Nutcracker Syndrome in Children: Role of Doppler Ultrasonographic Indices in Detecting the Pattern of Symptoms

Nutcracker syndrome in pediatrics: initial findings and long-term follow-up results

BACKGROUND

Nutcracker syndrome (NCS) describes a set of symptoms and signs resulting from compression of the left renal vein (LRV). There is a lack of knowledge about its natural course, diagnosis, and management, especially in children. Herein, we present our single-center experience with a large number of patients who have long-term follow-up results.

METHODS

All patients with NCS diagnosed between January 2011 and March 2021 were included and their data were obtained retrospectively.

RESULTS

A total of 123 NCS patients (85 females) were included. The median age at the time of diagnosis was 12 (IQR 10-14) years, and BMI percentiles were below 5% in 38% of the cases. At the time of diagnosis, two-thirds of the patients were asymptomatic. The most common laboratory finding was nephritic proteinuria (98%), followed by microscopic hematuria (16%). Signs of LRV compression were significantly more evident in upright position Doppler ultrasonography (DUS) examination. All patients have been followed conservatively; hematuria and/or proteinuria resolved in 43 of the 108 patients (40%) within 35.8 ± 25.8 months of follow-up. Control DUS was performed in 52 patients after a mean period of 39.1 ± 21.3 months. The median peak velocity and diameter ratios of the LRV in the upright position were found to be decreased significantly when compared to the initial assessment (p < 0.05). Normal DUS findings were noted in 13 patients at the final evaluation.

CONCLUSIONS

In unexplained proteinuria and/or hematuria, NCS should be considered, especially in asthenic adolescents. Our results support conservative management in children as the first-line treatment approach.

How I treat nutcracker syndrome

Anatomic compression of the left renal vein in the angle between the aorta and superior mesenteric artery may be asymptomatic or may result in symptoms, including flank pain, hematuria, or pelvic pain and/or congestion. Patients can be referred to a vascular surgeon due to symptoms and/or radiologic findings. Because symptoms of nutcracker syndrome can be vague and/or nondiagnostic, careful evaluation, assessment, and counseling with patients are required before undertaking intervention, which is often an open surgical procedure. The definitive diagnosis is ideally confirmed with diagnostic venography, including pressure measurements from the left renal vein and inferior vena cava. The optimal treatment includes open decompression of the left renal vein with renal vein transposition or gonadal vein transposition, with or without concomitant management of pelvic varicosities if symptomatic. Because most patients with nutcracker syndrome are young, long-term follow-up with scheduled ultrasound examinations should be maintained.

Diagnostic Clues in Pediatric Nutcracker Syndrome: From Two Clinical Cases to Current Literature Analysis

Nutcracker syndrome (NCS) is a rare pediatric disease caused by left kidney vein compression. Besides the "Triade's symptoms", including hematuria, proteinuria, and flank pain, a wide spectrum of clinical manifestations has been reported. As the significant hemodynamic changes secondary to the dilatation of the left renal vein, serious consequences such as renal vein thrombosis and severe anemia might occur in these children. NCS diagnosis includes a variety of invasive and non-invasive imaging tools, but cutoff values need to be further validated. A conservative treatment represents the most common therapeutic approach for these patients, but operative options are available in selected cases. To complicate matters, a standard diagnostic and treatment algorithm is currently lacking and scientific pediatric evidence in this field is still poor and limited. In this perspective, early recognition of NCS is crucial but challenging for pediatricians. Therefore, a better knowledge of the disease is recommended. Starting from two different clinical presentations of NCS, we aimed to provide a comprehensive overview of the disease in children.

Nutcracker syndrome in children: Appearance, diagnostics, and treatment - A systematic review

BACKGROUND

The nutcracker syndrome (NCS) is defined by compression of the left renal vein (LVR) and may present with a wide variety of symptoms. Due to its rarity in pediatric patients, incidence, diagnostics and performed therapy regimen are widely undefined. To this date, there are only case reports and small collectives of pediatric patients described but comprehensive research is lacking.

