Continuing Education Activity

Nutcracker syndrome, or left renal vein entrapment, describes an uncommon condition involving compression of the left renal vein, usually between the aorta and the superior mesenteric artery. While uncommon, nutcracker syndrome is likely underdiagnosed and can lead to severe complications if left untreated. Symptoms of nutcracker syndrome in all age groups can include intermittent gross or microscopic hematuria, flank pain, orthostatic proteinuria, varices, and autonomic dysfunction. Women may develop pelvic congestion syndrome, dyspareunia, or dysmenorrhea, and men may have left-sided varicoceles; nutcracker syndrome may contribute to infertility in both sexes.

Diagnosing nutcracker syndrome can be difficult; a high index of suspicion is required. Nutcracker syndrome is predominately a clinical diagnosis confirmed by imaging studies to document the characteristic left renal vein compression. While a course of conservative treatment is recommended for all patients regardless of age, most adults with nutcracker syndrome will eventually require an interventional procedure to achieve symptom relief. Treatment is pharmacologic in the pediatric age group but is generally procedural in symptomatic adults. This activity reviews the etiology, epidemiology, pathophysiology, typical clinical presentation, evaluation, and management of nutcracker syndrome and emphasizes the role of the interprofessional team in caring for patients with this condition.

Objectives:

• Correlate the pathophysiology of nutcracker syndrome with the common clinical findings.

• Determine the most appropriate diagnostic methods to employ when evaluating a patient with suspected nutcracker syndrome.

• Select the most efficacious therapeutic intervention for a patient with nutcracker syndrome.

• Develop and implement effective interprofessional team strategies to improve outcomes for patients with nutcracker syndrome.

Introduction

Nutcracker syndrome, or left renal vein entrapment, is symptomatic compression of the left renal vein, often between the aorta and the superior mesenteric artery.[1] Compression of the left renal vein causes venous congestion of the left kidney and distal structures.[1][2] The clinical presentation of nutcracker syndrome is variable and may include flank pain, hematuria, proteinuria, varicocele, varices, dysmenorrhea, and, less commonly, hypotension and tachycardia.[3] Nutcracker syndrome can result in significant morbidity, including chronic renal disease and venous thrombosis.[4]

The anatomical finding of left renal vein compression between the aorta and superior mesenteric artery was first described by the anatomist Grant in 1937; de Schepper is frequently credited with naming the anatomical finding in 1972.[5][6][7] Nutcracker syndrome describes patients symptomatic from the anatomical anomaly; nutcracker phenomenon refers to the anatomic finding in the absence of symptoms.[1][5][8][9] Asymptomatic left renal vein compression found incidentally on imaging is considered a normal variant.

While nutcracker syndrome can affect all age groups, it is thought to peak during the second and third decades, concurrent with the completed maturation of the vertebral bodies. There are two main anatomical configurations of nutcracker syndrome: the more common anterior nutcracker syndrome, where the left renal vein is compressed between the aorta and the superior mesenteric artery, and the less common posterior nutcracker syndrome, where the left renal vein is compressed between the aorta and the vertebrae. Left renal vein compression can also occur from other causes, such as malignancy, lymphadenopathy, severe lordosis, intestinal malrotation, pregnancy, and rapid weight loss.[10]

Etiology

Nutcracker syndrome occurs when the angle between the aorta and the origin of the superior mesenteric artery is reduced to less than 40°, compressing the left renal vein.[11][12] The normal 4 to 5 mm space between the vessels is maintained by retroperitoneal adipose tissue and the third portion of the duodenum; thinner individuals are more likely to develop symptoms of nutcracker syndrome, and the syndrome is sometimes relieved with weight gain.[10][13]

The typical course of the left renal vein is anterior to the aorta, emptying into the inferior vena cava, and is much longer compared to the shorter right renal vein. In patients with nutcracker syndrome, the origin of the superior mesenteric artery may be more lateral or inferior than usual, contributing to the abrupt angulation. 

