Pathophysiologic basis of exocrine pancreatic dysfunction in childhood

Exocrine Pancreatic Insufficiency in Children - Challenges in Management

Cystic fibrosis (CF) is the leading etiology for exocrine pancreatic insufficiency (EPI) in children, followed by chronic pancreatitis, Shwachman-Diamond syndrome, and other genetic disorders. Management of EPI in children poses several unique challenges such as difficulties in early recognition, lack of widespread availability of diagnostic tests and limited number of pediatric-specific pancreatic centers. Pancreatic enzyme replacement therapy is the cornerstone of EPI management and in young children difficulties in administering pancreatic enzymes are frequently encountered. Patients with EPI also should be screened for fat-soluble vitamin deficiencies and receive appropriate supplementation. Among disorders with EPI in children, CF is the relatively well-studied condition, and most management recommendations for EPI in children come from expert consensus and conventional practice guidelines. The impact of EPI can be greater in children given their high metabolic demands and rapid growth. Early diagnosis and aggressive management of EPI prevent consequences of complications such as malnutrition, fat-soluble vitamin deficiencies, and poor bone health and improve outcomes. Management by multi-disciplinary team is the key to success.

Development of the human pancreas and its exocrine function

The pancreas has both endocrine and exocrine function and plays an important role in digestion and glucose control. Understanding the development of the pancreas, grossly and microscopically, and the genetic factors regulating it provides further insight into clinical problems that arise when these processes fail. Animal models of development are known to have inherent issues when understanding human development. Therefore, in this review, we focus on human studies that have reported gross and microscopic development including acinar-, ductal-, and endocrine cells and the neural network. We review the genes and transcription factors involved in organ formation using data from animal models to bridge current understanding where necessary. We describe the development of exocrine function in the fetus and postnatally. A deeper review of the genes involved in pancreatic formation allows us to describe the development of the different groups (proteases, lipids, and amylase) of enzymes during fetal life and postnatally and describe the genetic defects. We discuss the constellation of gross anatomical, as well as microscopic defects that with genetic mutations lead to pancreatic insufficiency and disease states.

Endoscopic Pancreatic Function Testing (ePFT) in Children: A Position Paper From the NASPGHAN Pancreas Committee

Endoscopic pancreatic function testing (ePFT) is one of the few ways to directly diagnose exocrine pancreatic insufficiency, and considerable confusion regarding indications, utility, and interpretation of the test remains. This position paper of the Pancreas Committee of the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition reviews the history and indications for ePFT in children. We compare various methods in current practice and determine their strengths and limitations, and based on data from children and adults we provide guidance on a protocol on how to perform ePFT in children. Lastly, we pose areas in need of further research relating to ePFT in children.

Paediatric pancreatic diseases

Paediatric pancreatic diseases are often under-recognised and may be associated with severe diseases and significant clinical consequences. In recent years, advances have been made in key areas, particularly with the contributions from international societies and study groups focused on paediatric pancreatic disease research. This review focuses on the two key manifestations of pancreatic disorders in childhood, pancreatitis and exocrine pancreatic dysfunction.

Transient Exocrine Pancreatic Insufficiency in Children: An Existing Entity?

OBJECTIVES

Pancreatic insufficiency in children is usually associated with diseases such as cystic fibrosis, Shwachman-Diamond syndrome, or chronic pancreatitis. Fecal elastase-1 is a reliable laboratory test for the diagnosis of exocrine pancreatic insufficiency (EPI). Transient pancreatic insufficiency has been rarely described and data on this entity are lacking in the medical literature. In this retrospective study we report 17 cases of transient pancreatic insufficiency presented mainly with failure to thrive and/or diarrhea.

METHODS

We followed 43 children (age range 1 month-18 years) with low fecal elastase-1 in our institution between the years 2009 and 2017. We followed growth and laboratory results (particularly, complete blood count, albumin, transaminases, celiac serology, sweat test, and fat-soluble vitamins). Elastase levels <200 mg/g were considered as pancreatic insufficiency.

RESULTS

Twenty-six were excluded due to missing data, a comorbidity or being syndromatic. Enrolled children (17) were all otherwise healthy.The median age at diagnosis was 3 years (range 0.2-15 years), 11 girls and 6 boys. Their main presenting symptoms were failure to thrive and/or diarrhea. Median fecal elastase-1 levels were 71 mg/g (range 18-160). Median time for normalization was 6 months (range 1-48 months). Abdominal sonography, celiac serology, and sweat test were normal for all patients. Most patients were treated with pancreatic enzymes until resolution.

CONCLUSIONS

Transient EPI without clear etiology should be in the differential diagnosis of EPI after ruling out known etiologies. The resolving course pattern may be attributed to an unidentified infectious agent. Further studies to assess the etiology are mandated.

