Nutcracker syndrome | |
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Other names | Nutcracker phenomenon, renal vein entrapment syndrome, mesoaortic compression of the left renal vein |
The nutcracker syndrome results from compression of the left renal vein between the aorta and the superior mesenteric artery. |
The nutcracker syndrome (NCS) results most commonly from the compression of the left renal vein (LRV) between the abdominal aorta (AA) and superior mesenteric artery (SMA), although other variants exist. [1] [2] The name derives from the fact that, in the sagittal plane and/or transverse plane, the SMA and AA (with some imagination) appear to be a nutcracker crushing a nut (the renal vein).
There is a wide spectrum of clinical presentations and diagnostic criteria are not well defined, which frequently results in delayed or incorrect diagnosis. [1] The first clinical report of Nutcracker phenomenon appeared in 1950. [3]
This condition is not to be confused with superior mesenteric artery syndrome, which is the compression of the third portion of the duodenum by the SMA and the AA.
The signs and symptoms of NCS are all derived from the outflow obstruction of the left renal vein. The compression causes renal vein hypertension, leading to hematuria (which can lead to anemia) [4] and abdominal pain (classically left flank or pelvic pain). [5] The abdominal pain may improve or worsen depending on positioning. [5] Patients may also have orthostatic proteinuria, or the presence of protein in their urine depending on how they sit or stand. [6]
Since the left gonadal vein drains via the left renal vein, it can also result in left testicular pain [7] in men or left lower quadrant pain in women, especially during intercourse and during menstruation. [8] Occasionally, the gonadal vein swelling may lead to ovarian vein syndrome in women. Nausea and vomiting can result due to compression of the splanchnic veins. [7] An unusual manifestation of NCS includes varicocele formation and varicose veins in the lower limbs. [9] Another clinical study has shown that nutcracker syndrome is a frequent finding in varicocele-affected patients and possibly, nutcracker syndrome should be routinely excluded as a possible cause of varicocele and pelvic congestion. [10] In women, the hypertension in the left gonadal vein can also cause increased pain during menses. [10]
In normal anatomy, the LRV travels between the SMA and the AA. [8] Occasionally, the LRV travels behind the AA and in front of the spinal column. NCS is divided based on how the LRV travels, with anterior NCS being entrapment by the SMA and AA and posterior NCS being compression by the AA and spinal column. [8] NCS can also be due to other causes such as compression by pancreatic cancer, retroperitoneal tumors, and abdominal aortic aneurysms. [8] Although other subtypes exist, these causes are more uncommon in comparison to entrapment by the SMA and the AA. [8] Patients with NCS have a tendency to have a tall and lean stature, as this can lead to a narrower gap between the SMA and the AA for the LRV. [11]
Nutcracker syndrome is diagnosed through imaging such as doppler ultrasound (DUS), computed tomography (CT), magnetic resonance imaging (MRI), and venography. [12] The selection of the imaging modality is a step-wise process. DUS is the initial choice after clinical suspicion based on symptoms. CT and MRI are used to follow up afterwards, and if further confirmation is necessary, venography is used to confirm. [12]
Although its ability to detect renal vein compression is dependent on how a patient is positioned during imaging, DUS is recommended as an initial screening tool as it has a high sensitivity (69–90%) and specificity (89–100%). DUS measures the anteroposterior diameter, and a peak systolic velocity at least four times as fast as an uncompressed vein is indicative of NCS. [6]
CT and MRI can be used afterward to confirm compression by the AA and SMA with comprehensive measurements of the abdominal vasculature. A "beak sign" can often be seen in CT scans due to the LRV compression. However, CT and MRI cannot demonstrate the flow within the compressed vein. These two modalities can be used to confirm other evidence for NCS such as back-up of blood flow into the ovarian veins. [11] [6]
If further confirmation is necessary, venography is used as the gold standard test in diagnosing nutcracker syndrome. A renocaval pullback mean gradient of >3 mmHg is considered diagnostic. Although this method continues to be the gold standard, values in unaffected individuals may be vary considerably, leading to some measurements in NCS patients to be similar to those in normal individuals. [12] This may be partly due to compensatory mechanisms in the vasculature as a result of the increased blood pressure. The invasive nature of the procedure is another consideration in comparison to DUS and CT/MRI as imaging modalities. [8]
Treatment depends on the severity and symptoms. In addition to conservative measures, more invasive therapies include endovascular stenting, [5] renal vein re-implantation, [14] and gonadal vein embolization. The decision between conservative and surgical management is dependent on the severity of the symptoms. [12] Conservative management is used if the patient is a child and the hematuria is mild. [11] In contrast, more severe symptoms such as reduced renal function, flank pain, and anemia are managed with surgical interventions. [11]
