Andrew P. Evan

Endoscopic Evidence of Calculus Attachment to Randall’s Plaque

PURPOSE It has been proposed that calcium oxalate calculi begin as small stones attached to the renal papillae at sites of Randalls plaque. However, no study has investigated the prevalence of attached stones in calcium oxalate stone formers or the relationship between stone attachment site and Randalls plaque. In this study we used endoscopic examination of renal papillae in stone formers undergoing percutaneous nephrolithotomy to investigate both issues. MATERIALS AND METHODS Idiopathic calcium oxalate stone formers undergoing PNL for stone removal were enrolled in this study. Multiple papillae were examined and images were recorded by digital video. The presence or absence of papillary plaque and attached stones was noted, as was the site of stone attachment. RESULTS In 23 patients, 24 kidneys and 172 renal papillae were examined. All kidneys were found to have papillary plaque and 11 of the patients had attached stones. Most papillae (91%) contained plaque. CONCLUSIONS The prevalence of attached stones in calcium oxalate stone formers (48%) is greater than that previously reported for the general population. Attachment appears to be on Randalls plaque. The high prevalence of attached stones and the appearance of the attachment site are consistent with a mechanism of calcium oxalate stone formation in which stones begin as plaque overgrowth.

A New World Revealed: Early Experience With Digital Ureteroscopy

PURPOSE The latest digital ureteroscope, the DUR-D (Gyrus ACMI Inc., Southborough, Massachusetts) offers image quality that greatly exceeds current analog image capabilities. The purpose of this report was to document the applicability of this device in studying the earliest stages of stone formation. MATERIALS AND METHODS Symptomatic patients with nephrolithiasis (less than 1 cm in diameter) were prospectively enrolled and their renal papilla digitally mapped prior to stone removal. Recovered stones were photographed and analyzed using micro-computerized tomography. If the procedure could not be completed with the DUR-D, a conventional ureteroscope was used. Minors, pregnant patients and those with systemic disorders were excluded. RESULTS Eight patients (10 renal units), 2 cystine and 6 calcium oxalate stone formers, were studied with a mean age of 50.1 years. Excellent images were collected for all papilla except in 2 cases; a proximal ureteral stricture and acute angulation of the lower pole collecting system, respectively. There were no mechanical device failures. Of the 10 renal units 7 had stents postoperatively and there were no patient complications. CONCLUSIONS The ease of use and high quality images of digital ureterorenoscopy will allow the documentation of the earliest stages of calcium oxalate stone formation and, thereby, advance our understanding of the pathogenesis of calcium oxalate stone formation.

Clinical and laboratory characteristics of calcium stone‐formers with and without primary hyperparathyroidism

To compare the clinical presentation, laboratory features and outcome of treatment in stone formers (SF) with primary hyperparathyroidism (HPT) to those without systemic disease.

In idiopathic calcium oxalate stone-formers, unattached stones show evidence of having originated as attached stones on Randall’s plaque

Study Type – Diagnostic (exploratory cohort)
Level of Evidence 2b

Reduced renal function and benefits of treatment in cystinuria vs other forms of nephrolithiasis

A significant study from the USA compares cystine stone formers and routine stone formers; the former group had a higher requirement for therapeutic procedures, but this was less if they took chelating agents, although remaining higher than in the latter group. Other interesting findings are also presented.

Renal functional effects of simultaneous bilateral single‐tract percutaneous access in pigs

To present our findings of simultaneous bilateral percutaneous nephrolithotomy (sbPCNL) on bilateral renal haemodynamic and excretory function in an in vivo pig model, as despite sbPCNL being a treatment strategy for patients with bilateral renal stones, the functional response of both kidneys to such a procedure is unknown.

