Complications of kidney transplantation

What vascular complications occur after kidney transplantation?

Various vascular complications affecting the transplant arteries and veins can develop after kidney transplantation. The main types include:

• Renal Artery and Vein Thrombosis (Renal Artery and Vein Thrombosis) — occurs predominantly in the early postoperative period.
• Renal Artery Stenosis (Renal Artery Stenosis) — typically a late complication.
• Segmental Infarction (Segmental Infarction) — manifests as an area of reduced echogenicity and vascularization.
• Arteriovenous Malformation (Arteriovenous Malformation) — often the result of prior percutaneous interventions.
• Post-Transplant False Aneurysm (Post-Transplant False Aneurysm / Pseudoaneurysm) — also frequently occurs after biopsy or nephrostomy.

What specific opportunistic infections affect renal transplant recipients?

Renal transplant recipients undergoing immunosuppressive therapy are affected by the following specific opportunistic infections:

• Cytomegalovirus (CMV) — the most common infection, resulting from the reactivation of a latent infection or transmission of the virus from the donor organ.
• Pneumocystis (Pneumocystis / PCP) — medical prophylaxis is prescribed to patients to prevent this disease.
• BK virus — also belongs to specific infections of the post-transplantation period.

What types of postoperative fluid collections around the transplant exist besides urinoma and lymphocele?

Besides urinoma and lymphocele, other fluid collections can form in the pelvis after kidney transplantation. These include:

• Hematoma — a collection of blood that can occur in the postoperative period.
• Seroma — a collection of serous fluid in the surgical area.

These fluid collections are often discovered incidentally during routine ultrasound examinations. Large collections can cause pain due to compression of neighboring structures and lead to transplant hydronephrosis.

What are the normal resistive index (RI) values on renal transplant Doppler ultrasound?

On renal transplant Doppler ultrasound, a resistive index (RI) value up to 0.8 inclusive is considered normal. An RI value > 0.8 in a renal allograft is considered abnormal. The normal Doppler waveform is characterized by low-resistance blood flow (ski-slope pattern), in which diastolic velocity is approximately one-third of systolic velocity. Decreased diastolic velocity and an elevated resistive index typically indicate a pathological process, although an isolated parameter lacks specificity.

What complications can occur during renal transplant needle biopsy?

Hemorrhagic and vascular complications can occur during renal transplant needle biopsy. The main ones include:

• Bleeding — the most frequent complication, which may be localized to the calyceal system (calyceal system), perinephric tissues (perinephric tissues), or retroperitoneum (retroperitoneum).
• Arteriovenous Malformation (Arteriovenous Malformation) and arteriovenous fistula (Arteriovenous Fistula) — areas of disorganized or high-velocity blood flow.
• Pseudoaneurysm (Pseudoaneurysm) — a false aneurysm communicating with the vascular bed.

What are the ultrasound findings of acute renal transplant rejection?

Specific gray-scale ultrasound findings of acute renal transplant rejection are not described in sources, but specialized techniques are used. In contrast-enhanced ultrasound (Contrast-enhanced US), a sign of acute rejection is an increased contrast medium inflow time (timing of inflow). This helps differentiate rejection from acute tubular necrosis. Meanwhile, standard spectral Doppler ultrasound has limited clinical value as it cannot reliably distinguish between these two conditions.