Conservative management is advised in children as further growth may lead to an increase in tissue at the fork between the SMA and AA, providing room for the LRV to pass blood without obstruction. [12] Treatment in this case involves weight gain to build more adipose tissue, decreasing the compression. Venous blood may also be directed towards veins formed as a result of the higher blood pressure, which may contribute to symptomatic relief for individuals as they age. [12] 75% of adolescent patients have been found to have their symptoms resolved after two years. Medications that decrease blood pressure such as ACE inhibitors can also be used to reduce the proteinuria. [12]
There are several different procedures available to manage NCS include:
LRV transposition is the most common procedure done followed by renal autotransplantation and LRV bypass. [6] In all cases for open procedures, data is limited for long term follow-up. With respect to LRV transposition, most patients stated improvement of symptoms 70 months following the procedure. [6]
Laparoscopic procedures involve laparoscopic spleno-renal venous bypass and laparoscopic LRV-IVC transposition. [12] They are uncommon in comparison to open procedures, but the outcomes of such procedures are similar to those of open procedures. [12] Although robotic surgery is possible, data on robotic procedures is limited concerning outcomes and cost-effectiveness. [12]
Endovascular interventions involve the use of stents to improve blood flow in the area of LRV impingement. [12] Following catheterization, venography is done to visualize the vasculature and can provide confirmatory diagnosis of NCS prior to stenting. [12] Following stenting, 97% of patients have had improvement of symptoms by sixth months following the procedure, and long term follow-up showed no recurrence of symptoms after 66 months. Although less invasive, risks involved include incorrect placement of the stent as well as stent dislodging and migration to the right atrium. [12] Furthermore, patients must be on anticoagulation therapy after stenting for three months. [12]
Angioplasty, also known as balloon angioplasty and percutaneous transluminal angioplasty (PTA), is a minimally invasive endovascular procedure used to widen narrowed or obstructed arteries or veins, typically to treat arterial atherosclerosis.
Interventional radiology (IR) is a medical specialty that performs various minimally-invasive procedures using medical imaging guidance, such as x-ray fluoroscopy, computed tomography, magnetic resonance imaging, or ultrasound. IR performs both diagnostic and therapeutic procedures through very small incisions or body orifices. Diagnostic IR procedures are those intended to help make a diagnosis or guide further medical treatment, and include image-guided biopsy of a tumor or injection of an imaging contrast agent into a hollow structure, such as a blood vessel or a duct. By contrast, therapeutic IR procedures provide direct treatment—they include catheter-based medicine delivery, medical device placement, and angioplasty of narrowed structures.
Vascular surgery is a surgical subspecialty in which vascular diseases involving the arteries, veins, or lymphatic vessels, are managed by medical therapy, minimally-invasive catheter procedures and surgical reconstruction. The specialty evolved from general and cardiovascular surgery where it refined the management of just the vessels, no longer treating the heart or other organs. Modern vascular surgery includes open surgery techniques, endovascular techniques and medical management of vascular diseases - unlike the parent specialities. The vascular surgeon is trained in the diagnosis and management of diseases affecting all parts of the vascular system excluding the coronaries and intracranial vasculature. Vascular surgeons also are called to assist other physicians to carry out surgery near vessels, or to salvage vascular injuries that include hemorrhage control, dissection, occlusion or simply for safe exposure of vascular structures.
A pseudoaneurysm, also known as a false aneurysm, is a locally contained hematoma outside an artery or the heart due to damage to the vessel wall. The injury passes through all three layers of the arterial wall, causing a leak, which is contained by a new, weak "wall" formed by the products of the clotting cascade. A pseudoaneurysm does not contain any layer of the vessel wall.
A varicocele is, in a man, an abnormal enlargement of the pampiniform venous plexus in the scrotum; in a woman, it is an abnormal painful swelling to the embryologically identical pampiniform venous plexus; it is more commonly called pelvic compression syndrome. In the male varicocele, this plexus of veins drains blood from the testicles back to the heart. The vessels originate in the abdomen and course down through the inguinal canal as part of the spermatic cord on their way to the testis. Varicoceles occur in around 15% to 20% of all men. The incidence of varicocele increase with age.
The renal veins in the renal circulation, are large-calibre veins that drain blood filtered by the kidneys into the inferior vena cava. There is one renal vein draining each kidney. Each renal vein is formed by the convergence of the interlobar veins of one kidney.
The celiacartery, also known as the celiac trunk or truncus coeliacus, is the first major branch of the abdominal aorta. It is about 1.25 cm in length. Branching from the aorta at thoracic vertebra 12 (T12) in humans, it is one of three anterior/ midline branches of the abdominal aorta.
In human anatomy, the superior mesenteric artery (SMA) is an artery which arises from the anterior surface of the abdominal aorta, just inferior to the origin of the celiac trunk, and supplies blood to the intestine from the lower part of the duodenum through two-thirds of the transverse colon, as well as the pancreas.
