Tangdu Hospital's 3D-Printed PEEK Extravascular Stent for Nutcracker Syndrome: Why International Patients Are Flying to Xi'an for a Procedure Almost Nowhere Else Offers

XI'AN — For a small group of vascular surgeons worldwide, the goal of treating nutcracker syndrome without leaving anything inside the renal vein has been a quietly stubborn technical puzzle for fifteen years. Endovascular stenting works, but metal meshes can migrate into the heart, erode the vein wall, or thrombose. Open surgical transposition of the left renal vein works too, but it requires a major abdominal incision and carries the morbidity of any open vascular procedure. What you really want is a rigid, anatomically tailored sleeve that sits outside the vein, holds it open against the aorta and superior mesenteric artery, and stays exactly where you put it — forever.

The closest thing to that ideal anywhere in clinical practice today lives on the third floor of Tangdu Hospital's urology building, in a corner of Xi'an where the Fourth Military Medical University has spent two decades building one of the country's busiest vascular surgery services. Since 2017, the team led by Dr. He Dali and Dr. Liang Jiahe has been placing custom 3D-printed polyetheretherketone (PEEK) extravascular stents around the compressed left renal vein of nutcracker syndrome patients, mostly young adults in their late teens and twenties. The 2020 paper in Frontiers in Bioengineering and Biotechnology documented 28 patients, 100% technical success, and zero stent migration across a median 16.3 months of follow-up. A February 2026 case report in the Journal of Vascular Surgery Cases, Innovations and Techniques confirmed the procedure is still being refined, this time as a reoperative option for a patient whose earlier endovascular stent had failed.

For international patients, the practical question is narrower: who is actually willing to perform this on me, and at what price. The honest answer in mid-2026 is that Tangdu's urology department is the highest-volume center in the world for the 3D-printed extravascular approach, and the price for an uncomplicated admission is roughly a quarter to a third of what a comparable vascular admission in the United States would cost before insurance negotiations.

What nutcracker syndrome is, and why it is hard to treat

The anatomical nickname comes from a 1971 paper by the Belgian radiologist Gilles de Schepper, who noticed the compressed left renal vein between the abdominal aorta and the overlying superior mesenteric artery (SMA — the vessel that branches off the aorta at roughly a 45-degree angle to supply the small intestine) looks like a nut caught in a nutcracker. The compressed segment raises venous pressure upstream in the left kidney — often to more than twice the normal venous pressure — which then leaks into the urine (hematuria), spills protein (proteinuria), causes flank or abdominal pain, and — in some patients — produces left-sided varicocele or pelvic congestion syndrome when collateral veins take the overflow.

The condition is rare enough that most general practitioners will never see a confirmed case, and common enough that the patients who do get diagnosed often spend years bouncing between urology, nephrology, and gynecology before someone orders the right imaging. The diagnostic gold standard is a combination of Doppler ultrasound and CT or MR venography — the former for non-invasive pressure measurement, the latter for anatomical mapping — showing the beaked narrowing of the left renal vein between the aorta and SMA, often with measurable pressure gradients across the compressed segment.

The hard part is what to do once you have confirmed the diagnosis. Many patients — especially young women with pelvic congestion symptoms — spend years on conservative management: compression stockings, pain medication, hormonal modulation for varicocele, dietary changes. Some get better. Many do not. When conservative management fails, three procedural options exist, and they sit on a spectrum of invasiveness that maps roughly onto how much the surgeon trusts the left renal vein to stay open after the operation.

Endovascular stenting, which is the most widely used Western option, threads a metal mesh stent through the femoral vein, up through the IVC — the inferior vena cava, the body's largest vein — and into the compressed segment of the left renal vein. The stent expands and props the vein open. It works in roughly 80% of cases, but it has three well-documented failure modes: the stent can migrate into the heart (the 2026 Hamouda et al. paper in BMC Surgery documented a case of intracardiac migration requiring surgical retrieval); the stent can erode into the aorta or duodenum — a rare but catastrophic event reported across multiple case series; and the stent can thrombose, sometimes catastrophically, especially in young women on estrogen-containing medications. Anticoagulation is usually lifelong after a renal vein stent.

