Neural Differentiation Tracks Improved Recall of Competing Memories Following Interleaved Study and Retrieval Practice.

Selective retrieval of overlapping memories can generate competition. How does the brain adaptively resolve this competition? One possibility is that competing memories are inhibited; in support of this view, numerous studies have found that selective retrieval leads to forgetting of memories that are related to the just-retrieved memory. However, this retrieval-induced forgetting (RIF) effect can be eliminated or even reversed if participants are given opportunities to restudy the materials between retrieval attempts. Here, we outline an explanation for such a reversal, rooted in a neural network model of RIF that predicts representational differentiation when restudy is interleaved with selective retrieval. To test this hypothesis, we measured changes in pattern similarity of the BOLD fMRI signal elicited by related memories after undergoing interleaved competitive retrieval and restudy. Reduced pattern similarity within the hippocampus positively correlated with retrieval-induced facilitation of competing memories. This result is consistent with an adaptive differentiation process that allows individuals to learn to distinguish between once-confusable memories.

Measurement and prediction of thermal behavior and acute assessment of injury in a pig model of renal cryosurgery.

PURPOSE: To analyze in vivo end temperatures and histologic injury in a standardized cryo-iceball using a porcine kidney model in order to establish the threshold temperature for tissue ablation. To evaluate the ability to predict end temperatures using a thermal finite element model. MATERIALS AND METHODS: A single freeze/thaw cryolesion was created in five pig kidneys and the temperature history recorded. End temperature was calculated using a thermal finite element model. The threshold temperature for tissue injury was established by directly correlating end temperature and histologic injury. RESULTS: Reproducible geometry and temperature profiles of the cryo-iceball were found. End temperature could be accurately predicted through thermal modeling, and correlation with histologic injury revealed a threshold temperature of -16.1 degrees C for complete tissue ablation. CONCLUSION: Thermal modeling may accurately predict end temperature within a cryo-iceball. Provided threshold temperatures for tissue destruction are known, modeling may become a powerful tool in cryosurgery, improving the assessment of damage in normal and malignant tissue.

Radiofrequency ablation of rabbit kidney using liquid electrode: acute and chronic observations.

BACKGROUND AND PURPOSE: The percentage of small renal tumors being diagnosed has increased at least five-fold in the last 20 years. The question of how best to treat these lesions remains unanswered. We studied the effectiveness of "wet" radiofrequency (RF) ablation of renal tissue. MATERIALS AND METHODS: New Zealand white rabbits (N = 48) underwent a 1- or 2-minute ablation of renal parenchyma with a modified insulated spinal needle capable of infusing saline, measuring temperature and impedance, and delivering RF energy. Animals were followed and examined up to 54 days after surgery. RESULTS: All animals survived for the planned period. Intravenous urograms showed no fistula or urinoma formation and confirmed continued function of the remaining parenchyma. The 1-minute treatments consistently ablated 20% to 25% (average 7 cm) of the tissue, whereas the 2-minute treatments ablated 34% to 36% (average 10 cm). Acutely, there was coagulative necrosis and infiltration of inflammatory cells. Chronically, there were well-demarcated lesions with complete effacement of the tubular epithelium and destruction of the glomeruli. CONCLUSION: Wet radiofrequency ablation with a liquid electrode can reproducibly create large lesions safely and quickly. The technique may soon become an alternative, minimally invasive therapy for small renal tumors.

Role and long-term results of laparoscopic decortication in solitary cystic and autosomal dominant polycystic kidney disease.

