Ureteric Obstruction

Causes of Ureteric Obstruction

  • Intrinsic (intra-luminal)
    • Urolithiasis
    • Urothelial tumors
  • Extrinsic (extra-luminal)
    • Ureteric Strictures
    • Pelvic masses
    • Lymph node disease
    • Retroperitoneal fibrosis

Management of Ureteric Obstruction

Conservative management of Ureteric Obstruction

In the absence of any indications for decompression (mentioned below), ureteric stones can be managed conservatively to avoid unnecessary or multiple procedure and general anesthetics.
Is it safe to manage ureteric obstruction conservatively?
Yes it is safe to manage ureteric obstruction conservatively in the absence of any red flag signs (such as infection). MIMIC study reported only 0.6% rate of sepsis in patients managed conservatively for ureteric stone disease.

Decompression for Ureteric Obstruction

Indications for decompression

There are only 4 indications:
  • Sepsis i.e. an infected obstructed system (signs of sepsis or infection)
  • Renal impairment not improving with fluid resuscitation
  • Pain not controlled with analgesia
  • Single functioning kidney or Bilateral obstructing ureteric stones (Anuria)

Methods for decompression

There are 2 methods for renal decompression
  • Retrograde ureteric stent insertion
  • Antegrade Nephrostomy insertion

Optimal method of urgent decompression

‘Optimal method of urgent decompression of the collecting system for obstruction and infection due to ureteral calculi’ - Maggie Pearle 1998 Journal of Urology

Study Design:
  • Single centre randomized control trial
Study Population:
  • 42 patient (21/21) with ureteric stones with WCC ≥ 17 and/ or temperature ≥38C
  • WCC 17 was chosen as cut-off as patient with ureteric colic can have leucocytosis in the absence of infection
Study Outcomes
  • Time to normalization of temperature and WCC
Results
  • No significant difference between stent and nephrostomy groups
  • Time to normal temperature and time to normal WCC was ~2 days in both
Later studies validated the findings of Pearle et al. (Meta-analysis by Moon et al. 2024)
Therefore the choice of modality for decompression depends on patient and disease factors such as
  • Suitability for General Anesthetic
  • Availability of Radiology/ Urology service on site
  • Feasibility of procedure based on patient characteristics and nature of obstruction and patient preference (if appropriate)
    • PCN is preferred in large obstructing stones, extrinsic compression from oncological masses in the abdomen or pelvis or if patient is not safe for a general anesthetic (although not routine but stents can be done in LA)
    • Stent is preferred in coagulopathy or patients on blood thinners, if nephrostomy service is not available or if nephrostomy is not practically feasible due to location of kidneys or high BMI or patient is unable to comply with instruction
  • Planned subsequent management
    • PCN can be preferred who are likely to require PCNL for subsequent stone treatment
    • Stent can be preferred in patients who are likely to require ESWL or URS for subsequent stone management
  • Pregnancy
    • There is increase risk of encrustation during pregnancy (due to hypercalciuria, hyperuricosuria and urinary stasis due to gravid uterus)
      • Note that pregnancy has not shown to increase incidence/risk of urolithiasis itself as stone inhibition factors like urinary pH and urinary citrate excretion also increase.
    • The exchanges should be done more frequently to avoid difficulties in exchanges due to excessive encrustation(recommended 4-6 weeks)
    • PCN is preferred as it avoids a GA for insertion as well as for subsequent changes. Drainage from the PCN can be used as a surrogate marker for the status of the PCN and early exchange can be organized if any concerns are identified. Whereas in case of ureteric stent, the encrustation might remain silent until it becomes severe. However, there are a few small studies that report ureteric stenting to be a safe option in pregnancy as well. (Ngai et al. 2013, Choi et al. 2016)

EAU Guidelines on decompression

  • Stent and PCN are equally effective
  • Urgent decompression in sepsis with obstructing stones
  • Delay definitive management until sepsis is resolved
  • Start Abx immediately
  • Take urine for culture at time of decompression