The left renal vein is a derivative of the anterior embryologic branch, as the posterior portion normally degrades. Degeneration of the anterior instead of the posterior segment, or posterior regression failure, can lead to a retroaortic or circumaortic left renal vein that can be compressed between the aorta and the spine.[14] 

Other vascular anomalies have been associated with nutcracker syndrome, including bifurcation and branching of the left renal vein.[15][16] Less frequent etiologies for Nutcracker syndrome include:

• External mass effect by adjacent lymphadenopathy or tumor
• High-grade lordosis
• Pregnancy
• Intestinal malrotation
• Significant weight loss, typically within a short period
• Abdominal aortic aneurysm[17][18][19]

A condition with a similar etiology is superior mesenteric artery syndrome, characterized by compression of the duodenum between the aorta and the superior mesenteric artery.[20] See StatPearls' companion reference "Superior Mesenteric Artery Syndrome" for more information.

Epidemiology

The incidence of nutcracker syndrome varies with age, and the prevalence is not well known.[21] Nutcracker syndrome is underdiagnosed due to nonspecific symptoms, variations in clinical presentation, and the absence of strict diagnostic criteria.[3][22][23] The age at diagnosis ranges from infancy through the seventh decade but exhibits a bimodal distribution with one peak during the second to third decade and another in middle age.[4][24][25] It is hypothesized that the rapid development of the vertebral bodies and increasing height during puberty may contribute to the narrowing of the angle between the aorta and superior mesenteric artery, accounting for the increased incidence of nutcracker syndrome in this group.[4]

The prevalence of nutcracker syndrome is equal between men and women, but men tend to be diagnosed at the earlier age of 24 years compared to women at 29 years.[3][24][26] Specific ethnic groups in the pediatric population with nutcracker syndrome may have a higher predisposition to hematuria.[27]

The prevalence of nutcracker phenomenon may be quite high. Studies report more than half of all asymptomatic individuals show a greater than 50% increase in the diameter of the left renal vein lateral to the superior mesenteric artery, attributed to superior mesenteric artery compression; this is considered a normal variant.[21][28][29] 

Pathophysiology

Anterior nutcracker syndrome, where the left renal vein is compressed between the aorta and the superior mesenteric artery, is the most common variant. An angle between the aorta and the superior mesenteric artery of less than 40° produces symptoms; less than 35° is considered definitive.[11][12][30][31][32] Posterior nutcracker syndrome is rare and usually involves a retroaortic or circumaortic left renal vein compressed between the aorta and the spinal column.[1][14][33]  Other rare variations of vessel orientation have been described.[14][34] 

Compression of the renal vein causes renal venous hypertension, resulting in the formation of collateral vessels. Persistent hypertension in collaterals adjacent to the collecting system can result in rupture and clinical hematuria, but in some instances, the collateral network diffuses the pressure. Venous collateralization may involve the left gonadal and the communicating lumbar veins, the renal capsular vein, and other nearby vessels.[3][35] Venous congestion involving the gonadal vein may cause pelvic congestion syndrome or varicoceles, which may relieve the elevated venous pressure in the renal vein. The symptoms associated with nutcracker syndrome are uncommon in persons with varicoceles, pelvic congestion syndrome, and other substantive collaterals.[14][36] See StatPearls' companion references "Pelvic Congestion Syndrome" and "Varicocele" for more information.[37][38] Hypertensive venous collaterals might link two underdiagnosed entities, nutcracker syndrome and May-Thurner syndrome. May-Thurner syndrome is compression of the left iliac vein, most commonly by the right iliac artery. See StatPearls' companion reference "May-Thurner Syndrome" for more information.[39]

Loin pain hematuria syndrome is another rare entity with overlapping etiology and clinical symptoms with nutcracker syndrome. Loin pain syndrome typically presents as loin pain radiating to the abdomen, medial thigh, or groin. As many as 40% of patients with loin pain syndrome may have nutcracker syndrome.[10]  

The hematuria sometimes seen in patients with nutcracker syndrome is thought to be secondary to the markedly increased left renal venous pressure inducing rupture of the small, thin-walled renal veins into the left renal collecting system, usually at the renal fornices.[1][13][14][40] Rupture between engorged left renal venous sinuses and the adjacent calyces may also occur. Hematuria may be mild or significant enough to warrant transfusion.[4][13][40] In addition, many patients diagnosed with idiopathic hematuria are subsequently found to have left renal vein compression.[8][24][28][29][41] 

