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Workup

What happens during upper tract obstruction?

• Phase 1 (1-2hr): ureteral pressure and RBF increase, afferent arteriole vasodilates to offset drop in GFR (drops 50% in 4hr, 75% in 12hr, 95% in 24hr)
• Phase 2 (3-4hr): ureteral pressure rises but RBF decreases
• Phase 3 (5+hr): ureteral pressure and RBF decrease due to afferent arteriole vasoconstriction, RBF drops to 70% at 24hr, 50% at 72hr, 20% at 2wks, and 12% at 8wks
• Bilateral obstruction: RBF increases slightly for 90min, then RBF and medullary blood flow decline, ureteral pressure remains elevated x24hr

Initial evaluation

• Symptoms: flank pain/fullness, often asymptomatic if chronic
• Dietl's crisis: pain with increased fluid intake (specific not sensitive)
• History vesicoureteral reflux (may cause ureteral dilation and kinking)
• History stones (especially impacted), stone surgery (URS stricture rate < 1%)
• History malignancy, XRT
• History AAA or endometriosis (can cause periureteral fibrosis)
• History TB (can cause multifocal strictures)
• Prior surgery with risk for ureteral injury
• Prior UPJ surgery (affects treatment decision)

Imaging considerations

• CT/US to assess degree of anatomic obstruction, crossing vessel (do not need to confirm preop), mass
• NM renal scan (MAG3): to assess split function and severity of obstruction (Lasix T 1/2)
• Antegrade/retrograde: obtain simultaneously to assess location and length of stricture, assists with planning surgical repair
• Whitaker test: position prone, perfuse saline at 10mL/min via PCN, drain bladder with catheter, monitor pressures in renal pelvis, nonobstructed = 12-15cm, obstructed > 22cm, useful for otherwise equivocal obstruction

General management recommendations:

• Indications for treatment: symptomatic obstruction, worsening renal function, stones, infection, persistent hypertension
• Nephrectomy: consider if < 15-20% split function

UPJ Obstruction Management

Pyeloplasty

• Goal: widely patent anastomosis with watertight closure without tension
• Nephrostomy tube: only recommended if infection, severe pain, or worsening renal function (pelvic distension improves operative dissection)
• Techniques: Anderson Hynes dismembered pyeloplasty most common, but can perform Y-V, spiral flap
• Ureterocalycostomy: indicated for small intrarenal pelvis, horseshoe kidney, or salvage procedure
• Drain placement: consider to prevent urinoma formation, but do not place on suture line (creates fistula)

Endopyelotomy

• Technique: perform full-thickness lateral incision (avoids hilar vessels) into peripelvic fat, incise with laser or wire balloon
• Leave stent (tapered if possible) for ~4-6 weeks
• Pyeloplasty failure: reasonable option, no difference in outcomes even if prior pyeloplasty
• Consider antegrade access if simultaneous stone treatment required
• Contraindications: long stricture (> 2cm), active infection, coagulopathy, crossing vessel

Postop management

• Tube plan: usually remove foley first, confirm no increased drain output after foley removal, leave stent for 4-6 weeks
• Follow-up: repeat renal scan 1mo after stent removal, then follow up at 6mo then annually for 2-3yrs (will catch most failures)
• Renal US may show persistent hydronephrosis, renal scan is better study to confirm resolution of obstruction and check for recurrence
• Success rates: > 90% for pyeloplasty, 79-88% for endopyelotomy

(Benign) Ureteral Stricture Management

Endoscopic management

• Stent placement: successful in most (80+%) cases, metallic stents require less frequent exchanges, can be used as alternative to repair in properly selected patients
• Retrograde balloon dilation: option for short strictures (< 2cm) but may require multiple procedures, use 4cm 12-30Fr balloon, inflate for 10min at stricture site, leave stent for 2-4 weeks, success 50-85%
• Endoureterotomy: incise away from major vessels (proximal = lateral, distal = anterior), can use cold knife or laser, success 66-83%
• Follow-up: US or NM scan at 1mo after stent removal, then 3 and 6mo

