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Biomedical subjects

R V Clayman

Publications and source records attributed to R V Clayman.

At least 55 records · Page 3Linked to original sources
PubMed2000

In vitro comparison of shock wave lithotripsy machines.

PURPOSE: We tested the hypothesis that shock wave lithotripsy machines vary in the ability to fragment stones to small size. MATERIALS AND METHODS: Calcium oxalate monohydrate, calcium hydrogen phosphate dihydrate, cystine and magnesium ammonium phosphate hexahydrate calculi were fragmented in vitro with the 22 kV. Dornier HM3, section sign 20 kV. Storz Modulith SLX, parallel, 15.6 kV. Siemens Lithostar C, paragraph sign 24 kV. Medstone STS-T,** 26 kV. HealthTronics LithoTron 160,daggerdagger 20 kV. Dornier Doli section sign and 22.5 kV. Medispec Econolithdouble daggerdouble dagger lithotriptors. Stones were given 500 or 2,000 shocks, or the Food and Drug Administration limit. Post-lithotripsy fragment size was characterized using sequential sieves and compared. RESULTS: Stone mass was statistically similar in the cohorts (p >0.94). Fragment size decreased as the number of shocks increased when the machine and stone composition were constant. Magnesium ammonium phosphate hexahydrate calculi were completely fragmented by all devices. At Food and Drug Administration treatment limits the mean incidence per device of calcium hydrogen phosphate dihydrate, calcium oxalate monohydrate, cystine and magnesium ammonium phosphate hexahydrate stones rendered into fragments greater than 2 mm. was 0% for the HM3, Modulith SLX and Lithostar C, 10% for the STS-T, 3% for the LithoTron 160, 29% for the Doli and 18% for the Econolith (p = 0. 04); 0% for the HM3, Modulith SLX, Lithostar C, STS-T and LithoTron 160, 4% for the Doli and 9% for the Econolith (p = 0.15); 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doli and 9% for the Econolith (p = 0.44); and 1% for the HM3, 0% for the Modulith SLX, 1% for the Lithostar C, 10% for the STS-T, 14% for the LithoTron 160, 3% for the Doli and 9% for the Econolith (p = 0.44), respectively. CONCLUSIONS: Shock wave lithotriptors vary in fragmentation ability. The HM3, Modulith SLX and Lithostar C machines yield smaller fragments than other machines.

Evaluation Studies as Topic↗
PubMed2000

Laparoscopic augmentation cystoplasty with different biodegradable grafts in an animal model.

PURPOSE: Recently a variety of biodegradable organic materials have been used for bladder wall replacement. We sought to study the effectiveness of 4 different types of biodegradable materials for bladder augmentation using laparoscopic techniques. MATERIALS AND METHODS: Thirty one minipigs underwent successful transperitoneal laparoscopic partial cystectomy and subsequent closure (6 control) or patch augmentation (25): porcine bowel acellular tissue matrix (ATM) (6), bovine pericardium (BPC) (6), human placental membranes (HPM) (6) or porcine small intestinal submucosa (SIS) (7). An intracorporeal suturing technique with the EndoStitch device (U.S. Surgical, Norwalk, CT) and Lapra-Ty clips (Ethicon, Enodsurgery Inc. Cincinnati, OH) was used to anastomose the graft to the bladder wall. Postoperatively, a urethral catheter was left for one week. Bladders were evaluated by cystoscopy at 6 and 12 weeks and harvested at 12 weeks. RESULTS: Grafts remained in place in all groups except for the BPC group, where all grafts failed to incorporate. For the ATM and SIS groups, at 6 weeks, there was mucosal coverage of the grafts without evidence of encrustation. In the control group, at 12 weeks, the bladder capacity was 23% less than preoperatively. In the ATM, HPM and SIS groups, at 12 weeks, the bladder capacities were larger than preoperatively by 16%, 51% and 43% respectively; also the grafts had contracted to 70%, 65%, and 60% of their original sizes, respectively. Histologically, there was patchy epithelialization of ATM and SIS grafts with a mixture of squamoid and transitional cell epithelia. The graft persisted as a well-vascularized fibrous band in HPM, ATM, and SIS without evidence of significant inflammatory response. CONCLUSION: A laparoscopic technique for partial bladder wall replacement using a free graft is feasible. The biodegradable grafts of ATM, HPM and SIS are tolerated by host bladder and are associated with predominantly only mucosal regeneration at 12 weeks post-operatively.