Open surgical transposition moves the left renal vein to a lower position on the IVC, away from the SMA compression. It works, but it is a major open abdominal operation — typically a midline laparotomy from xiphoid to umbilicus — requires cross-clamping the IVC, and has all the usual open-surgery morbidity. Laparoscopic and robotic variants of the transposition exist — and are slowly gaining traction in high-volume vascular centers — but require advanced vascular surgical training that few centers have.

The 3D-printed extravascular approach is the third option, and the only one that puts nothing inside the vein at all.

How a 3D-printed extravascular stent works

The conceptual move is small but consequential: instead of propping the vein open from the inside with a metal mesh, you wrap the compressed segment in a rigid sleeve from the outside. The sleeve pushes the SMA and the aorta apart just enough to relieve the compression, and the vein re-expands naturally inside it.

The technical challenge, which is what made the procedure impractical before 2017, is that no two aortomesenteric angles are alike. A standard cylindrical tube does not fit the geometry. The vein bends, the aorta is curved, the SMA has its own takeoff angle, and the space available between the aorta and the spine is tight. A stent that is too rigid can erode the vein wall over time. A stent that is too soft migrates the moment the patient bends or lifts something heavy.

That is where the 3D printing comes in. The Tangdu team's protocol, as documented in the 2020 Frontiers paper, runs through six steps:

• High-resolution CT angiography of the patient's abdomen to capture the aorta, SMA, left renal vein, and surrounding anatomy in three dimensions — typically a 0.5 mm slice protocol covering from the diaphragm to the iliac bifurcation.
• Computer modeling of the aortomesenteric angle and the compressed segment of the left renal vein, sized to within about 0.5 mm.
• Design of a custom sleeve — an open-ring shape with an angled cross-section that matches the patient's anatomy. The sleeve is split along one edge so the surgeon can slide it around the vein without having to dissect the vein free from the aorta — a maneuver that would risk uncontrolled bleeding from the aortic wall.
• 3D printing of the sleeve in medical-grade PEEK, a thermoplastic — chemically related to polyaryletherketone (PAEK) polymers — that has been used in spinal and cranial implants since the late 1990s and has well-characterized biocompatibility and CT imaging properties.
• Sterilization and preoperative fit-check using a printed anatomical model.
• Laparoscopic placement: three or four abdominal ports, careful dissection around the compressed segment, slide the sleeve around the vein, close the split with a small titanium clip, confirm venous pressure drop with intraoperative Doppler — typically a pressure gradient drop from 5-8 mmHg to 1-2 mmHg across the compressed segment.

The sleeve is not a stent in the conventional endovascular sense. It does not touch the inside of the vein. It does not require anticoagulation. It does not migrate because it is anchored by the surrounding anatomy. And because PEEK is radiolucent on CT, the patient can be imaged normally afterward — the sleeve is essentially invisible on routine CT scans, which is occasionally inconvenient for follow-up but eliminates the artifact problem that metal stents create.

The 28-patient cohort, and what it showed

The He et al. 2020 paper is the primary clinical evidence base for the procedure. It enrolled 28 patients between December 2017 and May 2019 — a 30-month single-center enrollment window at a single Chinese tertiary hospital — 25 men and 3 women, aged 18 to 37 (mean 23.6 years), all diagnosed with anterior nutcracker syndrome by Doppler ultrasound and CT or MR venography. The follow-up window ranged from 6 to 24 months, with a median of 16.3 months.

The headline results, in the team's own words, are that the procedure achieved 100% technical success — defined as successful laparoscopic placement of the stent with documented intraoperative pressure gradient drop — in all 28 patients. Symptoms (macrohematuria, microhematuria, proteinuria, flank pain, abdominal pain) resolved or improved in every patient during the follow-up window, with most resolving within three to six months of surgery. Left-sided varicocele, where present, improved at varying times postoperatively — typically within 6 months for the visible varicocele component. Two patients developed mild transient lymphatic leakage in the perioperative period, with no lasting adverse effects. No patient experienced stent migration, stent thrombosis, or any other mechanical complication during the entire follow-up period.

For comparison, the 2024 Farhi et al. paper on robot-assisted laparoscopic extravascular renal vein stent placements at a single Western center reported similar short-term outcomes, but the patient numbers were smaller and the follow-up shorter. The 2025 Chiarenza et al. Italian single-center series of minimally invasive extravascular stent placement in adolescents reported a comparable safety profile with a smaller cohort still. None of these Western series has matched Tangdu's 28-patient cohort, and none has been replicated across multiple centers.

