Diagnostic Ultrasound - Abdomen and Pelvis

Transplant Renal Artery Thrombosis
TERMINOLOGY
Abbreviations
• Transplant renal artery thrombosis (TRAT)
Definitions
• Occlusion of transplant renal artery secondary to thrombus
IMAGING
General Features
• Best diagnostic clue
○ Absence of blood flow in renal artery
○ Absence of color flow in transplant kidney
• Location
○ Main artery or distal branch
○ May involve accessory renal artery causing segmental
ischemia
○ Important to know surgical vascular anatomy
– Single or multiple renal arteries
– End of graft artery-to-side of external iliac artery
anastomosis most common
– Patch of donor aorta (with single or multiple renal
arteries attached)-to-side of external iliac artery
– Venous interposition graft
– End of graft artery-to-end of internal iliac artery,
common iliac artery or aorta less common
Ultrasonographic Findings
• Grayscale ultrasound
○ Enlarged hypoechoic allograft
○ Hypoechoic peripheral wedge-shaped areas
• Color Doppler
○ Nonvisualization of entire renal transplant artery and
vein
– Diffuse absence of parenchymal perfusion on color or
power Doppler
– Segmental wedge-shaped peripheral areas of
decreased color flow when accessory or distal arteries
are occluded
○ Thrombosis of distal artery with patent flow proximally
(will progress to complete thrombosis)
• Spectral Doppler
○ Absence of Doppler signal in complete thrombosis
○ Blunted low-resistance waveforms in ischemic areas
(collateral flow)
○ Absence of venous flow
Imaging Recommendations
• Best imaging tool
○ US is first-line imaging modality for complications of
renal transplantation
• Protocol advice
○ Optimize color and spectral Doppler settings for slow
flow
DIFFERENTIAL DIAGNOSIS
Transplant Renal Vein Thrombosis
• Many features in common but arterial reversed diastolic
flow is present early in renal vein thrombosis
Acute Rejection/Acute Tubular Necrosis
• Markedly diminished flow in renal parenchyma with high
resistive index or reversed diastolic flow
Hyperacute Rejection
• Typically occurs during surgery or soon after resulting in
graft thrombosis
PATHOLOGY
General Features
• Etiology
○ Early postoperative period
– Surgical technique: Kinking, twisting, or dissection of
renal artery, trauma to iliac artery, thromboembolism
– Hypercoagulable state, hypotension
– Intentional or inadvertent ligation of small accessory
arteries
– Transplant torsion
○ Later: Severe rejection
Gross Pathologic & Surgical Features
• Infarcted kidney
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Abrupt onset of oliguria, decreased function, pain and
swelling of allograft
Demographics
• Epidemiology
○ Rare < 1%
Natural History & Prognosis
• Poor prognosis, graft loss is usual when single main artery is
thrombosed
• Accessory or segmental arterial thrombosis: Ischemia and
subsequent atrophy
Treatment
• Transplant nephrectomy
• Thrombectomy or thrombolysis rarely successful unless
diagnosis made early
DIAGNOSTIC CHECKLIST
Consider
• Severe acute rejection or tubular necrosis may cause
propagating small vessel thrombosis resulting in infarction
and mimic TRAT
Image Interpretation Pearls
• Urgent finding requiring prompt communication
SELECTED REFERENCES
1. Rodgers SK et al: Ultrasonographic evaluation of the renal transplant. Radiol
Clin North Am. 52(6):1307-24, 2014
2. Low G et al: Imaging of vascular complications and their consequences
following transplantation in the abdomen. Radiographics. 33(3):633-52,
2013
3. Eufrásio P et al: Surgical complications in 2000 renal transplants. Transplant
Proc. 43(1):142-4, 2011
Diagnoses: Kidney Transplant
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