PURPOSE: Access to retroperitoneal structures via the laparoscope has become established for various conditions. This minimally invasive approach has distinct advantages over conventional open surgery. We document our experience with laparoscopic cyst decortication for diseases of the kidney, including simple and complex cysts, multiple cysts and autosomal dominant polycystic kidney disease. MATERIALS AND METHODS: We retrospectively reviewed the records of 17 patients who underwent a total of 20 procedures. Cases were categorized as polycystic kidney disease and nonpolycystic kidney disease. Factors analyzed were estimated blood loss, length of surgical procedure, hospital stay and complications. Followup included radiographic studies (computerized tomography and/or renal sonography) and patient subjective pain relief, as determined by clinical records and telephone interview. RESULTS: Nine and 11 procedures were done for nonpolycystic kidney disease and polycystic kidney disease, respectively. Of the 8 patients with polycystic kidney disease 3 underwent repeat procedures. Followup was 3 to 63 months (average 26). All patients with simple cysts who were treated for pain were pain-free at the latest followup. Of the 10 procedures 9 (90%) performed for pain relief in polycystic kidney disease successfully produced immediate pain relief. Pain-free status decreased with time with 7 of 8 (87.5%) pain-free after 6 months, and 5 of 7 (71.4%) at 1, 4 of 6 (66.7%) at 2 and 1 of 4 (25%) at 3 years. A repeat operation successfully relieved recurrent pain in 2 of 3 cases (66.7%). Of the 7 patients with polycystic kidney disease who underwent surgery for pain relief 5 (71%) are currently pain-free. CONCLUSIONS: Laparoscopic renal cyst decortication is an effective minimally invasive treatment for painful simple cysts. It is also effective for short to intermediate pain relief in autosomal dominant polycystic kidney disease. Long-term followup suggests that a repeat procedure may be necessary to maintain adequate control of symptoms in polycystic kidney disease.

Transurethral prostate ablation with saline electrode allows controlled production of larger lesions than conventional methods.

A novel technique for prostate ablation using radiofrequency (RF) energy coupled to tissue with interstitial perfusion of saline solutions from a screw-tip catheter has been developed. The electrolyte spreads the current density away from the metal electrode and increases the effective electrode surface area, allowing more RF power input. This prevents tissue desiccation and impedance rise, resulting in controlled production of large lesions. In this study, we attempted to produce similar results using a straight needle and the saline electrode with a transurethral approach and compared the results with those of the same technique without electrolyte perfusion (conventional RF method). For this study, we designed an insulated 22-gauge needle with thermocouples embedded along its length and a 1-cm exposed tip with a retractable intraluminal thermocouple. This needle was inserted into the urethra of 10 dogs through a small perineal incision. Under transrectal ultrasound guidance, the exposed tip of the needle was placed in the center of each lobe. The intraluminal thermocouple was moved from the exposed tip up to the prostate capsule to monitor temperature. The highest power that could be applied in conventional RF methods without immediate desiccation was determined from preliminary experiments as 10 W. Subsequently, 10 W of RF power (475 kHZ) was delivered in one lobe until either the capsule temperature reached 48 degrees C or high impedance (> 400 omega) occurred. In the other lobe, 50 W of RF energy (475 kHz) and electrolyte perfusion (14.6% NaCl, 1 mL/min) were delivered until the capsule temperature reached 48 degrees C or high impedance occurred. Prostate lobe sizes ranged from 3.93 cm3 to 44.47 cm3 (mean 15.07 cm3). At 10 W without saline perfusion, high impedance from tissue desiccation occurred at 45 +/- 27 seconds, with lesions ranging from 0.06 cm3 to 0.93 cm3 (mean 0.34 cm3). At 50 W with saline perfusion, there was no tissue desiccation or impedance rise. The RF application time averaged 181 +/- 115 seconds until the capsule reached 48 degrees C, resulting in lesions ranging from 2.53 cm3 to 22.88 cm3 (mean 8.54 cm3). This study demonstrates that transurethral ablation of the prostate with a saline electrode allows controlled production of larger lesions than conventional RF methods. This may permit a single RF application in each lobe to produce lesions effective for the treatment of benign prostatic hyperplasia even in large glands.

Enhanced radiofrequency ablation of canine prostate utilizing a liquid conductor: the virtual electrode.

