Molmenti’s Kidney and Pancreas Transplantation: Operative Techniques and Medical Management, 2e

CHAPTER 97: Vascular Imaging

Mariano M Volpacchio; Catherine A D’Agostino; Sofia Bakken; Christopher J Palestro; Robin J Warshawsky; Gregory M Grimaldi; John S Pellerito; Ernesto P Molmenti

INTRODUCTION

Ultrasound evaluation is a fundamental part of the vascular study of the transplant kidney
This is especially true with the use of Doppler capabilities
- Color Doppler allows depiction of the vessels and their anastomoses
- Duplex Doppler allows for
  - Hemodynamic evaluation through spectral analysis
  - Assessment of multiple vascular functional parameters
  - Noninvasive screening and detection of multiple potential abnormalities that may be ultimately be confirmed with computed tomography (CT) angiography, magnetic resonance (MR) angiography, or classic angiography (still the golden standard)
Although the resistive index (RI) was initially regarded as a specific parameter of graft rejection, subsequent studies and experience proved it could not fulfill its original promise. It is probably associated with both resistance and compliance
Mean normal RI is 0.6 and a value > 0.8 is considered abnormal
RI is currently considered a nonspecific marker of graft dysfunction
- It is usually elevated (> 0.8) in acute rejection, acute tubular necrosis, calcineurin inhibitor toxicity, and renal vein thrombosis
- It is usually decreased in instances of renal artery stenoses, arteriovenous (AV) communications
We routinely obtain a duplex Doppler ultrasound study in the immediate postoperative period upon arrival of the recipient to the postanesthesia care unit

RI = \frac{peak systolic (PSV) - end diastolic velocity (EDV)}{peak systolic velocity (PSV)}

Such evaluation provides very useful information of the status of the kidney immediately after surgery, and serves as a baseline for future imaging studies
Duplex Doppler ultrasonography should be the first imaging study (unless otherwise determined by the treating physician) in the evaluation of abnormal renal function

NORMAL STUDIES (FIGURES 97-1 TO 97-6)

FIGURE 97-1

Normal gray-scale ultrasound study. Note the renal artery (RA, red arrow) anastomosed in an end-to-side fashion onto the external iliac artery (iliac A, pink arrow). The external iliac vein (blue arrow) lies below the iliac artery. A small postoperative fluid collection also can be seen (yellow arrow). The green arrows outline the transplant kidney.

A radiograph of a patient for a normal grayscale study highlights the different arteries and vein. The radiograph highlights the outline of a transplant kidney in a horizontal manner at the top and indicated by various inward arrows. The right bottom corner within the outline consists of a small pouch of postoperative fluid collection indicated by a left arrow. The renal artery is connected in an end-to-side manner along with the external iliac artery in V-shape. The external iliac vein is visible on the right bottom corner, just below the external iliac artery.

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FIGURE 97-2

Normal duplex Doppler ultrasound study. The normal spectral waveform consists of a brisk systolic upstroke (V1) and high diastolic flow (V2). The resistive index (RI) of 0.67 is within normal limits.

A radiograph along with spectral waveform for Doppler ultrasound study of a patient. A radiograph of a patient for the main renal artery shows scattered irregular patches on a half white background within a cluster. A normal spectral waveform shows high and low fluctuations of brisk systolic upstroke V1 (maximum value) equals 0.475 meters per second, high diastolic flow V2 (minimum value) equals 0.156 meters per second, the resistive index RI equals 0.67, and S by D equals 3.04.

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FIGURE 97-3

Normal duplex Doppler ultrasound studies of transplant renal veins. Note the venous waveform with mild undulation reflecting normal right atrial pressure changes and mild phasicity reflecting normal respiration.