What is nutcracker syndrome?

Nutcracker Syndrome: Definition, Diagnosis, and Management

Nutcracker syndrome (NCS) refers to the compression of the left renal vein, most commonly between the superior mesenteric artery and the aorta, resulting in renal vascular congestion that manifests as hematuria, proteinuria, flank pain, and other symptoms. 1, 2

Clinical Presentation

Nutcracker syndrome presents with various symptoms including:

• Hematuria (microscopic or macroscopic)
• Proteinuria (often orthostatic)
• Left flank pain or abdominal pain
• Pelvic congestion symptoms (in females)
• Varicocele (in males)
• Fatigue and orthostatic intolerance
• Dyspareunia and dysmenorrhea in women 2, 3

It's important to distinguish between "nutcracker phenomenon" (the anatomical compression without symptoms) and "nutcracker syndrome" (anatomical compression with clinical manifestations) 4.

Pathophysiology

The compression of the left renal vein leads to:

• Increased venous pressure in the left kidney
• Development of collateral venous pathways (especially gonadal and pelvic veins)
• Renal venous hypertension causing hematuria and proteinuria
• Pelvic congestion due to reflux into gonadal veins 3

Risk Factors

• Low body mass index (BMI)
• Rapid height increase during growth (especially in adolescents)
• Loss of retroperitoneal fat
• Abnormal angle between superior mesenteric artery and aorta 5

Diagnostic Approach

The American College of Radiology recommends a stepwise diagnostic approach:

1. Renal ultrasound with Doppler as the first-line imaging test 1, 6

   • Look for left renal vein compression and increased flow velocity

2. CT or MRI for further evaluation if ultrasound findings are suggestive 1, 7

   • Assess for anatomical compression and collateral formation

3. Venography with pressure measurements in selected cases

   • To confirm renocaval pressure gradient (>3 mmHg is diagnostic) 3

4. Intravascular ultrasound (IVUS) may be used in complex cases 7

Management Options

Treatment depends on symptom severity and patient characteristics:

1. Conservative management 3

   • Recommended for mild cases and especially in children who may outgrow the condition
   • Weight gain for underweight patients
   • Adequate hydration
   • Regular follow-up

2. Medical management

   • ACE inhibitors for orthostatic proteinuria
   • Pain management as needed

3. Surgical intervention for severe or persistent symptoms 4, 3

   • Left renal vein transposition (standard surgical approach)
   • Renal autotransplantation for recalcitrant cases
   • Endovascular stenting (less invasive option)
   • Laparoscopic exovascular stent placement (newer technique)

Follow-up

• Regular imaging to assess vein patency after intervention
• Monitoring for symptom resolution
• Assessment of renal function 1

Special Considerations

• In children, conservative management is preferred as many will outgrow the condition as they develop
• Surgical intervention should be considered only after failure of conservative measures
• The diagnosis should be considered in patients with unexplained hematuria, especially when accompanied by left flank pain 6, 1

Nutcracker syndrome remains an important diagnosis to consider in patients with unexplained hematuria, flank pain, and pelvic congestion symptoms, particularly in thin individuals with low BMI.