CUA: Ureteral Calculi (2015)

See Original CUA Guidelines

Selecting the optimal treatment for patients with upper urinary tract calculi

• Factors to consider (4): CATS
  • Clinical factors (symptom severity, patient's expectations, associated infection, obesity, coagulopathy, hypertension, and solitary kidney)
  • Anatomic factors (horseshoe kidney, ureteropelvic junction obstruction, and renal ectopia)
  • Technical factors (available equipment, expertise, and cost)
  • Stone factors (location, size, composition, presence and duration of obstruction)

Conservative management

• Not appropriate in presence of infectious or intolerable symptoms, or compromised renal function
• Observation
  • Spontaneous stone passage rate:
    • 2-4mm: 95%
    • <5mm: 68%
    • 5-10mm: 47%
  • Axial diameter on CT, as opposed to length, is closely correlated with stone passage rate
  • Ultrasound overestimates stone size, particularly for stone ≤ 5mm, compared with CT. [Stones >10mm are underestimated§] Therefore, CT-based measurement of stone size should be relied upon for determining treatment plan
  • “Conservative management” [Observation] appropriate for stones <5mm; >5mm should consider treatment options
• Medical expulsive therapy (MET)
  • Several RTCs
  • Sur et al. European Urology 2015
    • Population: 239 patients from multiple centers with a unilateral calculus of any ureteral location, 4-10mm
    • Randomized to silodosin 8mg or placebo for up to two weeks
    • Primary outcomes: spontaneous stone passage, based on imaging or history
    • Results:
      • No different in stone free rate at 4 weeks (52% silodosin vs. 44% placebo). In subgroup of distal stones, significant difference in favour of silodosin. Silodosin improved pain scores. No difference in time to stone passage, stone-related ER visits, hospital admissions, surgical interventions, nonsurgical interventions, or use of outpatient analgesics between groups.
    • Silodosin to Facilitate Passage of Ureteral Stones: A Multi-institutional, Randomized, Double-blinded, Placebo-controlled Trial. Sur et al. European Urology 2015.
  • SUSPEND Lancet 2015
    • Population: 1167 patients from multiple centers with a unilateral calculus ≤ 10mm in any ureteral location
    • Randomized to tamsulosin 4mg, nifedipine 30mg, or placebo for up to 4 weeks
    • Primary outcome was spontaneous stone passage, defined as the proportion of participants who did not need further intervention for stone clearance within 4 weeks of randomization.
    • Results:
      • At 4 weeks, no difference in need for further intervention (no intervention in 80% placebo vs. 81% tamsulosin vs. 81% nifedipine). Trend towards benefit in larger or distal stones for tamsulosin vs. placebo.
      • No difference in time to stone passage, pain, or analgesic use.
    • Medical expulsive therapy in adults with ureteric colic: a multicentre, randomised, placebo-controlled trial (SUSPEND). Pickard et al. Lancet 2015.
  • Furyk et al. Annals of ER 2016
    • Population: 316 patients with a unilateral distal ureteric calculus <10mm
    • Randomized to tamsulosin 4mg or placebo for 28 days
    • Coprimary outcomes were stone expulsion, based on CT and time to stone expulsion, based on history or first day of pain-free 48-hour period with stone-free CT
    • Results:
      • No significant difference in stone expulsion rate (87% tamsulosin vs. 82% placebo) or time to stone expulsion. Benefit in stones 5-10mm.
    • Distal Ureteric Stones and Tamsulosin: A Double-Blind, Placebo-Controlled, Randomized, Multicenter Trial. Furyk et al. Annals of ER 2016.
  • 2018 Cochrane Review
    • 15 RCTs, with 5,878 participants overall to assess the effects of alpha-blockers compared to standard therapy or placebo for ureteral stones 1 cm and less confirmed by imaging in adult patients presenting with symptoms of ureteral stone disease.
    • Results: Treatment with an alpha-blocker may result in a large increase in stone clearance (RR 1.45, 95% CI 1.36 to 1.55; low quality evidence), corresponding to 278 more stone clearances per 1000 participants. Treatment with an alpha-blocker may have little effect on major adverse events (RR 1.25, 95% CI 0.80 to 1.96; low quality evidence); this corresponds to 5 more major adverse events per 1000 participants. Patients treated with alpha-blockers may also experience shorter stone expulsion times (MD -3.40 days, 95% CI: -4.17 to -2.63), use less diclofenac and likely require fewer hospitalizations (RR 0.51, 95% CI 0.34 to 0.77). Meanwhile, the need for surgical intervention appears similar. There may be a different effect of alpha-blockers based on stone size with RRs of 1.06 (95% CI 0.98 to 1.15; P = 0.16; I² = 62%) for stones 5 mm or less versus 1.45 (95% CI 1.22 to 1.72; P < 0.0001; I² = 59%) for stones greater than 5 mm. We did not find evidence for possible subgroup effects based on stone location or alpha-blocker type.
    • Conclusions: In patients with ureteral stones, alpha-blockers likely increase stone clearance but probably also slightly increase the risk of major adverse events. Subgroup analyses suggest that alpha-blockers may be less effective in smaller (≤5 mm) than larger stones (> 5 mm)
    • Alpha-blockers as medical expulsive therapy for ureteral stones: a Cochrane Systematic Review.
• Recommendation: MET with alpha-antagonists potentially shortens the duration and increases the likelihood of spontaneous stone passage. Consideration should be given to offer it to patients with distal ureteral stones < 10mm in size

