William N. Taylor

A Prospective Trial Comparing the Efficacy and Complications of the Modified Dornier HM3 and MFL 5000 Lithotriptors for Solitary Renal Calculi

A prospective randomized study of 198 patients was conducted to compare the efficacy of the modified Dornier HM3 lithotriptor to the MFL 5000 lithotriptor. Entrance criteria included solitary stones at any location within the upper collecting system that had not previously been treated with lithotripsy. Following lithotripsy the patients were evaluated by a blinded radiologist with a plain abdominal film, tomograms and renal ultrasound at 1, 4 and 12 weeks. Patients were classified at 12 weeks after lithotripsy as failing treatment if any stone fragments were imaged. Of the patients 170 were available for complete 3-month followup. No statistical or clinical difference in stone-free rates was apparent for calculi in the ureter or renal pelvis in either group. Of patients with lower caliceal stones 80% had no residual fragments visualized at 12 weeks when treated with the modified HM3 device versus 56% with the MFL 5000 lithotriptor (p = 0.05). Treatment time on the MFL 5000 unit was significantly prolonged compared with the modified HM3 device (0.7 hours versus 0.4 hours, respectively) resulting in fewer patients being treated in a given day (p < 0.001). No statistical difference in complication rates could be found between the 2 machines. Steinstrasse were noted in 10% of the patients treated with the modified HM3 device and 6% of the MFL 5000 group. Subcapsular hematomas were noted in 4% of the MFL 5000 treatment arm compared to 1% in the modified HM3 group. Overall, the MFL 5000 lithotriptor was believed to offer no significant clinical advantage over the modified HM3 device in terms of lithotripsy efficacy, although the multifunctional table did offer more versatility for stone treatment. For a busy lithotripsy center, the modified HM3 lithotriptor is still the most efficacious.

Minimally invasive ureteral stent retrieval

PURPOSE We developed a minimally invasive (noncystoscopic) method for retrieving ureteral stents. MATERIALS AND METHODS A total of 30 consecutive patients underwent placement of a ureteral stent with a stainless steel bead attached to its distal end. The stent was later removed by a urethral catheter with a rare earth magnet attached to its proximal end. RESULTS In 29 of the 30 patients the stent with the attached bead was removed without difficulty or patient discomfort. The single failure occurred in a patient with a large median prostate lobe. CONCLUSIONS Minimally invasive, nonendoscopic ureteral stent retrieval was achieved in 97% of patients. The attractive force of the magnet for the bead was sufficient to attract and extract the stent. No adverse effects of the procedure or the stainless steel bead were noted. This magnet retrieval system is a feasible, simpler and less invasive alternative to cystoscopic retrieval of ureteral stents.