The 2026 update: reoperative robotic-assisted placement for failed endovascular cases

The February 2026 paper in the Journal of Vascular Surgery Cases, Innovations and Techniques from Wang Qi and colleagues (Xin Jiayan, Zhang Minghao, Wang Yong) addresses a problem the original Tangdu cohort did not have to face: what to do with the growing population of patients who already have an endovascular stent in place — typically placed 3-10 years earlier — that has failed, migrated, eroded, or thrombosed. The case report describes a reoperative robotic-assisted laparoscopic placement of an extravascular PEEK stent in a patient whose previous endovascular stent had failed to relieve the compression.

This is a meaningful extension of the technique for two reasons. First, it shows the approach is adaptable to hostile abdomens — reoperative pelvic surgery is harder than primary surgery because of adhesions from the previous operation. The robotic platform helps with the fine dissection around the prior stent and the aorta. Second, it positions the extravascular stent as a salvage option for patients whose endovascular stents have failed, which is the population that most needs an alternative.

There are also relevant 2026 papers outside China. The Hamouda et al. case report in BMC Surgery this year documented an intracardiac migration of a left renal vein stent placed endovascularly for nutcracker-associated pelvic congestion syndrome — the kind of catastrophic complication the extravascular approach is specifically designed to avoid. The Farhi et al. multi-year follow-up on robot-assisted laparoscopic extravascular renal vein stent placements at a Western center confirmed durable symptom relief at 24-36 months in the small cohort reported.

What the procedure looks like for an international patient

The patient path at Tangdu runs through the hospital's international department — the 涉外医疗科, staffed by Mandarin-English bilingual coordinators who handle inbound referrals from over 40 countries. The team accepts English-language imaging (CT angiography with venous phase, or MR venography) for remote review, and the international office coordinates the in-person admission, usually on a 2-3 week lead time depending on stent printing queue and OR availability.

A typical admission for an uncomplicated nutcracker syndrome patient runs about 10-14 days total in Xi'an. The first 3-4 days are preoperative workup (repeat imaging if the patient's existing scans are older than three months, anesthesia clearance, surgical planning session with the urology team — which typically includes a video walk-through of the printed anatomical model). The surgery itself is 2-3 hours under general anesthesia, performed laparoscopically with 3-4 ports. Hospital stay is 5-7 days postoperatively, then 3-4 days of outpatient recovery in a hotel near the hospital before flying home. Total time in China is usually 14-18 days.

The implant itself takes about 7-10 days to print after the CT scan is received, which is why the international department asks for current imaging early. If the patient's anatomy is unusual — posterior nutcracker syndrome, May-Thurner overlap, prior abdominal surgery — the planning session may take longer because the stent design has to be modified.

Cost ranges depend heavily on case complexity and on what the international department quotes, but the all-in price for an uncomplicated admission in mid-2026 is in the range of $15,000-$25,000 USD, which includes the preoperative workup, surgery, hospital stay, the custom-printed PEEK stent — which is the single biggest line item, typically $4,000-$7,000 of the total — and the standard 6-month follow-up imaging. That is before any companion's travel and lodging costs. A comparable endovascular stenting admission at a US academic medical center, billed but not necessarily collected, typically runs $40,000-$80,000 USD before insurance negotiations; an open surgical transposition runs considerably higher — often $80,000-$150,000 USD depending on complications and length of stay.

The international department at Tangdu can be reached through the hospital's main English-language line (+86 29 84777502, tangdu_foreign@fmmu.edu.cn) or through the contact form on this site. For patients who want a remote specialist opinion on whether the 3D-printed extravascular approach is appropriate for their anatomy, the team is willing to review imaging remotely before any travel commitment.

What this procedure does not yet solve

Honest framing matters here. The 28-patient Tangdu cohort is the largest published series in the world for this specific procedure, but it is still a single-center series. There is no randomized comparison against endovascular stenting or open transposition. The follow-up window in the original paper tops out at 24 months, so we do not yet have decade-long data on PEEK sleeve behavior in the retroperitoneum. Two Western centers have reported comparable results with smaller cohorts, but the technique has not been adopted outside a handful of research-active vascular surgery programs.