SWL vs. URS

• See Table 1 from Original CUA Guideline
• In general, SWL better for proximal and small stones and URS better for distal and larger stones
• Both are safe and effective
• Patients should be offered both options when suitable and available, and educated on the benefits and risk of each treatment modality

Other factors (than stone size and location) affecting SWL treatment success

• Composition: calcium oxalate will fragment well; cystine, calcium oxolate monohydrate, and brushite are more resistant to SWL. Uric acid stones are fragile but cannot be localized for SWL targeting
• Density (surrogate of composition): Linear relationship, poor stone fragmentation > 1000 HU (best to maximally magnify stone, use bone windows, and draw ellipse)
• Skin to stone distance: more likely to fail with skin to stone distance >10cm

Optimizing treatment outcomes

• SWL coupling
  • Ensure proper patient coupling to reduce air bubbles in the SWL blast path, particularly near the centre of the path
  • Adequate anesthesia and analgesia prevent patient movement and “decoupling” during treatment
• SWL targeting
  • Should occur at regular intervals throughout the treatment
  • Can be done through fluoroscopy or ultrasound
  • Compression belts may help reduce renal (and ureteric) excursion with treatment
• SWL energy
  • Should be maximized during treatment in order to maximize stone comminution. This is particularly true for mid and distal ureteral stones, where the renal parenchyma is not included in the blast path and thus the risk of renal injury is negligible. However, particularly for upper ureteric stones, SWL energy should be increased gradually, rather than beginning at maximum energy to reduce renal injury.
  • Renal injury is reduced by inducing renal vasoconstriction, which is protective in reducing the rate of renal hematomas.
• SWL rate
  • Optimal treatment rate is not clear; studies suggest that SWL at 60-90 shocks/min leads to better fragmentation than 120 shocks/min, particularly for larger stones.
    • Patients with upper ureteric stones >1cm, or stones that have failed prior treatment, should be treated with a SWL rate < 120 shocks/min
• SWL number of shocks
  • The adequate number of shocks varies based on recommendations from the specific SWL machine manufacturers, but generally ranges from 2000-4000 shocks for ureteric stones
• Optimal time interval between SWL treatments is unclear, but can be as short as within 2 days for mid and distal ureteric stones.
  • >2 treatments to the same ureteric stone have little incremental benefit and URS should be considered
• Alpha blockers, in particular tamsulosin, should be prescribed after SWL for ureteral stones to improve treatment success rates
• Ureteral stents
  • Does not improve stone-free rates (actually impede the passage of fragments resulting in lower stone free rates), reduce risk of steinstrasse, or reduce risk of infection following SWL
  • Should be used prior to SWL to treat obstruction, acute kidney injury, intolerable pain, sepsis, and in those with a solitary kidney.
    • If previously inserted for sepsis, a course of antibiotics should be given prior to SWL and the patient should not be exhibiting signs of sepsis at the time of treatment. [2015 CUA Abx prophylaxis guidelines recommend pre-operative prophylaxis for ESWL in high-risk patients]

URS

• Common methods of intracorporeal ureteroscopic lithotripsy include pneumatic, eletrohydraulic, and Holmium:YAG (Ho:YAG) laser. Of these, Holmium:YAG is the method of choice in terms of stone fragmentation, stone free rates, and need for auxiliary procedures.
• Use of a ureteral access sheath has traditionally been advocated at the time of flexible URS for renal stones for several reasons, including (4):
  1. Allowing easy multiple entry and re-entry to the upper urinary tract and renal collecting system
  2. Decrease in intrarenal pressure, which could potentially diminish kidney injury
  3. Improved irrigation flow thus optimizing vision
  4. The potential to improve stone-free rates by allowing passive egress or active retrieval of fragments.
  • However, evidence is very limited
• Semi-rigid ureteroscopes represent the mainstay for treating most ureteric stones due to (3):
  1. Superior optics
  2. Excellent irrigant flow
  3. Size of the working channel.
• The outer tip diameter of ureteroscopes typically varies between 4.5 and 8.5Fr. for semi-rigid ureteroscopes and 6.75 to 8.7Fr. for flexible ureteroscopes. Digital flexible ureteroscopes are bigger (8.7Fr. tip with 9.9Fr. shaft)
• Preoperative discussion should include the potential of failed access, placement of a ureteral stent, and delayed URS at another date
• Stenting following uncomplicated URS is still a controversial topic and there is evidence to support both sides.
  • If a ureteral access sheath is used during URS, a ureteral stent should be placed.
  • If bilateral URS is performed, depending on the situation, consideration should be given to stenting at least one side, to prevent the possibility of bilateral ureteric obstruction postoperatively.
  • Stenting does not affect stone-free rates or long-term complications such as strictures, but may result in less emergency room visits and narcotic use in the postoperative period
  • Stenting prior to URS is helpful to improve stone-free rates in stones > 1 cm. Stenting prior to URS also facilitates access to the ureter due to passive dilation