Rate of stent encrustation

Rate is more in stone patients less in non-stone patients
El-Faqih et al. 1991 reported their findings in polyurethane stents removed from patients at a single institution (n=~300).
Rate of encrustation as reported by El-Faqih:
By 6 weeks: ~10%
Between 6-12 weeks: ~50%
After 12 weeks: ~75%
Interestingly, 30% stents were reported to have luminal blockage, whereas only 4% patients were reported to develop clinical obstruction. Reinforcing the idea that urine drain around the stent in addition to through it.
Kawahara et al. 2012 later reported similar number in their data from their institute (n=~300) with reported rate of encrustation as,
By 6 weeks: ~25%
Between 6-12 weeks: ~60%
After 12 weeks: ~75%
They also reported that other than the temporal impact, stent calibre also effected the risk of encrustation, with stents >6Fr reported to have a lower risk of encrustations.
Conclusion:
A fourth (25%) of patient will develop encrustations within 6 weeks, half (50%) of patients will develop encrustations by 12 weeks, and 3 quarters (75%) of patients will have encrustations after 12 weeks.
Larger calibre stents can be used (>6Fr) in an attempt to minimise risk of encrustation in high risk patients.
Similarly silicone stents are marketed as having less risk of encrustation with a longer indwelling time of upto a year (Tomer et al. 2021).

MIMIC Calculator

Effect of Ureteric Obstruction on Renal Function

Animal Studies

Hinman 1959

Recovery of Renal Function After Ureteral Deligation
Hinman refers to a work by Widen which reported permanent loss of renal function to be directly proportional to the duration of the obstruction in animal experiments on dogs.

Vaughan & Gillenwater 1971 & 1973

Vaughan & Gillenwater described their experiments on dogs in 1970s.
notion image
They reported completely recovery after 7 days of obstruction and no recovery after 6 weeks of obstruction. They report 6 months post de-obstruction as the time to maximum recovery.

Fink 1980

RENAL IMPAIRMENT AND ITS REVERSlBlLlTY FOLLOWING VARIABLE PERIODS OF COMPLETE URETERIC OBSTRUCTION
A more comprehensive experiment with dogs divided into 7 groups with 5 dogs each. Unilateral ureteric obstruction was produced surgically and corrected after varying durations in the different groups.
notion image

Bander 1985

Reported on animal studies on rats. Their findings suggested some degree of permanent loss of functioning nephrons (~15%) even with de-obstruction after only 24hrs of unilateral obstruction. However this is compensated by the remaining functional nephrons and therefore GFR is remains comparable to the other healthy kidney.

Yokoyama - Japan 1994

Animals studies on Rats reported a decline of 50% renal function on DMSA 3 days after complete obstruction. Recovery of renal function was variably depending upon degree of obstruction and the duration of obstruction. Maximum recovery was observed in 7 days after which renal function on DMSA plateaued. In cases of mild partial obstruction, complete recovery was observed in as early as 3 days post release of obstruction.

Human Studies

Shapiro 1976

3 case reports of human patients with ureteric obstruction for 28, 28 and 150 days, having good renal cortex, which showed recovery in renal function after relief of the obstruction.

Jones and O’Reilly 1988

Reviewed recovery of renal function in patients with HPCR. Their findings suggested recovery to be biphasic with an early recovery phase that happens in first 2 weeks (tubular phase) and a later recovery phase that can take upto 3 months (Glomerular phase)

Conclusions

Findings from animal studies are extrapolated to human conditions and complimented by observational data in human disease. Based on this, following clinical judgement can be derived:
  • Permanent loss of functioning nephrons is possible even with only 24hrs of obstruction (Bander 1985)
  • Degree of renal impairment from ureteric obstruction depends duration of obstruction (Fink 1980) and the severity of obstruction (Yokoyama 1994)
  • Significant permanent loss of function can happen (90-100%) from 4-6 weeks of obstruction (Vaughan & Gillenwater 1971/73 & Fink 1980)
  • Recovery can take up to 4-6 months (Vaughan & Gillenwater 1971/73, Fink 1980 & Jones and O’Reilly 1988)
  • Renal preservation should be considered even in cases of prolonged obstruction where good renal cortex is observed, as recovery can still be seen in humans (Shapiro 1976)
  • Super-added infection would aggravate the loss of renal function (clinical reasoning)

