Kidney transplant stone treatment outcomes rest on shaky evidence, review finds

Kidney transplant recipients who develop stones in their new organ are usually treated with minimally invasive procedures, yet the evidence behind those treatments is far thinner than the stakes would suggest. A scoping review published in the African Journal of Urology has mapped how outcomes are reported across the literature on so-called graft lithiasis, and it concludes that nearly everything known about success rates rests on pooled, non-comparative figures from small, retrospective series. The review, conducted according to the Arksey and O’Malley framework and reported per the PRISMA-ScR checklist, searched PubMed/MEDLINE, Embase and Scopus, with searches last updated in July 2026. Nineteen studies met the eligibility criteria, of which fourteen provided extractable outcome data: eleven primary clinical reports and three systematic reviews, tabulated separately because the primary reports, published between 1998 and 2021, are likely nested within the later syntheses.

Graft lithiasis is uncommon but consequential. Reported prevalence ranges from 0.1 to 6.3 percent of kidney transplant recipients, and the stones may be donor-derived or develop de novo after transplantation. Unlike native-kidney stone disease, the condition threatens the function of a single, denervated, heterotopically placed kidney with no contralateral backup. The graft sits in the iliac fossa, its nerves are severed, and urine drains through a surgically constructed ureteroneocystostomy. Those features have practical consequences: denervation frequently delays diagnosis because classic renal colic is absent, so patients instead present with graft dysfunction, sepsis or incidental imaging findings, while the ectopic anatomy complicates both antegrade and retrograde access. Minimally invasive options, meaning retrograde or antegrade ureteroscopy, percutaneous nephrolithotomy (PCNL) and shock wave lithotripsy (SWL), have progressively replaced open surgery.

The centerpiece of the review is the largest available meta-analysis on the topic, covering 37 studies, 553 patients and 612 procedures. In that pooled synthesis, three-month stone-free rates were 96 percent for open surgery, a comparator included only for reference, 95 percent for antegrade ureteroscopy, 86 percent for PCNL, 81 percent for retrograde ureteroscopy and 75 percent for SWL. Those estimates derive from 25, 20, 118, 154 and 155 procedures respectively, meaning the highest rates come from the smallest denominators. The review’s author stresses that these are pooled, non-comparative figures from studies with heterogeneous stone-free definitions and should not be read as head-to-head comparisons. The conclusion that antegrade approaches outperform retrograde ureteroscopy and SWL is explicitly labeled hypothesis-generating, resting on a single meta-analysis.

What makes the pattern intriguing is that it appears to diverge from native-kidney practice, where treatment is individualized according to stone and patient factors, retrograde ureteroscopy and SWL are first-line for smaller calculi, and PCNL is reserved for larger ones. The review attributes the difference to graft anatomy rather than stone size, although this attribution is inferential. The transplant ureter is short and its ureterovesical anastomosis is ectopically located, most often near the bladder dome rather than the trigone, making retrograde cannulation difficult; earlier retrograde-access series reported success rates of only 68 to 93 percent for simply reaching the transplant ureter. Conversely, the graft’s anteriorly rotated, subcutaneous position makes percutaneous access technically more straightforward once the 180-degree reorientation of the calyceal anatomy is accounted for. The review also cautions that most published experience originates from a small number of high-volume transplant-urology centers, so an operator-experience effect may be difficult to disentangle from anatomy.

Safety data, where they exist, are encouraging but sparse. The largest multicenter PCNL cohort reported a 10.2 percent complication rate, including septic shock, bleeding requiring embolization and acute renal failure, with no graft loss. Smaller series reported no complications and no permanent graft damage, though the numbers were too small to estimate rare events. A dedicated single-center PCNL audit of six patients reported stone-free rates of 83.3 percent initially, 100 percent at three months and one year, and 66.7 percent at three years. Graft function, usually measured as serum creatinine, was generally stable or improved after successful clearance, but reporting was inconsistent and complications were mostly described narratively, without systematic Clavien-Dindo grading.

