Overview
Renal nutcracker syndrome, also called left renal vein entrapment syndrome or nutcracker phenomenon, is a condition where the left kidney's main vein (the left renal vein) gets squeezed or compressed as it passes between two large blood vessels in the abdomen — the aorta and the superior mesenteric artery. Think of it like a nutcracker squeezing a nut: the vein gets pinched, which causes blood to back up and pressure to build inside the kidney's blood vessels. This increased pressure can cause blood to leak into the urine, pain in the left side or lower back, and other symptoms. The condition affects people of all ages but is most often diagnosed in children, teenagers, and young adults. Symptoms can range from mild — such as finding blood in the urine during a routine test — to more severe, including significant pain, anemia from blood loss, and in some cases pelvic pain or swelling of veins in the pelvis. Treatment depends on how severe the symptoms are. Many younger patients, especially children, are managed with watchful waiting because the condition sometimes improves on its own as the body grows. For those with more serious symptoms, options include minimally invasive procedures to place a small stent inside the vein, or surgery to reposition the vein. The outlook for most people is good, especially with appropriate care.
Also known as:
Key symptoms:
Blood in the urine (urine may look pink, red, or cola-colored)Left-sided flank or lower back painPelvic pain or discomfort, especially in womenVaricocele (swollen veins in the scrotum) in malesFatigue or tiredness due to anemia from ongoing blood lossProtein in the urine detected on lab testsAbdominal pain, often on the left sidePainful or heavy periods in womenFeeling of fullness or pressure in the abdomenDizziness or lightheadedness, especially when standing
Clinical phenotype terms (25)— hover any for plain English
Sporadic
Usually appears on its own, not inherited from a parent
Variable
Can begin at different ages, from infancy through adulthood
FDA & Trial Timeline
7 eventsRapport Therapeutics Inc. — PHASE2
Yale University — PHASE1
Mayo Clinic — NA
The University of Texas Health Science Center, Houston — NA
The University of Texas Health Science Center, Houston — NA
Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.
Treatments
No FDA-approved treatments are currently listed for Renal nutcracker syndrome.
1 clinical trialare actively recruiting — trials can provide access to cutting-edge therapies.
View clinical trials →Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Renal nutcracker syndrome.
Community
No community posts yet. Be the first to share your experience with Renal nutcracker syndrome.
Start the conversation →Latest news about Renal nutcracker syndrome
Disease timeline:
New recruiting trial: Network Effects of Therapeutic Deep Brain Stimulation
A new clinical trial is recruiting patients for Renal nutcracker syndrome
New recruiting trial: A Long-term Study of the Safety and Effectiveness of RAP-219 in Adults With Focal Onset Seizures
A new clinical trial is recruiting patients for Renal nutcracker syndrome
New recruiting trial: Clinical and Electrographic Changes in Responsive Neurostimulation System (RNS) Patients with Acupuncture Treatment
A new clinical trial is recruiting patients for Renal nutcracker syndrome
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.Is my case mild enough to be monitored without treatment, or do I need an intervention now?,What are the risks and benefits of stenting versus surgery for my specific situation?,How often do I need follow-up tests, and what should I watch for at home?,Could my symptoms — such as pelvic pain or heavy periods — be related to this condition?,Is there a risk of long-term kidney damage if I choose watchful waiting?,What signs or symptoms should prompt me to seek emergency care?,Are there any activity restrictions I should follow while being monitored?
Common questions about Renal nutcracker syndrome
What is Renal nutcracker syndrome?
Renal nutcracker syndrome, also called left renal vein entrapment syndrome or nutcracker phenomenon, is a condition where the left kidney's main vein (the left renal vein) gets squeezed or compressed as it passes between two large blood vessels in the abdomen — the aorta and the superior mesenteric artery. Think of it like a nutcracker squeezing a nut: the vein gets pinched, which causes blood to back up and pressure to build inside the kidney's blood vessels. This increased pressure can cause blood to leak into the urine, pain in the left side or lower back, and other symptoms. The condition
How is Renal nutcracker syndrome inherited?
Renal nutcracker syndrome follows a sporadic inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
Are there clinical trials for Renal nutcracker syndrome?
Yes — 1 recruiting clinical trial is currently listed for Renal nutcracker syndrome on UniteRare. See the clinical trials section on this page for phase, sponsor, and site details sourced from ClinicalTrials.gov.
Which specialists treat Renal nutcracker syndrome?
2 specialists and care centers treating Renal nutcracker syndrome are listed on UniteRare, sourced from ClinicalTrials.gov principal investigators, published research, and the NPPES NPI registry.