Contemporary evidence in Ureteric Obstruction

Malignant Ureteric Obstruction (MUO) Study 2024

Study Design:
  • Scottish national multi-centre retrospective observational study
Study Population:
  • ~850 patient who underwent PCN or US insertion due to MUO
Study Outcome:
  1. Overall survival after decompression
  1. Renal function after 3 months
Results:
  1. ~10% died within a month, ~30% within 3 months and ~60% within a year of intervention
  1. ~45% patients showed improvement in their eGFR (by over 20%) 3 months after intervention
Therefore, intervention should be considered based on individual patient factors such as overall prognosis, baseline renal function, pain or AKI, need for improvement of AKI to allow chemotherapy.

MIMIC Study 2019 BJUI

MIMIC: Multi-centre cohort study evaluating the role of Inflammatory Markers In patients presenting with acute ureteric Colic
Study Design:
  • International multicentre retrospective cohort study
Study Populations:
  • ~4000 patients with acute ureteric colic and a CT confirmed single ureteric stone. Of which ~2500 were discharged with conservative management followed up for 6 months retrospectively.
Primary Outcome:
  • Rate of Spontaneous Stone Passage SSP (defined by the absence of need for intervention)
Results:
  • SSP rate of 74% (n = 1874/2518) (3 quarters of stones will pass spontaneously)
  • Rate of sepsis 0.6% only (n = 16/2518)
      • After multivariate analysis
  • WCC, Neutrophil count and CRP did not predict SSP
  • MET did not predict SSP
  • Stone size and location were significant predictors of SSP rate
 

SUSPEND Trial 2015 Lancet

SUSPEND: Spontaneous Urinary Stone Passage Enabled by Drugs
Study Design:
  • Multicentre, randomised, placebo-controlled, double blind trial conducted at 24 sites in the UK
  • 3 arm study with Tamsulosin (an α-adrenoceptor antagonist) 400 μg, nifedipine (a calcium channel blocker) 30 mg or placebo taken daily for up to 4 weeks
Study Population:
  • ~1100 adults aged 18–65 years undergoing conservative management for a CT confirmed single ureteric stone of size ≤10mm
  • Followed up with questionnaires at 4 weeks and 12 weeks
Primary Outcome:
  • Rate of Spontaneous Stone Passage SSP (defined by the absence of need for intervention) at 4 weeks
Results:
  • No difference in SSP at 4 week and 12 weeks
  • No difference in pain score or duration
  • No difference in time to stone passage or health state
  • The proportions of patients not needing intervention was reported to be 80% at 4 weeks and 73% at 12 weeks (i.e. 3 quarters did not need intervention)
  • No benefit reported of MET in any patient or stone characteristics on subgroup analysis
Limitations:
  • 75% patients in all groups had small <5mm stones
  • Endpoint was need for intervention at 4 weeks rather than imaging for confirmation of stone clearance. However questionaries were recorded at 12 weeks as well which did not change the findings of the study. And CT confirmation would not be pragmatic for any large scale study.
 