Conventional radiofrequency (RF) ablative techniques have shown promise for the treatment of symptomatic benign prostatic hyperplasia (BPH); however, present RF technology is limited by the small lesion size, necessitating several probe placements and heating cycles to achieve sizable lesions. This limitation is attributable primarily to a rapid increase in electrical impedance secondary to tissue desiccation and charring at the electrode tip. We devised a hollow screw-tip needle electrode that permits fixation to tissue, recording of temperature and impedance, infusion of fluid, and delivery of RF energy. Infusion of electrolyte solution (i.e., saline) into tissue prevents impedance rise by conducting RF energy away from the metal electrode and permits the creation of large lesions. By varying the conductivity of the perfusate (concentration and temperature), lesions of large diameter can be created in a controlled manner. To determine the long-term tissue effects, we applied this new modified RF technique to the prostates of five mongrel dogs in a chronic (0.5 to 8-week) study. The screw-tip electrode was serially embedded into each lobe of the perineally exposed glands with 1-minute infusion of 0.9% saline (2 mL/min) followed by application of RF energy (500 KHz, 50 W, 2-18 minutes) along with continuous saline infusion. Thermocouples were embedded 5 mm below and at the gland capsule, and RF application was discontinued when the temperature reached 50 degrees C at the periphery. Postoperatively, the animals were examined daily for clinical status and weekly for glandular changes using transrectal ultrasonography. At predetermined intervals, the animals were sacrificed and the prostates excised, measured, sectioned, and examined for histologic changes. Ablative tissue temperatures of 50 to 100 degrees C were produced while impedance remained stable. Four animals required a single catheterization for relief of urinary retention between days 2 and 3; otherwise, all animals demonstrated a quick and uneventful recovery with no edema detectable on day 7 ultrasound examination. The outside dimensions of the gland remained relatively constant throughout the study (+ or - 0.39 cm L + W + H). Histologic examination revealed coagulation necrosis (ablation) in both lobes of all prostates (69.94% + or - 16.62% of the gland) with tissueless cavities forming from the ablation area (28.71% + or - 8.24% of the gland) contained within the capsule surrounded by healthy tissue at the periphery. Intraprostatic lesions were obtained without any gross damage to surrounding tissue, including the bladder and rectal wall. Utilizing a liquid conductor in prostate tissue allows a single electrode-placement heating cycle for controlled ablation for the potential treatment of BPH. This new technique produces more extensive and uniform lesions than conventional RF procedures, and lesion size is limited only by the duration of RF energy application.

Complications of laparoscopic nephrectomy in 185 patients: a multi-institutional review.

PURPOSE: We document the incidence of complications associated with laparoscopic nephrectomy in a multi-institutional study. MATERIALS AND METHODS: The study included the initial 185 patients undergoing laparoscopic nephrectomy at 5 centers in the United States between June 1990 and July 1993. RESULTS: A total of 30 patients (16%) had 34 complications. There was no mortality. Access-related complications included 2 cases of hernia formation at the trocar site, 1 abdominal wall hematoma and 1 trocar injury to a hydronephrotic kidney. Intraoperative complications included 5 cases of vascular injury, 1 splenic laceration and 1 pneumothorax. Postoperative complications involved the gastrointestinal tract in 6 cases, cardiovascular system in 6, genitourinary tract in 4, respiratory system in 4 and musculoskeletal system in 2. Miscellaneous complications occurred in 3 patients. Open surgical intervention was required electively in 8 patients and on an emergency basis in 2. The incidence of complications decreased with experience: 71% occurred during the initial 20 cases at each institution. CONCLUSIONS: In our early experience the complication rate for laparoscopic nephrectomy was 12% in patients with benign renal disease and 34% in those with renal cancer. Based on this collective experience, recommendations for prevention, recognition and treatment of complications are made.

Long-term renal fate and prognosis after staghorn calculus management.

