Diagnostic Ultrasound - Abdomen and Pelvis

Renal Transplant Arteriovenous (AV) Fistula
TERMINOLOGY
Abbreviations
• Arteriovenous fistula (AVF)
Definitions
• Abnormal direct communication between artery and vein
IMAGING
General Features
• Best diagnostic clue
○ Focal area of increased color Doppler
• Location
○ Usually in renal parenchyma, may be extrarenal
• Size
○ Variable
• Morphology
○ Round when small, tubular when large
Ultrasonographic Findings
• Grayscale ultrasound
○ Not usually visible when small
○ Large AVFs are tubular serpiginous fluid filled structures
• Pulsed Doppler
○ Feeding artery shows high-velocity, low-resistance
waveform with spectral broadening
○ Pulsatile arterialized flow in draining vein when large
• Color Doppler
○ Focal aliasing at site of AVF
– Best detected when background normal color flow is
suppressed by using higher Doppler scale
○ Perivascular tissue vibration producing color in adjacent
tissues
Angiographic Findings
• Gold standard for diagnosis and first-line for treatment
• Abnormal communication between artery and vein with
early venous opacification
• More sensitive than ultrasound for complex AVF
Imaging Recommendations
• Best imaging tool
○ Color Doppler sonography for detection
○ Confirmed by characteristic Doppler waveform
• Protocol advice
○ Optimize detection by suppressing background normal
color flow
CTA and MRA
• Require injection of contrast media
• Arterial phase phase blush with early venous filling
DIFFERENTIAL DIAGNOSIS
Pseudoaneurysm
• Spherical intra- or extraparenchymal vascular lesion with
yin-yang flow on color Doppler
• Feeding artery shows to and fro waveform
Renal Artery Stenosis
• Narrowing of the renal anastomosis with increased peak
systolic velocity
• Poststenotic spectral broadening ± tardus parvus
PATHOLOGY
General Features
• Etiology
○ Complication of percutaneous transplant biopsy or
insertion of nephrostomy
○ Increased risk with number of biopsies, hypertension,
central renal biopsies, and renal medullary disease
○ Rarely surgical complication, usually anastomotic
• Associated abnormalities
○ AVF maycoexist with intrarenal pseudoaneurysm
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Most asymptomatic
• Other signs/symptoms
○ Hematuria
○ Clot colic causing urinary tract obstruction
○ Hypertension/renal dysfunction/heart failure from steal
phenomenon in large AVF
○ Rupture
Demographics
• Epidemiology
○ Post-biopsy incidence: 1-18%
Natural History & Prognosis
• 50% disappear within 48 hours,70% resolve spontaneously
within 1-2 years
• 30% symptomatic and persistent
• Extrarenal/sinus AVF larger, unlikely to resolve
spontaneously
Treatment
• Observation with serial ultrasound for majority
• Superselective embolization of the feeding artery (coils,
cyanoacrylate, glue)
• Surgery: Higher complication rate
DIAGNOSTIC CHECKLIST
Consider
• AVF when patients develop hematuria after renal
transplant biopsy
Image Interpretation Pearls
• High-velocity, low-resistance waveform with perivascular
color Doppler tissue vibration
SELECTED REFERENCES
1. Rodgers SK et al: Ultrasonographic evaluation of the renal transplant. Radiol
Clin North Am. 52(6):1307-24, 2014
2. Glebova NO et al: Endovascular interventions for managing vascular
complication of renal transplantation. Semin Vasc Surg. 26(4):205-12, 2013
3. Dimitroulis D et al: Vascular complications in renal transplantation: a singlecenter
experience in 1367 renal transplantations and review of the
literature. Transplant Proc. 41(5):1609-14, 2009
4. Kobayashi K et al: Interventional radiologic management of renal transplant
dysfunction: indications, limitations, and technical considerations.
Radiographics. 27(4):1109-30, 2007
Diagnoses: Kidney Transplant
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