AUA2021 Second Opinion Cases: Medullary Sponge Kidney and Non-Obstructing Stones Causing Pain

By: Jodi Antonelli, MD | Posted on: 03 Sep 2021

Patients with chronic flank pain and nonobstructing renal calcifications often seek second opinions on a quest to find a treatment that can ease their pain. It has been hypothesized that nonobstructing stones, particularly papillary calcifications, could cause renal collecting duct obstruction and this could be perceived as painful. Despite the lack of experimental support for this hypothesis, it has been further posited that surgery to release and remove these calcifications, and therefore eliminate the source of obstruction, could alleviate pain.

Given the lack of objective evidence linking nonobstructing stones to a pain pathway in the kidney, and the morbidity of open stone surgery, surgical removal of nonobstructing stones for the indication of pain historically was not recommended. As surgical technology for stone removal became less invasive, investigators began to explore whether treatment of nonobstructing stones was associated with pain relief. In 1988 Coury et al reported that 25 of 26 patients had complete resolution of pain after percutaneous nephrolithotomy or shock wave lithotripsy to treat nonobstructing stones in the setting of chronic pain attributed to the kidney.1 The authors noted pain from calyceal stones was different from renal colic, specifically describing it as located over the kidney and nonradiating, constant rather than spasmodic and often presenting as vague or anterior in location, making it easily confused with musculoskeletal or gastrointestinal pain.

As technology for the endoscopic management of stones continued to progress, flexible ureteroscopy offered an advantage over shock wave lithotripsy, with the ability to perform laser lithotripsy and basket extraction improving the stone clearance of adherent papillary and submucosal stones. In 2000 Kerbl and Clayman were the first to report on rendering a patient stone-free with resolution of pain utilizing flexible ureteroscopy with laser lithotripsy for the treatment of submucosal stones.2

Taub et al retrospectively evaluated the efficacy and durability of ureteroscopy with holmium laser papillotomy to treat 20 patients (27 renal units) with chronic pain and papillary calcifications in the absence of free renal or ureteral calculi.3 The authors described a technique of superficial ablation of the renal papillae with a goal of unobstructing collecting tubules, releasing trapped calculi and, in so doing, reducing hydrostatic pressure in the tubules. A substantial improvement in pain was reported after 85% of procedures. The authors found when fewer than 7 papillae were treated, the mean time to improvement of pain was shorter (1.5 versus 4.6 weeks, p=0.02). Overall satisfaction with the procedure was 93%. Inherent to any retrospective study, their data were limited by incomplete followup and lack of randomization, making it impossible to assess the impact of placebo effect on their results.3

In addition to this single center report, a multicenter retrospective review was conducted to assess longer term safety and durability of ureteroscopic laser papillotomy for the treatment of chronic pain associated with renal papillary calcifications.4 A total of 146 ureteroscopic laser papillotomies performed in 50 patients over 10 years at 3 institutions were included in the final analysis. Significantly less pain for at least 3 months was noted after 83% of the procedures, with 60% of patients reporting a mean remission time of more than 1 year. There was no significant decrease in renal function after the procedure. New onset hypertension was noted in 6% of patients. The authors cautioned that in order to maximize success, a full assessment of other sources of pain should be pursued, and only those without other cause of pain and with radiographic evidence of papillary calcifications or intraductal stones (see figure) should be offered ureteroscopy with laser papillotomy.4 Xu et al found similar results with pain relief using ureteroscopy with laser papillotomy in 25 patients with medullary sponge kidney (MSK) with radiographic evidence of intraductal papillary calculi.5

Figure. Medullary sponge kidney. Noncontrast computerized tomography shows dense nephrocalcinosis (A). Intravenous contrast shows calcifications within dilated tubules (B).4

While these retrospective results are compelling, it is important to recognize that even in MSK patients, where the physiological link is the strongest, there is a lack of experimental data to support the compelling hypothesis of pain caused by “micro-hydronephrosis” occurring in obstructed papillary collecting ducts.6 Certainly in patients with Randall’s plaque and adherent stones a physiological explanation for the mechanism of pain relief with stone removal has not been described. Despite this, the available, albeit limited, data do support a potential benefit of treatment in properly selected patients. While complete papillectomy has been shown to impair renal concentrating ability and increase free water clearance in animal models,7,8 renal papillotomy as described in these retrospective series had favorable short and longer term safety outcomes. Furthermore, techniques akin to papillotomy, specifically renal papillary biopsy and ablation of superficial papillary cell layers, have been reported as safe and feasible.9,10 Ultimately, with available evidence there is not a clear answer on how best to treat these patients, but a better understanding of proper patient selection and the nuances of surgical technique can maximize the success of treatment when a patient comes to you for a second opinion regarding this challenging but not uncommon situation.

  1. Coury TA, Sonda LP, Lingeman JE et al: Treatment of painful caliceal stones. Urology 1988; 32: 119.
  2. Kerbl K and Clayman RV: Endourologic treatment of nephrocalcinosis. Urology 2000; 56: 508.
  3. Taub DA, Suh RS, Faerber GJ et al: Ureteroscopic laser papillotomy to treat papillary calcifications associated with chronic flank pain. Urology 2006; 67: 683.
  4. Gdor Y, Faddegon S, Krambeck AE et al: Multi-institutional assessment of ureteroscopic laser papillotomy for chronic flank pain associated with papillary calcifications. J Urol 2011; 185: 192.
  5. Xu G, Wen J, Wang B et al: The clinical efficacy and safety of ureteroscopic laser papillotomy to treat intraductal papillary calculi associated with medullary sponge kidney. Urology 2015; 86: 472.
  6. Gambaro G, Goldfarb DS, Baccaro R et al: Chronic pain in medullary sponge kidney: a rare and never described clinical presentation. J Nephrol 2018; 31: 537.
  7. Dalton DP, Levin ML, Schaeffer AJ et al: Unilateral renal papillectomy via laser or incisional techniques: chronic functional effects in the dog. Urology 1994; 43: 310.
  8. Seifman BD, Rubin MA, Williams AL et al: Functional effects of unilateral laser papillectomy in the pig. Urology 2001; 57: 832.
  9. Knoll T, Michel MS, Cueva-Martinez A et al: Evaluation of superficial papillary ablation by endoscopic lasers in an ex vivo kidney model. J Endourol 2002; 16: 195.
  10. Kuo RL, Lingeman JE, Evan AP et al: Endoscopic renal papillary biopsies: a tissue retrieval technique for histological studies in patients with nephrolithiasis. J Urol 2003; 170: 2186.
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