Stable chronic hemodialysis patients are included in this observational study. After a midweek dialysis (test moment 1), the hemodialyzer is dried and scanned in a micro Computed Tomography scanner to quantify the number of patent fibers. All dialysis parameters are collected as well as the anticoagulation dose. During the same session, patients are asked about their bleeding and quality of life status. Four (test moment 2) respectively eight weeks later (test moment 3), patients are asked again for their bleeding and quality of life status using validated questionnaires.

All stable chronic hemodialysis (HD) patients having daytime dialysis in the Ghent University Hospital, are included.

From the patient's record, data are collected: demographic data (i.e. age, weight, dialysis vintage), blood data related to clotting (i.e. number of platelets, hemoglobin, International Normalized Ratio (INR), C-reactive protein (CRP)). All data is pseudomized.

The study has three test moments. During the entire study, patients are dialyzed with their usual dialyzer on their usual dialysis machine and with their usual dialysis settings and anticoagulation dosis. After the first midweek test session (test moment 1), the used hemodialyzer is rinsed with the standard rinsing procedure, dried in blood and dialysate compartment with positive pressure ventilation during 12-24h, eventually stored at 5°C, and finally scanned in a micro-CT scan in order to quantify the number of patent fibers. The dialyzer is vertically mounted on a rotating disc in front of the X-ray bundle. Scans are made every 0.15° with 2401 projections during 500ms each. After image reconstruction, visualisation are obtained from cross-sections of the hemodialyzer. Open fibers are counted with an open source computer program used for biological image analysis. By comparing the number of open fibers with the total number of fibers in an unused hemodialyzer, the percentage of open fibers can be quantified.

During the same week of the first test moment, several validated questionnaires will be completed: questionnaires about intention for bleeding (i.e. the International Society of Thrombosis and Haemostasis (ISHT) Bleeding Assessment Tool and the Hypertension, Abnormal Renal/Liver Function, Stroke, Bleeding History or Predisposition, Labile INR, Elderly, Drugs/Alcohol Concomitantly (HASBLED) score), and a questionnaire about quality of life (i.e. EuroQoL 5D (EQ5D)). Besides, a visual inspection is performed of the limbs of the patient in order to quantify bruising.

By comparing the percentage of open fibers with the administered anticoagulation dosis and the different questionnaires about bleeding, mutual relations can be drawn.

In order to check reliability, questionnaires and visual inspection are repeated after 4 weeks and 8 weeks (test moments 2 and 3).

Inclusion Criteria:

• treated with chronic daytime hemodialysis

Exclusion Criteria:

• no active infection at the time of inclusion

Stable chronic hemodialysis patients