Left Renal Vein Obstruction


Left renal vein obstruction, also known as Nutcracker phenomenon (NCP), occurs due to the external compression of the left renal vein (LRV) in between the angle formed by the origin of the superior mesenteric artery (SMA) from the aorta. The word "Nutcracker" was first used by Chait et al. in 1971, but in 1972, the Belgian physician De Schepper named it after his observation of the compression of LRV between the aorta and SMA which behave as 2 levers of the Nutcracker.[1][2]


LRV compression is a developmental anomaly. It occurs when the average angle between the SMA and the aorta of approximately 90 degrees reduces to less than 35 degrees.[3] This leads to the NCP. The term Nutcracker syndrome (NCS) is interchangeably used with NCP when clinical symptoms accompany the anatomical findings. The LRV courses in front of the aorta before draining into the inferior vena cava. It has an extended course of 6 to 7 cm compared to 3 to 4 cm of the right renal vein. There have been several arterial and venous anomalies associated with NCS. Venous anomalies include LRV bifurcation with branches coursing in front and back of the aorta. The LRV compresses between the aorta and vertebral body in cases where it takes a retro-aortic route leading to posterior NCS.[4] Arterial anomalies include the low or lateral origin of the SMA from the aorta leading to the most common type of compression between the SMA and aorta which is known as anterior Nutcracker syndrome. Anterior NCS can also co-exist with compression of the duodenum as part of the Wilkie syndrome (SMA syndrome). Excessive fibrous tissue along the origin of SMA which compresses the left renal vein. Les frequently, LRV can be externally compressed by pancreatic neoplasm, para-aortic lymphadenopathy, retroperitoneal tumor, and abdominal aortic aneurysm.[3]


The exact prevalence of Nutcracker syndrome is unknown. Although it is more common in women especially in the second and third decade of life as suggested by the reported cases, it can occur from first to the seventh decade of life. A low body mass index (BMI) has shown a positive association with the NCS, due to the rapid increase in body height and vertebral bodies maturation during puberty leading to narrowing of the angle between SMA and Aorta.[5] It is not a hereditary phenomenon, but coincidental cases in siblings have been reported.

History and Physical

Clinical manifestations differ widely among patients with NCS, but the most common complaint is hematuria with or without flank pain. Presentation in children is usually asymptomatic hematuria. In the female, it often presents with pelvic congestion syndrome with associated symptoms of dysmenorrhea, dyspareunia, dysuria, lower abdominal pain, post-coital pain, varices (gluteal/thigh) and emotional disturbance.[6] Other presentations include orthostatic proteinuria and varicocele in males.

Hematuria occurs in the background of rupture of thin-walled varices into the collecting system secondary to venous congestion and hypertension. Hematuria can be macroscopic or microscopic which can lead to resultant anemia. Pain is part of the pelvic congestion syndrome and can be aggravated by sitting, walking or riding in a vehicle. Sometimes, Left flank pain could be due to the passage of blood clots in the ureter leading to ureteric colic. Orthostatic proteinuria occurs more in puberty. Increased LRV pressure along with subclinical immune injury is thought to be the mechanism behind it. Left-sided varicoceles secondary to the Left renal vein hypertension occur in males.[2]


The path to diagnose NCS is often a difficult one, and most of the times it comes under the diagnosis of exclusion. The workup is usually related to the presentation of typical Hematuria which includes urinalysis, urine culture, cystoscopy, ureterorenoscopy, and even renal biopsy. The vascular anomaly can then be ruled out by doing ultrasound imaging and color Doppler scanning which has a sensitivity of 78% and specificity of about 100%. The anteroposterior diameter and peak velocities of LRV should be measured at 2 points in the transverse plane. First, at the level of renal hilum and second, when it crosses the aorta and SMA. When the peak velocity and AP diameter at these 2 points exceed by factor 5, the diagnosis should be suspected of NCS. Then further workup should be done by CT angiography or MRA to define the anatomical relation of LRV to aorta and SMA. With MRA being superior to CTA due to the fact of absence of radiation and having multi-planer imaging.[7] Anatomical abnormalities that could be found include an abnormal origin of SMA, an abnormal high course of LRV, dorsolateral torsion of the L kidney, abnormally low or lateral origin of the SMA.

The gold standard then to establish the final diagnosis is by doing the cine-video angiography and retrograde phlebography along with reno-caval pressure gradient measurement. The normal mean pressure gradients range from 0 to 1 mm Hg. To establish the diagnosis of NCS, the pressure gradient between the left renal vein and IVC should be greater than 3 mm Hg. The advantage of cine-video angiography is not only it allows visualization of LRV compression at the level of crossover between aorta and SMA, but it also shows reflux of collaterals into the adrenal and gonadal veins with stasis of contrast in the renal vein.[8]

Differential Diagnosis

  • Loin pain hematuria syndrome
  • Pulmonary embolism
  • Renal cell
  • Renal colic
  • Renal infarction
  • Renal papillary necrosis

