What is renal stenting?
A small metal tubular structure called a stent is inserted into the renal artery that supplies essential blood flow to the kidneys. The stent acts as scaffolding, keeping the artery stretched open and maintaining adequate blood flow through the vessel after it is opened with a balloon.
When does a patient’s condition require renal artery stenting?
Plaque build-up (atherosclerosis) and sometimes other abnormalities of the renal artery may cause enough narrowing or blockage so that blood supply to the kidney is reduced and the risk of kidney damage becomes very high. Because the kidneys serve as a filter to remove waste products and excess fluids from blood, the kidneys receive almost one third of the blood flow from the heart. The kidneys also play a major role in regulating blood pressure. If left untreated, renal artery stenosis can lead to a form of high blood pressure called renovascular hypertension, poor functioning of the kidneys, and/or kidney failure.
What tests can determine a need for renal artery stenting?
A renal arterial duplex ultrasound is a noninvasive test that uses sound waves to create an image of the renal arteries and to measure the speed at which blood flows through them in order to detect any narrowing or obstruction in the renal arteries. It is useful as a screening test and for follow up studies.
Computed tomography angiography (CTA) is a type of CAT scan that uses x-ray beams taken from different angles around the patient to create pictures of cross-sections of the body. Contrast medium is injected into the veins at the time of the CT scan so that the arteries will also be visualized. Using computerized techniques, the scanner can be programmed to show pictures of only the arteries, which is a CT angiogram.
A Magnetic Resonance Angiogram (MRA) is a variant of an MRI study that uses radio waves and a magnetic field to take pictures of blood vessels. Unlike CTA and invasive angiography, MRA does not use x-rays or any form of radiation. MRA also uses a different type of contrast medium that does not have the same potential for side effects and complications. Not all patients can have MRA.
A nuclear kidney scan, a form of radionuclide imaging, tracks a small amount of nuclear tracer as it moves through the renal arteries. Images are recorded and blockages or narrowing in the renal artery may be detected, but the test is only an indirect assessment of arterial blockage.
A renal angiogram, or arteriogram is an invasive procedure involving insertion of a catheter, usually through a leg artery, up to the renal arteries where contrast medium is injected and X-ray pictures are taken to show the inside of the renal vessels. A renal angiogram is the most accurate tests in the diagnosis of renal artery disease, and is used to pinpoint the location and severity of plaque build up and blockage.
How is renal artery stenting performed?
Renal stenting is a catheter- based procedure. The catheter acts as a guide to place the stent in the renal artery to open a narrowing or blockage. The stent is deployed at the time the blockage in the artery is dilated with a balloon. Stents come in a variety of strengths, sizes, and other properties. Stent selection for each procedure depends upon many factors, including the size of the artery, the location of the plaque build-up or blockage and the severity of arterial narrowing.
What should be expected after renal artery stenting?
Renal artery stents are exposed to blood flow and may cause clots to form until they become covered with tissue by the body. Medications are taken during this time, and possibly longer, to prevent thrombosis.
Sometimes new blockages develop in the renal arteries months or years later at a different site in a renal vessel. Occasionally, renal stents re-narrow (restenosis).
The usual recommendation for renal stent follow up is a diagnostic study at:
- Six weeks
- Six months
- One year
- Then Annually
STENTING FOR AORTOILIAC DISEASE
Peripheral arterial disease (PAD) affects huge population in the world per year. One subset of PAD is aortoiliac occlusive disease (AIOD). AIOD can occur anywhere from the distal aorta to the common femoral arteries and is therefore called an “inflow lesion.” Stenoses may be short- or long-segment, calcified, ulcerated, concentric or eccentric, single or multiple, unilateral or bilateral and may involve the aorta or iliac arteries alone or together. Hypoplastic aortoiliac syndrome is seen most commonly in female smokers, in which the atherosclerotic effects of smoking narrow an already small aorta and iliac arteries. Patients may have no symptoms, intermittent claudication (IC), or critical limb ischemia (CLI). Asymptomatic patients with PAD would be unlikely to benefit from endovascular or surgical treatment and may experience treatment-related complications, and, therefore, intervention should be limited to those with lifestyle-limiting claudication or limb-threatening ischemia.
IC of the legs is classically muscular pain brought on by activity and relieved by short rest. The prevalence of IC is 3% in those less than 40 and 6% in those older than 60.Intermittent claudication caused by AIOD typically involves the thigh/buttock and may cause male impotence. Patients with IC should have lifestyle-limiting symptoms and be expected to have reasonable symptom improvement from either endovascular or surgical revascularization prior to undergoing evaluation for revascularization.
