Abdelwahab K, El-Babouly IM, Mahmoud MM, et al. - The results demonstrated that screwed Amplatz sheath had shown less operative and fluoroscopy time. Furthermore, it enables urologists to have stable percutaneous nephrolithotomy (PNL) tract. So it is a useful tool to make PNL easier with a higher success rate and lower complications.

• Between December 2018 and July 2020, researchers randomly stratified 100 patients aged more than 18 years with renal calculi more than 2 cm with guy's score 1 by closed envelope in group A (50 patients) using conventional sheath and group B (50 patients) with new screwed sheath.

• No significant differences were observed between both groups regarding patients' demographics and stone demographics.

• In group B, operative time and fluoroscopy time were significantly lower rather than group A.

• The results showed that tract stability was in favor of group B as no tract loss was reported while in group A, 5 cases were recorded.

• In overall complications, no significant differences were observed between both groups.

• In group A, bleeding was higher (14%) than in group B (4%), but it was not statistically significant.

• The findings revealed that success rates were 78% for group A and 88% for group B but it was not statistically significant.