Among the review’s sharpest criticisms is the near-total absence of immunosuppression reporting. Immunosuppressive therapy is unique to this population, and at least two mechanistic pathways could plausibly link it to outcomes. Calcineurin inhibitors and corticosteroids are independently associated with hypomagnesemia, hypocitraturia, hypercalciuria and a distal acidification defect resembling incomplete renal tubular acidosis, a metabolic profile favoring calcium-stone formation that could modify recurrence risk. Overall immunosuppressive burden also affects infective risk, relevant to the threshold for staged versus single-session intervention. Yet none of the nineteen included sources analyzed a specific agent, trough level or cumulative burden as a covariate of outcome; where mentioned at all, therapy was described only qualitatively as standard triple therapy. The decline from 100 percent stone-free at one year to 66.7 percent at three years in the six-patient audit illustrates the problem: without metabolic data, residual fragments cannot be separated from de novo recurrence.

Stone composition is equally relevant and equally missing. The only compositional information in the review came from the pooled meta-analytic cohort, in which stones were predominantly calcium-based with a mean size of 11 millimeters and a range of 2 to 50 millimeters; the charted primary studies reported no composition data at all, and no source correlated composition with treatment choice, recurrence or metabolic work-up. The literature also spans nearly three decades, during which standard regimens have shifted from higher-exposure ciclosporin-based protocols toward lower-target, steroid-minimized tacrolimus-based regimens, making it uncertain whether apparent improvements in stone-free rates over time reflect endourologic technique or the evolving perioperative context. The review proposes a graft-specific composite outcome, a transplant-lithiasis Trifecta, combining zero-fragment status at a fixed interval, a graded complication threshold such as no complication above Clavien-Dindo grade II, and a graft-function criterion such as no sustained eGFR decline beyond a pre-specified threshold at three to six months.

Several technical questions remain open. Miniaturized percutaneous tracts have been used in the graft kidney, and a smaller tract should in principle cause less parenchymal injury and bleeding, which matters in a single kidney with no functional reserve; the superficial iliac-fossa position also shortens the skin-to-collecting-system distance, allowing small instruments with ultrasound-only guidance. But none of the charted sources compared mini- with standard PCNL in the graft, so the relative merits of tract size cannot be inferred from available data. A parallel development in native-kidney endourology, suction-assisted flexible ureteroscopy including direct in-scope suction, has so far reached the graft literature only through a single case report describing the first antegrade use of the technique to clear a large donor-derived ureteric calculus, achieving complete clearance without complications. The review emphasizes that this remains anecdotal and that prospective comparative data specific to graft lithiasis are entirely lacking.

The review itself carries limitations its author acknowledges. Screening was performed by a single reviewer, a departure from the dual-reviewer standard, and no formal risk-of-bias appraisal was performed, consistent with scoping methodology. The literature remains dominated by small, retrospective, single-center series and case reports, several of which likely share overlapping cohorts, which may have led to double-counting in pooled estimates, and publication bias favoring technically successful outcomes may inflate the summarized stone-free rates. The definition of stone-free was not standardized, follow-up intervals varied, imaging modalities differed, and the search was restricted to English-language sources. No study used a validated patient-reported outcome measure or a formal composite endpoint integrating clearance, complications and graft-function preservation.

The practical takeaways are measured. Because the transplanted kidney is frequently the patient’s only functioning kidney, the review supports a low threshold for cross-sectional imaging in unexplained graft dysfunction, sepsis or urinary tract infection rather than reliance on classical colicky symptoms, and several included series support earlier, proactive intervention or closer surveillance rather than prolonged watchful waiting. Modality choice in an individual patient should continue to be guided by stone burden and location, graft anatomy, infection status and local expertise. Given the rarity of the condition at any single center, the review argues that multidisciplinary transplant-urology clinics and multicenter collaboration, ideally through prospective registries with standardized reporting of immunosuppression, stone composition, metabolic profile, graded complications and eGFR change, represent the most realistic route to adequately powered future research in this high-stakes population.

Subject of Research: Outcome reporting in minimally invasive treatment of kidney transplant graft stones

Article Title: A scoping review of outcomes and clinical value in minimally invasive management of graft lithiasis

Article References: Dell’Atti, L. (2026). A scoping review of outcomes and clinical value in minimally invasive management of graft lithiasis. African Journal of Urology, 32(1), Article 77. https://doi.org/10.1186/s12301-026-00626-x

Image Credits: AI Generated

DOI: 10.1186/s12301-026-00626-x

Keywords: graft lithiasis, kidney transplant, urolithiasis, ureteroscopy, percutaneous nephrolithotomy, shock wave lithotripsy, stone-free rate, scoping review, immunosuppression, graft function, endourology, transplant urology