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Biomedical subjects

A Matamoros

Publications and source records attributed to A Matamoros.

At least 19 recordsLinked to original sources
PubMed2000

Laparoscopic and percutaneous radiofrequency ablation of the kidney: acute and chronic porcine study.

OBJECTIVES: The chronic effects of renal radiofrequency ablation are unknown. Herein, we investigate the anatomic and physiologic sequelae of laparoscopic and percutaneous renal radiofrequency ablation in acute and chronic porcine models. METHODS: Our study comprised two phases-an acute phase and a chronic phase. In the acute phase, bilateral laparoscopic renal radiofrequency ablation was performed in 6 animals (12 renal units), which were euthanized immediately after surgery. In the chronic study, bilateral percutaneous renal radiofrequency ablation was performed in 5 animals (10 renal units). One animal each was euthanized at postoperative day 3, 7, 14, 30, and 90. RESULTS: Ultrasound-monitored laparoscopic (n = 12) and percutaneous (n = 10) radiofrequency ablations of the lower pole of the kidney were technically successful in each instance. No intraoperative complications occurred. In the survival experiments, the radiolesions showed gradual spontaneous resorption and ultimate renal autoamputation, while maintaining pelvocalyceal integrity as confirmed by ex vivo retrograde ureteropyelogram. Serum creatinine and hematocrit remained stable in all survival animals. Postoperative complication occurred in 1 chronic animal with nonobstructive small bowel dilation at autopsy. CONCLUSIONS: Laparoscopic and percutaneous renal radiofrequency ablation are technically feasible. The anatomic and physiologic sequelae of renal radiosurgery are favorable. Improved techniques of real-time monitoring of the evolving renal radiolesion are necessary.

Animals↗
PubMed2000

Effect of surrogate tolerogenesis on the vascular rejection of pig heart xenografts.

BACKGROUND: Organ xenografts are fulminantly rejected by antibody-mediated vascular rejection. Surrogate tolerogenesis (ST), the induction of tolerance within the donor, is effective with aorta xenografts. This preliminary study assesses the effect of ST on preformed antibodies and rejection of porcine heart xenografts. METHODS: Tolerance to the donor pig was induced by infusing recipient marrow into fetal pigs. Later, pig splenocytes were transfused and heterotopic pig hearts transplanted using chimeric or nonchimeric pigs. Anti-pig antibodies were assessed. RESULTS: With ST alone, xenografts developed cellular rejection at 4-6 days, whereas control grafts developed vascular rejection at 3-4 days (cellular vs. vascular, P<0.03). There was a reduction in preformed antibodies (P<0.03). ST combined with moderate cyclosporine prevented rejection at 9+ and 25 days in sensitized recipients compared with vascular rejection at 0.5-2 days for controls (P<0.07). CONCLUSIONS: ST seems to provide protection against vascular rejection. The cellular rejection seems sensitive to cyclosporine.

Animals↗
PubMed1998

Pre-surgical CT/FEA for craniofacial distraction: I. Methodology, development, and validation of the cranial finite element model.

Recently, surgeons have begun to treat serious congenital craniofacial deformities including craniosynostoses with mechanical devices that gradually distract the skull. As a prospective means of treatment planning for such complex deformities, FE models derived from routine preoperative CT scans (CT/FEA) would provide ideal patient specific engineering analyses. The purpose of this study was to assess the dimensional and predictive accuracy of the CT/FEA process through the development of a 3D model of a dry human calvarium subjected to two-point distraction ex vivo. Comparative skull measurements revealed that CT/FEA construction error did not exceed 1% for transcranial dimensions, and the thickness error did not exceed 8.66% or 0.31 mm. CT/FEA strain predictions for the central region of the skull, between the distraction posts, were not statistically different from homologous gage values at P < 0.05. Peripherally, however, the strain fields were less well behaved and the FE predictions showed only general qualitative agreement with gage recordings.

Biomechanical Phenomena↗
PubMed1998

Color Doppler ultrasound assessment of urethral artery location: potential implication for technique of visual internal urethrotomy.

