Ureteric stent

Ureteric stents, also known as ureteral stents, double J stents, or JJ stents, are urological catheters that have two "J-shaped" (curled) ends, where one is anchored in the renal pelvis and the other inside the bladder.

Stents enable the free passage of urine from the kidney to the bladder, in adverse conditions such as postoperative urologic procedures, lithotripsy and ureteral obstructions.

Ureteric stents may be placed from an antegrade approach by an interventional radiologist or a retrograde approach by a urologist. Stent placement may replace a percutaneous nephrostomy that has been performed in the acute setting. This is popular with patients as it 'internalises' the method of obstruction bypass without the negatives of a nephrostomy.

The remainder of this article pertains to antegrade stent placement via an interventional radiology approach; readers are encouraged to seek urology texts for further information on retrograde stents.

Indications

Stents may be used short or long term depending on the indication:

• obstructive calculi causing acute pyelonephritis, anuria or sepsis where a ureteric stent maybe urgently needed to relieve the obstruction ²

• extraluminal malignant obstruction

  • antegrade stenting may be considered first line particularly in pelvic malignancies, as there is a higher failure rate in retrograde stenting mainly due to the difficulty in cannulating the ureteric orifice ³

• benign strictures

• retroperitoneal fibrosis

Contraindications

While there is no universally agreed list of contraindications, the main contraindications generally relate to procedural risks of hemorrhage and ability to tolerate the procedure ³:

• uncorrected coagulopathy (INR >1.5, platelet count <50x10³/µL, and recent antiplatelet therapy)

• iodinated contrast allergy

• inability to maintain prone position

Procedure

Preprocedure evaluation

Patient factors to assess prior to the procedure include ³:

• bleeding risk

  • full blood count and coagulation studies are necessary to ensure minimum target INR and platelet count as above

  • antiplatelet therapy should be withheld for 5 days prior to procedure

  • heparin should be stopped (3 hours for unfractionated heparin, 24 hours for fractionated heparin)

  • warfarinised patients require repeat INR until <1.5

• respiratory compromise

  • prone procedure exacerbates underlying respiratory compromise; if there is concern, an anesthetics review is indicated

• antibiotic prophylaxis should be given one hour prior to the procedure to cover common Enterobacteriaceae spp. in accordance with local antimicrobial guidelines, however commonly used choices include ⁴:

  • ceftriaxone 1 g IV

  • ampicillin/sulbactam 1.5-3 g IV

  • ampicillin 1g + gentamicin 120 mg IV

  • ciprofloxacin 500 mg PO

Room setup

The procedure is typically performed in an interventional radiology suite with fluoroscopy equipment. The suite should have standard theater sterility precautions. The patient should be positioned in the prone position.

Equipment

The majority of stents are plastic, but metallic stents are now available for use in malignancy to reduce the chance of ingrowth into the stent. It is a trade-off as these stents are significantly more expensive than traditional stents.

A variety of delivery systems exist:

• pusher mechanism

• string release

• sheath (similar to an IVC filter)

Equipment required includes:

• angled 0.035 150 cm hydrophilic wire

• 145 cm 0.035 Amplatz super-stiff wire

• 8F sheath

• ureteric stent (typically 6F, 28 cm)

• 8F catheter (for covering nephrostomy)

• analgesic and sedative medications (e.g. meperidine, midazolam)

Technique

The technique for antegrade ureteric stenting as described by Perrio and Chapman is as follows ³:

• patient is positioned prone

• ultrasound scan is used to identify the dilated pelvicalyceal system, and the site for puncture is marked

  • upper or middle pole calyx is preferable to avoid navigating tortuosity of the lower pole calyx

• aseptic skin preparation of the skin overlying the affected kidney

• local anesthetic infiltration using 22G spinal needle from skin to renal cortex +/- light sedation (e.g. opioid, benzodiazepine) as required

• calyceal puncture using micropuncture needle under ultrasound guidance

  • once urine is aspirated, iodinated contrast is injected to confirm position using fluoroscopy

• insert hydrophilic guidewire and advance down ureter into the bladder

  • confirm wire position within urinary bladder with fluoroscopy

  • once confirmed, exchange hydrophilic wire for stiff wire

• peel-away sheath inserted over stiff wire to mid-ureter

• if required, pre-dilate stenosis using 5 mm balloon to allow advancement of stent

• double-J stent passed over wire

  • confirm distal loop position in bladder with fluoroscopy

  • pull wire back to allow distal loop to coil

• withdraw sheath into the calyx, then deploy proximal loop by withdrawing wire and pushing on the pusher mechanism

• confirm stent patency with contrast

• nephrostomy drain may be passed via peel-away sheath if required

• sheath is peeled off

Post-procedural care

• analgesia

• monitor for bleeding and infection

Complications

• failure to insert, typically due to a stricture that is impassable; rate of failure ranges from 12.2% to 34.6% ²

• one end of the stent may migrate or in rare circumstances completely dislodge. Distal migration into the urinary bladder or pelvis can be up to 9.5% ²

  • if the stent migrates into the urethra, incontinence will occur

• urosepsis following the process of insertion

• blockage (although the urine may also pass outside, not through the tube)

• ureteric stent encrustation - making replacement difficult ²

Outcomes

Stents are typically left for a maximum of 3-6 months. If long-term stents are required exchanges (replacement) are usually due to encrustation.

History and etymology

Somewhat surprisingly the word 'stent' is actually an eponym, originally named after Charles Stent (1807-1885), a largely forgotten British dentist. He invented an improved material for forming dental impressions and set up a company to manufacture it. During the Great War, J F Esser, a Dutch surgeon used a mold of Stent's Compound as a fixative for skin grafting in injured infantrymen. This innovative use was rapidly adopted into practice, and stenting as a concept rapidly segued into multiple specialities. Despite its eponymic origin, the word stent is not routinely capitalized.

See also

• antegrade ureteric stent

• metallic ureteric stent

• percutaneous nephrostomy

• medical devices in the abdomen