Distal Calculi Research Articles

Removal of upper urinary tract calculi with flexible ureteropyeloscopy

Flexible ureteropyeloscopy is an endoscopic technique which can give access to theentire intrarenal collecting system. Retrieval instruments or lithotriptors, electrohydraulic or pulsed dye laser, can be employed. In 70 patients, 72 procedures were used to treat 77 calculi. The calculus could be reached in each patient. Previous treatment included shock-wave lithotripsy or attempts at repositioning and open surgical exploration. There were multiple calculi in 18 patients, and 3 patients weighed more than 300 pounds. Calculi were successfully removed or moved to the distal ureter in 62 of 77 cases (80.5 %). The success rate was better with mid or proximal ureteral stones and renal pelvic stones than distal calculi. In 21 patients lithotripsy was employed. Flexible ureteropyeloscopy can be utilized for the successful treatment of upper urinary tract calculi.

Laser lithotripsy: a review of 20 years of research and clinical applications.

Four new technologies have transformed the treatment of urinary calculi: electrohydraulic lithotripsy, ultrasonic lithotripsy, extracorporeal shock wave lithotripsy, and laser lithotripsy. Initial attempts to ablate urinary calculi by continuous wave CO2, ruby, and Nd-YAG lasers failed because of excess thermal injury and inability to pass the laser energy via a flexible fiber. Basic laboratory studies then demonstrated that short pulsed laser energy absorbed by the calculus resulted in fragmentation. The parameters that produced optimal urinary calculus fragmentation were found using the flashlamp pumped tunable dye laser, with the following parameters: wavelength: 504 nm; pulse duration: 1 microsec; fiber: 250 micro silica-coated quartz; repetition: 5-20 Hz. Use of pulsed dye laser caused no tissue damage. The mechanism of fragmentation is light absorption, plasma development, and repetitive acoustic shock wave action with resultant fragmentation. The techniques for application of laser to calculi have been successful, and new, miniature instruments have been developed. Laser lithotripsy is a successful method for fragmenting ureteral calculi. The small caliber of the laser fiber makes this method useful for treating calculi in narrow, tortuous ureters; impacted calculi; distal calculi in ureters that cannot be dilated, via the percutaneous route for stones in calyces or impacted in the upper ureter. Investigations are continuing to optimize fragmentation of harder calculi and to use laser fragmentation within the kidney. Laser lithotripsy may also be used to fragment biliary calculi.

Improved visualization of choledocholithiasis by sonography

During a 20 month period, real-time sonography performed on 26 patients achieved an overall sensitivity of 75% for detecting choledocholithiasis. Although previous publications have stressed very low sensitivities for diagnosing choledocholithiasis (13%-55%), it was postulated that the reasons for these disappointing results are primarily related to technique. Most laboratories evaluate the distal common bile duct (where most calculi are located) by obtaining parasagittal scans. Detection of choledocholithiasis can be substantially improved by scanning the intrapancreatic part of the bile duct in a transverse fashion with the patient in an erect position. Advantages of the transverse view include the ability to demonstrate the distal common bile duct in a high percentage of patients and to differentiate shadowing caused by duodenal gas from ductal calculi. The proximal duct is best imaged by obtaining parasagittal scans with the patient in a supine left posterior oblique position. Using these scanning techniques, eight (89%) of nine proximal and 16 (70%) of 23 distal calculi were visualized.