Treating blood vessel problems after a kidney transplant

Vascular Complications After Kidney Transplantation: A Prospective National Multicenter Study - The DAN-PTRAIII Study

This effort will try catheter-based angioplasty and advanced imaging to see if they help kidney transplant recipients with graft dysfunction or stubborn high blood pressure from possible transplant blood‑vessel problems.

Quick facts

• Study type: Observational
• Enrollment: 60 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: University of Aarhus (other)
• Locations: 3 sites (Aarhus and 2 other locations)
• Trial ID: NCT07531966 on ClinicalTrials.gov

What this trial studies

This is a nationwide observational program in Denmark that applies uniform clinical and radiological criteria to identify arterial inflow and venous outflow problems after kidney transplantation. Patients who meet predefined clinical signs (graft dysfunction or persistent resistant hypertension) and radiologic criteria undergo catheter angiography with pressure measurements and intravascular ultrasound, and may receive percutaneous transluminal angioplasty (PTA). The project tracks short-term safety, procedural complications, and clinical outcomes including kidney function and blood‑pressure control. It also tests whether novel imaging and functional diagnostics predict which patients will respond to balloon treatment.

Who should consider this trial

Good fit: Ideal candidates are kidney transplant recipients with unexplained graft dysfunction or persistent resistant hypertension who meet the study's radiologic criteria for transplant arterial or venous lesions.

Not a fit: Patients whose graft problems are clearly due to rejection, obstruction, infection, or who lack radiologic evidence of vascular lesions are unlikely to benefit from the vascular-focused interventions in this program.

Why it matters

Potential benefit: If successful, this could improve blood flow to transplanted kidneys, lower resistant blood pressure, and reduce the risk of graft dysfunction or loss.

How similar studies have performed: Balloon angioplasty (PTA) is a well-established treatment for transplant renal artery stenosis and can improve blood flow, but evidence on long-term graft function, blood‑pressure control, and the added value of stenting or advanced predictive imaging remains mixed.

Eligibility criteria

Inclusion Criteria:

1\. At least one of the following clinical criteria (1 or 2) must be fulfilled:

1. Graft dysfunction, defined by at least one of the following:

   * Acute reduction in estimated glomerular filtration rate (eGFR) \>15% on two consecutive measurements at least 2 weeks apart, with other causes excluded (rejection, obstruction, infection).
   * eGFR \<50% of the expected value 30 days after kidney transplantation of unknown cause.
   * Decline in eGFR \>30% after initiation of an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker.
2. Persistent resistant hypertension for more than 6 weeks after kidney transplantation, defined as:

   * 24-hour ambulatory systolic blood pressure \>130 mmHg despite treatment with at least three classes of antihypertensive medication at maximally tolerated doses (including diuretics, if tolerated).

Together with at least one of the following radiological criteria:

1. CT or MR angiography demonstrating a lumen reduction ≥50%.
2. Doppler ultrasound showing:

   1. Peak systolic velocity in the renal artery ≥200 cm/s and a renal renal ratio (velocity at stenosis / velocity in distal artery) \>4.
   2. Acceleration time \>70 ms in intrarenal arteries.

2\. In cases of strong clinical suspicion of a vascular complication where CT or MR angiography cannot reliably exclude graft artery or vein stenosis, patients may be referred for confirmatory invasive investigations.

Before PTA, catheter-based angiography and translesional pressure measurements are performed to confirm whether the patient meets the radiological eligibility criterion for PTA:

1. Stenosis ≥70%.
2. Stenosis 50-69% if at least one of the following criteria is met:

   * Mean translesional pressure gradient ≥10 mmHg.
   * Systolic pressure gradient ≥20 mmHg.
   * Renal Pd/Pa ≤0.8.
   * If pressure measurements cannot be obtained, treatment is based on the operator's clinical judgement.

Exclusion Criteria:

1. Inability to provide informed consent.
2. Concurrent biopsy demonstrating rejection requiring treatment.
3. Pregnancy.
4. Previous PTA of the same vessel.
5. Patients unable to tolerate any form of antithrombotic therapy and therefore not eligible for stent placement.

Where this trial is running

Aarhus and 2 other locations

• Aarhus University Hospital — Aarhus, Denmark (RECRUITING)
• Rigshospitalet — Copenhagen, Denmark (RECRUITING)
• Odense University Hospital — Odense, Denmark (RECRUITING)

Study contacts

• Principal investigator: Mark Reinhard, MD, PhD — Aarhus University Hospital
• Study coordinator: Mark Reinhard, MD, PhD

Conditions: Kidney Transplant Recipient, Kidney Transplant, Complications, Transplant Renal Artery Stenosis, Renovascular Disease, Renal Transplant Graft Failure, Renovascular Hypertension, Heart Failure