Estimation of lipid assimilation from faecal samples using ¹⁴C-triolein as tracer and ⁵¹CrCl₃ as non-absorbable marker

Abstract

¹⁴C-triolein was investigated as tracer of dietary lipids from faecal measurements in 48 consecutive gastrointestinal patients. Simultaneously, ⁵¹CrCl₃ was investigated as non-absorbable marker. Faecal ⁵¹Cr was measured in a whole-body scintillation counter and faecal ¹⁴C by means of a combustion technique. This technique permitted accurate measurement of faecal ⁵¹Cr and faecal ¹⁴C in each stool collected over a 6-day period.

The investigation showed that the transit time of ⁵¹Cr was slightly shorter than the transit time of ¹⁴C-triolein in patients with high faecal excretion of ¹⁴C. Nevertheless, total faecal ¹⁴C, estimated from the ratio between ¹⁴C and ⁵¹Cr in two stools, correlated very closely with measured, cumulative faecal ¹⁴C (r = 0.99, P<0.001). ⁵¹CrCl₃ was therefore considered useful as a non-absorbable marker.

The ¹⁴C-labelling of triolein was stable during gastrointestinal transit. Qualitatively, estimated faecal ¹⁴C agreed with faecal fat diagnosing steatorrhoea in 97% (95% confidence limits 90–100%) of the patients with quantitative faecal collections. Quantitatively, a significant correlation with faecal fat was found (r = 0.82, P<0.001). The 95% tolerance limits of this correlation were identical with those of duplicate faecal fat measurements, which suggested much of the inaccuracy to be due to the inaccuracy of faecal fat measurements.

Key Words:

• ¹⁴C-triolein
• faecal measurements
• test of malabsorption