The role, yield and cost of paediatric faecal elastase-1 testing

OBJECTIVE

Faecal elastase-1 (FE1) is a sensitive marker for exocrine pancreatic enzyme insufficiency. Pancreatic insufficiency (EPI) leads to maldigestion and subsequent poor weight gain. Thus, FE1 is performed as work-up for children with failure to thrive (FTT). However, EPI in the paediatric population outside of cystic fibrosis (CF) is rare. This study aimed to identify the indications for FE1 testing and their diagnostic yield in children. The secondary aim was to evaluate the cost per case of EPI detected for the various indications.

DESIGN

All FE1 tests performed on children (0-18 years) at a tertiary paediatric hospital in Sydney, Australia between 2010 and 2013 (inclusive) were identified. A retrospective chart audit was performed to identify the indication for testing FE1. The diagnostic yield based on FE1 cut-offs <200 and < 100 μg/g were assessed.

RESULTS

The most common indication for testing FE1 was "FTT only" (71/216, 32.9%), however, in this cohort of patients, FE1 was least likely to be positive with only 2 out of the 71 (2.8%) patients returning a positive result. In comparison, CF was the second most common indication for testing (60/216, 27.8%), but nearly half (48.8%) of tests returned a positive result in this cohort. The cost per case detected (FE1 <200 μg/g) reflected the test yield with an average cost per positive test of $262.50 (AUD2015) for FTT with short-gut syndrome and $420.00 (AUD2015) for CF-related indications.

CONCLUSION

Our study shows that for patients with isolated failure to thrive, FE1 testing is low yield and costly.

Towards the ideal quantitative pancreatic function test: analysis of test variables that influence validity

BACKGROUND & AIMS

Although pancreatic stimulation tests quantify acinar and ductal exocrine pancreatic function, no standard methodology exists. We evaluated the impact of several variables on test accuracy.

METHODS

We performed a retrospective analysis of pancreatic stimulation tests, which involved continuous stimulation with cholecystokinin and secretin, 3 sampling periods (20-min each), and perfusion markers to correct for intestinal losses. Results were recalculated using the following variables: no correction for losses; shortened sampling time (20-min); no correction and shortened sampling time; and enzyme concentration. We examined how these variables influenced measurements of pancreatic secretion and classification of pancreatic function status (sufficient or insufficient).

RESULTS

We analyzed 363 tests in control patients (20), and patients with cystic fibrosis (137), Shwachman-Diamond syndrome (40), or other pancreatic or intestinal disorders (166). Recovery of pancreatic juice varied markedly between tests (median, 59%; range, 4%-106%) and was significantly poorer during the first 20-minute period compared with the 2 subsequent periods (P < .01). Failure to correct for intestinal losses underestimated secretory capacity (median trypsin output reduced by >50%, P < .0001) and shortened sampling time increased test variability. Both variables together resulted in greater discrepancies. More than 25% of the pancreatic-sufficient patients with impaired pancreatic function were misclassified as pancreatic insufficient when uncorrected output plus a shortened sampling time or enzyme concentration were used to define categories.

CONCLUSIONS

Pancreatic function tests using brief aspiration periods without marker perfusion or measures of concentration greatly underestimate pancreatic secretory capacity and misclassify the clinical status of an unacceptably large number of patients.

Foregut mesenchyme contributes cells to pancreatic acini during embryonic development in a chick-quail chimera model

To understand causes of developmental abnormalities of the pancreas, it is essential to understand its normal embryonic development. Current understanding of the development of pancreatic exocrine tissue is that it develops solely from embryonic epithelium, while the role of the surrounding mesenchyme is to signal to this epithelium and form connective tissue. Recent work in our laboratory has shown that pancreatic bud mesenchyme can contribute cells to islets during embryonic development. However, no published studies have investigated in detail whether mesenchyme contributes cells to the exocrine structures of the pancreas. The aim of this study was to investigate whether cells from foregut mesenchyme can contribute to pancreatic acini during embryonic development. Chick-quail chimera recombinant organs were constructed using pancreatic epithelium and mesenchyme from either the pancreas (n=12) or stomach (n=25). These were cultured for 7 days in 3-D collagen gels. The resulting specimens were analysed using morphological criteria and fluorescent immunocytochemistry against pancreatic amylase, insulin, and the quail-specific nucleolar antigen QCPN. Two independent observers determined the origins of acini as either solely epithelial, solely mesenchymal, or of mixed origin. Results are expressed as percentages of total acini identified in each group. Statistical analysis was performed using chi(2) tests (P<0.01 was considered statistically significant). Recombinations of pancreatic epithelium and pancreatic mesenchyme yielded 11 acini, of which 45% were derived from epithelium only, 45% from mesenchyme only, and 10% of mixed origin. Recombinations of pancreatic epithelium and stomach mesenchyme yielded 78 acini, of which 40% were derived from epithelium only, 32% from mesenchyme only, and 28% of mixed origin. When acini with any mesenchymal cellular contribution were considered as a group, there was no significant difference between stomach and pancreatic mesenchymal contribution (P=0.72). This is the first study to demonstrate the cellular contribution of mesenchyme to pancreatic exocrine structures. Our data show that mesenchyme contributes cells to pancreatic acini during development in this model and that mesenchyme derived from stomach and pancreatic sources are both able to form acini.