Early Whole Ureteral Stent Encrustation (EWUSE) is an uncommon adverse event.(1) Since we observed 5 EWUSE cases occurring all in a very short period after a scorching heat summer in year 2017, we considered weather condition as a possible external risk factor.
We indwelled a JJ ureteral stent (4.7 or 6 Fr), because of stone related hydronephrosis, in 51, 73 and 64 patients respectively in year 2016, 2017 and 2018. None EWUSE cases occurred in 2016, 5 in 2017 (6.8%), and 1 in year 2018 (1.5%). All the EWUSE cases brought the JJ during one or more summer months. All stents were removed before the limit of 180 days suggested by the producer. Stent material was Percuflex with HydroPlus™ coating produced by Boston Scientific. We did not consider patients with encrustation only on distal J that could be simply removed in the endoscopic office. Patients’ characteristics (age, sepsis, stone size and position, date of stent indwelling, number of weeks with stent) were considered and regional weather data of year 2016, 2017, and 2018 (obtained from archives available on weather’s internet sites) were analyzed.(2)
Common weather factors, that may interfere with human hydration, such as Temperature (maxim, medium and minimum) (Tmx, Tmd, Tmn) in Celsius (°C), Dew Point (DP) in °C, Relative Humidity (RH) in percent, Wind Velocity (WV) in km/h and Atmospheric Pressure (AP) in mbar were considered. RH is the ratio between amount of moisture in air to the maximum amount of water the air can absorb. DP is the temperature at which liquid first forms from a vapor. DP changes linearly for every given RH level.
Since in 2016 we did not register any EWUSE cases, we fixed as thresholds the average highest temperatures and the average lowest DP and RH, that were all happening in July 2016. We counted the days in each month with DP, RH inferior and Tmx, Tmd, Tmn superior to the thresholds.
Summer weather condition of year 2016 and 2018 were similar. Interesting differences were found in summer 2017 for DP, RH, Tmx, Tmd, and Tmn showing that it was warmer and drier, and warmer and drier for a longer period.
Furthermore on August 2017 the temperature went on increasing and RH and DP decreasing comparing to the already hot and dry July 2017, while generally the apex of temperatures happens on July. Average Tmx in August 2017 was 3.5°C more than August 2016 and even 1.2°C more than July 2017).
In year 2017 the number of days with Tmx, Tmd, Tmn superior to our thresholds (31, 26, 21°C) were respectively: 8|9|9 days in June; 17|19|18 July; 15|21|20 August; 1|2|5 September. Which means that July and August 2017 had together 40 days with temperature higher than the thresholds and in those months for 13 days Tmx was over 35°C.
The number of days in 2017 with DP, RH inferior to our thresholds (16°C, 55%) were: 26|14 in June; 26|27 July; 26|27 August; 25|8 September. Which means that almost all July and August 2017 were under the thresholds for DP and RH, and almost all June and all September were with DP under the threshold.
While the analysis of WV, AP and patients’ characteristics did not show any interesting result.
The 5 EWUSE patients occurred in year 2017 had no metabolic factor causing stone formation, while the only EWUSE case of year 2018 had hyperuricemia has metabolic factor. Only 3 encrustation from the EWUSE cases were analyzed and all of them were brushite (Calcium hydrogen phosphate; CaHPO4.2H2O).
In the recent years many articles are trying to correlate weather parameters to the incidence and prevalence of human diseases. Stone formation has a known multifactor etiology, an important role it has always been given do the income of daily water intake and the hydration status of the patient because highly concentrated salts and slow flow of urine in the collecting system facilitate precipitation of crystals and stone formation.(3)
“Stifling heat” is when both Temperature and RH are high. In this condition people suffer the heat and the sweat cannot evaporate easily from the body, because of the amount of moisture already present in the air.
“Scorching heat” is when, at a generally low RH, the Temperature is high and the DP is low. In this condition, in order to decrease the body temperature, the thermoregulation system induce sweating that immediately evaporate facilitating fast dehydration.
The 5 EWUSE patients (6.8% of the indwelled stent in year 2017, but also 28% of the indwelled stent in summer 2017) brought the stent during August and September 2017, and 3 of them also during July 2017, which were the months with the highest number of days with DP, RH and temperatures over the thresholds.
Results show that the “Scorching Heat” (high temperatures united with low RH and low DP) registered for so many days during summer 2017 acted as an external risk factor facilitating dehydration due to increased perspiration for thermoregulation.
Patients carrying stent should be advice to avoid condition that facilitate dehydration and increase water daily intake.
1) Long-term complications of JJ stent and its management: A 5 years review. Ray RP, Mahapatra RS, Mondal PP, Pal DK. Urol Ann. 2015 Jan-Mar;7(1):41-5.
3) Seasonal Variation in the Frequency of Presentation with Acute Ureteral Colic and Its Association with Meteorologic Factors. Roche EC, Redmond EJ, Yap LC, Manecksha RP.J Endourol. 2019 Nov 21.