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Explore clinically focused review articles designed to help physicians refine patient selection, understand risk factors, optimise SWL protocols, and apply evidence-based decision-making in daily stone management.
Background: Diabetes mellitus (DM) affects more than 537 million adults worldwide and is increasingly prevalent among patients presenting with urolithiasis, constituting 10–15% or more of the extracorporeal shock wave lithotripsy (ESWL) caseload in many centres. The metabolic derangements of diabetes — particularly insulin resistance and impaired renal ammoniagenesis — fundamentally alter stone composition, operative risk, and post-procedural recovery in ways that distinguish the diabetic patient from the general stone population.
Objectives: This article synthesizes the available evidence on three clinically critical dimensions of ESWL in the diabetic patient: (1) the nature and implications of stone disease in diabetes, with emphasis on the predominance of radiolucent uric acid stones; (2) the diabetic patient’s unique complication profile — encompassing infection risk, nephropathy-related renal vulnerability, and autonomic neuropathy; and (3) the contested hypothesis that ESWL may induce or exacerbate diabetes through subclinical pancreatic injury.
Methods: A structured narrative review was conducted incorporating landmark studies, population-based cohort analyses, and major guideline statements — including the 2025 American Urological Association (AUA) Surgical Management of Kidney and Ureteral Stones Guideline. Key data sources include a series of 2,464 calculi demonstrating uric acid stone predominance in Type 2 DM (Daudon et al., JASN 2006), a retrospective cohort of 1,838 ESWL treatments identifying diabetes as an independent predictor of post-procedural complications (Lildal et al., Scand J Urol 2017), and multiple long-term studies evaluating ESWL as a potential risk factor for new-onset diabetes, including the Mayo Clinic 19-year case-control study (Krambeck et al., J Urol 2006) and the Ontario population-based cohort of all ESWL and ureteroscopy treatments between 1994 and 2014 (PMID: 30358066).
Results: Uric acid stones constitute 35.7% of calculi in Type 2 diabetic patients compared to 11.3% in non-diabetic stone formers — a near three-fold enrichment with direct implications for ESWL targeting, as these stones are radiolucent on fluoroscopy and require ultrasound guidance. Non-contrast CT Hounsfield unit measurement serves a dual function, predicting both stone fragility (uric acid stones typically < 500 HU) and composition. Urine culture — not urinalysis alone — is mandated by the 2025 AUA Guideline for all diabetic patients prior to ESWL due to elevated infectious risk; diabetes was confirmed as an independent predictor of post-ESWL complications, with infection as the primary complication type. Diabetic nephropathy increases renal parenchymal vulnerability to shock wave injury; patients with eGFR < 45 mL/min/1.73m² should be considered for ureteroscopy. The ESWL–diabetes causation hypothesis generated significant concern following the Krambeck Mayo Clinic study (OR ≈ 3.75 for new-onset DM at 19 years); however, the largest and most rigorously controlled population-based studies — including the Ontario cohort and Rochester Epidemiologic Project — found no elevated DM risk after appropriate covariate adjustment, and the NHANES-matched study of 1,869 patients demonstrated statistically identical DM incidence between ESWL-treated and control populations.
Conclusions: ESWL remains a safe and appropriate treatment modality for carefully selected diabetic stone patients, but requires a significantly more deliberate pre-procedural assessment than for the general stone population. Mandatory urine culture, glycaemic status evaluation, renal function assessment, stone composition characterisation via non-contrast CT, and ultrasound guidance availability are essential prerequisites. Modern ESWL does not carry a proven risk of inducing new-onset diabetes; however, minimising cumulative high-energy sessions is a reasonable precaution, particularly for left-sided stones where pancreatic proximity is greatest. A practical evidence-based clinical protocol for pre-treatment assessment, intraoperative modifications, and post-procedural surveillance is presented to guide safe ESWL practice in the diabetic patient.
Diabetes mellitus (DM) is one of the most prevalent chronic conditions in contemporary urological practice. With global prevalence exceeding 537 million adults and rising, the diabetic patient presenting with urolithiasis is no longer the exception — in many busy lithotripsy centers, diabetic patients constitute 10–15% or more of the ESWL caseload. The intersection of diabetes and urinary stone disease is, however, far from straightforward. Diabetes alters the metabolic milieu of urine, skews stone composition toward uric acid, impairs immune defenses, compromises renal microcirculation, and — through its association with obesity and metabolic syndrome — creates a patient phenotype that demands a more deliberate pre-treatment assessment than the general stone patient.
