Original articleFecal elastase-1 is useful in the detection of steatorrhea in patients with pancreatic diseases but not after pancreatic resection
Introduction
Malabsorption is present in several pancreatic, intestinal and biliary diseases, but it may be particularly severe in patients with pancreatic failure. The onset of malabsorption is a late consequence of the disease, and therefore the detection of malabsorption has only a limited role in the diagnostic work-up, since imaging techniques provide relevant information in earlier phases. In pancreatic disorders the quantification of malabsorption maintains its importance in the course of the follow-up, as an indication for therapy, and for the assessment of the efficacy of pancreatic enzyme supplements both in clinical trials and in every day practice.
The gold-standard for assessing malabsorption is the measurement of fecal fat balance during a 72 h stool collection. The assay requires the complete consumption of a diet with known fat content and an accurate collection of stools. It requires stool handling and homogenization (poorly accepted by laboratory staff) so that, even though methods such as near infrared reflectance analysis (NIRA) and more recently NMR have simplified the analysis [2], [3], it is scarcely used in clinical practice.
A different approach to the study of pancreatic dysfunction is represented the measurement not of products of digestion, but of pancreatic enzymes. Pancreatic enzymes may be measured at different levels along the digestive tract (pancreatic juice, duodenal aspirate, stools). The complete collection of juice in the duodenum after hormonal stimulation or after a test meal is considered the gold standard for pancreatic function assessment. It is in duodenal juice that a lipase activity less than 10% of normal has been shown to be associated with steatorrhea [4].
Fecal elastase-1(FE-1) is often used to assess pancreatic function. This assay is simple, quick, non-invasive, not influenced by the concomitant intake of pancreatic supplements and may be carried-out on a spot fecal sample. Elastase-1 is not significantly degraded during intestinal transit and its concentration in stools is five to six-fold compared with pancreatic juice, reflecting exocrine pancreatic function and intestinal water reabsorption [5], [6], [7], [8]. It can detect moderate to severe exocrine pancreatic dysfunction, before the occurrence of overt malabsorption and in this respect compares favorably with indirect tests, such as the pancreolauryl [9] or the PABA tests [10].
In chronic pancreatitis, low FE-1 values are consistent with the morphological changes found at magnetic resonance- or endoscopic retrograde- cholangio pancreatography [11], [12], [13], and are specific for pancreatic steatorrhea [14], so that FE-1 is recommended to identify the pancreatic origin of chronic diarrhea [15].
Only limited data exist on the operative characteristics of FE-1 in respect not to the diagnosis of pancreatitis but of pancreatic malabsorption. In other words, FE-1 has been compared with fecal fat excretion in patients with known pancreatic disorders only in small series [16], [17], and we have no reliable information on the relationship between FE-1 and fat losses. Even more limited are the data when pancreatic insufficiency is due to pancreatic resection, when fat malabsorption is due not only to reduced enzyme output, but also to extrapancreatic factors (e.g., acidic duodenal pH, bile acid precipitation, deranged mixing and stimulation).
Aims of our study were therefore to clarify the relationship between FE-1 values and fecal fat balance either in patients with chronic pancreatic disorders and in patients with a previous pancreatic resection, and the diagnostic efficacy of FE1 to detect malabsorption in these two groups of patients.
Section snippets
Patients
We studied patients affected by well defined pancreatic disorders (inflammatory, neoplastic, postsurgical or genetic) and with suspected malabsorption, referred to our third level national referral center for pancreatic disorders for investigation and/or treatment in the period January 2009–May 2011. The diagnosis was already clear before admission to the study, and neither FE-1 nor fecal fat output played a role in the diagnosis. A malabsorption was suspected in the presence of any of the
Results
Eighty-two patients (53 males) were enrolled, age range 10–85 years. Eighteen were diabetics. Their final diagnoses are reported in Table 1. Fecal weight was 252 ± 27.9 g/day (range: 23–1169). Fecal fat output (19.5 ± 2.2 g/day, range 0.5–84.8) was pathological in 50 patients.
FE-1 (137.3 ± 20.1 μg/g, range: 0.1–575) was normal in 24 patients, and consistent with pancreatic impairment in 58 (severe in 50, moderate in 8).
Table 2 shows the demographic characteristics (sex distribution and age) and
Discussion
FE-1 has been widely used in clinical practice for many years. However, the data of the present study are peculiar, since our target was not the diagnosis of a pancreatic disease, for which imaging techniques are certainly better, but the onset of maldigestion. We found the same relationship between steatorrhea and elastase in stools as the one previously reported between steatorrhea and lipase in duodenal juice [4]. Only an extreme reduction of the enzyme was associated with an increase in
References (24)
- et al.
Italian consensus guidelines for chronic pancreatitis
Dig Liver Dis
(2010) - et al.
Comparative analysis of fecal fat quantitation via nuclear magnetic resonance spectroscopy (1H NMR) and gravimetry
Clinica Chim Acta
(2009) - et al.
Elastase and chymotrypsyn B in pancreatic juice and feces
Clin Biochem
(1989) - et al.
Comparing the urinary pancreolauryl ratio and faecl elastase-1as indicators of pancreatic insufficiency in clinical practice
Pancreatology
(2005) - et al.
Rapid method for the determination of fat in feces
J Biol Chem
(1949) - et al.
High prevalence of exocrine pancreatic insufficiency in diabetes mellitus: a multicenter study screening fecal elastase 1 concentrations in 1,021 diabetic patients
Pancreatology
(2003) - et al.
Some patients with irritable bowel syndrome may have exocrine pancreatic insufficiency
Clin Gastroenterol Hepatol
(2010) - et al.
Near infrared spectrometry for fecal fat measurement: comparison with conventional gravimetric and tritimetric methods
Gut
(1989) - et al.
Relations between pancreatic enzyme ouputs and malabsorption in severe pancreatic insufficiency
N Engl J Med
(1973) - et al.
Fecal elastase 1: a novel, highly sensitive, and specific tubeless pancreatic function test
Gut
(1996)