In renogran report, right kidney, it reads- there is hold up of the activity in the collection system with complete wash out after lasix (furosemide). meaning?

No obstruction: The Lasix (furosemide) renal scan you had is good for differentiating a dilated collectong system from true obstruction. Sometimes urine will not clear immediately from the collecting system if there is some dilation, but this doesn't necesserily mean it is obstructed. Lasix (furosemide) is given to help flush out the radiotracer; if it washes out then there is no obstruction.