This article addresses the ESWL-specific considerations in the diabetic patient from three distinct angles: first, the nature of stone disease itself in diabetic patients, which directly impacts both the imaging and treatment decision; second, the procedural risks and complications unique to or amplified by diabetes; and third, a practical clinical protocol for safe, effective ESWL in this cohort. I also address the controversial and much-debated question of whether ESWL itself may induce or worsen diabetes — a question that has generated provocative data from multiple directions.
The most clinically significant and practically impactful feature of stone disease in the diabetic patient is the dramatic shift in stone composition toward uric acid. The biological mechanism is well-established: insulin resistance, the hallmark of Type 2 DM, impairs ammonium production in the renal tubule. This results in a chronically acidic urinary pH — typically below 5.5 — which is the primary driver of uric acid crystallization and stone formation. At such pH levels, the poorly soluble undissociated form of uric acid predominates over the more soluble urate anion, creating conditions favorable to nucleation and stone growth.
The quantitative data are striking. In a landmark series of 2,464 calculi analyzed by Daudon, Traxer, and colleagues (Journal of the American Society of Nephrology, 2006), the proportion of uric acid stones was 35.7% in patients with Type 2 diabetes compared to only 11.3% in non-diabetic stone formers (p < 0.0001). Reciprocally, the proportion of patients with Type 2 diabetes was significantly higher among uric acid stone formers than among calcium stone formers (27.8% vs 6.9%; p < 0.0001). This is not a marginal difference — it represents a three-fold enrichment of uric acid stones in the diabetic population, and it has direct implications for ESWL planning.
A more recent spectroscopic study of 128 diabetic patients with kidney stones (Iasi, Romania; Journal of Clinical Medicine, 2024) further refined the picture by separating Type 1 and Type 2 diabetes. Type 2 diabetic patients predominantly formed mixed uric acid stones (52.3%), while Type 1 diabetic patients more commonly developed pure uric acid stones (p < 0.001). Patients with pure uric acid stones had higher serum creatinine values, more frequent stone recurrence, and a shorter time to recurrence compared to patients with other stone types.
Non-contrast CT Hounsfield unit (HU) measurement is the single most useful pre-ESWL investigation in the diabetic patient, serving a dual function: it predicts stone fragility (uric acid stones are typically < 500 HU and therefore highly amenable to ESWL, while calcium oxalate monohydrate stones > 1000 HU are substantially harder), and it enables stone visualization regardless of composition. A diabetic patient with a stone measuring < 500 HU on non-contrast CT, combined with a urinary pH consistently below 5.5 and the clinical metabolic profile of Type 2 DM, can be presumed to have a predominantly uric acid stone.
Such stones, while invisible on fluoroscopy, are paradoxically ideal for ESWL in terms of fragility: their lower density means they typically require fewer shock waves and lower energy to achieve adequate fragmentation. Ultrasound-guided ESWL is the preferred modality for these patients. In centers where real-time ultrasound guidance is not available, Contrast guided ESWL with fluoroscopy is an alternative.
Before committing to ESWL, the diabetic patient with a pure uric acid stone should be offered a trial of urinary alkalinization as primary therapy. By raising urinary pH to 6.5–7.0 through oral potassium citrate (typically 30–60 mEq/day in divided doses), uric acid stones can be completely dissolved in a significant proportion of patients without any procedural intervention. This approach is especially appealing in diabetic patients who may have compromised healing and elevated infection risk. In patients with small-to-medium pure uric acid stones (≤ 15 mm), a 4–8 week trial of alkalinization is entirely reasonable before considering ESWL. The practical reality, however, is that: (1) many diabetic patients present with obstructing or symptomatic stones requiring more urgent treatment; (2) many uric acid stones are mixed, with calcium components that will not dissolve; and (3) patient compliance with long-term alkalinization is variable.
The most consequential perioperative risk in the diabetic ESWL patient is urinary tract infection and its septic sequelae. Diabetes is a well-recognized state of immune compromise: neutrophil chemotaxis, phagocytosis, and oxidative burst are all impaired, particularly in the setting of poor glycaemic control. This translates into a substantially higher risk of UTI, and — when ESWL is performed in the presence of unrecognized bacteriuria — of post-lithotripsy urosepsis.
A large retrospective cohort of 1,838 ESWL treatments performed between 2009 and 2015 (Ängelholm Hospital, Sweden; PubMed PMID: 28770662) directly examined complication rates using multivariable analysis. The overall complication rate at 14 days was 6.4%, with infection accounting for 2.4% of all cases. Diabetes was identified as an independent predictor of complications on multivariable analysis — alongside larger stone size. Infection was the most common complication overall, and the significantly elevated background infection risk in diabetic patients amplifies this signal considerably.
