Oral chemolysis is an effective, non-invasive therapy for urinary stones suspected of uric acid content

Abstract

Despite the possible benefit from avoiding stone surgery with all its possible complications, oral chemolysis is rarely performed in patients with urinary stones suspected of uric acid content. Among the reasons for its limited use is the sparse and low-quality data on its efficacy and the lack of reliable factors predicting its outcome. We thus performed a retrospective single-center cohort study of 216 patients (median patient age 63 years) with 272 renal (48%) and/or ureteral (52%) stones treated with oral chemolysis from 01/2010 to 12/2019. Patients with low urine pH (< 6), low stone density upon non-contrast enhanced computed tomography (NCCT), radiolucent urinary stones on plain radiography, and/or a history of uric acid urolithiasis were included. Potassium citrate and/or sodium/magnesium bicarbonate were used for alkalization (target urine pH 6.5-7.2). Median stone size was 9 mm, median stone density 430 Hounsfield Units. Patients with ureteral stones < 6 mm were excluded since stones this small are very likely to pass spontaneously. The stone-free status of each patient was evaluated after 3 months using NCCT. Oral chemolysis was effective with a complete and partial response rate of stones at 3 months of 61% and 14%, respectively; 25% of stones could not be dissolved. Lower stone density (OR = 0.997 [CI 0.994-0.999]; p = 0.008) and smaller stone size (OR = 0.959 [CI 0.924-0.995]; p = 0.025) significantly increased the success rate of oral chemolysis in multivariate logistic regression analysis. More precise stone diagnostics to exclude non-uric-acid stones could further improve outcome.

Imaging in stone diagnosis and surgical planning

“…Oral dissolution therapy was associated with a stone-free rate of 16% in 1 month and 50% in 3 months [128 & ]. Likewise, three nonrandomized recent studies have reported 3 months stone free rates of 61-64% [129,130] as well as a 6 months stone free rate of 83% [131]. Patient selection factors associated with response included smaller stones, lower density, and lower HUD [129][130][131].…”

Towards automatic recognition of pure and mixed stones using intra‐operative endoscopic digital images

“…For example, calcium oxalate monohydrate (COM [or Ia]), or calcium oxalate dihydrate (COD [or IIb]), criteria would support the prescription of an immediate diet containing potassium citrate, as reported in Soyg€ ur et al [10]. Recognition of uric acid (UA [or IIIb]) morphological criteria would steer the medical decision towards postoperative urinary alkalinization with potassium citrate or sodium bicarbonate to dissolve residual fragments [11].…”

“…[ 10 ]. Recognition of uric acid (UA [or IIIb]) morphological criteria would steer the medical decision towards postoperative urinary alkalinization with potassium citrate or sodium bicarbonate to dissolve residual fragments [ 11 ].…”

Single-energy CT predicts uric acid stones with accuracy comparable to dual-energy CT—prospective validation of a quantitative method

“…Distinguishing UA from non-UA stones is of particular interest for the urologist, as the former can be treated with alkalization of the urine, allowing for secondary prophylaxis after ex vivo composition analysis of a passed or surgically removed stone [4][5][6][7]. Ideally, a UA stone is identified and dissolved in vivo, to facilitate stone passage and obviate surgical removal [8,9]. At present, in vivo stone composition analysis is mostly accomplished with dual-energy CT (DE-CT), which has shown high accuracy in several studies [10][11][12][13][14][15].…”

“…It is highly reproducible for measuring stone size and useful for predicting spontaneous stone passage [ 6 , 14 , 16 ]. If, in addition, this method could also predict the composition of the stone, the patient would be able to leave the emergency room with a tailored treatment on the first day of radiologic diagnosis [ 9 ].…”