Renal artery dissection (RAD) is a serious vascular event involving the main blood vessel that supplies blood to the kidney. This condition occurs when the layers of the renal artery wall abruptly separate, severely compromising blood flow to the organ. Because the kidneys filter blood and regulate blood pressure, any disruption to their blood supply can lead to rapid and dangerous physiological changes.
Understanding the Mechanism of Dissection
The renal artery wall is composed of three layers: the inner tunica intima, the muscular tunica media, and the outer tunica adventitia. A dissection begins with a tear in the tunica intima, allowing high-pressure arterial blood to rush into the middle layer. This influx of blood splits the layers apart.
When blood enters the space between the intima and media, it creates a new channel known as a false lumen. This false lumen expands with every heartbeat, rapidly compressing the original, or true, lumen of the artery. As the true channel narrows, blood flow to the kidney is severely restricted, causing ischemia. The false lumen can also lead to blood clot formation, further blocking the artery, or potentially causing the artery wall to rupture.
Recognizing the Warning Signs
The onset of renal artery dissection is marked by sudden and severe pain, which is the most common initial symptom. This discomfort is often localized to the flank, the side of the body between the ribs and the hip, or it may present as acute abdominal pain. The pain is frequently described as tearing or ripping.
A rapid rise in blood pressure, known as renovascular hypertension, is another frequent sign. This occurs because the kidney senses reduced blood flow and releases hormones to constrict blood vessels and raise systemic pressure. Other acute signs that may indicate compromised kidney function include hematuria (blood in the urine) and signs of a kidney infarct, where tissue dies due to lack of oxygen.
Identifying Underlying Causes
The most common underlying cause for spontaneous renal artery dissection, particularly in younger individuals and women, is Fibromuscular Dysplasia (FMD). FMD is a non-inflammatory condition causing abnormal cell growth within the artery walls, leading to structural irregularities and weakening. This disease primarily affects medium-sized arteries, most commonly the renal and carotid arteries.
Another group of causes includes pre-existing conditions that weaken the arterial wall structure. Atherosclerotic disease, characterized by the buildup of fatty plaques, makes the artery stiff and brittle, increasing the risk of a tear. Inherited connective tissue disorders, such as Ehlers-Danlos syndrome or Marfan syndrome, also compromise the integrity of the artery wall by producing abnormal collagen and elastin.
Blunt force trauma to the abdomen or lower back can also directly injure the artery. Injuries resulting from events like a motor vehicle accident or a fall may initiate a dissection.
Treatment Approaches and Outcomes
Immediate management focuses on stabilizing the patient and preserving kidney function. This begins with medical management, centered on controlling severe hypertension with antihypertensive medications to reduce stress on the damaged vessel wall. Anticoagulant or antiplatelet therapy may also be initiated to prevent blood clot formation within the compromised artery lumen or the false lumen.
The decision to escalate treatment depends on the severity of blood flow restriction and the patient’s symptoms. If the dissection causes significant kidney ischemia or hypertension remains uncontrolled, interventional procedures are considered.
Endovascular techniques, such as angioplasty with stenting, involve threading a catheter through the artery to deploy a mesh tube. This tube helps prop open the true lumen and seal the intimal tear.
In complex cases, or when the dissection involves branch arteries deep within the kidney, open surgical repair may be required to bypass the damaged segment. The long-term prognosis is influenced by the extent of permanent kidney damage. The main long-term concern is chronic renovascular hypertension, which requires lifelong monitoring and medication. Regular follow-up imaging of the renal arteries is necessary to ensure the dissection does not reoccur or lead to complications like aneurysm formation.