#07 Newsletter February 26, 2022

Hello and welcome to the stone newsletter, where we discuss every 2 months the most recent and relevant studies in stone disease.

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Hello stones fans! and welcome to the 2022 Stone newsletter cycle. We had a very good time with last years’ Stone News and we want to continue keeping you updated with the most recent and relevant studies in stone disease.

In today’s newsletter we address three important issues in stone management. We will talk about those difficult lower pole angles and how it can affect the efficiency of a flexible ureteroscopy. The second topic will be related with metabolic evaluations and specifically on patient’s adherence to medication when trying to reduce stone recurrences. You’ll see how bad is for patients not to follow these instructions. Finally, as the ALARA concept and radiation exposure has become increasingly a hot topic we will see if using ultrasound or fluoroscopy have differences when performing a PCNL access.

img Influence of Lower Pole Infundibulopelvic Angle on Success of Retrograde Flexible Ureteroscopy and Laser Lithotripsy for the Treatment of Renal Stones. Dresner SL et al. J Endourol, 2020. img 3'
https://pubmed.ncbi.nlm.nih.gov/31968995/ img

We know that the lower pole is one of the trickiest (and annoying) situation in flexible ureteroscopy. Not only the lower pole can de difficult to reach but It may reduce the chance of fragments passing out after dusting or fragmentation. In this paper, the authors analysed 243 renal units measuring the infundibulopelvic angle (IPA) at the intersection of the uretero-pelvic axis and the central axis of lower pole infundibulum. After dusting kidney stones, they evaluated stone free rates and recurrence free survival at 2 months postop with CT or KUB. With an average stone size of 8 mm (2 to 28 mm) the stone free rate was 52.3% and 38.3% had residual stones in the lower pole.

The average IPA was 78° and 74.5% of patients had an IPA of less than 90°. The variables related to higher rates of residual stones, as we imagined, were stones located in the lower pole and larger stone sizes. Regarding the angles, an IPA of less than 90° also had higher rates of residuals. The multivariate analysis, showed that an IPA of less than 90°and larger stone burden were significantly associated with surgical recurrence.

This article reminds us how tricky the lower pole can be and how many tricks can be performed in order to avoid this situation as relocating the stones from the lower to the upper pole to increase stone free rates and reduce scope damages. Many authors suggest that lower pole stones larger than 1.5 cm (especially hard stones) should be treated directly with miniPCNL. What is clear is that flexible ureteroscopy for stones larger than 2 cm have a higher chance of residuals, maybe needing ancillary procedures.

Base in this article, the IPA should also be considered to counsel patients and choose the best approach to ensure a stone free status.

img Impact of the adherence to medical treatment on the main urinary metabolic disorders in patients with kidney stones. Manzo BO, et al. Asian J Urol, 2021. img 2'
https://pubmed.ncbi.nlm.nih.gov/34401334/ img

All urologists dealing with stones know how difficult is to counsel patients and make them understand how important the medication is to prevent stone recurrences. We just hope our patients realize that this is a chronic disease and even if they don’t have symptoms (…for now) the medications works. This paper evaluated the adherence to medical treatments in patients with stone disease at 6 months after the prescription. All patients were evaluated with 24h urine tests and urinary ph measures before treatment and at 6 months. Patients were counseled and given dietary recommendations and medication if needed. A good adherence was defined as taking the medications at least 80% of the time during follow up (Now, how many of your patients you think reaches this threshold?).

Ninety patients were evaluated, of which 40% received a single drug (mostly potassium citrate) and 45.5% were prescribed with multiple medications as potassium citrate, allopurinol or thiazides. The adherence at 6 months was surprisingly high: 73.3%. (61.2% in patients with a single drug and 85.4% in patients with multiple drugs). But more than knowing how good our patients did we can give our attention to those patents that didn’t took the medication showing lower urine citrates levels (meaning increased risk of recurrence). This paper reminds us how important is taking time to counsel our patients to follow correctly the metabolic evaluation and take the medication to to avoid stone recurrences.

img Ultrasound or Fluoroscopy for Percutaneous Nephrolithotomy Access, Is There Really a Difference? A Review of Literature. Corrales M, et al. J Endourol, 2021 img 2'
https://pubmed.ncbi.nlm.nih.gov/32762266/ img

Radiation exposure is a big problem in our job and long term effects can be seen among physicians including skin rashes or extreme eczemas, cataracts or cancers. Evaluating our own procedures is very important to assess our own risks.

PCNL is one of the most challenging procedures in endourology and a flurosocopic guided access (FG), although very precise, may lead to an excessive radiation exposure, particularly in surgeons learning the procedure. But these authors wondered if doing the puncture with ultrasound (US) really decreased this exposure, or was better in any way. A literature review was done evaluating 12 studies that compared FG and US, including 6 RCT’s and 3 Meta-analysis. As expected FG has higher radiation exposure (described in one article as 2.6 min longer fluoro time). Curiously there were no differences regarding, quality of access, operative time, bleeding, renal pelvis perforation, fever, hospital stay, success punctures rates, stone free rates or even colonic perforations, as we know, the use of US do not discard 100% the presence of colon in the tract.

We may say that once the surgeon has gone trough the learning curve US and FG can be performed safely and efficiently. Regarding the ALARA concept I agree with the authors suggestion that US may always be complementary to FG and endourologists must know both techniques.

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