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
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
Algorithm for treatment of benign ureteral strictures, from Campbell's
Stricture length treated with each repair, from Campbell's
(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
Ureteroenteric anastomotic stricture management, from Campbell's
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