Diagnostic Ultrasound - Abdomen and Pelvis
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Diagnostic Ultrasound - Abdomen and Pelvis

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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 575

Renal Transplant Pseudoaneurysm Diagnoses: Kidney Transplant TERMINOLOGY • Contained rupture secondary to defect in artery wall IMAGING • Usually in renal parenchyma, rarely extrarenal • Usually ≤ 1 cm • Extrarenal pseudoaneurysm (PA) may be larger • Mimics simple or complex renal cyst • High velocity jet into sac with internal turbulent flow • To-and-fro waveform in neck • Swirling yin-yang internal flow • Saccular, round or ovoid • Pulsations or swirling internal echoes • Internal clot when large • CTA/MRA ○ Outpouching from arterial lumen enhancing during arterial phase ○ Provide more information about state of arterial tree as well as size and morphology of pseudoaneurysm KEY FACTS TOP DIFFERENTIAL DIAGNOSES • Cyst • Arteriovenous fistula • Perinephric collection PATHOLOGY • Intrarenal: Iatrogenic injury during biopsy or percutaneous procedure CLINICAL ISSUES • Most asymptomatic • Hematuria, abnormal renal function • Pain, bleeding/hypotension from rupture DIAGNOSTIC CHECKLIST • Increased risk of rupture when extrarenal and > 2 cm • Always turn on color Doppler when evaluating renal cystic lesions (Left) Longitudinal color Doppler ultrasound shows a pseudoaneurysm ſt in the lower pole of a renal transplant. Yin-yang internal swirling flow is present. Color aliasing is noted in the feeding artery st. (Right) Longitudinal spectral Doppler ultrasound of a pseudoaneurysm ſt shows disorganized turbulent flow st at the base of the pseudoaneurysm. (Left) Longitudinal Doppler ultrasound shows a pseudoaneurysm ſt in the lower pole of a renal transplant. To-and-fro flow st in the neck is characteristic. (Right) Digital subtracted selective renal arteriogram shows a pseudoaneurysm ſt filling from a lower pole artery st. This was embolized. 576

Renal Transplant Pseudoaneurysm<br />

Diagnoses: Kidney Transplant<br />

TERMINOLOGY<br />

• Contained rupture secondary to defect in artery wall<br />

IMAGING<br />

• Usually in renal parenchyma, rarely extrarenal<br />

• Usually ≤ 1 cm<br />

• Extrarenal pseudoaneurysm (PA) may be larger<br />

• Mimics simple or complex renal cyst<br />

• High velocity jet into sac with internal turbulent flow<br />

• To-<strong>and</strong>-fro waveform in neck<br />

• Swirling yin-yang internal flow<br />

• Saccular, round or ovoid<br />

• Pulsations or swirling internal echoes<br />

• Internal clot when large<br />

• CTA/MRA<br />

○ Outpouching from arterial lumen enhancing during<br />

arterial phase<br />

○ Provide more information about state of arterial tree as<br />

well as size <strong>and</strong> morphology of pseudoaneurysm<br />

KEY FACTS<br />

TOP DIFFERENTIAL DIAGNOSES<br />

• Cyst<br />

• Arteriovenous fistula<br />

• Perinephric collection<br />

PATHOLOGY<br />

• Intrarenal: Iatrogenic injury during biopsy or percutaneous<br />

procedure<br />

CLINICAL ISSUES<br />

• Most asymptomatic<br />

• Hematuria, abnormal renal function<br />

• Pain, bleeding/hypotension from rupture<br />

DIAGNOSTIC CHECKLIST<br />

• Increased risk of rupture when extrarenal <strong>and</strong> > 2 cm<br />

• Always turn on color Doppler when evaluating renal cystic<br />

lesions<br />

(Left) Longitudinal color<br />

Doppler ultrasound shows a<br />

pseudoaneurysm ſt in the<br />

lower pole of a renal<br />

transplant. Yin-yang internal<br />

swirling flow is present. Color<br />

aliasing is noted in the feeding<br />

artery st. (Right) Longitudinal<br />

spectral Doppler ultrasound of<br />

a pseudoaneurysm ſt shows<br />

disorganized turbulent flow<br />

st at the base of the<br />

pseudoaneurysm.<br />

(Left) Longitudinal Doppler<br />

ultrasound shows a<br />

pseudoaneurysm ſt in the<br />

lower pole of a renal<br />

transplant. To-<strong>and</strong>-fro flow st<br />

in the neck is characteristic.<br />

(Right) Digital subtracted<br />

selective renal arteriogram<br />

shows a pseudoaneurysm ſt<br />

filling from a lower pole artery<br />

st. This was embolized.<br />

576

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