Thrombotic dysfunction is a common complication of tunneled cuffed catheters (TCC) leading to inadequate dialysis dose, need to catheter replacement with as consequence progressive exclusion of vascular sites. Thrombolytic agent can be used as therapeutic locking solution to dissolve the clotting formed in of around the catheter lumen. There are few studies on the optimal approach of TCC-related thrombosis with thrombolytic containing locking solution (dose, number of administrations, timing of administration - intra or interdialytic use). The primary objective of this retrospective study was to compare the efficacy of inter versus intradialytic Urokinase containing locking solution on restoration of the TCC blood flow. The investigators also assess the question of multiple administrations of Urokinase are more efficient than one single administration

Inclusion Criteria:

• Hemodialysis patients over 18 years old, receiving hemodialysis between 1st May 2010 and 31st October 2014 via a tunneled cuffed catheter at the Hemodialysis Unit of Universitair Ziekenhuis Brussel Hospital.

Exclusion Criteria:

• Patients younger than 18 years old
• Patients with a temporary dialysis catheter
• Patients who never received a tunneled hemodialysis catheter in this period
• Patients who didn't have a medical file at the Universitair Ziekenhuis Brussel Hospital

Incident and prevalent patients on hemodialysis, more than 18y old, receiving dialysis via a tunneled cuffed catheter between 1st May 2010 and 31st October 2014.