The 2025 AUA Surgical Management of Kidney and Ureteral Stones Guideline explicitly identifies diabetes as a clinical condition warranting urine culture (not merely urinalysis) prior to stone surgery — including SWL — specifically because of the conferred higher infectious risk. The Guideline also lists diabetes alongside immunocompromised state, history of obstructive sepsis, struvite stone history, and chronic indwelling tubes as conditions requiring mandatory urine culture before proceeding.
Diabetic nephropathy, present in varying degrees in a substantial proportion of long-standing Type 2 diabetic patients, alters the renal parenchyma in ways that parallel — and potentially compound — the risk profile described for hypertensive patients. The hallmark lesions of diabetic nephropathy — glomerulosclerosis, thickening of the glomerular basement membrane, afferent and efferent arteriolar hyalinization, and interstitial fibrosis — result in a kidney with impaired microvascular reserve and reduced capacity to withstand the cavitation forces delivered by shock waves.
The practical consequence is that serum creatinine and eGFR are essential pre-ESWL investigations in all diabetic patients, not optional ones. A patient with CKD Stage 3 or higher (eGFR < 45 mL/min/1.73m²) deserves special consideration: the potential for ESWL-induced acute renal parenchymal injury superimposed on already-compromised renal function — with associated recovery impairment — should factor prominently in the decision to proceed with ESWL versus ureteroscopy. Ureteroscopy, which avoids shock wave delivery to the renal parenchyma entirely, may be the preferable modality in diabetic patients with significant nephropathy, particularly for ureteric stones.
The skin-to-stone distance also warrants mention. Diabetes is closely associated with obesity, and increased body habitus is a well-recognized factor reducing ESWL efficacy — both through signal attenuation and through the challenge of accurate stone targeting. A skin-to-stone distance > 10–12 cm is an independent predictor of lower stone-free rates, and should be factored into the pre-treatment counselling of obese diabetic patients.
Long-standing diabetic patients may have significant autonomic and peripheral neuropathy. While this might theoretically reduce pain perception during ESWL and lower analgesic requirements, it also means that these patients may have impaired awareness of post-procedure complications — hematoma, ureteric obstruction from steinstrasse, or early infection — that would normally present with clear pain signals. This has practical implications: diabetic patients with known neuropathy may warrant a more proactive post-procedure surveillance protocol, including a routine ultrasound at 48–72 hours regardless of symptom status, rather than the symptom-driven follow-up that suffices for most patients.
The potential for ESWL to injure the pancreas has biological plausibility: the pancreas, particularly the pancreatic tail, lies in close anatomical proximity to the left kidney. When shock waves are delivered for left renal or proximal ureteric stones, the pancreatic parenchyma may lie within or near the focal zone, depending on lithotripter geometry, patient positioning, and stone location. Isolated case reports of acute pancreatitis following ESWL for left renal stones — including at least one case of acute necrotizing pancreatitis — have been published (Karakayali et al., Int J Urol, 2006). While rare, these reports established the anatomical basis for concern about cumulative subclinical pancreatic injury from repeated ESWL.
The study that placed ESWL-induced diabetes on the urological map was published by Krambeck, Gettman, Rohlinger et al. from the Mayo Clinic in Journal of Urology (2006; 175:1742–1747). This retrospective case-control study compared 630 patients treated with ESWL in 1985 with a control group managed conservatively for kidney stones at the same time, with 19 years of follow-up. The results were striking: at long-term follow-up, the ESWL group had developed diabetes at nearly four times the rate of controls (odds ratio approximately 3.75, persistent after adjustment for BMI). This finding generated significant concern and was widely reported in both urological and mainstream media.
The study had important methodological limitations: it used a single, early-generation lithotripter (a 1985 model using electrohydraulic technology with a different focal zone and energy profile from contemporary electromagnetic machines); the control group was not randomized; and the case-control design is susceptible to selection and detection biases. Nonetheless, the authors and the Mayo Clinic themselves concluded that patients should be counselled about this potential risk, and that stone prevention strategies should be prioritized to minimize the need for repeated ESWL.