CLI is defined as pain at rest and/or tissue loss. The differential diagnosis for rest pain includes diabetic neuropathy, complex regional pain syndrome, nerve root compression, and musculoskeletal disorders. In blue-toe syndrome, patients embolize distally, and this may occur even in the absence of claudication or significant stenosis. Symptoms must be present for more than 2 weeks to be considered chronic.
Risk factors for development of AIOD include nonwhite ethnicity, smoking, diabetes mellitus, dyslipidemia, hypertension, age, male gender, C-reactive protein elevation, hyperhomocystinemia, hyperviscosity/hypercoagulability, and chronic renal insufficiency. Optimization of modifiable risk factors is an important component of successful management of patients with AIOD.
The noninvasive methods for the evaluation for lower-extremity PAD include a focused history and physical examination, physiological ultrasound, computed tomographic angiography and magnetic resonance (MR) angiography. Patients with CLI should undergo an expedited vascular evaluation. The Society of Interventional Radiology standard of practice regarding physiological evaluation of extremity arteries suggests the use of segmental blood pressures, continuous Doppler waveforms, and/or volume plethysmography to evaluate for PAD. Color flow duplex ultrasonography may also be helpful to characterize stenoses, although in the aortoiliac system, this may be difficult based on patient body habitus. Computed tomographic angiography may be used to localize and diagnose severity of stenoses in individuals with PAD, especially in those with a contraindication to MR angiography. MR angiography should be performed with gadolinium. Impaired renal function prevents using gadolinium due to the association with nephrogenic systemic fibrosis.
Because of the usefulness and ready availability of noninvasive imaging modalities, catheter angiography is rarely used now as a primary diagnostic modality but rather as a problem-solving tool. When necessary, digital subtraction angiography should be used when evaluating the aorta, iliac, and runoff vessels. Digital subtraction angiography is most often combined with simultaneous endovascular treatment, when appropriate.
Smoking cessation and hyperlipidemia, diabetes, and hypertension management as well as antiplatelet therapy according to current treatment guidelines is recommended for asymptomatic patients. Aspirin and other antiplatelet agents (clopidogrel) are important to reduce the risk of cardiovascular events in those with PAD, but they have not been shown to reduce claudication. Also to be considered is the use of angiotensin-converting enzyme inhibiting medication for cardiovascular risk reduction in asymptomatic individuals with PAD. Smoking cessation and successful management of hypertension and dyslipidemia can slow the progression of PAD. Supervised exercise therapy may also be effective in some, especially older male patients.
Severe lifestyle-limiting claudication; rest pain, nonhealing ulcer, gangrene, or tissue loss; stenosis of the iliac system preventing other endovascular treatment; and decreasing renal function or hypertension in patients with renal transplant are indications for aortoiliac endovascular intervention. Contraindications include lack of symptoms, uncorrected anticoagulation, or operator inexperience with lack of appropriate surgical backup in the event of complication. Endovascular treatment options include angioplasty and/or stenting. After endovascular intervention, primary patency is defined as patency without any additional treatment. Many studies have shown that both angioplasty and stenting of infrarenal abdominal aortic stenoses, ileofemoral stenoses are safe treatments. Immediate complications include thrombosis, distal embolization, pseudoaneurysm, and arterial rupture. Long-term complications include stent fracture, intimal hyperplasia, and thrombosis.
UTERINE FIBROID EMBOLIZATION
Uterine fibroids are very common non-cancerous (benign) growths that develop in the muscular wall of the uterus. They can range in size from very tiny (a quarter of an inch) to larger than a cantaloupe. Occasionally, they can cause the uterus to grow to the size of a five-month pregnancy. In most cases, there is more than one fibroid in the uterus. While fibroids do not always cause symptoms, their size and location can lead to problems for some women, including pain and heavy bleeding.
Fibroids can dramatically increase in size during pregnancy. This is thought to occur because of the increase in estrogen levels during pregnancy. After pregnancy, the fibroids usually shrink back to their pre-pregnancy size. They typically improve after menopause when the level of estrogen, the female hormone that circulates in the blood, decreases dramatically. However, menopausal women who are taking supplemental estrogen (hormone replacement therapy) may not experience relief of symptoms
Uterine fibroids are the most common tumors of the female genital tract. You might hear them referred to as "fibroids" or by several other names, including leiomyoma, leiomyomata, myoma and fibromyoma. Fibroid tumors of the uterus are very common, but for most women, they either do not cause symptoms or cause only minor symptoms
These develop under the outside covering of the uterus and expand outward through the wall, giving the uterus a knobby appearance. They typically do not affect a woman's menstrual flow, but can cause pelvic pain, back pain and generalized pressure. The subserosal fibroid can develop a stalk or stem-like base, making it difficult to distinguish from an ovarian mass. These are called pedunculated. The correct diagnosis can be made with either an ultrasound or magnetic resonance (MR) exam.
