Changes in composition of the urine in ureter and bladder at low urine flow

Abstract

The movements of water and solutes across the ureter and bladder have been studied under conditions approximating those routinely used in physiological experiments at low urine flows. When the ureter and bladder are perfused at flows of less than 1 ml/ min. movements of water, urea, sodium, potassium, chloride, creatinine and hydrogen ion occur. The magnitude of these changes increases as the rate of perfusion is decreased or when urine is allowed to pool in the bladder. All movements of water and solute are in the direction of their concentration gradients. The movements are not affected by changes in antidiuretic activity, anaesthesia or surgical manipulation. Fluid collected from an indwelling Foley catheter draining continuously at a rate of 0.1 ml/min. may have an osmolality approximately 10% lower than that of the fluid entering the ureter and a urea concentration about 15% lower. When urine is allowed to accumulate in the bladder during 30-minute periods at the same flows, the changes may be 50–100% greater. At low urine flows, the composition of urine collected from the bladder does not accurately represent the composition of the urine as it leaves the kidney.