in this study we are going to evaluate the efficacy of intra-ureteric aminophylline instillation in facilitating ureteric access sheath placement prior to flexible ureteroscopy in reducing ureteric injury rates.

Urolithiasis (kidney and ureteral stones) is a common urologic condition with increasing prevalence. Flexible ureteroscopy (FURS) is a minimally invasive technique widely used for upper ureteric and renal stones. Aminophylline, a methylxanthine derivative, has been shown to relax smooth muscles and was previously used intravesically to facilitate rigid ureteroscopy with reduced complications. This study aims to assess whether intra-ureteric aminophylline instillation improves the ease of ureteral access sheath (UAS) placement during FURS and reduces ureteric injuries.

patients will be divided into 3 groups:

1. Group A (Aminophylline Group): Intra-ureteric instillation of aminophylline
2. Group B (Ureteral Dilator Group): Traditional ureteral dilators
3. Group C (Combination Group): Aminophylline instillation + Ureteral dilators follow up of the patients will be through the success rate or failure of ureteric access sheath placement, operative time, bleeding, intra/postoperative complications and stone clearance (3-week follow-up with CT scan)

Inclusion Criteria:

• Upper ureteric stones or renal stones < 2 cm

Exclusion Criteria:

1. Ureteric strictures.
2. anatomic renal disorders
3. functional renal disorders
4. Urinary tract infection.
5. Coagulopathy and uncorrected bleeding disorders.
6. Prior DJ stenting
7. any contraindication for aminophylline use: (hypersensitivity to theophylline, ethylenediamine, or any component of the drug formulation, pregnancy or lactation, active peptic ulcer, presence of cardiologic diseases, presence of neurologic diseases, presence of renal impairment and presence of hepatic dysfunction)