Sometimes these fistulas can become narrowed or blocked, requiring urgent treatment in order for patients to continue receiving dialysis. A fistulogram is a test we perform at PVI to look for narrowing of blockages in the AV fistula. During the procedure, a small tube (catheter) is inserted into the AV fistula. A dye is then injected into the area to look for narrowing or blockages. If narrowing or blockage is discovered, another tube is inserted with a small balloon attached. The balloon is then positioned at the site of narrowing or blockage and inflated and deflated several times. In cases where there continues to be blockages, a metal tube (stent) is inserted to keep the vessel open and improve blood flow. Sometimes the fistulogram will show a blood clot blocking the vessel. In these cases a special drug or device is inserted into the area to dissolve the clot.