Abstract: A drainage bag (3), part of a dialysis set, comprises a wrapper (4), fluid-sealed, and a transparent pocket (10) superposed on a part of the wrapper (4); an edge of the pocket (10) has a first part (11a) which is fixed to the wrapper (4), and a second part (11b) which is free and delimits an opening of the pocket (10). The pocket (10) at least partially contains a drainage tube of the used dialysis liquid which is fluidly connected with an inside of the bag (3). The bag (3) keeps the tubing forming the dialysis set in a stable conformation both during a production process thereof and at moment of use, reducing a risk of endoluminal contamination of the dialysis set. The bag (3) is usable in particular for collection of a used and used peritoneal dialysis liquid.