The same Mayo Clinic group revisited this question with a more rigorous methodology in a subsequent study using the Rochester Epidemiologic Project (REP), published in Urology (de Cógáin, Krambeck, Rule et al., 2011). This population-based cohort study identified all Olmsted County, Minnesota residents diagnosed with urolithiasis from 1985 to 2008 — 5,287 incident stone formers without pre-existing diabetes, with mean follow-up of 8.7 years. Of these, 423 patients (8%) were treated with SWL. Using Cox proportional hazards models, SWL was not found to be an independent predictor of new-onset diabetes after adjustment for relevant covariates. The authors noted that the earlier findings were likely susceptible to selection bias, and concluded that SWL in a population-based cohort setting did not carry the alarming DM risk originally reported.
The same Mayo Clinic group revisited this question with a more rigorous methodology in a subsequent study using the Rochester Epidemiologic Project (REP), published in Urology (de Cógáin, Krambeck, Rule et al., 2011). This population-based cohort study identified all Olmsted County, Minnesota residents diagnosed with urolithiasis from 1985 to 2008 — 5,287 incident stone formers without pre-existing diabetes, with mean follow-up of 8.7 years. Of these, 423 patients (8%) were treated with SWL. Using Cox proportional hazards models, SWL was not found to be an independent predictor of new-onset diabetes after adjustment for relevant covariates. The authors noted that the earlier findings were likely susceptible to selection bias, and concluded that SWL in a population-based cohort setting did not carry the alarming DM risk originally reported.
One of the methodologically strongest studies on this question was a retrospective population-based cohort study of all ESWL and ureteroscopy (URS) stone treatments performed in Ontario, Canada between January 1994 and March 2014, utilizing linked encoded healthcare databases (PubMed PMID: 30358066). The primary outcome was new-onset DM more than 90 days after treatment. After multivariable Cox proportional hazards analysis controlling for age, sex, region, income, year of treatment, and comorbidity index, no increased risk of DM was found in ESWL-treated patients compared to those treated with URS. A sensitivity analysis restricted to left renal or proximal ureteric stone treatments — where pancreatic exposure would theoretically be highest — similarly showed no significant difference.
Makhlouf and colleagues (Urology, 2009) studied 1,869 patients treated with the Medstone-STS electrohydraulic lithotripter from 1999 to 2002, matched for age, sex, and BMI to controls from the National Health and Nutrition Examination Survey (NHANES) database. At ESWL, 8.67% of patients had DM; at median 6-year follow-up, this had risen to 13.9%. In the matched NHANES group, 8.34% had DM at baseline and 14.1% at follow-up. The rate of new DM cases was statistically identical between the two groups (5.2% vs 5.8%; p = 0.47). Multivariate analysis confirmed that age, sex, BMI, and family history — not ESWL treatment parameters — were the predictors of DM development.
A somewhat contrasting signal was reported in a Swiss retrospective study published in International Urology and Nephrology (2018). This study compared patients treated with SWL for kidney stones versus those treated with SWL for distal ureteric stones only (where shock waves do not traverse renal or pancreatic parenchyma) and also compared against the Swiss Health Survey (SHS) dataset. After a median follow-up of 13.7 years, the odds ratio for reporting diabetes was 1.54 (95% CI: 1.21–1.97) in the renal SWL group versus the SHS dataset. Hypertension showed a similarly elevated OR of 1.30. The authors hypothesized that this reflected both direct pancreatic injury from shock waves (explaining the DM signal) and renal parenchymal injury (explaining the hypertension signal). Importantly, this was a questionnaire-based study with no biochemical validation of DM diagnosis, and the use of the general population rather than stone-disease controls may have introduced unmeasured confounding.
An Iranian cohort study published in Urology Annals (2017) followed 307 patients who had undergone ESWL from 1991 to 1994, re-evaluating them in 2009 at 15–19 years post-procedure. The mean fasting blood sugar (FBS) increase across the cohort was 11.86 g/dl. Importantly, the FBS elevation was more significant at shock wave intensities above 15.5 kV, suggesting a dose-energy relationship. The 8.1% DM prevalence in this cohort using ADA criteria compared to a general population background rate of approximately 5.8% at similar follow-up. The authors did not find a significant relationship between age, sex, BMI, or total number of shock waves and FBS changes — only intensity emerged as a predictor.
The totality of evidence on ESWL-induced diabetes is inconsistent but not dismissible. The largest and most rigorously controlled population-based studies (Ontario cohort, Rochester REP, NHANES-matched study) find no elevated DM risk. The earlier case-control study and the Swiss retrospective analysis do find an elevated signal. The probable explanation for the discrepancy lies in: (1) older lithotripter technology in the positive studies, which may have delivered larger focal zones and higher peak pressures than contemporary machines; (2) methodological limitations including detection bias and inadequate confounding control; and (3) the dose-dependent nature of the potential injury, which is attenuated with modern protocol optimization (rate reduction, ramping, total shock wave limitation).