Animals↗
PubMed2000

Flow characteristics of 3 unique ureteral stents: investigation of a Poiseuille flow pattern.

PURPOSE: The pattern of flow in the stented ureter (intraluminal and/or extra luminal) has only been defined for the standard pigtail stent. No data are available on stent flow for any specialty stents. To our knowledge we present the first investigation characterizing the type of flow through a stent (Poiseuille versus nonPoiseuille flow). MATERIALS AND METHODS: Flow was measured in an unstented ureter, a standard 7Fr double pigtail stent and the 7/3Fr Tail stent, 7Fr Spirastent and 14/7Fr endopyelotomy stent using a previously developed stent flow model. In vitro pressure flow studies were also done in nonfenestrated 14/7Fr, Tail and standard 7Fr stents. These stents were infused at a constant flow rate of 2 to 10 ml. per minute with monitoring of the corresponding pressure gradients. Resistance to flow was determined for these stents using pressure flow plots and Poiseuille's law. RESULTS: In vivo the 7Fr pigtail, 14/7Fr endopyelotomy and 7/3Fr Tail stents had statistically similar flow rates. Flow through each of these stents exceeded the flow through an unstented ureter. The Spirastent had the least flow in all categories tested. There was no correlation of Poiseuille flow parameters measured in vitro for nonfenestrated stents with in vivo stent flow. CONCLUSIONS: In stented ureters fluid drains through and around the stent regardless of its design. The flow characteristics of these 3 specialty stents were not predictable according to lumen or stent size. In vitro Poiseuille's flow did not correlate with in vivo stent flow.

Animals↗
PubMed2000

Laparoscopic nephrectomy and nephroureterectomy for renal and upper tract transitional cell cancer.

The best management for renal tumors is surgical excision. The laparoscopic technique of radical or total nephrectomy for renal cell carcinoma and radical nephroureterectomy for transitional cell carcinoma is rapidly gaining momentum as an effective method of extirpative surgery. The transperitoneal and retroperitoneal approach to either of these procedures is proving to be equally effective to open surgery with respect to tumor removal, providing similar disease-free rates. Laparoscopic surgery leads to a significantly lower intraoperative blood loss, postoperative analgesic requirement, and quicker convalescence. Presently the only drawbacks to laparoscopic surgery are longer operative times and higher costs. Fortunately, these factors are slowly approaching those of open surgery because of increased experience, improved instrumentation, and modification of the surgical technique.

Carcinoma, Transitional Cell↗
PubMed1999

Retrograde endopyelotomy in association with active distal ureteral dilation: a contraindication for the use of the 7F ureteral "tail" stent.

Since its introduction in 1997, the 7F "Tail" stent has been used after a variety of endourologic procedures. We describe 2 patients who underwent retrograde endopyelotomy with distal ureteral dilation; in both patients, after placement of a 7F "Tail" stent, a clinically significant urinoma developed. We believe that in the setting of extensive distal ureteral manipulation or distal active ureteral dilation to greater than 10F, placement of a "Tail" stent is contraindicated.

Adult↗
PubMed1999

Is the laparoscopic approach justified in patients with xanthogranulomatous pyelonephritis?

OBJECTIVES: Xanthogranulomatous pyelonephritis (XGP) is an atypical form of chronic renal infection. The treatment of choice is open nephrectomy, which is challenging, given the extent of the disease and the not uncommon involvement of the renal hilum and contiguous structures. We compared our experience with laparoscopic nephrectomy for histologically confirmed XGP with the open approach. METHODS: Review of all nephrectomy specimens at Washington University School of Medicine from July 1990 to March 1998 disclosed 9 patients with a pathologic diagnosis of unilateral XGP, of whom 5 patients underwent laparoscopic nephrectomy and 4 underwent open nephrectomy. XGP was suspected preoperatively in 56% of the patients. RESULTS: For the laparoscopic group, the average operating room time was 360 minutes, average blood loss was 260 mL, and complications occurred in 60% of patients (1 conversion to open, 1 ileus, 1 pulmonary embolus). For the open group, the average operating room time was 154 minutes, average blood loss was 438 mL, and there were no complications. Both groups were similar regarding time to oral intake, analgesia requirement, hospital stay, and time to complete recovery. CONCLUSIONS: Our early experience demonstrates that the benefits of laparoscopic nephrectomy, at present, do not extend to patients with XGP. Conventional open surgery is quicker, associated with fewer complications, and results in a similar use of analgesics, hospital stay, and recovery time.

Aged↗
PubMed1999

Laparoscopic replacement of urinary tract segments using biodegradable materials in a large-animal model.