The orthostatic proteinuria noted in some patients with nutcracker syndrome may be caused by positionally or posturally induced pressure increases in an already hypertensive left renal vein.[4][33][42][43][44][45] The increased pressure leads to higher levels of serum norepinephrine and angiotensin II, changes in the glomerular microcirculation that increase protein filtration, and low-grade immunological damage to the kidney.[4][33][43] Postural proteinuria from nutcracker syndrome is more commonly seen around the age of puberty.[44] 

Nutcracker syndrome is correlated with low body mass index (BMI), and symptoms might resolve with weight gain. The lack of supporting mesenteric and retroperitoneal fat aggravates renal ptosis and postural changes.[46][47] 

Symptoms of autonomic dysfunction in nutcracker syndrome are rare but include hypotension, syncope, and tachycardia.[1][48] Cases of nausea and weight loss, unexplained pelvic pain, and left flank pain with postprandial exacerbation have been described.[2][49][48] Anemia may be seen in patients with prolonged or significant hematuria.[4][5]

History and Physical

The most common symptoms of Nutcracker syndrome are unexplained intermittent gross or microscopic hematuria, left flank or abdominal pain, and proteinuria.[8][41][50][51][52] A study of 112 patients with nutcracker syndrome reported hematuria in 79%, left flank pain in 38%, varicocele in 36%, proteinuria in 31%, and anemia in 13%.[26] Women with nutcracker syndrome may exhibit symptoms secondary to dilated and incompetent ovarian and uterine veins, including pelvic pain, dyspareunia, dysmenorrhea, and incontinence. Patients with concomitant or resulting pelvic congestion syndrome often describe pelvic pain over the prior 6 months that worsens with standing; prior pelvic ultrasonography may have revealed dilated pelvic veins.[37][53] 

Nutcracker syndrome is often identified in taller, thinner patients who are otherwise healthy. The physical examination may reveal enlarged and tortuous lower extremity varicose veins.[49] Men with nutcracker syndrome may present with left-sided varicoceles that cause dull testicular pain, feelings of scrotal heaviness, or palpable lumps. Varicoceles are typically soft, conspicuous, compressible, nontender lumps above the testicle, often described as a "bag of worms." The physical examination of women may reveal vulvar or pelvic varices. 

Evaluation

Nutcracker syndrome is primarily a clinical diagnosis of exclusion; imaging will frequently confirm the clinical diagnosis.[4] Laboratory studies are frequently performed but are nondiagnostic. Gross or microscopic hematuria demonstrated by urinalysis requires an evaluation and serial hemoglobin measurements. Proteinuria in patients with a clinical diagnosis of nutcracker syndrome should be quantitatively evaluated with a spot urine protein to creatinine ratio or 24-hour urine collection. The vague symptoms of nutcracker syndrome are frequently initially evaluated with computed tomography (CT), which may reveal to the astute radiologist the acute angle between the superior mesenteric artery and the aorta and any present venous collaterals.

Proposed Diagnostic Approach to Patients With Suspected Nutcracker Syndrome

The diagnostic approach to a patient with suspected nutcracker syndrome will be driven by the clinical situation, including the severity of the presenting symptoms, comorbidities, and the need to rule out other pathologic processes. The following protocol has been suggested as a general guideline:[4][10][25][54]

• All patients with known or suspected nutcracker syndrome should undergo renal Doppler ultrasonography, including younger patients with otherwise unexplained intermittent gross or microscopic hematuria, proteinuria, and left flank pain. If ultrasonography is ambiguous, CT or magnetic resonance imaging (MRI) is recommended.

• Cystoscopy and ureteroscopy are not required components of the diagnostic protocol for nutcracker syndrome but may be needed to exclude other causes of hematuria.

• Patients considering surgical intervention should have contrast venography to measure vessel diameters and assess pressure gradients; intravascular ultrasound can be performed simultaneously with venography if desired.