Pearls and Other Issues

NCS remains underdiagnosed, and a  proper understanding of NCS or NCP is essential to keep it in mind when seeing a patient with clinical symptoms and signs of hematuria, pelvic pain, pelvic varicosities, and varicoceles. Lack of knowledge of the natural history of this condition leads to improper diagnostic criteria and treatment. Patients who are in their adolescence with a benign course require a more conservative approach as they will outgrow their symptoms with physical development. Those with severe symptoms require vascular intervention or surgery to treat the condition.[12]

Enhancing Healthcare Team Outcomes

Left renal vein occlusion is a rare disorder that is difficult to diagnose. Because of its diverse presentation and complexity in diagnosis, it is best managed by an interprofessional team that includes nurses and pharmacists. Since NCS is uncommon, management over the recent decades has been a subject of debate, and it varies a lot depending on the symptoms and age of the patient. Young patients who are in their adolescence with short periods of mild hematuria and insignificant pain can be observed without any treatment for at least 2 years as with physical development the increase in fat and fibrous tissue relieve the LRV obstruction.[9] In patients with orthostatic proteinuria ACE inhibitors have a role in improving it.[10] On the other hand, patients who are symptomatic with flank pain and hematuria can be tried for different surgical options ranging from intravascular or extravascular stenting, intrapelvic chemical cauterization and open surgical procedures such as nephrectomy to renal autotransplantation. Recently endovascular stenting has been attempted but the procedure has been associated with stent dislodgment and migration.

The outcomes remain unknown because of the few cases and lack of controlled trials.

Article Details

Article Author

Muhammad Hanif

Article Editor:

Sandeep Aggarwal


8/26/2020 6:29:38 PM



["Nutcracker" phenomenon of the renal vein and venous pathology of the left kidney]., de Schepper A,, Journal belge de radiologie, 1972 Sep-Oct     [PubMed PMID: 4660828]


Nutcracker phenomenon and nutcracker syndrome., Kurklinsky AK,Rooke TW,, Mayo Clinic proceedings, 2010 Jun     [PubMed PMID: 20511485]


Left Renal Vein Compression Syndrome: Cracking the Nut of Clinical Dilemmas - Three Cases and Review of Literature., Siddiqui WJ,Bakar A,Aslam M,Arif H,Bianco BA,Trebelev AE,Kelepouris E,Aggarwal S,, The American journal of case reports, 2017 Jul 6     [PubMed PMID: 28680033]


Park JH,Lee GH,Lee SM,Eisenhut M,Kronbichler A,Lee KH,Shin JI, Posterior nutcracker syndrome - a systematic review. VASA. Zeitschrift fur Gefasskrankheiten. 2018 Jan;     [PubMed PMID: 29165061]


Oh MJ, Superior Mesenteric Artery Syndrome Combined with Renal Nutcracker Syndrome in a Young Male: A Case Report. The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi. 2017 Dec 25;     [PubMed PMID: 29277094]


Nutcracker Syndrome with Pelvic Congestion: A Case Report., Ito K,Ookawara S,Ueda Y,Morishita Y,, Internal medicine (Tokyo, Japan), 2017 Oct 15     [PubMed PMID: 28924134]


Magnetic resonance angiography in nutcracker phenomenon., Kaneko K,Ohtomo Y,Yamashiro Y,Obinata K,Kurokawa S,Aizawa S,, Clinical nephrology, 1999 Apr     [PubMed PMID: 10230562]


Current trends in the diagnosis and management of renal nutcracker syndrome: a review., Ahmed K,Sampath R,Khan MS,, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery, 2006 Apr     [PubMed PMID: 16431142]


Spontaneous remission of persistent severe hematuria in an adolescent with nutcracker syndrome: seven years' observation., Tanaka H,Waga S,, Clinical and experimental nephrology, 2004 Mar     [PubMed PMID: 15067520]


ACE inhibition can improve orthostatic proteinuria associated with nutcracker syndrome., Ha TS,Lee EJ,, Pediatric nephrology (Berlin, Germany), 2006 Nov     [PubMed PMID: 16902785]


Reed NR,Kalra M,Bower TC,Vrtiska TJ,Ricotta JJ 2nd,Gloviczki P, Left renal vein transposition for nutcracker syndrome. Journal of vascular surgery. 2009 Feb;     [PubMed PMID: 19216958]


A systematic review on management of nutcracker syndrome., Velasquez CA,Saeyeldin A,Zafar MA,Brownstein AJ,Erben Y,, Journal of vascular surgery. Venous and lymphatic disorders, 2017 Dec 29     [PubMed PMID: 29292117]


Pinto Sousa P,Machado R,Sá Pinto P,Almeida R, Renal Autotransplantation - The Solution for Different Pathologies. Revista portuguesa de cirurgia cardio-toracica e vascular : orgao oficial da Sociedade Portuguesa de Cirurgia Cardio-Toracica e Vascular. 2017 Jul-Dec;     [PubMed PMID: 29701380]


Endovascular stent placement for nutcracker phenomenon., Li H,Sun X,Liu G,Zhang Y,Chu J,Deng C,Zhou B,Chen W,Yang J,, Journal of X-ray science and technology, 2013     [PubMed PMID: 23507855]


Extravascular stent management for migration of left renal vein endovascular stent in nutcracker syndrome., Tian L,Chen S,Zhang G,Zhang H,Jin W,Li M,, BMC urology, 2015 Jul 24     [PubMed PMID: 26205510]