Transient Exocrine Pancreatic Insufficiency or Misleading Tests?

A recent retrospective study (J Garah et al. JPGN 2019; 68: 574-77) showed that many cases of exocrine pancreatic insufficiency, based on a low fecal elastase (<200), resolved over ~6 months.

Background:

  • 17 of 43 children had adequate data and no other recognized comorbidities which could explain low elastase levels
  • In these 17 children the median age was 3 years
  • Presenting symptoms were failure to thrive, or diarrhea. Children with known etiologies (eg. cystic fibrosis, Shwachman-Diamond, cholestatic liver disease) were excluded.
  • Median elastase at time of diagnosis was 71

Key findings:

  • Median time for normalization of elastase was 6 months. Patients received pancreatic supplements until elastase normalized.
  • 11 of the 17 had values of elastase <100, and an additional two had values of 105.
  • In all 17 children without identifiable underlying diseases, the pancreatic insufficiency was transient.
  • Only two children had fat soluble vitamin deficiency associated with pancreatic insufficiency

The article discusses the use of elastase for diagnosis of pancreatic insufficiency in comparison to more direct/invasive testing which can be difficult to perform.  It is important to recognize that elastase values are often unreliable in the presence of diarrhea or if diluted by urine.  Repeated assays may be needed to have confidence that elastase

My take: This report identifies “transient pancreatic insufficiency” as a frequent explanation for many children and may represent a postinfectious etiology. Thus, if no comorbidity is identified, the prognosis is favorable in most children.

Sculptured Cypress Trees in Retiro Park, Madrid

Shwachman-Diamond Syndrome

A recent study provides an update on the variable clinical presentation of Shwachman-Diamond syndrome (SDS) (J Pediatr 2014; 163: 866-70).

SDS, an autosomal recessive disorder, is characterized by exocrine pancreatic dysfunction, bone marrow dysfunction, and predisposition to myelodysplasia/leukemia.  It is due to a mutation in the SBDS gene located on chromosome 7q11 (found in ~90% of classically presenting cases of SDS.

Using a North American Registry, the authors reviewed the records of 37 patients (all who have had mutations in SBDS gene). Key findings:

  • Neutropenia was evident at presentation in 30/37 (81%)
  • Only 51% had both neutropenia and steatorrhea at presentation
  • 24/37 (65%) had congenital anomalies: 3 with ventricular septal defects, 1 malrotation, 1 imperforate anus, 9 thoracic dystrophy (rib abnormalities), 2 with short arms/legs, 4 with metaphyseal dysplasia, 1 with Chiari malformation (type 1), 2 with testicular atrophy.
  • Medical comorbidities included elevated LFTs in 15, adrenal insufficiency in 1, hypopituitarism in 1, type 1 diabetes in 1, hypothyroid in 1, and eczema in 11.

Take-home message: Normal pancreatic imaging studies and normal fecal elastase do not rule out SDS. In addition, frequently there are associated anomalies and comorbidities.

Postgraduate Course Notes -Pancreatitis Module

When and how to assess pancreatic function: an update for clinicians –Sohail Z. Husain, MD (page 31)

Reviewed methods of detecting pancreatic insufficiency

Indirect (non-stimulatory) Methods

Stool:

  • Fecal Fat Analysis: Coefficient of fat absorption (CFA): (fat intake – fat in stool / fat intake) * 100
  • Normal > 93% (> 85% in less than 6 mo.
  • old)
  • 72 hr collection gold standard

ELASTASE-1: Stable, specific for human pancreas

  • Normal > 200 μg elastase/g stool
  • Particularly good for monitoring the development of PI in patients with CF
  • Low levels (false-positive) with diarrhea
  • Only detects severe PI

Other tests

  • Chymotrypsin: less sensitive; requires discontinuation of enzymes
  • Steatocrit: cheap; has low sensitivity
  • Serum
  • Breath
  • Direct (stimulatory)
  • Dreiling tube
  • Endoscopic pancreatic function testing (ePFT)
  • Secretin-enhanced MRCP (sMRCP)

Causes of Pancreatic Insufficiency

-85% of patients with Cystic Fibrosis have pancreatic insufficiency

Shwachman-Diamond Syndrome

  • Mutation in SBDS, found in ~90% of SDS patients
  • PI affects almost all SDS pts

