Deep Vein Thrombosis / Pulmonary Embolism
Deep vein thrombosis (DVT) is formation of a blood clot in the deep leg vein, and can lead to permanent damage to the leg (post-thrombotic syndrome) and life-threatening pulmonary embolism. Contractions of the muscles surrounding the deep leg veins and arterial-venous pumps help return blood to the heart against gravity. One-way valves prevent the back-flow of blood between contractions. Slowing of blood circulation due to illness, injury, or inactivity promotes clot formation. Interventional radiologists can treat DVT with catheter-directed thrombolysis, balloon angioplasty, or stenting. Catheter-directed thrombolysis involves inserting a catheter into a vein in the leg to deliver tPA to dissolve the blood clot. Patients who are not ideal candidates for catheter-directed thrombolysis can be treated with the insertion of an IVC filter, a small umbrella-like device inserted in the inferior vena cava to capture blood clots and prevent occlusion of vital vessels.
Peripheral Arterial Disease
Peripheral arterial disease (PAD) commonly results from atherosclerosis as cholesterol and scar tissue build up along vessel walls. Occlusion of the vessel lumen results in decreased blood flow to the legs, which can lead to intermittent claudication, and eventually gangrene and amputation. Symptoms include painful cramping in the leg or hip that occurs when walking or exercising and typically disappears when the person stops the activity, numbness or tingling in the legs/feet, and pain in legs/feet at night. Interventional radiologists can treat PAD using angioplasty and stenting, which involves inserting and inflating a balloon to open the narrowed artery and keeping the vessel open with a cylindrical mesh. Atherectomy can be performed which involves inserting a small catheter at the site of blockage that is able to "shave" the plaque from inside of the artery to re-establish normal blood circulation.
Vascular anomalies are a heterogenous group of conditions that can broadly be divided into vascular tumors and vascular malformations. The conditions that IRs are often asked to treat include lymphatic malformations, venous malformations, and arteriovenous malformations (AVMs). These lesions can cause patients pain and disfigurement as well as high-output heart failure and steal syndromes in the setting of AVMs. The main treatment options are surgical excision or sclerotherapy where an IR carefully infuses a sclerosant that destroys the abnormal vessels. Since surgery can be dangerous and not feasible for many of these lesions, many patients choose to undergo sclerotherapy.
Dialysis Catheters, Venography, and Declots
The kidneys are the master chemists of the body, filtering blood to remove toxins and balance electrolytes and fluid status. When the kidneys fail, they can be replaced via a variety of therapies, the most common being hemodialysis. This requires access to significant blood flow ~3xs per week to filter the blood externally and deliver it back to the body. Initially, IRs are often involved in placing a temporary catheter in the neck to facilitate this. However, if long-term replacement is required, patients often have a conduit surgically created between an artery and vein in the arm (an arteriovenous fistula). To guide this surgery, IRs inject contrast and map-out the venous anatomy of both arms (venography). Unfortunately, these fistulae are associated with clot formation that can cause them to malfunction. IRs can often salvage the fistula be breaking up the clots, called a "declot."
Renal and Genitourinary Interventions - Pre-Clinical Medical Student Guide (For video voice-over click here)
Kidney stones (nephrolithiasis) is a common problem that can be extremely painful. Smaller stones can pass on their own, and larger stones can be removed by urological procedures such as lithotripsy. However, some large stones (or tumors) can obstruct the out flow of urine, creating back pressure that can damage the kidneys. This is particularly problematic if there is a co-existing urinary tract infection, pressing bacteria back into the kidneys and bloodstream. Some of these patients are too sick to undergo a urological procedure to remove the stone or obstructing mass, so IRs can place a tube into the kidney to drain urine from behind the obstruction. This is called a percutaneous nephrostomy tube or "perc neph tube."
Varicose veins are enlarged, swollen vessels that develop when weak valves allow blood to flow backwards and pool. Symptoms include aching, throbbing, fatigue, and weakness that worsen as the day goes on. Interventional radiologists can treat varicose veins using endovenous ablation. In this procedure, laser or radiofrequency is applied via a catheter to the inside of the abnormal saphenous vein to seal it closed.
Portal hypertension is increased blood pressure in the portal vein, which connects the GI and spleen to the liver, and its branches and tributaries. Causes of portal hypertension include liver diseases such as cirrhosis and hepatitis, which decrease the portal vascular radius resulting in increased vascular resistance and portal blood pressure. Interventional radiologists can treat portal hypertension using a transjugular intrahepatic portosystemic shunt (TIPS) procedure. TIPS relieves high blood pressure in the portal system by creating a channel connecting the portal vein (which brings blood from digestive organs to the liver) to a hepatic vein (which carries blood from the liver back to the heart).