METHODS

A systematic literature research on pediatric NCS was carried out on Medline and Scopus databases according to PRISMA principles using predefined search terms and inclusion criteria. The PROSPERO registered review (CRD42021237415) identified patients' characteristics regarding age, sex, clinical symptoms, applied diagnostic methods and treatment options.

RESULTS

In total 47 articles were included. Overall, 423 children (218 boys and 205 girls) with diagnosed NCS were included in the analysis. Mean age was 12.0 (boys 12.9, girls 12.0) years. Hematuria was most common presentation (55.5%), followed by proteinuria (49.9%). Classical flank pain was only detected in 19.1% of patients. Sonographic evaluation was the most commonly used diagnostic tool (99%). Invasive diagnostic studies were performed in 97 children. 86.8% patients were treated conservatively and 94.9% showed complete resolution (42.8%) or at least improvement (52.2%) of symptoms. Type of operative treatment comprised of open surgery with transposition of LRV, endovascular stenting and laparoscopy.

CONCLUSIONS

Overall, data quality regarding NCS in children is poor. However, conservative approach in pediatric patients is recommended and should be regarded first treatment option. Diagnostic and treatment should follow a defined algorithm when NCS is suspected. Sufficient observation and follow-up must be assured in all patients to get significant results in this heterogenous syndrome.

LEVEL OF EVIDENCE

V-IV.

Left renal vein entrapment in postural proteinuria: the diagnostic utility of the aortomesenteric angle

Nutcracker syndrome related to the left kidney vein compression is a cause of orthostatic proteinuria during childhood. Some studies have shown that the ratios between maximum velocities and anterior-posterior diameters of hilar and aortomesenteric segments of the left kidney vein between upright and supine positions must be more than 4 in order to make a Nutcracker syndrome diagnosis. Our aim was to investigate whether the use of a decrease in aortomesenteric angle between upright and supine positions in the presence of isolated orthostatic proteinuria can be a criterion for the diagnosis of Nutcracker syndrome. Relevant patient information, which included demographic data, clinical examination findings, laboratory data, urinary system ultrasound, and kidney color flow Doppler ultrasound results, were prospectively collected. Thirty-nine pediatric patients with orthostatic proteinuria were included in the study. Left kidney vein compression findings were demonstrated in 31 patients. The ratio of maximum velocities of hilar and aortomesenteric segments of the left kidney vein between upright and supine positions was above 4 in only 7 of our patients. Ratio of aortomesenteric angle between upright and supine positions was significantly decreased for patients with left kidney vein compression findings.  Conclusion: The use of a decrease in the ratio of aortomesenteric angle between upright and supine positions in the presence of orthostatic proteinuria, instead of the ratios for maximum velocities and anterior-posterior diameters of hilar and aortomesenteric segments, can be more helpful for the diagnosis of Nutcracker syndrome in the differential diagnosis of orthostatic proteinuria. What is Known: • Proteinuria may be a sign of an impending kidney disease • Nutcracker syndrome is a cause of orthostatic proteinuria. What is New: • Ratio of aortomesenteric angle between upright and supine positions > 0.6 can be used for Nutcracker syndrome diagnosis.

Value of magnetic resonance imaging indices of left renal vein entrapment in the diagnosis of nutcracker syndrome in children

BACKGROUND

Nutcracker syndrome (NCS) is also known as left renal vein (LRV) compression syndrome. Magnetic resonance imaging (MRI) can better depict the anatomical structure of soft tissues in the area of compression. Diagnosis of NCS using MRI in adults is not uncommon. However, there are few studies on the diagnosis of NCS using MRI in children. Therefore, we conducted this study to evaluate the clinical value of the MRI indices of the LRV in the diagnosis of NCS in children.

