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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

Expected changes 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