In certain clinical scenarios, the initial imaging study may be intravenous or retrograde pyelography; these studies are frequently normal in patients with nutcracker syndrome. However, the most common abnormal finding in nutcracker syndrome is notching of the ureter due to extrinsic compression from dilated collateral vessels. Narrowing of the left renal vein, as it passes the superior mesenteric artery, venous collateralization, left gonadal vein distention, and pelvic congestion may also be demonstrated.[4][49] 

Doppler ultrasonography

Renal Doppler ultrasonography, the ideal initial imaging modality in children and pregnant patients, has a reported sensitivity of 69% to 90% and a specificity of 89% to 100% for nutcracker syndrome.[5][55] When nutcracker syndrome is suspected, this study should be performed in the semi-recumbent position; supine positioning may induce an artificial compression of the left renal vein. Renal Doppler ultrasonography may be diagnostic of nutcracker syndrome in some patients and mitigate the need for further imaging studies.[56]

Renal Doppler ultrasonography requires precise measurements in multiple planes; patients should be well-hydrated and ideally have completed a 6- to 8-hour fast. The study should exclude a mass at the level of compression and subsequently measure the superior mesenteric artery angle. The luminal diameter of the left renal vein should be measured proximal and distal to the compression, and peak flow velocities should be estimated. The ultrasonographic diagnostic criteria for nutcracker syndrome in children and adults are:

• Children:
  • The ratio of the anteroposterior diameters of the hilar portion of the left renal vein to the aortomesenteric portion is greater than 4.2.[52]
  • The peak flow velocity ratio of the left renal vein at the site of narrowing compared to the flow proximal to the narrowing is greater than 4.[52]

•  Adults:
  • The ratio of the anteroposterior diameters of the hilar portion of the left renal vein to the aortomesenteric portion is greater than 4.[41]
  • The peak flow velocity ratio of the left renal vein at the site of narrowing compared to the flow proximal to the narrowing is greater than 5.[41]

The peak flow velocity ratio has a reported sensitivity of 80% and specificity of 95% for nutcracker syndrome.[55][57] 

Additional ultrasonographic findings suggestive but nondiagnostic for nutcracker syndrome include venous collaterals and perinephric or pelvic varicosities.[55][56] The vessels within the inguinal, scrotal, or ovarian region should be assessed at rest and during cough to evaluate for reflux; varices should be measured.[8][55][58] 

Computerized tomography angiography

CT angiography (CTA) can provide detailed information about the renal vasculature without the risks associated with invasive studies. CTA additionally offers information about surrounding anatomical structures.[55] However, CTA does not provide flow information. The sensitivity and specificity of CTA for nutcracker syndrome are 92% and 89%, respectively.[59] Selective digital subtraction angiography of the left renal vein is another diagnostic option.[60]

The CTA diagnostic criteria for nutcracker syndrome relies on the ratio of the vessel diameter between the renal vein at the hilum and the compressed segment, as well as the angle of the superior mesenteric artery.[31][32][61] These diagnostic criteria include: 

• Ratio of the diameter of the renal vein at the hilum to the narrowed portion of the left renal vein of greater than 4.9.
• Ratio of the diameter of the lateral, uncompressed proximal portion of the left renal vein to the compressed renal vein segment of greater than 2.25.
• Direct visualization of left renal vein compression between the aorta and the superior mesenteric artery.
• The angle between the superior mesenteric artery and the aorta is less than 40°; an angle of less than 35° is considered definitive.
• Dilated collateral veins from the renal hilum, renal capsule, pelvis, and retroperitoneum.
• Contrast-jetting across the compressed portion of the left renal vein in the early cortical phase of the CT.
• Increased blood flow along the anterior aspect of the inferior vena cava in early-phase CT.

The "beak sign" is the compressed left renal vein in the fork between the aorta and the superior mesenteric artery in the axial plane. The beak sign is 89% specific and 92% sensitive for nutcracker syndrome.[30][62][63] The hilar-to-compressed renal vein diameter ratio has a reported sensitivity of 67% and a specificity of 100%.[30][62][63] A particularly elevated compression ratio is 91% sensitive and 91% specific for nutcracker syndrome.[62]

Magnetic resonance imaging

MRI has an advantage over CT due to the lack of radiation exposure, making MRI preferable for children and pregnant persons. MRI provides superior soft tissue visualization with comparable sensitivity and specificity to CT.[64] Noncontrast, enhanced imaging via special sequencing techniques may be employed.

