The Hemodialysis Unit of the Hospital Ramon y Cajal is a pioneer in the implementation of a program of incremental hemodialysis, starting with two sessions a week in patients with residual renal function.

The main objective is to compare whether the initiation of hemodialysis with two sessions a week over conventional pattern of initiation of three sessions a week better preserves residual renal function.

The primary specific objective is to assess the loss of renal function defined as 24 hours diuresis less than 100 ml at 12 months of starting treatment. Secondary objectives are: erythropoietin dose, concentration of beta 2-microglobulin, p-cresol, fenol, the state of hydration and nutrition, adverse effects, hospital admissions, mortality and quality of life, comparing both arms of treatment.

DESIGN: Multicenter randomized clinical trial. Randomization will be performed by an external agent that guarantees an homogeneous balance between both arms. The randomization sequence will not be available for the investigators responsible of the patients.

Inclusion criteria: Patients starting hemodialysis that maintain residual diuresis and urea clearance greater than or equal to 2.5 ml / min with a minimum follow-up of one year.

Exclusion criteria: Anuric patients, patients with acute renal failure and patients who start hemodialysis after having going through a renal transplant.

The variables that will be analyzed are 24h diuresis, urea clearance, creatinin clearance, haemoglobin, leukocytes, platelets, creatinin, urea, Na, K, albumin, prealbumin, Ca, P, PTH, PCR, ferritin, B2microglobulin, BNP, KT/V, Erythropoietin dose, state of hydratation and life quality.

Sample size should be of 42 patients on each arm of treatment to obtain a 95% confidence (α=0,05) and a 80% of statistical power (β=0,20).

The normality of the data will be analyzed with Kolmogorov-Smirnov test which will allow to use parametric tests (T-student) or non-parametric tests (U-Mann-Whitney). Association of categoric variables of both arms will be analyzed with Chi2 test, or using Fisher statistic.

Loss of renal function will be analyzed up to 12 months and time studies will be performed through non-parametric test (Kaplan-Meier), obtaining the estimated probability of loss of renal function in both arms and comparing survival functions through "Log-Rank" statistic.

The demonstration of efficacy and safety through a clinical trial would spread this clinical practice in the nephrology community and therefore in our national health system.

Inclusion Criteria:

• Subjects starting renal replacement therapy from January 2017 to June 2018.
• Subjects who consent to sign the Informed Consent Form.
• Subject who maintain residual diuresis and urea clearance equal or superior to 2,5 ml/min.

Exclusion Criteria:

• Anuric patients.
• Patients with acute renal failure.
• Patients who revoke the Informed Consent Form.
• Patients who start hemodialysis after having going through a renal transplant.