Diet and Stone Disease in 2022

PGE2 binding to EP2 promotes ureteral stone expulsion by relaxing ureter via the cAMP-PKA pathway

BACKGROUND

This study investigated the relaxation effect of PGE2 on the ureter and its role in promoting calculi expulsion following calculi development.

METHODS

By using immunofluorescence and Western blot, we were able to locate EP receptors in the ureter. In vitro experiments assessed the impact of PGE2, receptor antagonists, and agonists on ureteral relaxation rate. We constructed a model of ureteral calculi with flowable resin and collected ureteral tissue from postoperative side of the ureter after obstruction surgery. Western blot analysis was used to determine the protein expression levels of EP receptors and the PGE2 terminal synthase mPGES-1. Additionally, PGE2 was added to smooth muscle cells to observe downstream cAMP and PKA changes.

RESULTS

The expression of EP2 and EP4 proteins in ureteral smooth muscle was verified by Western blot analysis. According to immunofluorescence, EP2 was primarily found on the cell membrane, while EP4 was found in the nucleus. In vitro, PGE2 induced concentration-dependent ureteral relaxation. Maximum diastolic rate was 70.94 ± 4.57% at a concentration of 30µM. EP2 antagonists hindered this effect, while EP4 antagonists did not. Obstructed ureters exhibited elevated mPGES-1 and EP2 protein expression (P < 0.01). Smooth muscle cells treated with PGE2 displayed increased cAMP and phosphorylated PKA.

CONCLUSIONS

PGE2 binding to EP2 induces ureteral relaxation through the cAMP-PKA pathway. This will provide a new theoretical basis for the development of new therapeutic approaches for the use of PGE2 in the treatment of ureteral stones.

Hydration for Adult Patients with Nephrolithiasis: Specificities and Current Recommendations

Nephrolithiasis affects around 10% of the population and is frequently associated with impaired dietary factors. The first one is insufficient fluid intake inducing reduced urine volume, urine supersaturation, and subsequently urinary lithiasis. Kidneys regulate 24 h urine volume, which, under physiological conditions, approximately reflects daily fluid intake. The aim of this study is to synthesize and highlight the role of hydration in the treatment of nephrolithiasis. Increasing fluid intake has a preventive effect on the risk of developing a first kidney stone (primary prevention) and also decreases the risk of stone recurrence (secondary prevention). Current guidelines recommend increasing fluid intake to at least at 2.5 L/day to prevent stone formation, and even to 3.5-4 L in some severe forms of nephrolithiasis (primary or enteric hyperoxaluria or cystinuria). Fluid intake must also be balanced between day and night, to avoid urinary supersaturation during the night. Patients should be informed and supported in this difficult process of increasing urine dilution, with practical ways and daily routines to increase their fluid intake. The liquid of choice is water, which should be chosen depending on its composition (such as calcium, bicarbonate, or magnesium content). Finally, some additional advice has to be given to avoid certain beverages such as those containing fructose or phosphoric acid, which are susceptible to increase the risk of nephrolithiasis.

New Technologies in Endourology and Laser Lithotripsy: The Need for Evidence in Comprehensive Clinical Settings

Flexible ureteroscopy (fURS) with laser lithotripsy is currently the gold standard surgical treatment for ureteral and kidney stones with a maximum diameter of 2 cm [...].

Patient compliance to dietary recommendations: tips and tricks to improve compliance rates

Urinary stone disease continues to be a public health problem with growing incidence and recurrences. Recurrence is nearly detected in 50% of the patients within 5 years after the first episode. However, stone recurrence rates can be reduced to a certain extent. The American Urological Association (AUA) and the European Urological Association (EAU) guidelines advice dietary, fluid intake, and medical treatment to prevent or minimize stone recurrence. However, studies have shown that compliance to dietary and fluid intake recommendations is low. Beside this, nutritional evaluation of the patients is sufficient. Using food frequency questionnaires (FFQs), 24 h recall methods (short, individual-oriented, and easily applicable) or mobile apps can be used. In addition, cooperation with registered dietitians (RD) and planning tailored dietary programmes may have positive effect on compliance. Providers who give dietary advices should improve their knowledge about the topic and communication skills to create a patient-provider trust relationship. Simplifying the advices (shorter lists, applicable advices), spending more time, and giving education until being sure for patients' understanding with regular remindings may improve adherence. Moreover, patients increased awareness and knowledge about dietary advices are beneficial. Smart devices for fluid uptake or urine pH monitoring, mobile apps or web-based portals, and telemedicine applications can be used to maintain the compliance on dietary advices. Compliance with dietary modifications and fluid intake recommendations can be well achieved by individualized evaluation/close follow-up and the elimination of the problems limiting the patient compliance.