SONOWORLD : Renal pseudoaneursym
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Vascular » Visceral vascular
Renal pseudoaneursym
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Presentation A 48 year old man with right renal transplant underwent an allograft biopsy. Three weeks later, he presents with pain over the right iliac fossa. An ultrasound with color Doppler was performed.
Caption: Color Doppler view of the lower pole of kidney.
Description: The anechoic lesion seen in the lower pole of the kidney completely fills with color. Flow is seen in a swirling pattern, compatible with a pseudoaneurysm.
Caption: Power Doppler study.
Description: Power Doppler view demonstrating the pseudoaneurysm.
Caption: Spectral analysis of the vascular lesion.
Description: An arterial waveform is noted, with an elevated peak flow velocity and high diastolic flow. This suggests the presence of a concurrent arteriovenous fistula.
Caption: Sagittal view of the transplanted kidney.
Description: A small, rounded anechoic area is seen in the lower pole of the transplant kidney. Minimal perinephric fluid is noted. A complex fluid collection [not shown] was also detected below the kidney.
Differential Diagnosis Renal pseudoaneurysm with an arteriovenous fistula.
Final Diagnosis Renal pseudoaneurysm with an AV fistula in the transplanted kidney.
Discussion Renal vascular complications following biopsy are more common in transplanted kidneys as compared to the native kidneys. Pseudoaneurysms and arterivenous fistulas are the most frequent complications. Color Doppler and spectral analysis are the initial methods of choice for the detection of these vascular lesions and are almost always diagnostic. These lesions usually pursue a benign course and close spontaneously, rarely requiring surgery. Intervention is required if the fistulas start to bleed, forming perinephric collections, or if they cause a steal phenomenon.

Pseudoaneurysms are diagnosed based on a characteristic anechoic area in the renal parenchyma, at the biopsy site. These fill up with color and show a ‘to and fro’ signal or a detectable bidirectional blood flow. Arterivenous fistulas are characterized by high frequency shift blood flow within the anechoic lesions. A study by Middleton, et al reported higher peak systolic flow velocities in the arteries supplying the fistulas, ranging from 55 to 180 cm/sec (mean, 92 cm/sec), while the range in normal arteries was 20-52 cm/sec (mean, 32 cm/sec). Our case also showed  high flow velocity in the range of 110 cm/sec. The resistive indices in these arteries were found to be lower than in the normal arteries due to high diastolic flow. Localized tissue vibration may also be seen, which is suggestive of flow turbulence.

Most of the studies conducted report spontaneous closure of these vessel abnormalities; however a few cases may need angiography and embolization or surgical repair. It is suggested that post percutaneous needle biopsy in allograft kidneys, periodical color Doppler of the allograft should be performed, as asymptomatic pseudoaneurysms and AV fistulas may be detected. Most of these can then be simply followed up, unless the discussed effects supervene.

Case References 1. Brandenburg VM, et al. Color-coded duplex sonography study of AV fistulae and pseudoaneurysms complicating percutaneous renal allograft biopsy. Clin Nephrol. 2002 Dec;58(6):398-404.
2. Yokoyama H, et al. Color Doppler ultrasound for detection of renal AV fistulas. Nippon Hinyokika Gakkai Zasshi. 2002 Jul;93(5):615-20.
3. Deane C, et al. AV fistulas in renal transplants: color Doppler ultrasound observations. Urol Radiol. 1992;13(4):211-7.
4. Middleton WD, et al. Postbiopsy renal transplant AV fistulas: color Doppler US characteristics. Radiology. 1989 Apr;171(1):253-7.
5. Gainza FJ, et al. Evaluation of complications due to percutaneous renal biopsy in allografts and native kidneys with color-coded Doppler sonography. Clin Nephrol. 1995 May;43(5):303-8.
6. Hubsch PJ, et al. Evaluation of AV fistulas and pseudoaneurysms in renal allografts following percutaneous needle biopsy. Color-coded Doppler versus duplex Doppler sonography. JUM 1990;9(2):95-100.
Follow Up In view of the complex collection in the right lower quadrant, probably secondary to the AV fistula, this patient underwent surgery. The hematoma was evacuated and the pseudoaneurysm was sutured. A follow up Doppler after four weeks revealed no abnormality.
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