Johanson-Blizzard syndrome (JBS): Key findings

  • PI
  • Severe developmental delay
  • Hypoplasia or aplasia of the nasal wings

Pearson marrow pancreas syndrome Key findings: Severe hypoplastic,macrocytic anemia,  Pancreatic insufficiency (due to pancreatic fibrosis)

Diagnosis: Clinical picture, High serum lactate/pyruvate,  Southern blot for mtDNA rearrangements

Other causes of pancreatic insufficiency

  • Chronic pancreatitis
  • Pancreatic obliteration after severe, acute pancreatitis
  • Pancreatic tumors
  • Celiac disease
  • Diabetes
  • IBD

Managing nutrition in cystic fibrosis: the role of the pediatric gastroenterologist  Sarah Jane Schwarzenberg, M.D. (page 41)

Good nutrition status correlates with better heights, better lung function, and better survival.  (Presentation did not delve into the issue of potential reverse causation.)

  • Patients with a Weight-for-Age percentile >50% at age 4 years reached a much higher height-for-age early in life and maintained this advantage into adulthood
  • Pulmonary function (FEV1%predicted) was much lower in CF patients with WAP<10% at age 4 years. This finding tracked through age 18 years.
  • Small bowel overgrowth is common in CF
  • Small bowel bacterial overgrowth contributes to poor nutritional intake and increased nutrient losses

Options to improve nutrition in CF

  • Review and optimize enzyme dose and adherence
  • Review patient’s diet with an experienced CF dietician
  • Consider adding a PPI to improve intestinal pH
  • Consider confounding disease
  • Evaluate for signs and symptoms of small bowel overgrowth and consider trial of metronidazole or rifaximin
  • Ask patient about abdominal pain
  • Evaluate for gastroparesis
  • Evaluate for DIOS
  • Consider non-CF gastrointestinal disease
  • Consider oral glucose tolerance test

Therapy to improve nutrition

  • Time-limited interventions
  • Behavior therapy to improve intake
  • Offer oral supplements
  • Consider cyproheptadine as an appetite stimulant
  • Consider a G-tube for nocturnal feeds
  • Consider Endocrinology consult

Beyond the Basics in the Management of Pancreatitis  –Aliye Uc, M.D. (page 51)

INSPPIRE To Study Acute Recurrent and Chronic Pancreatitis in Children-180 children from 14 centers enrolled to study the etiologies, epidemiology, natural history and outcome.

Pediatric Acute Recurrent and Chronic Pancreatitis-etiologies

  • Genetic (49%) (61 of 91 tested)
  • PRSS1-30%, CFTR-22%, SPINK1-14%, CTRC-3%
  • Obstructive (34%)
  • Idiopathic (20%)
  • Toxic-Metabolic (17%)
  • Autoimmune (3%)

Genetics of Pancreatitis:

1. PRSS1 (cationic trypsinogen): Autosomal dominant, 80% penetrance, Mutations are due to increased activation or decreased inactivation of trypsin (i.e. R122H, N29I).

2. SPINK1 (trypsin inhibitor): Autosomal recessive/complex inheritance, 2% have mutation, <1% have pancreatitis (i.e. N34S), Pancreatitis is dose-related (homozygous>>>het), Associated with other mutations (CFTR)

3. CFTR (>1700 mutations):

  • 2 Severe mutations = Cystic Fibrosis
  • 1 severe, 1 mild mutation = mild or atypical CF, ARP, CP
  • CF carriers = 3-4 fold increase risk in pancreatitis.
  • 1 any +SPINK1 = CFTR-associated pancreatitis
  • 1 any +divisum = CFTR-associated pancreatitis

4.New Modifier Genes in ARP and CP

  • CTRC (trypsin degrading enzyme)
  • CASR (a calcium-sensing receptor)
  • CLDN2 (tight junction protein on X chromosome)
  • CPA1 (Carboxypeptidase 1)  increased riskf for CP in younger patients

Management:

  • Unclear if antioxidants helpful for pain.
  • The role of pancreatic enzymes in CP is equivocal.

