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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

• Dietl's crisis: pain with increased fluid intake (specific not sensitive)
• History vesicoureteral reflux (may cause ureteral dilation and kinking)
• History stones and stone surgery
• 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 or 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)
• If repairing a ureteral stricture, obtain simultaneous antegrade/retrograde to assess location and length of stricture
• Whitaker test: perfuse saline at 10mL/min via PCN, drain bladder with catheter, monitor pressures in renal pelvis, nonobstructed = 12-15cm, obstructed > 15cm, useful for otherwise equivocal obstruction

Indications for intervention

• Symptomatic obstruction (can be difficult to confirm)
• Worsening split renal function
• Development of stones or infection
• Persistent hypertension

UPJ Obstruction Management

Considerations for treatment

• Consider nephrectomy if < 15-20% split function
• Can repeat studies after stent or PCN if unclear with obstruction
• Indications for treatment: functional compromise, symptomatic obstruction, infection, kidney stones

Pyeloplasty

• Key goal: widely patent anastomosis with watertight closure without tension
• Preop drainage only recommended if infection, severe pain, or worsening renal function (pelvic distension improves operative dissection)
• Most common technique is Anderson Hynes dismembered pyeloplasty, but can perform Y-V, spiral flap, ureterocalycostomy
• Ureterocalycostomy: indicated for small intrarenal pelvis, horseshoe kidney, or salvage procedure
• Place stent and leave for 4-6 weeks
• Consider temporary drain to prevent urinoma formation, but do not place on suture line (creates fistula)

Endopyelotomy

• Perform full-thickness lateral incision (avoids hilar vessels) into peripelvic fat
• Incise with laser, wire balloon
• Leave stent (tapered if possible) for ~4-6 weeks
• Reasonable option after failed pyeloplasty
• Consider antegrade access for simultaneous stone treatment
• Contraindications: long stricture (> 2cm), active infection, coagulopathy, crossing vessel entanglement (otherwise not a contraindication)

Postop management

• 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
• Chronic stent exchanges can be used instead of definitive repair, patient-specific selection
• Metallic stents can stay longer than plastic (12mo)
• Retrograde balloon dilation: option for short strictures (< 2cm) but may require multiple procedures, use 4cm 5-8mm 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%

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
• Leave stent for 4-6 weeks in most situations

Specific causes of ureteral obstruction

Ureteroenteric anastomotic stricture

• Occurs 4-9%, more common on left side (greater tension)
• Perform loopogram, antegrade nephrogram, or CTU to assess degree of obstruction and rule out malignancy
• May benefit from PCN placement to relieve obstruction and better assess degree of obstruction
• Differentiate from expected obstruction due to refluxing anastomosis
• 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
• Pain relieved by aspirin
• Can present with back/flank pain, weight loss, DVT and leg edema, HTN, hematuria
• 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

Sources

• AUA Core Curriculum
• Nakada, S. and S. Best. "Management of Upper Urinary Tract Obstruction." Campbell-Walsh Urology 12 (2020).