Shock Wave Injury to the Kidney in SWL: Review and Perspective

Shock wave lithotripsy (SWL) is a first‐line option for treatment for urinary calculi—particularly effective for the removal of uncomplicated stones from the upper urinary tract. The success of lithotripsy is tempered, however, by the occurrence of acute injury that has been reported to progress to long‐term complications. SW trauma to the kidney is a vascular lesion characterized by parenchymal and subcapsular bleeding. The acute lesion is dose‐dependent, and typically localized to the focal volume of the lithotripter. Cavitation has been implicated in vessel rupture, but SW‐shear has the potential to be a primary mechanism for damage as well. Possible chronic adverse effects of SWL may include new‐onset hypertension, development of diabetes, and exacerbation of stone disease. If acute trauma could be reduced, it seems likely that serious long‐term effects could be minimized, or even eliminated. Reducing the dose of SW’s needed for stone breakage is one option. Improved coupling improves stone breakage, and slowing SW rate significantly improves stone‐free outcomes. Experiments with animals now show that treatment protocols can be designed to protect against tissue injury. Initiating treatment with low energy SW’s dramatically reduces lesion size, and reducing the rate of SW delivery virtually eliminates SW trauma altogether. SWL stands to gain from new advances in technology, as lithotripters become safer and more effective. Perhaps the greatest progress will be made when we have determined the physical mechanisms of SW action both for stone breakage and tissue damage, and have better characterized the biological response to SW’s—as this will provide the principles needed to achieve the best combination of safety and efficiency with whatever lithotripter is at hand.

Effect of Shock Wave Lithotripsy on Renal Hemodynamics

Extracorporeal shock wave lithotripsy (SWL) can injure tissue and decrease blood flow in the SWL‐treated kidney, both tissue and functional effects being largely localized to the region targeted with shock waves (SWs). A novel method of limiting SWL‐induced tissue injury is to employ the “protection” protocol, where the kidney is pretreated with low‐energy SWs prior to the application of a standard clinical dose of high‐energy SWs. Resistive index measurements of renal vascular resistance/impedance to blood flow during SWL treatment protocols revealed that a standard clinical dose of high‐energy SWs did not alter RI during SW application. However, there was an interaction between low‐ and high‐energy SWL treatment phases of the “protection” protocol such that an increase in RI (vasoconstriction) was observed during the later half of SW application, a time when tissue damage is occurring during the standard high‐energy SWL protocol. We suggest that renal vasoconstriction may be responsible for reducing the...

Treatment Protocols to Reduce Injury and Improve Stone Breakage in SWL

Here we provide a capsule summary of key observations showing that adverse effects can be reduced and stone breakage outcomes can be improved by the choice of the treatment protocol used in SWL. The take home message is—technique in lithotripsy can be used to significant advantage. SW‐rate is key, and so is the sequence of SW delivery. Patient studies have shown that stone breakage is significantly improved at 60SW/min compared to a rate of 120SW/min, and laboratory experiments with pigs show that acute SWL injury to the kidney can be reduced dramatically by further slowing the SW firing rate to 30SW/min. The sequence of SW administration has a profound effect on the kidney, and renal injury is significantly reduced when the treatment protocol incorporates a priming dose of SW’s followed by a brief pause before treatment is resumed. Continued developments in lithotripsy technology are welcome and will hopefully lead to improved SWL systems. Current experience suggests, however, that technology is not a su...

Pathogenesis of Stone Disease

All stones share similar presenting symptoms, and urine supersaturation with respect to the mineral phase of the stone is essential for stone formation. However, recent studies using papillary biopsies of stone formers provide a view of the histology of renal crystal deposition which suggests that the early sequence of events leading to stone formation may differ depending on the type of stone and on the urine chemistry leading to supersaturation. Three general patterns of crystal deposition are seen: interstitial apatite plaque in idiopathic calcium oxalate stone formers, which is the site of stone attachment; tubule deposition of apatite, seen in all calcium phosphate stone formers; and mixtures of apatite and another crystal phase, such as cystine or calcium oxalate, seen in patients with cystinuria or enteric hyperoxaluria. The presence of apatite crystal in either the interstitial or tubule compartment (and sometimes both) of the renal medulla in stone formers is the rule, and has implications for th...