Contrast-enhanced venography and intravascular ultrasonography

Direct measurement of the left renal vein to vena cava pressure gradient is considered the definitive diagnostic test for nutcracker syndrome, although it is usually unnecessary.[8][25][55][65][66] Venography is invasive and is reserved for cases where additional information is required for surgical planning. Contrast-enhanced venography can directly demonstrate left renal vein compression at the level of the superior mesenteric artery, enlarged collateral veins, and vascular reflux into other vessels.[4] Intravascular pressure indices can determine the pressure gradient to establish a more definitive diagnosis.[67] A difference in pressure of 3 mm Hg or more between the left renal vein and the inferior vena cava is considered significant but may be seen in persons without nutcracker syndrome. Likewise, some patients with nutcracker syndrome who develop collaterals may have normal pressure gradients.[8][25][55][65][66]

Intravascular ultrasonography directly measures renal vein diameter and can be performed concurrently with venography.[68] An intravascular ultrasonic catheter is inserted through the same femoral access sheath used for the venogram. Continuous imaging is performed as the catheter tip is slowly withdrawn from the left renal vein, across the superior mesenteric artery, and finally to the inferior vena cava. Intravascular ultrasonography is useful when sizing endovascular stents, and confirming flow and positioning after stent placement.[55][69][70][71][72]

Cystoscopy and Ureteroscopy 

Direct visualization of the bladder and ureteric mucosa via cystoscopy and ureteroscopy are not required in the evaluation of nutcracker syndrome but may be necessary to exclude other causes of hematuria, if present. In patients with nutcracker syndrome, particularly those with a low body mass index, cystoscopy may reveal blood coming from the left ureteral orifice without any abnormalities of the left renal pelvis.[13] However, the hematuria of nutcracker syndrome is frequently intermittent; cystoscopic examination may reveal no abnormalities if performed when the patient is not actively bleeding.[8] 

Treatment / Management

By consensus, the asymptomatic nutcracker phenomenon does not require treatment.[1][4][5][55] The treatment of nutcracker syndrome is driven by symptoms. Treatment may be nonoperative management, endovascular stenting, or surgery. Guidelines from the European Society for Vascular Surgery propose a treatment algorithm in which 6 months of conservative therapy is recommended for adult patients with mild symptoms, and 24 months of conservative therapy is recommended for children 18 years and younger with mild symptoms.[4][25] 

Conservative Treatment 

Pediatric patients with nutcracker syndrome should be treated with conservative management whenever possible due to the possibility of spontaneous symptom resolution after growth, with the increased deposition of adipose tissue and the possible development of venous collaterals.[8][10][55][73][74][75] Nearly 75% of all patients diagnosed with nutcracker syndrome before 18 years of age will experience a complete resolution of symptoms within 2 years of diagnosis.[5] In symptomatic pediatric patients, medical management with angiotensin-converting enzyme (ACE) inhibitors is recommended.[10]

Patients with orthostatic proteinuria may benefit from low-dose aspirin or ACE inhibitor treatment.[5][4][76] Elastic compression stockings may alleviate pelvic or flank pain.[69][77] Underweight patients, or those with a low-normal body mass index, may benefit from weight gain, which can resolve the symptoms of nutcracker syndrome in up to 30% of patients in this cohort.[69][78]

Surgical Treatment 

Surgical intervention for adults with nutcracker syndrome is recommended in the setting of symptomatic gross hematuria and severe pain. Other indications for surgical intervention include autonomic dysfunction, severe proteinuria, renal failure, and varicocele.[25][55][77] Commonly performed surgical interventions include renal vein transposition, gonadal vein transposition, venous bypass, renal autotransplantation, and endovascular stenting. Nephrectomy is reserved for cases without options for venous decompression.[4][55]

Left renal vein transposition 

This procedure was first described in 1982 and quickly became the standard surgical approach to nutcracker syndrome. Between 80% and 100% of patients report relief of flank pain and hematuria following renal vein transposition.[4][79] The complications of this invasive procedure include but are not limited to deep vein thrombosis, postoperative ileus, and retroperitoneal hematoma formation. Venous stenosis rates following transposition approach 40%, and endovascular treatment may be required.[55][79][80] In cases of gonadal venous reflux, gonadal vein transposition can decompress the kidney and relieve pelvic congestion. The gonadal vein is ligated and tunneled to the inferior vena cava, where it is anastomosed with an interrupted 6-0 suture.[55]