Diet

  • When to start feeds? depends on the severity of AP, OK to start early; correlate with clinical readiness, abd pain
  • What mode of nutrition? prefer enteral over TPN, NG vs. NJ
  • What to feed?  recent studies in adults with mild AP support full diet

(Moraes JM et al. J Clin Gastroenterol 2010 44:517)

No evidence that low-fat diet is helpful

IV Fluids: With acute presentation, Lactated Ringer’s preferred over Normal saline.

NG Suction

  • Not shown to decrease symptoms,mortality or hospital stay.
  • May be useful if: severe gastric distention, refractory nausea and vomiting, or obstruction seen on abdominal x-ray

Fluctuating Elastase Levels in Infants with Cystic Fibrosis

A recent study sheds light on the variability of elastase levels in both pancreatic sufficient (PS) and pancreatic insufficient (PI) infants with cystic fibrosis (CF) (J Pediatr 2013; 162: 808-12).

After eliminating infants who did not have elastase values prior to 3.5 months and after 9 months, the study consisted of 61 formula-fed infants who had been diagnosed with CF.  Diagnosis was established based on either a positive sweat test or having two known CF mutations.

Background: Pancreatic elastase is produced by pancreatic acinar cells and is not degraded during intestinal transit.  It can be measured while on pancreatic enzyme replacement therapy (PERT) because it is specific for human elastase rather than porcine elastase.  In addition, samples are stable at room temperature for weeks.

Among this cohort, 28 (46%) were homozygous for the F508del mutation. Infants were part of a large docosahexaenoic acid (DHA) study; as such, they were randomized to receive either standard formula or formula supplemented with DHA.  Monthly stool samples were collected.

Results:

  • Of 29 infants with initial fecal elastase <50 mcg/g, all had a value <200 mcg/g at one year.  However, 3 had a value >200 mcg/g at some time during the first year of life.
  • Of 36 infants with initial elastase <100 mcg/g, 32 had a level <100 mcg/g at 1 year.  Only one infant in this group had a value consistent with PS and this infant had a mutation associated with increased likelihood of PS.
  • Of 12 infants with initial values between 100-200 mcg/g, more variability was noted in their multiple samples.  This group accounted for the majority of infants who were reclassified from PI initially to PS after one year of life.  Among all 48 with values <200 mcg/g, 4 were considered PS at final evaluation.  However, 13 had values >200 mcg/g at some point.
  • 13 infants were considered PS at initial evaluation with a value >200 mcg/g.  At the study conclusion, 3 had values <180 mcg/g.
  • The majority of fluctuation in elastase values occurred during the first 6 months of life.

These results lead to the following conclusions:

  1. Fluctuations in elastase levels during the first year of life indicate that some infants with PS become PI and vice versa.  Retesting at one year of life is important.
  2. The authors recommend that all CF patients with elastase values below 200 mcg/g receive PERT.
  3. One can extrapolate these findings to other populations.  A single normal or abnormal elastase value may not indicate ultimately whether a patient will remain pancreatic insufficient or sufficient. Though, values <50 mcg/g are more likely to indicate persistent PI status.

The authors do provide some speculation regarding these fluctuations.  They note that “a fecal elastase obtained very early in life might not reflect the child’s true functional pancreatic status.  Intestinal mucosal damage can cause secondary pancreatic insufficiency by decreasing signaling of the pancreas from enteroendocrine cells.”

Related blog links:

References:

  • -JPGN 2007; 44: 219.  Use of elastase in CF.  Pancreas secretes elastase; not degraded & does not cross react with porcine elastase, thus allowing measurement even in individuals on enzyme treatment.  Excellent sensitivity/specificity.
  • -J Pediatr 2004; 145: 322 & 285,  A fecal elastase-1   >100mcg/g has a 99% predictive value for excluding pancreatic insufficiency.
  • -JPGN 2003; 36: 314, 392.  Fecal elastase-1 is marker for exocrince pancreatic function & enteropathy.
  • J Peds 2009; 155: supplement. Clinical practice guidelines for infants/children <2 years of age with CF:
  1. -routinely give salt 1/8-1/4tsp/day
  2. -measure elastase & supplement if PI
  3. -Dose: 2000-5000 units lipase per feed –can go as high as 2500 units/kg (max daily 10000 units/kg/day)
  4. -monitor & supplement ADEK
  5. -consider 7% saline Rx & azithromycin in symptomatic