For the treating physician, the practical conclusion is: ESWL does not carry a proven clinically significant risk of inducing new-onset diabetes with modern machines and protocols. However, in patients who already have diabetes or impaired glucose tolerance, cumulative repeated high-energy ESWL should be minimized, and if multiple sessions are anticipated, ureteroscopy is a reasonable alternative to limit pancreatic exposure, particularly for left-sided stones.
| Assessment Parameter | Action Required | Rationale |
|---|---|---|
| Urine culture | Mandatory — not optional. Treat if positive before proceeding. | AUA 2025 Guideline: DM is a high-infection-risk condition |
| HbA1c + fasting glucose | Document glycaemic control. HbA1c > 9%: discuss optimization with physician. | Poor control impairs immune function and wound healing |
| Serum creatinine / eGFR | Stage CKD if present. eGFR < 45: consider ureteroscopy as alternative. | Diabetic nephropathy increases renal parenchymal vulnerability |
| Non-contrast CT (NCCT) | Measure HU of stone. Record SSD. Confirm stone location. | HU < 500 suggests uric acid; confirms radiolucency; guides modality choice |
| Urinary pH (spot or 24hr) | pH consistently < 5.5 strongly supports uric acid composition. | Low pH in DM = insulin resistance/impaired ammoniagenesis |
| Obesity / SSD | SSD > 10–12 cm: counsel regarding reduced stone-free rate. | Attenuation of shock waves through excessive body habitus |
| Prior stone analysis | Review if available. Uric acid stone = consider alkalinization first. | Avoids ESWL if medical dissolution is feasible |
| Favor ESWL | Favor Ureteroscopy |
|---|---|
| Uric acid stone (low HU) with successful ultrasound targeting | Uric acid stone — but poor ultrasound visualization |
| Sterile urine confirmed on culture | History of recurrent UTI / persistent bacteriuria despite antibiotics |
| eGFR > 60 (no significant nephropathy) | CKD Stage 3b or worse (eGFR < 45) |
| SSD ≤ 10 cm / BMI < 30 | BMI > 35 or SSD > 12 cm (predicted poor SFR with ESWL) |
| Stone ≤ 15 mm, non-lower-pole, upper tract | Obstructing stone with upper tract dilatation requiring urgent treatment |
| Patient preference for non-invasive approach | Ureteric stone (where URS achieves higher single-session SFR) |
Not all diabetic stone patients are best served by ESWL. The following table summarizes the clinical factors that should shift the decision toward ureteroscopy in the diabetic patient:
For diabetic patients proceeding to ESWL, I apply the following intraoperative modifications in addition to standard lithotripsy protocol:
| Parameter | Modification / Recommendation |
|---|---|
| Stone targeting modality | Ultrasound guidance preferred for uric acid or mixed stones (fluoroscopy-invisible) |
| Shock wave rate | 60/min — reduces tissue injury; supported by Indiana University experimental data |
| Ramping protocol | Mandatory: begin at lowest energy and titrate upward step-wise |
| Total shock waves | Limit to ≤ 2,000–2,500; avoid maximum dosing in single session |
| Targeting confirmation | Re-confirm stone position every 200–300 shock waves (stone migration risk with hydronephrosis in diabetics) |
| Blood glucose check | Pre-procedure blood glucose check; hypoglycaemic agents/insulin: follow anaesthetic team guidance |
| Antibiotic cover | If any residual doubt about urine sterility, single-dose prophylactic antibiotic at induction |
| Contraindication Type | Condition |
|---|---|
| Absolute | Untreated bacteriuria or positive urine culture at time of ESWL (sepsis risk) |
| Absolute | Active UTI or fever at time of procedure |
| Absolute | Uncorrected coagulopathy |
| Absolute | Pregnancy |
| Relative | Poorly controlled diabetes (HbA1c > 9%) — optimize before elective ESWL |
| Relative | CKD Stage 3b or worse (eGFR < 45) — consider ureteroscopy |
| Relative | Radiolucent stone without ultrasound guidance capability |
| Relative | Skin-to-stone distance > 12 cm — counsel regarding expected reduced stone-free rate |
| Relative | History of urosepsis following previous stone manipulation — exceptionally high vigilance required |
