Evaluating the association of water intake and hydration status with nephrolithiasis risk at the population level.

It is a cross-sectional study in which daily total plain water intake and total fluid intake were estimated together with blood osmolality, urine creatinine, urine osmolality, urine flow rate (UFR), free water clearance (FWC) and urine/blood osmolality ratio (Uosm:Bosm). The associations of fluid intake and hydration markers with nephrolithiasis were evaluated using multivariable logistic regression.

General US population.

A total of 8195 adults aged 20 years or older from the National Health and Nutritional Examination Survey 2009–2012 cycles.

The population medians (interquartile ranges, IQR) for daily total plain water intake and total fluid intake were 807 (336–1481) and 2761 (2107–3577) ml/d, respectively. The adjusted OR (95 % CI) of nephrolithiasis for each IQR increase in total plain water intake and total fluid intake were 0·92 (95 % CI 0·79, 1·06) and 0·84 (95 % CI 0·72, 0·97), respectively. The corresponding OR of nephrolithiasis for UFR, blood osmolality, Uosm:Bosm and urine creatinine were 0·87 (95 % CI 0·76, 0·99), 1·18 (95 % CI 1·06, 1·32), 1·38 (95 % CI 1·17, 1·63) and 1·27 (95 % CI 1·11, 1·45), respectively. A linear protective relationship of fluid intake, UFR and FWC with nephrolithiasis risk was observed. Similarly, positive dose–response associations of nephrolithiasis risk with markers of insufficient hydration were identified. Encouraging a daily water intake of >2500 ml/d and maintaining a urine output of 2 l/d was associated with a lower prevalence of nephrolithiasis.

This study verified the beneficial role of general water intake recommendations in nephrolithiasis prevention in the general US population.

Is ultrasonography a safe and practical alternative to computed tomography for the initial investigation of suspected nephrolithiasis?

Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med 2014;371(12):1100-10.

To assess the safety and efficacy of ultrasonography as a first-line imaging investigation for patients with suspected nephrolithiasis.

Do calcium channel blockers or alpha blockers improve renal stone passage when compared with placebo?

Pickard R, Starr K, MacLennan G, et al. Medical expulsive therapy in adults with ureteric colic: a multicentre, randomised, placebo-controlled trial. Lancet 2015;386(9991):25-31, doi: 10.1016/S0140-6736(15)60933-3.

The lifetime prevalence of ureterolithiasis is approximately 13% for men and 7% for women in the United States. Tamsulosin, an α-antagonist, has been used as therapy to facilitate the expulsion of lithiasis. Whether it is a good treatment for distal lithiasis remains controversial. We conducted a systematic review and meta-analysis to evaluate the effect of tamsulosin on the passage of distal ureterolithiasis.

A systematic search was conducted using MEDLINE, EMBASE, and Cochrane Central. Trial eligibility was evaluated by two investigators. All randomized controlled trials (RCTs) comparing tamsulosin to standard therapy or placebo for the treatment of a single distal ureterolithiasis ≤ 10 mm in adult patients with renal colic confirmed by radiographic imaging were included. Data extraction was conducted in duplicate. Primary outcome was the expulsion rate, and secondary outcomes were the mean time for ureterolithiasis expulsion, analgesic requirements, and side effects. Mantel-Haenszel random effect models were used, and heterogeneity was assessed using I2 statistics. Data were presented with relative risks (RRs).

The search strategy identified 685 articles, of which 22 studies were included. Combined results suggested a benefit for the expulsion of ureterolithiasis (≥ 10 mm) when tamsulosin was used compared to a standard treatment (RR 1.50 [95% CI 1.31–1.71], I2 = 70%). A decrease in the average time of expulsion of the ureterolithiasis of 3.33 days in favour of tamsulosin was observed (95% CI −4.23, −2.44], I2 = 67%).

Tamsulosin increases the rate of spontaneous passage of distal ureterolithiasis (≤ 10 mm).

Because a majority of urinary tract stones (UTSs) pass spontaneously and clinically significant alternative pathology is rare, we hypothesize that many computed tomographic (CT) scans to diagnose them are likely unnecessary. We sought to measure the impact of renal CT scans on resource use and to justify a prospective study to derive a score that predicts an emergent diagnosis in patients with suspected UTS by doing so in our retrospective series.

We conducted a retrospective study of ED patients who had noncontrast CT of the abdomen for suspected UTS. A split-sample was used to derive and validate a score to predict the presence of an emergent diagnosis on CT.

Of the 2,315 patients (50.8% female, mean age 45 years), 49 (2.1%) had an emergent outcome observed on CT. An additional 12 (0.5%) patients had an urgent outcome and 239 (10.6%) had a urologic procedure within 8 weeks of the CT. Serum white blood cell count, highest temperature, urine red blood cell count, and the presence of abdominal pain were significant predictors of the primary outcome. A score derived using these predictors had a potential range of 22 (0.26% predicted risk, 0.5% actual risk of the outcome) to 6 (52% predicted risk). The score was moderately discriminatory with c-statistics of 0.752 (derivation) and 0.668 (validation) and accurate with Hosmer-Lemeshow statistics of 10.553 (p = 0.228, derivation) and 9.70 (p = 0.286, validation).

A sensible, relevant score derived and validated on all patients presenting with symptoms suggestive of renal colic could be useful in reducing abdominal CT scan ordering.