Editing CUA: Ureteral Calculi (2015) (section)

== 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):'''
*# '''Metabolic abnormalities'''
*# '''Recurrent infections with urease-splitting organisms'''
*# '''Prolonged urinary stasis'''
*# '''Prolonged exposure of urine to non-absorbable materials'''
*# '''Anatomical changes following diversion'''
*# '''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:'''
*# '''Select cases with a large, impacted proximal ureteral stone or following failure of a retrograde URS attempt for a large, impacted proximal ureteral stone'''
*# '''When performed in conjunction with renal stone removal'''
*# '''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.'''§