Renal autotransplantation 

Renal autotransplantation may be required to reduce pressure in the left renal vein. The kidney is usually placed in the contralateral iliac fossa.[24][31][32][59][81] Renal autotransplantation has a prolonged operative and anesthesia time compared to renal vein transposition and requires greater surgical exposure and 2 additional anastomoses. Laparoscopic and robotic renal autotransplantation procedures have been described; the prolonged training and operative times and costs may offset the benefit of less-invasive procedures.[4][82] 

Endovascular stenting 

Endovascular stenting as a decompressive measure was first described in 1996, and the results have been favorable.[32][83][84][85] A 6- to 8-cm self-expanding stent is placed in proximity to the first division of the renal vein to minimize stent migration. Endovascular stenting with stent-assisted coil embolization and complete aneurysm resection have been employed in rare cases of left renal vein aneurysm in nutcracker syndrome.[86][87] Balloon angioplasty can be used if left renal vein stenosis persists after stent placement, but it is often unnecessary.[88] In one series, nearly 200 patients with nutcracker syndrome treated with endovascular stenting had significant improvement or total elimination of their symptoms.[83][85][88][89][90] 

Stent migration, erosion into adjacent structures, and kinking are the most common complications of endovascular procedures. The potential for migration to the right atrium introduces a significant risk an open procedure avoids. Factors contributing to migration include the effect of aortic pulsations, early patient mobilization, and the orientation of the stent in the renal vein.[55][59] A hybrid procedure can be used to suture the stent to the vein wall, and using oversized stents can reduce risk.[4][55][81][82][88][91][92][93]

Three months of postoperative anticoagulation therapy is recommended during stent endothelialization. The typical regimen includes 3 days of low-molecular-weight heparin, 1 month of clopidogrel, and 3 months of aspirin.[24][25][94][88] Patients are reevaluated via ultrasound at 3 months, then annually for 3 years, then every 3 to 5 years or as needed.

Differential Diagnosis

Hematuria and flank pain, the most common presenting features of nutcracker syndrome, can be caused by a range of pathologic processes, including malignancy, nephropathy, pelvic congestion unrelated to nutcracker syndrome, pyelonephritis, and renal calculi. Nutcracker syndrome may present concurrently with May-Thurner syndrome, pregnancy, or IgA nephropathy, among others; overlapping symptoms create more diagnostic uncertainty. Additional causes of left renal vein compression include retroperitoneal tumors, aortic dissection, lymphadenopathy, and loin pain hematuria syndrome; nutcracker syndrome can occur alongside superior mesenteric artery syndrome.[20][95][96][97] 

Hematuria may be the presenting symptom of any number of disease processes, including but not limited to trauma, infection, or malignancy. Thin basement membrane nephropathy, formerly known as benign familial hematuria, and benign essential hematuria can also result in asymptomatic hematuria.[98][99]

Prognosis

Nutcracker syndrome resolves in almost 75% of affected young patients; weight gain, growth, and venous collaterals contribute to this improvement. In persistently symptomatic patients, nutcracker syndrome may lead to left renal vein thrombosis and renal injury. Hematuria requiring transfusion has been documented and carries additional risk.[4][50] 

Complications

Untreated nutcracker syndrome can lead to progressive renal dysfunction. Two cases of saccular aneurysm of the left renal vein have been described in the setting of nutcracker syndrome. Aneurysm formation can lead to rupture or thrombus formation with embolization to the venous circulation and pulmonary vasculature.[86][87][100][101] Insufficient venous outflow from the left gonadal vein can cause venous congestion and dilatation, resulting in left-sided varicoceles in men and pelvic congestion syndrome in women; both processes can cause infertility. Other complications have been reported, including massive hematuria and significant orthostatic proteinuria.[5][25] In patients with concurrent nutcracker and May-Thurner syndromes, correction of one in isolation may aggravate the symptoms of the other.[102] 

