specialist pathway if acid inactivation remains plausible.
- 3Investigate coeliac disease, bile-acid diarrhoea, bacterial overgrowth, infection, small-bowel disease, diabetes and cancer progression according to symptoms.
- 4EscalationUse objective weight and deficiency response to judge success, escalating to specialist nutrition support when oral treatment cannot maintain status.
Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
Pancreatin pancreatic enzyme replacement
Usually start at least 50,000 lipase units with meals and 25,000 with snacks, then titrate.Take throughout food, confirm product strength, do not crush enteric-coated granules, review porcine allergy and very high-dose risks, and follow current supply-substitution advice.
Proton pump inhibitor adjunct
Standard licensed acid-suppression regimen trialled after adequate PERT timing and dose review.Do not use as a substitute for sufficient enzymes; review indication and long-term magnesium, infection, fracture and interaction risks according to individual exposure.
Micronutrient replacement
Deficiency-specific oral or parenteral regimen prescribed with biochemical and dietetic monitoring.Avoid blind high-dose fat-soluble vitamins because accumulation can be toxic; persistent deficiency should trigger PERT, adherence and alternative-malabsorption reassessment.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Protein-energy malnutrition
Persistent maldigestion causes weight loss, sarcopenia, fatigue and impaired immune or wound function even without obvious steatorrhoea.
Fat-soluble vitamin and bone disease
Deficient vitamins A, D, E and K contribute to low bone density, coagulopathy, neuropathy and visual or muscular effects.
Reduced treatment tolerance
Undernutrition worsens recovery from pancreatitis or surgery and limits resilience during pancreatic cancer therapy, making objective dietetic follow-up important.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Review stool quality, urgency, bloating, meal-associated pain, enzyme use and weight after initiation and every clinically important change.
- Trend muscle function, dietary intake, fat-soluble vitamins and relevant minerals; symptom improvement alone may leave nutritional deficits unresolved.
- Check glycaemia periodically and after pancreatic surgery or disease progression, coordinating pancreatogenic diabetes care with meal absorption and hypoglycaemia risk.
- Assess bone and vitamin D risk in chronic disease, arranging DEXA and replacement when indicated by the specialist pathway.
- During national or local PERT shortage, verify dispensed strength and continuity at each contact and use NHS SPS or PSGBI substitution advice rather than rationing unsafely.
- Re-image or re-refer urgently when new jaundice, progressive pain, rapidly falling weight or changing diabetes suggests evolution of the pancreatic cause.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Elastase is concentration dependent
A watery specimen dilutes faecal elastase and may generate a misleading low result. Repeat on formed stool when the clinical setting does not fit.
Enzymes follow food
PERT works by mixing with chyme. Splitting capsules across a longer meal often improves contact more than taking the entire dose long beforehand.
Weight can mislead
A patient with obesity can lose substantial muscle and micronutrients without crossing an underweight BMI threshold; trajectory and function remain important.
Fat restriction compounds harm
Avoiding fat may reduce visible steatorrhoea while worsening calorie and fat-soluble vitamin intake. Treat maldigestion rather than concealing its stool sign.
PEI is a cause-finding diagnosis
A low elastase explains digestion but not why the pancreas failed. New PEI can be the first clue to obstructing malignancy or chronic pancreatitis.
11Common pitfallsFrequent interpretation and management errors.
- 01
Waiting for obvious steatorrhoea before considering PEI in pancreatic cancer or after major pancreatic resection.
- 02
Accepting a low elastase from profuse watery diarrhoea without checking dilution and clinical fit.
- 03
Prescribing one fixed capsule per meal without checking capsule strength, meal size, snacks and supplements.
- 04
Telling patients to take PERT before food but not explaining that doses should be distributed through the meal.
- 05
Restricting dietary fat and calories instead of optimising enzyme replacement.
- 06
Escalating PERT endlessly while missing coeliac disease, bile-acid diarrhoea, bacterial overgrowth or cancer progression.
- 07
Treating the laboratory deficiency without imaging or investigating its pancreatic cause.