Estimation of the 3-Day Faecal Fat Excretion and Fat Concentration as a Differential Test of Malabsorption and Maldigestion

Abstract

The diagnostic efficiency of estimating the faecal fat excretion and faecal fat concentration in uncontrolled 3-day collections was estimated from a prospective series of 87 consecutive patients. The diagnoses were established on the basis of morphologic criteria, and the assimilation was established from the faecal ¹⁴C-triolein/³H-oleic acid test. These investigations showed the diagnostic sensitivity of the 3-day faecal fat excretion to be 90%. The 3-day mean faecal fat concentration was ⩽5.1% w/w in patients with normal lipid assimilation. Of the patients with malassimilation 90% had a faecal fat concentration ⩾5.1% w/w. The faecal fat concentration was especially high in patients with maldigestion. When 10% w/w was used as the discrimination level between malabsorption and maldigestion, the faecal fat concentration correctly distinguished between these in 66% of the patients with malassimilation. The day-to-day variation of the faecal fat concentration was modest. Diagnosis of the lipid assimilation as estimated by the 1-day faecal fat concentration agreed with the diagnosis of the mean 3-day faecal fat concentration in 115 of the 122 1-day samples. The 1-day faecal fat concentration seems useful as a first screening test when malassimilation is suspected.

Key Words:

• Digestion
• faecal analysis
• malabsorption
• ³H-oleic acid
• ¹⁴C-triolein