We analyzed retrospectively 177 consecutive staghorn calculus patients to determine risk factors for ultimate renal deterioration and renal cause specific death. Mean followup was 7.7 years. Overall rate of renal deterioration was 28%. Renal deterioration was associated more frequently among patients with solitary versus nonsolitary kidneys (77% versus 21%, p < 0.001), previous versus initial stones (39% versus 14%, p = 0.03), recurrent versus nonrecurrent calculi (39% versus 22%, p = 0.07), hypertension versus normotension (50% versus 22%, p = 0.006), complete versus partial staghorn calculi (34% versus 13%, p = 0.02), diversion versus no diversion (58% versus 19%, p < 0.001) and neurogenic bladder versus normal voiding (47% versus 21%, p = 0.006), as well as those who refused treatment versus treated patients (100% versus 28%, p < 0.001). No patient with complete clearance of fragments died of renal related causes compared to 3% of those without clearance of fragments and 67% of those who refused treatment (p < 0.001). Our study suggests that long-term renal preservation in the staghorn calculus patient may depend on normal blood pressure, staghorn size, absence of diversion or voiding dysfunction, and complete stone eradication.

Laparoscopic pelvic lymph node dissection, laparoscopically assisted seminal vesicle mobilization, and total perineal prostatectomy versus radical retropubic prostatectomy for prostate cancer.

OBJECTIVES: The outcomes of patients with prostate cancer who were candidates for radical prostatectomy were compared with patients who underwent either: (1) radical retropubic prostatectomy (RRP); or (2) laparoscopic pelvic lymph node dissection, laparoscopically assisted seminal vesicle mobilization, and total perineal prostatectomy (LN-SV-TPP). METHODS: The staging, surgical, and early postoperative characteristics of 10 consecutive patients treated by RRP were compared with 12 consecutive patients who underwent LN-SV-TPP. RESULTS: Patients who underwent LN-SV-TPP versus RRP had respective median blood loss of 450 versus 1250 cc (P = 0.001), median anesthesia time of 330 versus 287.5 minutes (P = 0.05), median surgical time of 237.5 versus 237.5 minutes (P = 0.6), median units transfused of 0 versus 1 (P = 0.05), median time to ambulation of 1 versus 2 days (P = 0.002), median time to oral intake of 1 versus 3.5 days (P < 0.001), median hospital stay of 3 versus 6 days (P < 0.001), and median morphine requirements of 44 versus 119 mg (P < 0.001). CONCLUSIONS: LN-SV-TPP is less morbid than RRP concerning blood loss, blood transfusions, pain, and postoperative recovery. Compared with LN-SV-TPP, RRP is faster and is particularly indicated for ease of performing a nerve-sparing radical prostatectomy.

Laparoscopic marsupialization of the painful polycystic kidney.

Autosomal dominant polycystic kidney disease patients may present with intractable cyst pain. Common practice has been to attempt percutaneous drainage of the affected cyst and, if unsuccessful, to offer open surgical decortication. We report laparoscopic renal cyst marsupialization for painful autosomal dominant polycystic kidney disease among 6 patients who failed prior percutaneous drainage. Mean surgical and anesthesia times were 3 hours and 3 hours 35 minutes, respectively. Mean blood loss was 140 cc. Median intervals to ambulation, oral intake and hospital discharge were 1.5, 1.5 and 3 days, respectively. All 6 patients reported pain relief with followup of 6 to 40 months. These results suggest that laparoscopic marsupialization of painful autosomal dominant polycystic kidney disease is technically feasible and safe, and the laparoscopic approach may offer a palliative option for patients in whom prior percutaneous management failed.

Laparoscopic retroperitoneal lymphadenectomy: multi-institutional analysis.