OBJECTIVE: We elected to evaluate laparoscopic segmental bladder and ureteral replacement with free biodegradable graft materials in a large-animal model. MATERIALS AND METHODS: In 18 Yucatan minipigs, a 1.5- to 2.8-cm segment of the upper ureter was excised. In 15 study animals, the ureter was laparoscopically replaced: by a stinted (6F double-J stent) tube graft made of acellular matrix (AMX) prepared from minipig ureters (MUMX) in 6 animals, acellular matrix prepared from domestic pig ureters (DUMX) in 3, and small-intestinal submucosa (SIS) in 6. In 3 control animals, the ureteral gap was bridged only by an indwelling stent. The stent was removed at 6 weeks, and retrograde ureteropyelography was performed preoperatively and at 8 and 12 weeks postoperatively, when animals were sacrificed. In 18 Yucatan minipigs, 3 x 3-cm bladder dome segments were laparoscopically replaced: by acellular matrix prepared from minipig small bowel (MBMX) in 6 animals, and SIS in 6 animals. The bladder was closed primarily in 6 control animals. Bladder capacity was assessed preoperatively and at 6 and at 12 weeks, when the animals were sacrificed. RESULTS: The average operating time for ureteral replacement was 187 (range 105-360) minutes. At 12 weeks, all animals had complete obstruction at the level of the replacement, with fibrosis +/- bone formation at the level of the stricture. For the bladder replacement groups, the average operating time was 147 (range 85-200) minutes. At 12 weeks, the bladder capacity was 60% of the preoperative capacity in the control group, 118% in the MBMX group, and 142% in the SIS group. Histologic examination showed regeneration of urothelium and some muscle with both MBMX and SIS. CONCLUSIONS: We were able to develop a reliable laparoscopic technique for both segmental ureteral and partial bladder replacement in a porcine model. With AMX and SIS replacement, regeneration of urothelium occurred in both ureter and bladder. However, functional replacement was successful only in the bladder.

Absorbable Implants↗
PubMed1999

The effect of patient position on intrarenal anatomy.

BACKGROUND AND OBJECTIVE: Although flexible ureteroscopes are designed with mechanisms for active and passive tip deflection, one of the major problems is the not infrequent inability to enter the lower pole calices. Accordingly, we measured the change in the lower pole infundibulopelvic (LIP) angle when the patient's position was varied (i.e., prone, supine, head down) during intravenous urography (IVU). PATIENTS AND METHODS: The LIP angle was measured in 20 right and 26 left adult kidneys during an IVU with the patient in six different positions: supine level, supine 20 degrees head down, supine 45 degrees head up, prone level, prone 20 degrees head down, and prone 45 degrees head up. None of the patients had a history of renal surgery. RESULTS: In all cases, the broadest angle of entry to the lower pole infundibulum was obtained with the patient in a prone position and 20 degrees head down. CONCLUSIONS: The LIP angle broadens when the patient lies in a prone 20 degrees head down position. This maneuver could improve the surgeon's ability to access the lower pole calices when performing flexible ureteronephroscopy.

Adult↗
PubMed1999

Mechanism of ureteral stent flow: a comparative in vivo study.

BACKGROUND AND OBJECTIVES: The flow characteristics of ureteral stents have yet to be clearly defined. In this study, flow mechanics were studied in several silicone-based stents including 4.8F, 7F, and 10.3F pigtail; 7F Tower; and a prototype mesh stent. MATERIALS AND METHODS: Forty-five female Yucatan minipigs underwent bilateral laparoscopic occlusion of their renal vessels to stop urine production. A nephrostomy tract was established by retrograde puncture. A stent was placed in the ureter, and three measurements were taken with flow from a bag of irrigant 20 cm above the kidney: stent occluded with a guidewire (extraluminal flow), stent unobstructed (total flow), and laparoscopically placed extraureteral ligature (luminal flow). RESULTS: Luminal flow and, to a lesser extent, total flow appeared to increase as the internal and external diameters of the stent increased. The Tower stent, which had no sideholes, had much lower flow rates in all categories, while the prototype mesh stent showed greater total flow compared with the other stents. Extraluminal flow did not increase with stent size greater than 7F. CONCLUSIONS: Luminal flow, but not extraluminal flow, increased with an increase in the internal diameter of the stent. In general, the least favorable flow occurred with a Tower stent, which had the smallest internal diameter. The greatest flow was seen with the prototype mesh stent.

Animals↗