METHODS

This study was a single-center retrospective analysis. One hundred seventy-four patients with suspected NCS were enrolled from January 2017 to July 2020. The inclusion criteria for suspected NCS were mainly based on clinical symptoms or signs, laboratory examinations and imaging reports. Other diseases that may cause hematuria and/or proteinuria were excluded. We grouped the patients based on the diagnostic criteria for NCS into a nutcracker group and a control group. The receiver operating characteristic (ROC) curve was constructed for evaluating the value of MRI indices in the diagnosis of NCS.

RESULTS

The majority of NCS patients presented with orthostatic proteinuria (OP) (67.2%), followed by hematuria (55.2%), abdominal pain (19.0%), and left flank pain (15.5%). The areas under the curve (AUCs) for the superior mesenteric artery (SMA) angle, beak sign, and compression ratio (CR) in the diagnosis of NCS were 0.870, 0.895, and 0.878, respectively, and the best cutoff values of the SMA angle and CR were 36.8 and 3.99, respectively. The specificities of SMA angle <36.8°, beak sign, CR >3.99, SMA angle <36.8° and beak sign, SMA angle <36.8° and CR >3.99, and beak sign and CR >3.99 were 82.5%, 93.8%, 93.8%, 97.9%, 95.9% and 97.9%, respectively.

CONCLUSIONS

Children with SMA angles less than 36.8°, beak signs and CR greater than 3.99 should be highly suspected of having NCS. Among these parameters, "beak sign" showed the highest diagnostic accuracy by MRI, and the combination of any two of the above parameters achieved a higher specificity than the single parameters.

Haematuria without diagnosis? Think about the rare causes…

We describe a case of a 17-year-old man admitted in the emergency room with a 2-month history of intermittent macroscopic haematuria and left lumbar pain. Physical examination and vital signs were normal. Investigation indicated a recurrent non-glomerular haematuria. The Doppler ultrasound revealed a compression of the left renal vein with upstream dilatation which was subsequently confirmed by CT angiography. These findings are in keeping with a case of nutcracker syndrome (NutS). Although asymptomatic in most cases, it can be a rare cause of haematuria. The teenager was referred to paediatric nephrology and was treated conservatively with spontaneous resolution of macroscopic haematuria. With this case, we would like to highlight that in children or adolescents with haematuria without an apparent cause, a high level of suspicion and appropriate imaging are necessary for the diagnosis of NutS.

Value of micro-proteinuria in combination with ultrasonography of the left renal vein in the diagnosis of orthostatic proteinuria

Background

This study aimed to evaluate the clinical value of micro-proteinuria in combination with ultrasonography of the left renal vein (LRV) in the diagnosis of orthostatic proteinuria (OP).

Methods

The patients with suspected OP received West test, upright lordotic position test, Robinson test, ultrasonography of the LRV, and detection of morning urine micro-proteinuria and micro-proteinuria after activity. The sensitivity (Se), specificity (Sp), positive and negative predictive values (PPV and NPV), positive and negative likelihood ratios (PLR and NLR) and Youden's index (YI) for micro-proteinuria, ultrasonography of the LRV and both of them in the diagnosis of OP were analyzed.

Results

From January 2013 to January 2018, 75 patients (M/F: 38/37) were recruited. Sixty patients were diagnosed with OP (M/F: 29/31, median age at onset: 10.6±2.80 years); 15 patients had no OP (M/F: 9/6, median age at onset: 10.9±3.25 years); the LRV entrapment, urine Alb/Cr, IgG/Cr, and NAG/Cr after activity were significantly different between OP group and non-OP group (Z=-3.55, -4.10, -4.01, -3.04, P<0.05). The area under the curve (AUC) of urine Alb/Cr, IgG/Cr, NAG/Cr, and the ratio of anteroposterior (AP) for LRV in the hilar and narrow portions (a/b) was 0.84, 0.84, 0.76 and 0.58, respectively, and the best cut-off value was 13.2 mg/mmol, 2.52 mg/mmol, 0.64 U/mmol and 4.06, respectively. The combination of ultrasonography of the LRV and elevated micro-proteinuria after activity could achieve the Se, Sp, PPV, NPV, PLR (weighted by prevalence, W), NLR (W) and YI at 93.3% (95% CI: 0.83-0.98), 66.7% (95% CI: 0.39-0.87), 91.8% (95% CI: 0.81-0.97), 71.4% (95% CI: 0.42-0.90), 11.2 (95% CI: 4.82-26.00), 0.40 (95% CI: 0.17-0.97) and 60%, respectively, in the diagnosis of OP.

