CHAPTER 67: Vascular Complications After Kidney Transplantation

INTRA-OPERATIVE DOPPLER

• An intraoperative Doppler Duplex ultrasound evaluation of the donor and recipient vessels can be obtained to document satisfactory flow after the kidney has been placed in the position where it will lay after closure of the abdomen.

• If flow is not satisfactory, consider:

  • Malpositioning of the allograft.

    • The kidney should be repositioned so that the renal artery and vein lie in a comfortable way with no kinks or twists

  • Anastomotic defects

    • Re-performing the arterial or venous anastomosis entails a delicate process that includes additional ischemic time.

    • Pathologies in the recipient native vessels such as atherosclerotic lesions, dissections, strictures, and thrombi

    • External compression

DUPLEX DOPPLER ULTRASOUND EVALUATION

A duplex Doppler ultrasound imaging study of the transplant kidney in the recovery room immediately after transplantation will evaluate and document:

• Adequate arterial and venous flow in the transplant renal vessels (both intra and extra parenchymal)

• Flow at the anastomoses

• Absence of hydronephrosis in the transplant kidney

• Adequate arterial and venous flow in the recipient vessels used for implantation of the allograft

• Collections (absent, present, actively expanding)

• Baseline findings that can serve for comparison with future studies.

ARTERIAL FLOW VELOCITIES

• Immediate postoperative period

  • Usually elevated (especially at the renal artery anastomosis)

    • In the absence of clinical findings suggestive of allograft dysfunction, they can usually be managed by clinical observation and follow up studies.

    • In cases of impaired function, additional diagnostic studies such as angiography (or MR or CT) are indicated.

• Short, intermediate, and long term postoperative period

  • If elevated, suspect arterial stenosis

    • Proceed with additional studies (angiogram, pressure measurements, CT, MR) to further evaluate

RESISTIVE INDEX

• RI range: 0–1 (or 0–100%)

• Normal arterial RI: 0.5–0.8

• Low arterial RI (<0.5) suggestive of

  • impaired flow (arterial strictures, kinks, twists, thromboses, external arterial compression)

    • characterized by diminished peak systolic velocity

  • arteriovenous fistulae

    • characterized by elevated peak diastolic velocity

• Elevated arterial RI (>0.8) suggestive of

  • Increased parenchymal resistance (ATN, rejection, edema),

  • Impaired outflow (venous thromboses external venous compression)

    • characterized by reversal of diastolic flow with RI > 1.0

• RI: >1 (>100%)

  • indicates reversal of diastolic flow

    • most frequent causes include

      • renal vein thrombosis in the setting of a still-patent renal artery and transplant kidney (a surgical emergency that should be addressed immediately in order to prevent the impending thrombosis of the transplant renal artery and allograft)

      • intra-parenchymal thrombosis in the setting of a still-patent renal artery (almost never correctable)

      • increased capillary resistance (associated with multiple factors such as ATN, edema, rejection)

ABSENT OR SEVERELY IMPAIRED FLOW TO THE TRANSPLANTED KIDNEY

• Constitutes an emergency

• Can result from:

  • Thrombosis of the transplant organ and/or its vessels

  • Twists or kinks in the vessels

  • Anastomotic defects

  • Impaired flow ...