Faecal inflammatory markers after bariatric surgery

Roux-en-Y gastric bypass (RYGB) alters the gastrointestinal anatomy. This
influences food absorption, gut function and microbiome, also gastrointestinal
histological changes have been seen (1, 2). It may influence faeces
composition.
A recent study showed elevated concentrations of calprotectin, an inflammatory
marker, in the faeces of 87% of patients after RYGB (4). This may indicate the
occurrence of persisting (low-grade) gastrointestinal inflammation in the
majority of patients after RYGB.
Calprotectin is a protein mainly found in granulocytes, though also seen in
monocytes and epithelial cells. Faeces calprotectin testing is used in the
diagnosis and follow-up of inflammatory bowel diseases (IBD). This test must be
interpreted with caution after RYGB to prevent unnecessary invasive
endoscopies.
Other faecal inflammatory markers are lactoferrin and calgranulin-C (S100A12).
The latter being more specific for neutrophil granulocytes. Concentrations in
the faeces may be an indicator for infiltration of neutrophil granulocytes in
the gastrointestinal mucosa and gut inflammation.
Etiology and clinical relevance of the elevated faecal calprotectin after RYGB
is unknown. Also progression over time and place of issue of calprotectin has
yet to be investigated. If after bariatric surgery gastrointestinal
inflammation occurs, clinical relevance needs to be determined.
Some patients experience gastrointestinal complaints after RYGB, frequently
incompletely elucidated. It is unknown if these complaints are linked to the
concentration of inflammatory markers in the faeces. A frequently used method
to determine the degree of gastrointestinal complaints is by the
Gastrointestinal Symptom Rating Scale questionnaire. Persisting low-grade
gastrointestinal inflammation may partly explain these complaints.

The primary objective of this study is to determine the progression over time
of concentrations of faecal inflammatory markers before and after RYGB.
Secondary objectives
- To determine if patients with a sleeve gastrectomy have lower concentrations
of faecal inflammatory markers than patients with a RYGB.
- To determine the correlation between gastrointestinal complaints and
concentration of markers of inflammation in the faeces after bariatric surgery.

Prospective longitudinal cohort study.
Once before and 6 weeks, 6 months and 1 year after RYGB or sleeve gastrectomy a
faeces sample is obtained from patients and analysed for concentrations of
calprotectin, lactoferrin and calgranulin-C. At the same moments, patients
will fill in the GSRS to determine gastrointestinal complaints.

The burden and risk for the participating patients are low. Patients have to
collect a faeces sample and fill in a questionnaire once before and three times
after surgery and bring this to the hospital during regular follow-up. No extra
hospital visits of investigations are needed.