The use of flexible ureteroscopy and minimally-invasive percutaneous techniques, which utilize smaller tract sizes, has been established as a way to decrease the invasiveness of procedures and improve patient outcomes compared to conventional percutaneous nephrolithotomy (PCNL) and flexible mini-PCNL has emerged as a novel technique previously first as an auxiliary procedure and then as a standalone technique. This study aims to assess the feasibility and effectiveness of flexible nephoscopy in improving stone clearance compared to standard retrograde intrarenal surgery using a flexible ureteroscope.

Urinary stones are one of the most common rising health concerns around the world. Urolithiasis is particularly common in high-income countries, with more than 10% of people suffering from it. Renal stones often manifest as colicky loin pain, often known as renal colic.

Percutaneous nephrolithotomy (PCNL) is highly recommended by international guidelines as the primary treatment for renal stones larger than 20 mm. However, for stones ranging from 10 to 20 mm in size, treatment options may include shock wave lithotripsy (SWL), PCNL, or retrograde intrarenal surgery (RIRS).

Significant advancements have been achieved in surgical techniques recently, leading to the emergence of minimally invasive percutaneous nephrolithotomy (mini-PCNL) as a viable and effective treatment option for the removal of large renal and proximal ureteral stones.

In recent years, there has been a consistent reduction in the size of endoscopic instruments. The primary objective of these tools is to minimize the amount of blood lost during surgery, lower the occurrence of complications both during and after the operation, and ultimately reduce the length of hospital stays.

Despite the use of a smaller nephroscope, the rigidity of the mini-nephroscope poses a limitation in maneuvering into renal calyces at acute angles. This limitation may necessitate the creation of additional tracts, leading to an increase in morbidity. To tackle this challenge, a new technique flexible mini-nephroscope has been developed. This innovative instrument allows for access to all regions of the pelvi-caliceal system through a single access tract.

Retrograde Intrarenal Surgery (RIRS) is a prominent approach utilized to eliminate kidney stone disease. In contrast to PCNL, RIRS offers the benefit of utilizing a natural orifice, thereby eliminating the need for an additional pathway for lithotripsy. Consequently, this treatment option ensures enhanced safety and facilitates a more favorable postoperative recovery process.

RIRS has some significant limitations that make it challenging to retrieve a large number of fragments after the lithotripsy of large stones. Additionally, there is a complicated balance between irrigation and intrarenal pressure that must be maintained. While continuous rinsing of renal cavities is necessary to improve visibility, an imbalanced fluid evacuation can lead to a rise in pressure within the collecting system. Due to these limitations, large stones cannot be treated with a single RIRS procedure, and multiple sessions may be required. This exposes the patient to repeated anesthesia and the risk of ureteral damage and stenosis, making it important to limit operative time and prevent complications.

This study aims to compare the clinical outcome in the form of safety and efficacy between flexible mini-nephroscopy in minimally-invasive PCNL and retrograde intra-renal surgery in patients with symptomatic renal stones.

Inclusion Criteria:

• All patients above the age of 16 years of either sex presented to the Urology clinic in our university hospitals
• kidney stones with a size not exceeding 3.0 cm (estimated by CTUT as the greatest dimension or the summation of the greatest dimensions in case of more than one stone detected)

Exclusion Criteria:

• Patients with lumber hernia on the same site of the surgery
• Patients with a stone burden exceeding 3cm
• Patients with renal anomalies preventing access
• Patients with coagulopathies/bleeding tendency
• Patients with untreated or active UTI