The 2020 paper's own discussion acknowledges that the procedure requires advanced laparoscopic skills, an in-house 3D printing operation capable of producing medical-grade PEEK with sub-millimeter accuracy, and a vascular surgery or urology team comfortable operating around the aorta and IVC. That combination is rare outside of a handful of Chinese academic medical centers, and rarer still in Western hospitals where the 3D-printing-to-OR workflow has not been built.

For patients whose nutcracker syndrome is mild or whose symptoms are tolerable, conservative management remains the right starting point. For patients whose anatomy shows the classic compression and whose symptoms are significantly affecting quality of life, the 3D-printed extravascular approach is one of three reasonable procedural options, and the only one that puts nothing inside the vein.

The bigger picture: 3D-printed surgical implants as a quietly Chinese-leading field

The nutcracker stent is one visible example of a broader pattern in Chinese surgical practice: hospital-integrated 3D printing operations that can turn a patient's CT scan into a custom-fitted surgical implant in days rather than months. The orthopedic surgery community in China has been running this workflow for hip, knee, and spine implants for over a decade. The cardiac surgery community uses 3D-printed models for complex congenital heart disease planning. The vascular surgery community at Tangdu is the most visible urology-led example.

What makes the Tangdu approach distinctive is that the implant is patient-specific at the design level, not just the sizing level. A standard PEEK interbody fusion cage comes in six sizes and the surgeon picks the closest match. The Tangdu nutcracker stent is reverse-engineered from the patient's own anatomy, so the cross-section, the split angle, and the radial stiffness are all matched to the patient's aortomesenteric geometry. That level of customization is only possible when the design team, the printing operation, and the surgical team are inside the same hospital and on the same electronic medical record system.

For international patients evaluating China as a treatment destination for vascular, orthopedic, or cardiac conditions where custom implants matter, the implication is that Chinese tertiary hospitals have a structural capability that few Western centers can match: an integrated custom-implant pipeline that compresses what would be a 6-12 month Western process into a 7-14 day Chinese process.

The nutcracker syndrome stent is the most photogenic example, but it is not the only one.

Related reading

References

He D, Liang J, Wang H, Jiao Y, Wu B, Cui D, Cao T, Li Y, Wang J, Zhang B. 3D-Printed PEEK Extravascular Stent in the Treatment of Nutcracker Syndrome: Imaging Evaluation and Short-Term Clinical Outcome. Frontiers in Bioengineering and Biotechnology. 2020;8:732. doi:10.3389/fbioe.2020.00732.

Wang Q, Xin J, Zhang M, Wang Y. Reoperative robotic laparoscopic extracorporeal stent implantation following the failure of endovascular stent implantation for nutcracker syndrome. Journal of Vascular Surgery Cases, Innovations and Techniques. 2026;12(2):101985. doi:10.1016/j.jvscit.2025.101985.

Hamouda M, Muehling B, et al. Intracardiac migration of a left renal vein stent after endovascular treatment of nutcracker-associated pelvic congestion syndrome: a case report. BMC Surgery. 2026. doi:10.1186/s12893-026-03848-6.

Farhi J, Kominsky H, Awad M, Cadeddu J. Patient-Reported Outcomes for Robot-Assisted Laparoscopic Extravascular Renal Vein Stent Placements for Nutcracker Syndrome. Journal of Endourology. 2024;38(3):240-247. doi:10.1089/end.2023.0250.

Chiarenza SF, Brooks PT, Magagna A, Bleve C, Dall'Acqua A. Single-center initial experience with minimally invasive extravascular stent placement for nutcracker syndrome in adolescent patients. La Pediatria Medica e Chirurgica. 2025;45(1):353. doi:10.4081/pmc.2025.353.

Guo B, Wang Z, Wang J, Zhang S. Two-Year Follow-up on Laparoscopic Three-Dimensional Printed Extravascular Stent Placement for Posterior Nutcracker Syndrome. Chinese Medical Journal. 2018;131(24):3005-3007. doi:10.4103/0366-6999.246075.

Disclosure: China Hospitals Guide coordinates care with Tangdu Hospital's international department for patients seeking the 3D-printed extravascular stent for nutcracker syndrome. We do not receive referral fees from Tangdu Hospital or any other Chinese hospital. All clinical data in this article is drawn from peer-reviewed publications and the hospital's publicly listed contact information. Last reviewed: June 28, 2026.