The present study demonstrated an increase in the expression of local matrix metalloproteinases in obstructed ureters compared with normals. The right question is which patient with the same degree of hydronephrosis will require a pyeloplasty. The difference of histopathological environment between obstructed and the normal UPJ junction is now clear. However, the problem is the difference of histologic analysis between segments from patients candidate for surgery and follow-up. As you stated, we are likely never able to solve this problem with tissue samples. Understanding the histopathology of this anomaly
may lead to the way to the use of the agonists or antagonists of certain mediators in the neonatal period to offer nonsurgical therapy choices, to play a critical role in evaluating therapeutic alternatives, and to establish postoperative or nonsurgical follow-up criteria.
The incorporation of urinary proteome analysis might generate a new hypothesis in the physiopathology of UPJ obstruction. Analysis of a newly identified urinary marker, proSAAS (proprotein convertase subtilisin/kexin type 1 inhibitor), could predict their clinical outcome in newborns with UPJ obstruction.