These develop within the lining of the uterus and expand inward, increasing the size of the uterus, and making it feel larger than normal in a gynecologic internal exam. These are the most common fibroids. Intramural fibroids can result in heavier menstrual bleeding and pelvic pain, back pain or the generalized pressure that many women experience.
These are just under the lining of the uterus. These are the least common fibroids, but they tend to cause the most problems. Even a very small submucosal fibroid can cause heavy bleeding - gushing, very heavy and prolonged periods.
Prevalence of Uterine Fibroids
Twenty to 40 percent of women age 35 and older have uterine fibroids of a significant size. Uterine fibroids are the most frequent indication for hysterectomy in premenopausal women and, therefore, are a major public health issue.
Uterine Fibroid Symptoms
Most fibroids don’t cause symptoms—only 10 to 20 percent of women who have fibroids require treatment. Depending on size, location and number of fibroids, they may cause:
- Heavy, prolonged menstrual periods and unusual monthly bleeding, sometimes with clots. This can lead to anemia.
- Pelvic pain and pressure
- Pain in the back and legs
- Pain during sexual intercourse
- Bladder pressure leading to a frequent urge to urinate
- Pressure on the bowel, leading to constipation and bloating
- Abnormally enlarged abdomen
Imaging Expertise Enables Interventional Radiologists to Provide Gynecologists and Their Patients Better Diagnosis and Nonsurgical Treatment Options!!
Women typically undergo an ultrasound at their gynecologist’s office as part of the evaluation process to determine the presence of uterine fibroids. It is a rudimentary imaging tool for fibroids that often does not show other underlying diseases or all the existing fibroids. For this reason, MRI is the standard imaging tool used by interventional radiologists.
Magnetic resonance imaging (MRI) improves the patient selection for who should receive nonsurgical uterine fibroid embolization (UFE) to kill their tumors. Interventional radiologists can use MRIs to determine if a tumor can be embolized, detect alternate causes for the symptoms, identify pathology that could prevent a women from having UFE and avoid ineffective treatments. Using an MRI rather than ultrasound is like listening to a digital CD rather than a record – the quality is better in every way. By working with a patient’s gynecologist, interventional radiologists can use MRIs to enhance the level of patient care through better diagnosis, better education, better treatment options and better outcomes.
TAKE a Second Opinion Prior to Hysterectomy!!
For true informed consent before surgery, patients should be aware of all of their treatment options. Patients considering surgical treatment should also get a second opinion from an interventional radiologist, who is most qualified to interpret the MRI and determine if they are candidates for the interventional procedure. You can ask for a referral from your doctor or call our Interventional Neuroradiology & Endovascular therapy Department to know more about this!
Uterine fibroid embolization (UFE), also known as uterine artery embolization, is performed by an endovascular interventional radiologist, a physician who is trained to perform this and other types of embolization and minimally invasive procedures. It is performed while the patient is conscious, but sedated and feeling no pain. It does not require general anesthesia. The vascular interventional radiologist makes a tiny nick in the skin in the groin and inserts a catheter into the femoral artery. Using real-time imaging, the physician guides the catheter through the artery and then releases tiny particles, the size of grains of sand, into the uterine arteries that supply blood to the fibroid tumor. This blocks the blood flow to the fibroid tumor and causes it to shrink and die.
UFE Recovery Time
Fibroid embolization usually requires a hospital stay of one night. Pain-killing medications and drugs that control swelling typically are prescribed following the procedure to treat cramping and pain. Many women resume light activities in a few days and the majority of women are able to return to normal activities within seven days.
- On average, 85-90 percent of women who have had the procedure experience significant or total relief of heavy bleeding, pain and/or bulk-related symptoms.
- The procedure is effective for multiple fibroids and large fibroids.
- Recurrence of treated fibroids is very rare. Short and mid-term data show UFE to be very effective with a very low rate of recurrence. Long-term (10-year) data are not yet available, but in one study in which patients were followed for six years, no fibroid that had been embolized regrew.
Effect on Fertility
There have been numerous reports of pregnancies following uterine fibroid embolization, however prospective studies are needed to determine the effects of UFE on the ability of a woman to have children. One study comparing the fertility of women who had UFE with those who had myomectomy showed similar numbers of successful pregnancies. However, this study has not yet been confirmed by other investigators.
Less than two percent of patients have entered menopause as a result of UFE. This is more likely to occur if the woman is in her mid-forties or older and is already nearing menopause.