Inferior vena cava syndrome (IVCS) is a very rare constellation of symptoms resulting from either an obstruction, or stenosis of the inferior vena cava. It can be caused by physical invasion or compression by a pathological process or by thrombosis within the vein itself. It can also occur during pregnancy. Pregnancy leads to high venous pressure in the lower limbs, decreased blood return to the heart, decreased cardiac output due to obstruction of the inferior vena cava, sudden rise in venous pressure which can lead to placental separation, and a decrease in kidney function. All of these issues can arise from lying in the supine position during late pregnancy which can cause compression of the inferior vena cava by the uterus. Symptoms of late pregnancy inferior vena cava syndrome consist of intense pain in the right hand side, muscle twitching, hypotension, and fluid retention.
Renal vein thrombosis (RVT) is the formation of a clot in the vein that drains blood from the kidneys, ultimately leading to a reduction in the drainage of one or both kidneys and the possible migration of the clot to other parts of the body. First described by German pathologist Friedrich Daniel von Recklinghausen in 1861, RVT most commonly affects two subpopulations: newly born infants with blood clotting abnormalities or dehydration and adults with nephrotic syndrome.
May–Thurner syndrome (MTS), also known as the iliac vein compression syndrome, is a condition in which compression of the common venous outflow tract of the left lower extremity may cause discomfort, swelling, pain or iliofemoral deep vein thrombosis.
The testicular vein, the male gonadal vein, carries deoxygenated blood from its corresponding testis to the inferior vena cava or one of its tributaries. It is the male equivalent of the ovarian vein, and is the venous counterpart of the testicular artery.
The pampiniform plexus is a venous plexus – a network of many small veins found in the human male spermatic cord, and the suspensory ligament of the ovary. In the male, it is formed by the union of multiple testicular veins from the back of the testis and tributaries from the epididymis.
Chronic venous insufficiency (CVI) is a medical condition in which blood pools in the veins, straining the walls of the vein. The most common cause of CVI is superficial venous reflux which is a treatable condition. As functional venous valves are required to provide for efficient blood return from the lower extremities, this condition typically affects the legs. If the impaired vein function causes significant symptoms, such as swelling and ulcer formation, it is referred to as chronic venous disease. It is sometimes called chronic peripheral venous insufficiency and should not be confused with post-thrombotic syndrome in which the deep veins have been damaged by previous deep vein thrombosis.
Superior mesenteric artery (SMA) syndrome is a gastro-vascular disorder in which the third and final portion of the duodenum is compressed between the abdominal aorta (AA) and the overlying superior mesenteric artery. This rare, potentially life-threatening syndrome is typically caused by an angle of 6–25° between the AA and the SMA, in comparison to the normal range of 38–56°, due to a lack of retroperitoneal and visceral fat. In addition, the aortomesenteric distance is 2–8 millimeters, as opposed to the typical 10–20. However, a narrow SMA angle alone is not enough to make a diagnosis, because patients with a low BMI, most notably children, have been known to have a narrow SMA angle with no symptoms of SMA syndrome.
Ovarian vein syndrome is a rare condition in which dilation of the ovarian vein compresses the ureter. This causes chronic or colicky abdominal pain, back pain and/or pelvic pain. The pain can worsen on lying down or between ovulation and menstruation. There can also be an increased tendency towards urinary tract infection or pyelonephritis. The right ovarian vein is most commonly involved, although the disease can be left-sided or affect both sides. It is currently classified as a form of pelvic congestion syndrome.
In medicine, the median arcuate ligament syndrome is a rare condition characterized by abdominal pain attributed to compression of the celiac artery and the celiac ganglia by the median arcuate ligament. The abdominal pain may be related to meals, may be accompanied by weight loss, and may be associated with an abdominal bruit heard by a clinician.
Pelvic congestion syndrome, also known as pelvic vein incompetence, is a long-term condition believed to be due to enlarged veins in the lower abdomen. The condition may cause chronic pain, such as a constant dull ache, which can be worsened by standing or sex. Pain in the legs or lower back may also occur.
Pelvic compression syndrome is characterized by intermittent or persisting pain in the abdomen, which is exacerbated by abdominal pressure. A swelling of the veins in the valveless pampiniform plexus causes it.
Isolated superior mesenteric artery dissection (ISMAD) is a rare but potentially life-threatening condition that causes acute abdominal pain. It refers to a dissection that occurs solely in the superior mesenteric artery (SMA), typically spontaneously, and does not involve the aorta. Although aortic dissection can frequently extend into its peripheral territories, it is rare for these branches to have dissection without main aortic trunk involvement. The SMA is the most common site of dissection among visceral arteries compared to other gastrointestinal arteries.