Bile Duct Obstruction
In patients with liver cancer, bile duct cancer, cholecystitis, cholangitis, or other hepatobiliary pathology, the bile duct may become blocked and bile cannot drain from the liver. A stent, a small metal cylinder, or catheter can be placed to help with biliary drainage.
Interventional radiologists play an integral role in the diagnosis and treatment of different cancers including bone, breast, kidney, liver, and lung. Pathological diagnosis remains the gold standard for diagnosis of most cancers. Interventional radiologists perform needle biopsies for definitive diagnoses. Interventional radiologists are also able to treat using methods such as ablations and chemoembolization.
- Radiofrequency ablation employs radiofreqency heat to "cook" and destroy tumor cells. Radiofrequency ablation can be used to treat kidney tumors, liver cancer, lung cancer, and adrenal cancer.
- Cryoablation uses extreme cold to freeze and destroy cancer cells. Cryoabation can be used to treat kidney tumors, liver cancer, and prostate cancer.
- Chemoembolization involves delivery of a cancer-killing drug through a catheter directly to the organ and embolization of arteries to the tumor to deprive the tumor of its blood supply and prevent the cancer-killing drug from flowing to other areas of the body.
Vertebral Compression Fractures
Vertebral compression fractures are often due to osteoporosis and commonly occur in the thoracic or lumbar spine. When pain from vertebral compression fractures fail to respond to conventional treatments such as analgesics, vertebroplasty and kyphoplasty are two available options. In vertebroplasty, medical-grade bone cement is injected into the spine to stabilize the collapsed vertebrate and reduce pain caused by bone rubbing against bone. In kyphoplasty, a balloon is inserted into the vertebrate to create a cavity before cement is injected.
Stroke and Carotid Artery Stenosis
Strokes are classified into two type: ischemic (caused by blood clots) and hemorrhagic (caused by blood vessel rupture). CT, MRI, and angiography can be employed to identify type of stroke and localize affected areas of the brain. Within the first three hours from onset of symptoms of an ischemic stroke, tPA (tissue plasminogen activator) can be given to dissolve the clot. Remember that tPA catalyzes the conversion of plasminogen to plasmin, which degrades fibrin clots. If tPA fibrinolysis cannot be performed within the first three hours, interventional radiologists can treat ischemic strokes through intra-arterial thrombolysis treatment. A catheter is inserted through the femoral artery and guided to the blood clot to deliver tPA directly or mechanically breakup the clot. Interventional radiologists can treat hemorrhagic strokes using tiny metal coils to embolize and block the abnormal vessel. The same technique can be used to treat aneurysms and AVMs.
Renal Artery Stenosis
Renal artery stenosis is often caused by atherosclerosis or fibromuscular dysplasia. It is a common cause of secondary hypertension. Stenosis decreases blood flow to glomerulus. Juxtaglomerular apparatus responds by secreting renin, which converts angiotensinogen to angiotensin I. Angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE). Angiotensin II raises blood pressure by contracting arteriolar smooth muscle (increasing peripheral resistance) and promoting adrenal release of aldosterone (which increases resorption of sodium in the distal convoluted tubule and results in expanded plasma volume).
Interventional radiologists can treat renal artery stenosis using balloon angioplasty or stenting. In angioplasty, a deflated balloon is tunneled to the narrowed artery then inflated to open up the vessel and restore blood flow. The addition of a stent strengthens vessels walls to prevent collapse of the artery.
Uterine fibroids are noncancerous growths that develop in the muscular wall of the uterus. Found in 20-40% of women age 35 and older, fibroids are the most common tumors of the female genital tract. Most women with uterine fibroids are asymptomatic, but 10-20% may experience symptoms such as heavy menstrual periods, pelvic pain, frequent urination (due to pressure on bladder), and abnormally enlarged abdomen. This latter subset of patients can be treated with uterine fibroid embolization (UFE), also known as uterine artery embolization (UAE). The interventional radiologist guides a catheter to the uterine arteries and releases small particles which occlude the fibroid's blood supply and shrink the tumor.
A common cause of female infertility is blockage or narrowing of the fallopian tubes through which eggs pass from the ovary to the uterus. In selective salpingography and fallopian tube recanalization, interventional radiologists thread a catheter to the fallopian tube to correct the blockage and allow passage of the egg to the uterus.