Renal arteriovenous malformation
Renal arteriovenous malformations (renal AVMs) are an uncommon vascular anomaly, which may be confused with a renal arteriovenous fistula (renal AVF).
Like arteriovenous malformations elsewhere in the body, a renal AVM is formed by connection between the arterial and venous structures, without flowing through a capillary bed. An AVM has a vascular nidus.
An arteriovenous fistula is similar, but in the kidney, AVFs are mostly due to trauma (usually iatrogenic from a renal biopsy). An AVF also does not have a vascular nidus.
Renal AVMs and AVFs may look similar on imaging, and given its relative scarcity, the best time to suggest an AVM in the diagnosis is if the patient does not have a history of trauma, as a history of a syndrome with other AVMs (e.g. Osler-Weber-Rendu syndrome), or has unexplained symptomatology (such as hematuria).
- irregular, hypoechoic region in the renal parenchyma
- may be confused with an irregular cyst or collecting system abnormality unless color Doppler is used
- Doppler: high flow lesion with possible pulsatility in the downstream draining renal vein
- well-marginated renal lesion that enhances similar to the blood pool
- early enhancement of the draining renal vein
- T2: well-marginated signal void
- T1 C+ (Gd): enhances quickly
Treatment and prognosis
Currently, the most common treatment of renal AVM (and AVF) is transcatheter embolization 2. Surgery can be performed if this fails or if there is associated malignancy.