Conclusions

The micro-proteinuria in combination of ultrasonography of the LRV is helpful for the preliminary screening of OP in patients with suspected OP.

Individual and Environmental Factors Associated with Proteinuria in Korean Children: A Multilevel Analysis

Proteinuria is a significant sign of childhood renal disorders. However, little is known about how sociodemographic and environmental factors are related to the presence of proteinuria among children and adolescents. This paper focuses on the prevalence of proteinuria and its risk factors among children and adolescents. This study conducted a secondary analysis of data from the 2016 Sample Schools Raw Data of Health Examination for School Students (SSRDHESS). Data collected from 27,081 students who had undergone a health screening were analyzed using Chi-square tests, independent t-tests, and multilevel logistic regression analysis. The prevalence of proteinuria was higher in the thin group than in the normal weight group (adjusted odds ratio (aOR) = 1.77; 95% confidence interval (CI) = 1.34–2.33) and lower in the overweight/obese group (aOR = 0.64; 95% CI = 0.51–0.80). Additionally, those in metropolitan and small–medium sized cities had a proteinuria prevalence about 1.5-fold higher than that of those in rural areas (95% CI = 1.08–2.02, 95% CI = 1.19–1.92, respectively). Proteinuria was associated with environmental pollution, including smoking rate, ambient particulate matter and heavy metals in drinking water (aOR = 1.10; 95% CI = 1.01–1.20; aOR = 1.06; 95% CI = 1.01–1.11, aOR = 1.001; 95% CI = 1.0001–1.0015). These results suggest that to improve health management effectiveness, kidney disease prevention efforts for children and adolescents should focus on geographical area and environmental pollution, as well as body weight as individual factors.

Left renal vein entrapment syndrome: nutcracker syndrome!

Nutcracker syndrome (NCS) is a rare vascular compression disorder that involves compression of the left renal vein most commonly between the aorta and the superior mesenteric artery (SMA), although variations exist. It is associated with the formation of the left renal vein from the aortic collar during the 6th-8th week of gestation and abnormal angulation of the SMA from the aorta. Collateralisation of venous circulation including mainly the left gonadal vein and the communicating lumbar vein are the most significant effects. It has a female predilection occurring in the third to fourth decade and it tends to be diagnosed earlier in men. Affected individuals may present with a myriad of symptoms such as haematuria, left flank pain and proteinuria. As patients often present with these non-specific symptoms to primary care, knowledge of NCS is essential. The diagnosis can be rendered with Doppler ultrasonography, retrograde venography, CT angiography, intravascular ultrasound and magnetic resonance angiography. The authors describe the case of a 39-year-old woman with a low body mass index (BMI) presenting with generalised abdominal and flank pain as well as chronic microcytic anaemia. Physical examination findings were suggestive of biliary or renal colic. Laboratory investigations confirmed her anaemia (haemoglobin 88 g/L, mean corpuscular volume (MCV) 72 fL), but were otherwise unremarkable. Urinalysis showed proteinuria and haematuria. However, ultrasonography was unremarkable with a normal gallbladder and no evidence of calculi. Her CT scan showed marked compression of the left renal vein between the aorta and the SMA (nutcracker phenomenon), with upstream left renal, left gonadal and left lumbar vein dilatation. She was managed conservatively. This paper provides an overview of the aetiology, embryology, clinical manifestations, imaging modalities and management of NCS.