Magnetic Anastomosis for Ureteral Obstruction

Magnetic Compression Anastomosis of Benign Short-Segment Ureteral Obstruction

Clinical Question

Is magnetic compression anastomosis safe, effective and feasible in benign short-segment ureteral obstruction.

Take Away Point

Magnetic compression anastomosis is safe and effective technique in combating the short benign ureteral obstruction demonstrating over 90% successful technical rate and no adverse events.

Reference

Ünal E, Çiftçi TT, Akinci D. Magnetic compression anastomosis of benign short-segment ureteral obstruction. Journal of Vascular and Interventional Radiology. 2024;35(3):398-403. doi:10.1016/j.jvir.2023.11.020

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Study Design

Retrospective, observation, descriptive study

Funding Source

No reported funding

Setting

Academic, Hacettepe University School of Medicine, Ankara, Turkey

Figure

Figure 2. A 48-year-old woman with previous history of surgery and radiotherapy for cervical carcinoma developed right hydroureteronephrosis. Cystoscopy-guided ureteral double-J stent placement performed at an outside hospital resulted in misplacement of a double-J stent into the lumen of the inferior vena cava (Video 1, available online at www.jvir.org). Perforation and false passage through the retroperitoneal space resulted in a diffusely narrowed ureter. (a) First, retrograde ureteral access was gained (white arrowheads) with the support of a vascular sheath (black arrow) and angled 5-F catheter (white arrow). (b) Anterograde access was obtained through the indwelling nephrostomy (not shown), and both access routes were used to reach the stricture (arrowheads). The short ureteral obstruction could not be traversed from the anterograde or retrograde access. (c) Magnets were pushed over the stiff guide wires to the ureteral obstruction as far as possible (arrows). (d) When the magnets were close enough to each other, they coupled and exerted pressure on the intervening tissue. On the fourth day, apposition of the magnets was evident radiographically. After magnetic compression anastomosis, the ureteral obstruction could be traversed by a guide wire. (e) Biopsy forceps were advanced through the lumen of a long vascular sheath (arrow) to push or to grab the magnets. (f) The magnets were pushed through the bladder and out of the urethra via through-and-through access (arrow). (g) Magnets (arrowheads) adhered to the guide wire (Amplatz, arrow) because of the ferromagnetic composition of the core and windings of the guide wire. (h) Finally, a double-J stent was placed from below, and the percutaneous nephrostomy tube was removed.

Summary

Magnetic compression anastomosis is becoming more popular due to its effectiveness and ease in tackling certain pathologies such as biliary strictures. The authors of this paper decided to investigate the feasibility, effectiveness, and safety of this technique against benign short-segment ureteral strictures with failed antegrade and retrograde recanalization attempts for double-J stent placement. Favorable results would allow significant improvement in patient’s quality of life, especially among those whom surgery is contraindicated or would otherwise have to tolerate a permanent nephrostomy tube with interval exchanges.

The authors performed a retrospective observational study across the time span from March 2018 to June 2022. Inclusion criteria was the presence of benign ureteral stricture and for whom surgery was contraindicated. Exclusion criteria were as follows: less than 18 years of age, malignant ureteral obstruction, length of ureteral gap of stricture exceeding magnet’s attraction capacity, and urinary tract infection refractive to medical therapy. The study comprised of 11 patients (3 male and 8 female), all of whom had indwelling nephrostomy tubes and had prior difficulty with anterograde/retrograde ureter stent placement. 5 of these patients had ileal conduits.

Technical success rate was defined as successful adherence of the magnets and subsequent ureteral stent placement. Adverse events were classified according to Society of Interventional Radiology classification system. The following parameters were also recorded: length of time of magnetic adherence, single-rotation fluoroscopy times of first and second steps procedure.

The first and second steps of the procedure are summarized below.

First step:
Both retrograde and anterograde access were performed to place the magnets in their respective positions. A combination of hydrophilic wire, 9 French vascular sheath, and 5 French 45 degrees angled catheter was used to gain access into the ureters via retrograde approach with eventual exchange to a stiff guidewire to place the magnet in the caudal portion of the stricture. A combination of 5 French catheter and hydrophilic wire was used during anterograde approach to reach the cranial part of the stricture for placement of the second magnet via stiff guidewire. Magnets’ positions relative to each other were evaluated using serial abdominal plain films until adherence was achieved.

Second step:
Anterograde and retrograde accesses were achieved in the ureters in the same manner as from the first step. Hydrophilic wire was used to traversed the magnets, with contrast injection confirming successful traversal. Balloon catheters or forceps were then used to remove the magnets, either by push or pull maneuvers through the urethra using a through-and-through access stiff guidewire. Afterwards, balloon dilatation was performed at the magnetic compression site and either 8 French double J stent or 8-12 French biliary drainage catheter was placed. Nephrostomy catheters were removed, and no antibiotics were given prior to patient discharge.

Technical success was 91% with no adverse events. 73% of the patients developed microscopic hematuria after the procedure which resolved within 72 hours. The mean time for magnetic adherence was 5.7 days. The mean fluoroscopic time for the first step was 9.45 minutes and the mean time for the second step was 15.7 minutes.

The reason this procedure works is that the magnets cause ischemia of the intervening tissues. The remaining tissues eventually adhere to each other and recanalization is achieved without compromising the integrity of the ureter. This optimizes the chances of subsequent intraluminal guidewire traversal, unlike other procedures such as the rendezvous technique which risks extraluminal traversal.

The study referenced several limitations, namely the retrospective design and the small patient population with only preliminary results provided. The author also emphasized the importance of proper patient selection for this technique as it is potentially useful in only limited context, such as the length of the stricture being within the capacity of the magnets.

Commentary

Magnetic compression anastomosis is not only a cool concept, but is also elegant and efficient when tackling certain problems. As a resident, I lost count of the times I saw my attending frustratingly attempting to pass strictures. Now I wonder how many of those cases could have been ameliorated by this technique, how much shorter the procedural times would have been, and how much radiation we could have minimized.

One thing not to gloss over is the importance of follow-up. The potential long-term complications of intra-abdominal magnets can be dreadful. Other than the abovementioned exclusion criteria, patients who have trouble with medical management compliance may not be optimal candidates for this technique. In the article’s defense, the data presented thus far are preliminary data, inviting opportunities for further research and optimal patient selection can be investigated in future studies.

Post author

Naeem Patel, DO
Radiology Resident, PGY4
Department of Radiology, Interventional Radiology Division
Hartford Hospital, Hartford, CT
@Naeemp7Patel