compare the outcomes of SWL for renal and upper lumbar ureteric stones using the alternating bidirectional approach versus the standard approach.

Shock wave lithotripsy (SWL) has been considered the preferred method for treating upper urinary tract stones since 1980s due to its minimally invasive characters and low morbidity. The overall stone free rates have been reported to be 80% to 90% .

In the presence of pregnancy, untreated urinary tract infection, decompensated coagulopathy, uncontrolled arrhythmia and abdominal aortic aneurysm, other treatment methods should be considered .

SWL is associated with some complications. The most common complications of SWL are renal colic (40%), gross hematuria (32%), urinary obstruction (30.9%), symptomatic bacteriuria (9.7%) and perirenal hematoma or subclinical subcapsular hematoma (4.6%).

There are many factors affecting the success of SWL as patient age, sex, body mass index (BMI), stone size, site and number, radiological renal features, congenital renal anomalies and presence of double-J (DJ) ureteric stent .

Regarding the renal stones, stones smaller than 10 mm had a success rate of 90%, while those larger than 10 mm had a success rate of 70%. Stones located in the renal pelvis and upper pole had a success rate of 87.3 and 88.5% respectively, while those located in the lower pole had a success rate of 69.5%. A single renal stone had a 78.3% success rate compared to 62.8% in multiple renal stones . Regarding the ureteric stones, stone size more than 10 mm was one of the strongest independent predictors of failure of SWL

Patients appear to have the best chance for successful SWL when they have small BMI and their stones are single and located in the renal pelvis . Skin to stone distance (SSD) measured by non-contrast computerized tomography scan (NCCT) has a significant role in the treatment of renal stones using SWL. Slow shock wave rate (60/min) is associated with increase in the success rate and decrease in pain, complication and number of session to achieve success when compared to rapid shock wave rate (120/min)

Some techniques were developed to increase the efficacy of SWL. In 1999, the bidirectional synchronous twin-pulse technique with variable angles between the shock wave reflectors was developed and it improved the quality and rate of stone disintegration in vitro and it was more effective than the traditional single generator and also it decreases the overall treatment times

The TWINHEADS 101 lithotripter comprises two identical under and over table reflectors to permit synchronous shock waves emission from two perpendicular directions to the same focal point. This technique intensifies and localizes the cavitations effects by the interacting focal zones of both reflectors, resulting in a better quality and rate of stone disintegration, especially with a right angle between the axes of the reflectors.

The first prospective clinical study was done in 2005 regarding synchronous twin-pulse SWL and it seems safe and effective for treating patients with renal and upper ureteric stones. The stone-free rate was 74% after one session and 100% after two sessions within a month

Based on the principle of the TWINHEADS lithotripter, we will use Dornier Gemini lithotripter to emit the shock waves from two different directions to the same focal point asynchronously for renal and upper lumbar ureteric stones.

Inclusion Criteria:

• Patient criteria:

  1. Ability to give informed consent.
  2. Normal laboratory profile as regarding serum creatinine, liver function, platelets count and prothrombin time.

• Stone criteria:

  1. Single renal stone less than two cm or upper lumbar ureteric stone less than one cm.
  2. Radio-opaque stones.

Exclusion Criteria:

1. Bleeding tendency.
2. Poor kidney function.
3. Pregnancy.
4. Abdominal aortic aneurysm.
5. Indwelling DJ ureteric stent or percutaneous nephrostomy tube (PCN).
6. Congenital anomalies of the urinary tract.
7. Untreated urinary tract infection.
8. Obstructed urinary tract distal to the stone.