Special considerations

Pregnancy

• Diagnosis
  • Ultrasound is the preferred choice in suspected urolithiasis in pregnancy due to lack of radiation; however, ultra-low dose CT (<1.9 mSV) or MRI are good alternatives with very little or no radiation [Note that use of KUB plain film (0.7mSV) is not described]
  • If ultrasound imaging is non-diagnostic and low-dose CT or MRI are unavailable, URS can be used as both diagnostic and therapeutic procedure.
    • URS with laser lithotripsy with flexible or semi-rigid is feasible and safe; ideally done in the second trimester as teratogenic effects and risks are higher in the first trimester
• Treatment
  • First-line: conservative therapy (including hydration and analgesia)
    • Indications for immediate diversion same as non-pregnant patients, but also include induction of premature labour
  • Second-line: URS
    • Postoperative stenting following URS in this situation is recommended to reduce postoperative complications
    • SWL contraindicated in pregnancy
    • PCNL, if necessary, should be delayed until after birth as the procedure requires prolonged anesthesia and radiation exposure

Anti-coagulation

• SWL, laparoscopic, percutaneous, or open surgery contraindicated in uncorrected coagulopathy/on anticoagulation
• In consulting with a hematologist or cardiologist, coagulopathy needs to be corrected and withheld preoperatively
• Patients with increased risk of thromboembolic disease could be managed with bridging
• URS with laser lithotripsy is acceptable while on anti-coagulation

Urinary diversion

• High risk of stone formation due to (6):
  1. Metabolic abnormalities
  2. Recurrent infections with urease-splitting organisms
  3. Prolonged urinary stasis
  4. Prolonged exposure of urine to non-absorbable materials
  5. Anatomical changes following diversion
  6. Reflux of mucous into the upper tract
• Most common stone types are magnesium ammonium phosphate (struvite) and calcium phosphate
• Treatment
  • Small, non-obstructive, asymptomatic stones could be managed conservatively
  • SWL can be attempted for obstructive stones
  • If SWL fails, retrograde URS with laser lithotripsy could be attempted
  • If percutaneous approach contemplated, need CT scan to determine if there are overlying bowel loops. If present, ultrasound guided access needed
  • When percutaneous procedures fail, ureterolithotomy is the last option
• Close follow-up mandatory because of risk of re-growth and recurrence (63% at 5-year follow-up)

Antegrade URS and ureterolithotomy

• Can be considered in:
  1. Select cases with a large, impacted proximal ureteral stone or following failure of a retrograde URS attempt for a large, impacted proximal ureteral stone
  2. When performed in conjunction with renal stone removal
  3. When the ureteral stone is in a transplanted kidney

Uric acid stones

• pH ≤ 5.5 is regarded as the most important factor in formation of uric acid stones
• Constitute 10% of urolithiasis in general population
• More common in metabolic syndrome and gout
• Typically radiolucent on plain radiograph and low HU <500 on CT
• Alkalinization with potassium/sodium citrate or sodium bicarbonate can be used in conjunction with MET or endourological procedures

Infected obstructing ureteral stones

• Nephrostomy tubes vs. stents
  • RCTs
    • NT vs. stent in patients with obstructing stone smaller than 15mm and found no difference in time to defervescence, hospital stay, resolution of obstruction, and overall clinical improvement§
    • X-ray exposure was shorter in the percutaneous nephrostomy group (p = 0.052). Administration of analgesics was more frequent in the stent group (p = 0.061). Percutaneous nephrostomy indwelling time was shorter (50% less than 2 weeks) than that of stents (25% less than 2 weeks, p = 0.043). Antibiotics were administered for greater than 5 days in 0% of patients who underwent percutaneous nephrostomy versus 64% in those with stents (p = 0.174). Reduction in quality of life was moderate but more pronounced in patients with stents compared to those who underwent percutaneous nephrostomy, and was more distinct in males and younger patients. The quality of life progressively improved in the course of diversion with percutaneous nephrostomy but deteriorated with stents.§