Bowel Habits and the Association With Uremic Toxins in Non-Dialysis-Dependent Chronic Kidney Disease Patients.


Nutrition Program, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil; Hospital do Rim - Fundação Oswaldo Ramos, São Paulo, Brazil; Division of Nephrology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil. Electronic address: [Email]


OBJECTIVE : The aim of this study is to evaluate the association between bowel habits and microbial-derived uremic toxins p-cresyl sulfate (PCS) and indoxyl sulfate (IS) in patients with non-dialysis-dependent chronic kidney disease (NDD-CKD).
METHODS : This is a cross-sectional analysis including 43 nondiabetic NDD-CKD patients (58% men; 59.0 ± 13.5 years; estimated glomerular filtration rate, 21.3 ± 7.9 mL/min/1.73 m2). Bowel habit was assessed by the Bristol Stool Scale (BSS <3, characterized by hard consistency of stools and/or low frequency of evacuation and BSS ≥3, representing a more regular bowel habit) and by the Rome III criteria. PCS and IS (serum, free and total; urinary, total) were determined by high-performance liquid chromatography. Dietary intake was assessed by the 3-day food records.
RESULTS : The frequency of constipation assessed by BSS and Rome III criteria was 33% (n = 14/43) and 35% (n = 15/43), respectively. The BSS <3 exhibited higher PCS, independent of renal function and dietary protein-fiber ratio (β [95% confidence interval {CI}]: serum, total PCS = 1.54 [1.06-2.23], P = .02; serum free PCS = 1.40 [1.00-1.97], P = .05; urinary PCS = 1.78 [1.10-2.90], P < .02). According to the Rome III criteria, a tendency for a higher serum total PCS (β [95% CI]: 1.39 [0.95-2.03 μmol/L], P = .09) and a significantly higher urinary PCS (β [95% CI]: 1.80 [1.11-2.94 μmol/24 h], P = .02) was found in constipated participants. No effect of a compromised bowel habit (Rome III criteria or BSS) was found on IS.
CONCLUSIONS : Constipation may lead to production of PCS in nondiabetic NDD-CKD patients.

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