Radiological Case

Incidental Renal Arteriovenous Malformation

Omar Daher, MD; Niharika Shahi, BS; David Kisselgoff, MD; Anatoly Shuster, MD

Disclosures

Appl Radiol. 2021;50(3):47-49. 

In This Article

Discussion

Renal AVMs are abnormal direct communications between intrarenal arterial and venous systems, avoiding flow through the capillary bed. They were first described in 1928 by Varela and are uncommon in the general population, representing approximately 1% of all AVMs.[1] Renal AVMs are congenital or acquired in etiology. The term "AVM" more commonly refers to the congenital type of vascular abnormality, whereas acquired malformations are usually referred to as arteriovenous fistulas.[2] Although congenital AVMs are more prevalent, their etiology is not well understood. It is thought that they may occur during the first trimester of gestation as a result of focal spontaneous errors in vascular development.[3]

Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu disease, was postulated to be associated with congenital renal AVMs.[4,5] A rare, autosomal dominant genetic disorder, HHT is characterized by spontaneous recurrent epistaxis, musculocutaneous and visceral telangiectasias and AVMs, with a strong family predisposition.[4,5] A clinically significant proportion of HHT patients have AVMs of the internal viscera. As recently shown, endoglin and activin receptor-like kinase 1 are likely correlated to the pathogenesis of congenital AVM formation.[4–6]

Acquired AVMs, on the other hand, can be idiopathic or develop as a sequela of trauma, percutaneous renal biopsy, ureteroscopy, previous partial nephrectomy, or renal malignancy.[7] In patients with hypertension following penetrating renal injury, AVMs may be found in one-third of cases; conversely, patients with AVMs are reported to have effects on the renin-angiotensin-aldosterone system (RAAS) and to develop hypertension resulting from secondary aldosteronism.[1,3]

The signs and symptoms of vascular renal lesions vary widely from asymptomatic to hematuria (72%), hypertension (50%), flank pain, abdominal mass, perinephric hematoma, flank bruit, and high-output heart failure.[1,6] Renal AVMs are usually found while investigating a patient presenting with gross hematuria; flank pain and hypertension are less common.[4]

Our patient complained mainly of lightheadedness and reported no hematuria, abdominal pain, or increased blood pressure at examination. However, the patient had a history of hypertension, which may have resulted from renal AVM owing to its impact on the RAAS.[1,3] The patient also had a history of bleeding diathesis, which was attributed to NSAID use. The significance of an underlying hematological disorder may potentially be further related to renal AVM formation. The patient had no other signs of renal function impairment, except for slightly elevated creatinine, but was found to have normocytic anemia, which eventually led to the diagnostic endoscopic procedure revealing a colon cancer.

Dedicated kidney arterial- and venous-phase CT is the preferred minimally-invasive imaging technique to identify and classify renal vascular abnormalities.[8] Doppler sonography and magnetic resonance angiography are also beneficial tools that reduce the need for radiation exposure and the use of iodine-contrast materials. Renal digital subtracted angiography remains the imaging "gold standard" for diagnosing renal vascular malformations.[2,3]

The goal of renal AVM treatment is to preserve the renal parenchyma while alleviating symptoms and maintaining hemodynamic stability. Asymptomatic or minimally symptomatic small peripheral AVMs with hemodynamic stability can be managed conservatively. Transcatheter arterial embolization has replaced major surgical intervention as the treatment of choice.[8] However, open surgery should be considered in cases related to malignancy and those in which patient anatomy is not favorable to endovascular treatment.[8]

The goal of embolization therapy is to occlude the abnormal arterial and venous connections while maintaining patency of the mainstem vessels.[9] Nephrectomy can be considered in complicated cases.[1,8,9] Successful treatment can resolve hematuria and cure or improve hypertension in 60–85% of patients.[5,9]

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