![]() This concern for variance is compounded upon consideration of the span of time over which many of the cited large series were published. Even with the use of modern techniques at high-volume reference laboratories, however, reproducibility between assays can be suboptimal. The technique for performing stone analysis can involve a variety of different imaging and chemical-based technologies which have been refined over the past several decades. Further complicating matters is the issue of the heterogeneity of technical stone analysis and the incumbent standard error that exists for that process. It has been postulated that increases in obesity rates in the United States over the past few decades could be contributing to the trend since obesity and the metabolic syndrome are known to be risk factors for stone formation, although this does not account for the fact that the trend is being observed internationally as well. The reasons behind this apparent shift toward a predominance of metabolic stone types in modern staghorn series are not immediately clear. The compositions of the stones within the metabolic group were CaP 52%, UA 18%, CaOx 18%, and cystine 12%. Forty-four (61%) had metabolic stones, and 28 (39%) had infection stones. In a separate series with strikingly similar findings, Haden and colleagues reported on the results of 72 patients who underwent PNL for staghorn calculi between 20. Thirteen of the 29 (48%) patients with metabolic stones completed 24-h urine testing, and all of them were noted to have metabolic abnormalities. Predominant stone compositions within the metabolic group were calcium phosphate (CaP) 55%, uric acid (UA) 21%, calcium oxalate (CaOx) 14%, and cystine 10%. Of the 52 staghorn stones that were treated, 29 (56%) were metabolic stones compared to 23 (44%) infection stones. Viprakasit and colleagues reported on their series of 48 patients with staghorn calculi who underwent percutaneous nephrolithotomy (PNL) between 20. Metabolic stone compositions, as reportedĬaP: 17% CaOx: 17% Mixed CaP/CaOx: 50% Cystine: 17%Ĭalcium: 38% Mixed: 53% UA: 6% Cystine: 3%ĬaP: 12% CaOx: 14% Mixed CaP/CaOx: 22% UA: 17% Cystine: 2.5%ĬaP: 55% CaOx: 14% UA: 14% Cystine: 10%ĬaOx: 47% UA: 18% Mixed CaP/CaOx: 16% Cystine: 4.4%ĬaP: 52% CaOx: 18% UA: 18% Cystine: 12%ĬOnly 13 patients, all with metabolic stone types, underwent metabolic testing, and all had multiple abnormalities. The second issue which deserves attention-and which is in many ways related to the first-is to better define the role of the metabolic evaluation in patients with staghorn calculi, particularly in those for whom surgical stone removal is not possible. ![]() The first question is whether it is safe or efficacious to treat staghorn calculi medically rather than pursuing aggressive surgical removal. In order to be able to treat these complex cases optimally, we must address two major gaps in clinical knowledge. However, it is a fact that there are patients with staghorn calculi who are either cannot safely undergo surgery or alternatively who refuse surgical management altogether. The advent of newer, smaller, and better surgical instrumentation and techniques over the past 30 years has revolutionized the modern urologist's ability to surgically removal large stones through a minimally invasive approach. In most cases, the cornerstone of management for staghorn calculi is maximal surgical removal. The presence of any component of calcium oxalate, uric acid, or cystine is indicative of an underlying metabolic abnormality, and these stones are commonly referred to as “metabolic” stones. Infection stones are strongly associated with urinary tract infections caused by urease-producing bacteria. The term “infection stone” is used to describe stones comprised of magnesium ammonium phosphate (struvite) with or without admixed calcium carbonate apatite (carbonate apatite). Patient history may also be revealing in this regard for instance, patients with infection staghorn calculi often report a history of recurrent urinary tract infections with or without fever. Staghorn calculi may be of metabolic or infectious origin, and whenever possible it is beneficial to obtain stone analysis data in order to determine this information for guiding treatment and patient counseling. (A) Skeleton of a stag moose, cervalces scotti, housed at the Royal Ontario Museum (B) Plain abdominal X-ray depicting bilateral staghorn calculi.
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