Open repair

• Ureteroureterostomy (UU): upper/mid strictures, perform spatulated tension-free anastomosis with running stitch x2, leave foley and drain for 1-2 days, success rates 90%
• Transureteroureterostomy (TUU): contraindicated with hx stones, RPF, malignancy, prior XRT, chronic pyelo, correct reflux if present, tunnel donor ureter under sigmoid mesentery proximal to IMA and minimize mobilizing recipient ureter
• Ureteroneocystotomy: distal strictures, includes any reanastomosis of ureter to bladder, more difficult with small/contracted bladders, no benefit for antireflux repair
• Psoas hitch: provides 5cm extra length, may require ligation contralateral bladder pedicle, avoid suturing genitofemoral nerve
• Boari flap: provides 10-15cm extra length, useful when defect extends proximal to pelvic brim
• Renal mobilization: rotate inferiorly and medially on vascularpedicle, then hitch lower pole to retroperitoneal muscle
• Ileal ureter: anastomose isoperistaltic segment, less reflux if > 15cm used, contraindications are CKD, BOO, IBD, and XRT enteritis, can perform bilaterally with use of one long segment (reverse 7 technique), consider endoscopic surveillance for malignancy starting after 3yrs
• Buccal graft: rare, cover with omental flap
• Autotransplant: anastomose via gibson, can anastomose renal pelvis directly to bladder
• Stent: leave for 4-6 weeks in most situations

Specific causes of ureteral obstruction

Ureteroenteric anastomotic stricture

• Prevalence: 4-9%, more common on left side (greater tension)
• Workup: perform loopogram, antegrade nephrogram, or CTU to assess degree of obstruction and rule out malignancy, differentiate from expected obstruction due to refluxing anastomosis
• Nephrostomy tube: may be beneficial relieve obstruction and better assess degree of obstruction
• Management: consider endoscopic (laser vs balloon) if > 6-12mo initial surgery and stricture < 1-2cm, otherwise perform definitive surgical repair
• Success: 75% for open repair vs 15% for balloon dilation at 3yrs

Retroperitoneal fibrosis

• Develops near L4-L5 near aorta, causes extrinsic ureteral compression
• Presentation: can present with back/flank pain, weight loss, DVT and leg edema, HTN, hematuria, pain relieved by aspirin
• Imaging: CT, IVP, RGPG will show medial deviation of ureters, RPF best characterized with MRI
• Medical management: refer to rheumatology, mainly use steroids but may require other immunosuppresants, 80% show clinical improvement, 60mg daily tapering to 5mg daily, 50% relapse rate
• Ureterolysis: start distally and work proximally, use split and roll technique, consider wrapping with omentum or intraperitonealizing ureters, 90+% success for relieving obstruction

Malignant obstruction

• Stent failure: occurs in 24-44% stent placement (compared to 10% for benign disease)
• Metal coil stents: more resistant to compressive forces, do not require as frequent exchanges, MRI compatible
• Surveillance: perform pyelogram (antegrade/retrograde) to assess continued need if obstruction adequately treated

Infundibular stenosis

• Causes: prior PCNL (occurs ~2%), chronic inflammation, congenital
• Fraley syndrome: intrarenal crossing vessel obstructs upper pole infundibulum
• Imaging: CT/US, dilated calyx with non-dilated pelvis
• Repair indications: worsening renal function, pain, infection, stones
• Management: balloon dilation, endoscopic incision (avoid anterior/posterior incisions), surgical repair, partial/total nephrectomy, chronic stent/PCN

References

• AUA Core Curriculum
• Nakada, S. and S. Best. "Management of Upper Urinary Tract Obstruction." Campbell-Walsh Urology 12 (2020).
• Wieder JA: Pocket Guide to Urology. Sixth Edition. J.Wieder Medical: Oakland, CA, 2021.