Table 3.

Characteristics of colon-derived solutes

CharacteristicColon-Derived SolutesNoncolon-Derived Solutes
Ratio of solute clearance to creatinine clearance in the native kidney of >224/32 (75%)a114/367 (31%)
Free fraction <10%15/32 (47%)a31/367 (8%)
Ratio of plasma ultrafiltrate level in patients on hemodialysis relative to control patients is >1049/60 (82%)a232/432 (54%)
Solutes with known chemical structure that are sulfate or glucuronide conjugates18/46 (40%)a36/383 (10%)
Solutes without known chemical structure presumed to be sulfate or glucuronide conjugates on the basis of results of sulfatase treatment23/38 (61%)a78/334 (23%)
  • a P<0.001 proportion of colon-derived solutes compared with noncolon-derived solutes. Clearance values and free fractions were compared for 399 solutes for which metabolomic peak areas were reported in both urine and plasma ultrafiltrate in at least eight out of 17 control patients. The ratio of average plasma ultrafiltrate levels in patients on dialysis and control patients was calculated for all of the 492 solutes classified as uremic. Solutes that are sulfate or glucuronide conjugates were identified by their chemical formula among 429 solutes with known chemical structure found in the urine of at least eight out of 17 control patients, and by sulfatase treatment among 372 solutes without known chemical structure found in at least three out of six treated urine samples, as described in the Materials and Methods.