Modified unilateral laparoscopic retroperitoneal lymph node dissection was attempted in 20 patients with nonseminomatous testicular cancer. The procedure was completed in 18 men at a median operative length of 6 hours. Median estimated blood loss was 250 cc and median number of lymph nodes removed was 14.5. Nodal disease spread was noted in 3 of 18 patients (17%). Most patients were hospitalized for 3 days or less and had returned to normal activity levels within 2 to 3 weeks. Antegrade ejaculation was preserved in all 20 patients. Significant complications occurred in 6 of 20 patients (30%), with bleeding being the most common adverse event encountered. In 2 patients an abdominal incision and completion of the procedure by open retroperitoneal lymph node dissection were required due to significant bleeding following injury to the gonadal vessels. With a median followup of 10 months (range 2 to 25), 2 men had pulmonary disease recurrence and none had abdominal recurrence. Laparoscopic retroperitoneal lymph node dissection can be completed successfully in patients with stage I testicular cancer and may be most appropriate in those with limited risk of metastatic disease spread. The morbidity may be largely attributed to a steep learning curve. The efficacy of laparoscopic retroperitoneal lymph node dissection compared with standard techniques and determination of its role in patients with testicular cancer will require longer followup in larger groups of patients.

Laparoscopic ablation of symptomatic renal cysts.

We report a laparoscopic approach to the drainage and ablation of symptomatic simple renal cysts. Ten patients with chronic pain, 6 of whom failed primary aspiration, underwent laparoscopic cyst ablation: 6 had solitary renal cysts, 3 had multiple cysts and 1 had a peripelvic cyst. The approach was transabdominal in 9 patients and extraperitoneal in 1. Intraoperatively, cyst fluid was obtained for cytological examination, and cyst walls were excised and sent for pathological examination. When possible, the remaining inner cyst walls were fulgurated to prevent recurrence. Mean total operating room time was 2 hours 27 minutes and blood loss was minimal. The sole complication was a postoperative retroperitoneal hematoma, which was managed conservatively. Malignancy was diagnosed in 2 patients, each of whom had a negative preoperative aspiration. These patients subsequently underwent radical nephrectomy. All remaining patients were asymptomatic at a mean followup of 10 months. Laparoscopic ablation of renal cysts is a safe and effective alternative to open surgery in patients who have failed conservative measures. Preoperative and intraoperative evaluation for malignancy should be performed.

Spermatic vein occlusion with hot contrast material: angiographic results.

Spermatic vein occlusion by means of selective injection of boiling contrast material into the spermatic vein was attempted in 175 men with symptomatic varicoceles or infertility. Seventy-six patients (43%) returned for follow-up venography. Of 115 veins injected, 96 (83%) were totally occluded on the follow-up venogram obtained at 6 weeks to 2 years after injection. In the latter portion of the study, the technique was changed slightly, with injection of larger volumes of hot contrast material, resulting in a 91% occlusion rate. Each vein that was found patent on the follow-up venogram (19 of 115 [16%]) was assessed radiographically, and results were categorized as grade 1, a complete failure in which there was no change from the presclerotherapy appearance (nine of 19 [47%]); grade 2, a failure in which the treated vein was smaller but patent (five of 19 [26%]); or grade 3, a failure in which the treated vein was occluded with newly developed collateral vessels (five of 19 [26%]). The pretreatment size of the spermatic vein and the quantity of hot contrast material injected were both statistically significant factors in the treatment outcome.

Perineal abscess after prostatic urethroplasty with balloon catheter: report of a case.

A 72-year-old patient underwent uneventful prostatic urethroplasty by means of a balloon catheter. The immediate follow-up retrograde urethrogram failed to demonstrate any areas of extravasation and showed a significant increase in prostatic urethral caliber. Three weeks after the patient was discharged, computed tomography demonstrated a large perineal abscess that was attributed to either the prostatic urethroplasty or subsequent Foley catheter manipulations. The abscess was drained percutaneously, and the patient recovered uneventfully. It was concluded that the abscess was a possible isolated complication and that the procedure is warranted in an adequate clinical setting.