UFE is a very safe method and, like other minimally invasive procedures, has significant advantages over conventional open surgery. However, there are some associated risks, as there are with any medical procedure. A small number of patients have experienced infection, which usually can be controlled by antibiotics. These complication rates are significantly lower than those of hysterectomy and myomectomy.
Bronchial Artery Embolization
Life-threatening hemoptysis is one of the most challenging conditions encountered in critical care and requires a thorough and timely investigation. Despite advances in medical and intensive care unit management, massive hemoptysis remains a serious threat. Conservative management of massive hemoptysis carries a mortality rate of 50%–100%. The cause of death is usually asphyxiation, not exsanguination. The reported mortality rates for surgery performed for massive hemoptysis range from 10-20%. However, the mortality rate increases significantly, up to about 40%, when the surgery is undertaken as an emergency procedure.
Bronchial artery embolization (BAE) has become an established procedure in the management of massive and recurrent hemoptysis. The efficacy, safety, and utility of BAE in controlling massive hemoptysis have been well documented.
Definition and Causes
Massive hemoptysis has been described as the expectoration of an amount of blood ranging from 100 mL to more than 1,000 mL over a period of 24 hours, and the most widely used criterion is the production of 300–600 mL per day. However, depending on the ability of the patient to maintain a patent airway, a life-threatening condition may be caused by a rather small amount of hemorrhage. Thus, a more functional definition of “massive” as an amount sufficient to cause a life-threatening condition should be used in deciding whether to undertake interventional management.
Massive hemoptysis may result from various causes, and the frequency with which these causes occur differs greatly between the Western and the non-Western world. In the non-Western world, pulmonary tuberculosis, including tuberculosis bronchiectasis, is the most common underlying cause of massive hemoptysis. Bronchogenic carcinoma and chronic inflammatory lung diseases due to bronchiectasis, cystic fibrosis, or aspergillosis are the more prevalent causes of hemoptysis in Western countries. Other causes include lung abscess, pneumonia, chronic bronchitis, pulmonary interstitial fibrosis, pneumoconiosis, pulmonary artery aneurysm (Rasmussen aneurysm), congenital cardiac or pulmonary vascular anomalies, aortobronchial fistula, ruptured aortic aneurysm, and ruptured bronchial artery aneurysm.
The source of massive hemoptysis is usually the bronchial circulation (90% of cases) rather than the pulmonary circulation (5%).
Bronchial Artery Embolization
Prior to BAE, the number and origin sites of bronchial arteries from the aorta should be carefully evaluated to determine the optimal angiographic approach. This can be accomplished with a preliminary descending thoracic aortogram. Abnormal bronchial arteries are visualized on an initial thoracic aortogram in the majority of affected patients. A descending thoracic aortogram is also useful in the detection of nonbronchial systemic arteries that supply parenchymal lesions.
Angiographic findings in massive hemoptysis include hypertrophic and tortuous bronchial arteries, neovascularity, hypervascularity, shunting into the pulmonary artery or vein, extravasation of contrast medium, and bronchial artery aneurysm .
A variety of embolic materials are used for BAE. Absorbable gelatin sponge is widely used because it is inexpensive, easy to handle, and has a controllable embolic size. However, disadvantages of absorbable gelatin sponge are its resolvability and lack of radiopacity. Its use may lead to recanalization of the embolized artery and may sometimes be responsible for recurrent bleeding . Polyvinyl alcohol particles are nonabsorbable embolic materials, and particles 350–500 μm in diameter are the most frequently used worldwide. Their use may prevent the early recurrence of hemoptysis due to recanalization of the embolized artery, as might be anticipated with absorbable gelatin sponge.
BAE is very effective in controlling acute massive hemoptysis. Long-term recurrence rates have been reported to be 10%–52%. However, the long-term success rate can be improved with repeat BAE. Hemoptysis may recur after successful BAE if the disease process is not controlled with drug therapy or surgery because embolization does not address the underlying disease but rather treats the symptom. Massive hemoptysis constitutes a significant and often life-threatening respiratory emergency. Bronchial and nonbronchial systemic artery embolization is a safe and effective nonsurgical treatment for patients with massive hemoptysis. Knowledge of bronchial artery anatomy, together with an understanding of the pathophysiologic features of massive hemoptysis are essential for performing BAE. The pulmonary artery can be the source of massive hemoptysis in a minority of cases, and pulmonary arterial disease should be considered in cases of recurrent hemoptysis. CT scan is useful in diagnosing the disease that causes massive hemoptysis, localizing the bleeding site, and selecting vessels to be embolized. The patient can be then treated for the original disease that led to massive haemoptysis.