References

  • Moon YJ, Jun DY, Jeong JY, Cho S, Lee JY, Jung HD. Percutaneous Nephrostomy versus Ureteral Stent for Severe Urinary Tract Infection with Obstructive Urolithiasis: A Systematic Review and Meta-Analysis. Medicina (Kaunas). 2024;60(6):861. Published 2024 May 24. doi:10.3390/medicina60060861
  • Ho-Yin Ngai, Hawre Qadir Salih, Ayad Albeer, Ismaeel Aghaways, Noor Buchholz,
    Double-J ureteric stenting in pregnancy: A single-centre experience from Iraq,
    Arab Journal of Urology, Volume 11, Issue 2, 2013, Pages 148-151,
    ISSN 2090-598X, https://doi.org/10.1016/j.aju.2013.02.002.
  • Choi CI, Yu YD, Park DS. Ureteral Stent Insertion in the Management of Renal Colic during Pregnancy. Chonnam Med J. 2016 May;52(2):123-7. doi: 10.4068/cmj.2016.52.2.123. Epub 2016 May 20. PMID: 27231677; PMCID: PMC4880577.
  • El-Faqih, S. R., et al. "Polyurethane internal ureteral stents in treatment of stone patients: morbidity related to indwelling times." The Journal of urology 146.6 (1991): 1487-1491.
  • Kawahara, Takashi, et al. "Ureteral stent encrustation, incrustation, and coloring: morbidity related to indwelling times." Journal of endourology 26.2 (2012): 178-182.
  • Tomer, Nir et al. “Ureteral Stent Encrustation: Epidemiology, Pathophysiology, Management and Current Technology.” The Journal of urology vol. 205,1 (2021): 68-77. doi:10.1097/JU.0000000000001343
  • Campbell Walsh Urology, Chapter 40, Pathophysiology of Urinary Tract Obstruction
  • HINMAN, F Jr. “Recovery of renal function after ureteral deligation.” A.M.A. archives of surgery vol. 78,4 (1959): 518. doi:10.1001/archsurg.1959.04320040014005
  • Vaughan, E D Jr, and J Y Gillenwater. “Recovery following complete chronic unilateral ureteral occlusion: functional, radiographic and pathologic alterations.” The Journal of urology vol. 106,1 (1971): 27-35. doi:10.1016/s0022-5347(17)61219-9
  • Vaughan, E D Jr et al. “Unilateral ureteral occlusion: pattern of nephron repair and compensatory response.” The Journal of urology vol. 109,6 (1973): 979-82. doi:10.1016/s0022-5347(17)60599-8
  • Fink RL, Caridis DT, Chmiel R, Ryan G. Renal impairment and its reversibility following variable periods of complete ureteric obstruction. Aust N Z J Surg. 1980 Feb;50(1):77-83. doi: 10.1111/j.1445-2197.1980.tb04502.x. PMID: 6928768.
  • Bander, S J et al. “Long-term effects of 24-hr unilateral ureteral obstruction on renal function in the rat.” Kidney international vol. 28,4 (1985): 614-20. doi:10.1038/ki.1985.173
  • Yokoyama M, Seki N, Oda T, Takeuchi M, Tanada S. Recovery period from ureteral obstructions of different duration and severity in the rat kidney. Int J Urol. 1994 Sep;1(3):212-5. doi: 10.1111/j.1442-2042.1994.tb00037.x. PMID: 7614379.
  • Shapiro, S R, and A H Bennett. “Recovery of renal function after prolonged unilateral ureteral obstruction.” The Journal of urology vol. 115,2 (1976): 136-40. doi:10.1016/s0022-5347(17)59101-6
  • Jones, D A et al. “The biphasic nature of renal functional recovery following relief of chronic obstructive uropathy.” British journal of urology vol. 61,3 (1988): 192-7. doi:10.1111/j.1464-410x.1988.tb06376.x
  • Pickard, Robert et al. “Use of drug therapy in the management of symptomatic ureteric stones in hospitalised adults: a multicentre, placebo-controlled, randomised controlled trial and cost-effectiveness analysis of a calcium channel blocker (nifedipine) and an alpha-blocker (tamsulosin) (the SUSPEND trial).” Health technology assessment (Winchester, England) vol. 19,63 (2015): vii-viii, 1-171. doi:10.3310/hta19630
  • Shah, Taimur T et al. “Factors associated with spontaneous stone passage in a contemporary cohort of patients presenting with acute ureteric colic: results from the Multi-centre cohort study evaluating the role of Inflammatory Markers In patients presenting with acute ureteric Colic (MIMIC) study.” BJU international vol. 124,3 (2019): 504-513. doi:10.1111/bju.14777
  • Blackmur, James, and Scottish Malignant Ureteric Obstruction Study Group . “Management of malignant ureteric obstruction with ureteric stenting or percutaneous nephrostomy.” The British journal of surgery vol. 111,2 (2024): znae035. doi:10.1093/bjs/znae035