Mechanism of urinary excretion of creatinine by the cat.

Creatinine and [14C]inulin clearance values were nearly the same during stop-flow and free-flow conditions in the cat. We conclude that glomerular filtration is the sole factor in renal excretion of creatinine in this species. Anatomic (bladder vs kidney) and dynamic (slow vs fast urine flow rate) studies indicated insignificant changes occurred in creatinine content of urine as it traversed the ureter and bladder of cats. We conclude that the cat ureter and bladder under conditions of moderate distension are relatively impermeable to creatinine.