Surgical complications encountered when treating nutcracker syndrome can include retroperitoneal hematoma, ileus, and deep vein thrombosis. Over time, restenosis can occur. Complications from endovascular stenting and coiling include coil displacement and migration into the vena cava, heart, or pulmonary artery.[103][104][105][106] A 2016 retrospective evaluation of 75 patients who underwent endovascular stenting at a single center reported stent migration in 5 patients during a mean 55 months of follow-up. The authors concluded that preoperative left renal vein measurements, stent selection, stent deployment, and early complication detection reduce stent migration incidence.[103] 

Postoperative and Rehabilitation Care

Three months of anticoagulation therapy is recommended for patients undergoing therapeutic intervention of nutcracker syndrome. Anticoagulation therapy may need to be continued indefinitely for hypercoagulable patients. Patients should be reevaluated 3 months following intervention and annually after that. If the patient remains asymptomatic, evaluation intervals may be extended to 3 to 5 years. Patients with recurrent symptoms should be evaluated with CTA or direct contrast venography.

Consultations

Treating patients with nutcracker syndrome requires multidisciplinary care, including vascular surgeons, nephrologists, interventional radiologists, and their pediatric counterparts.

Deterrence and Patient Education

Patients should be educated on the complications of untreated nutcracker syndrome. The risk of infertility in those with pelvic congestion syndrome or varicoceles should be discussed. Screening is unnecessary for family members, as nutcracker syndrome is not a heritable condition.[1]

Pearls and Other Issues

• Nutcracker syndrome should be considered when evaluating patients with unexplained recurrent hematuria, especially if they are younger or have a low body mass index.
• Orthostatic hypotension and autonomic dysfunction are rarely associated with nutcracker syndrome and can be treated with ACE inhibitors.
• Nutcracker syndrome often occurs when the angle between the superior mesenteric artery and the aorta is less than 40°.
• The nutcracker phenomenon may be an anatomic variant and is an incidental finding in asymptomatic persons.
• There may be overlap with other conditions such as pelvic congestion syndrome, varicocele, and loin pain hematuria syndrome.
• Other rare causes of left renal vein compression include mass effect from lymphadenopathy or malignancy, lordosis, pregnancy, intestinal malformation, abdominal aortic aneurysm, and sudden weight loss.
• While the diagnostic standard for nutcracker syndrome is CTA, the diagnosis is frequently easily made with renal Doppler ultrasonography; this is the recommended initial imaging study.
• In patients younger than 18 years with nutcracker syndrome, conservative management is recommended for at least 24 months due to frequent spontaneous resolution of symptoms. For adults, conservative management is often recommended for at least 6 months. 
• Several surgical procedures and endovascular interventions are therapeutic options for patients with nutcracker syndrome who are unresponsive to conservative management.
• Embolization or ligation of enlarged or dilated collateral veins should be performed in conjunction with left renal vein decompressive procedures to minimize subsequent increases in renal vein hydrostatic pressure.

Enhancing Healthcare Team Outcomes

Patients with nutcracker syndrome can experience a range of symptoms and morbidity. Early identification and treatment of patients with clinically significant pain and hematuria is imperative. The diagnosis and treatment of these patients require a collaborative approach among healthcare professionals to ensure patient-centered care and improve overall outcomes. Emergency medicine physicians, pediatricians, vascular surgeons, interventional radiologists, nephrologists, advanced practitioners, nurses, pharmacists, and other health professionals involved in the care of these patients should possess the essential clinical skills and knowledge to diagnose and manage nutcracker syndrome, including expertise in utilizing diagnostic techniques effectively. 

A strategic approach is necessary to optimize treatment plans and minimize adverse effects. Ethical considerations must guide decision-making, ensuring informed consent and respecting patient autonomy in treatment choices. Each healthcare professional must know their responsibilities and contribute their unique expertise to the patient's care plan, fostering a multidisciplinary approach. Effective interprofessional communication is paramount, allowing seamless information exchange and collaborative decision-making among the team members, resulting in patient-centered care, ultimately improving patient outcomes, and enhancing team performance.

Further studies, including large multi-center randomized controlled trials and meta-analyses, are needed to establish reasonable diagnostic criteria and evaluation protocols, elucidate the long-term safety and efficacy of the various treatment modalities discussed, and develop consensus management guidelines.