PURPOSE: We assessed the location of urethral arteries in patients with urethral stricture using color Doppler ultrasound. MATERIALS AND METHODS: We performed 41 color ultrasound studies of the urethra in 33 patients 17 to 76 years old. The linear array transducer was placed on the ventral surface of the penis and perineum to image the urethra and periurethral structures. In addition to evaluating the extent of stricture disease, color Doppler ultrasound determined the location of the urethral arteries at the segment with stricture. RESULTS: The number and site of the urethral arteries vary among individuals. Contrary to the common belief that these arteries are located at the 3 and 9 o'clock positions, we have found that in the bulbous urethra the arteries are at the 1 to 2 o'clock positions in 14% of cases, 3 to 4 in 22%, 5 to 6 in 17%, 7 to 8 in 18%, 9 to 10 in 18% and 11 to 12 in 11%. The arteries may be close to the surface of the urethral lumen, especially in patients who have undergone previous urethral procedures. Preoperative evaluation of urethral artery location may be helpful for preventing arterial bleeding at visual internal urethrotomy. CONCLUSIONS: Color Doppler ultrasound can effectively assess the extent of stricture disease and urethral artery sites. Because the location of the urethral arteries varies among patients, individual preoperative assessment is advisable. Color Doppler ultrasound is currently our imaging method of choice for evaluating strictures of the pendulous and bulbous urethra.

Adolescent↗
PubMed1997

Color Doppler ultrasound criteria to diagnose varicoceles: correlation of a new scoring system with physical examination.

OBJECTIVES: Color Doppler ultrasound (CDU) diagnostic criteria for varicoceles are poorly defined, and the role of CDU in diagnosing varicoceles is controversial. The purpose of this study is to assess the diagnostic accuracy of CDU for varicoceles compared to physical examination. METHODS: We prospectively studied 64 patients with CDU and collected the following data: maximum diameter of scrotal veins, the presence of a venous plexus, sum of the diameter of up to six veins of the plexus, and the duration and amplitude of flow change on Valsalva maneuver. To avoid interphysician variation, all patients were examined by one designated senior urologist with the sonographer remaining unaware of the findings. RESULTS: CDU parameters of 127 testis units in 64 patients were analyzed and compared to the physical findings. Fifty-nine testis units were positive and 57 units were negative for varicocele on physical examination. In 11 testis units, results of physical examination were inconclusive regarding the presence of varicocele. The commonly accepted CDU criterion for varicocele (maximal vein diameter of 3 mm or greater) had a sensitivity of 53% and specificity of 91% compared to physical examination. We developed a new scoring system incorporating the maximal venous diameter (score 0 to 3), the presence of a venous plexus and the sum of the diameters of veins in the plexus (score 0 to 3), and the change of flow on Valsalva maneuver (score 0 to 3). Using a total score of 4 or more to define the presence of CDU-positive varicocele, we observed a sensitivity of 93% and a specificity of 85% when compared to physical examination. All moderate to large varicoceles found on physical examination were positive by CDU diagnosis using the scoring system, but the same group had only a 68% positive rate by traditional CDU diagnostic criteria. CONCLUSIONS: Using the proposed new scoring system, CDU has been shown to be a reliable and accurate method of diagnosis for varicoceles compared to the current reference standard physical examination. CDU has the advantages of being able to objectively examine venous plexus and measure blood flow parameters and to be less observer-dependent than physical examination.

Adult↗
PubMed1997

Staple occlusion of the infrarenal aorta: a videoscopic retroperitoneal approach.

PURPOSE: The purposes of this study were to determine whether available laparoscopic stapling devices could be used to interrupt the diseased human aorta, and to develop a videoscopic technique for retroperitoneal exposure and control of the infrarenal aorta in pigs. Our long-term goal is to develop a minimally invasive approach to the treatment of abdominal aortic aneurysms by exclusion and extraanatomic bypass. METHODS: Ten diseased, formalin-preserved human cadaver aortas underwent stapling using a laparoscopic stapling device. The aortas were then pressurized to superphysiologic levels to assess the integrity of the staple line. Ten swine underwent retroperitoneal video-assisted exploration with control and staple occlusion of the aorta and iliac artery. RESULTS: The staple line was complete and remained intact after pressurization in nine of 10 cadaver aortas, despite the presence of complex calcified disease. One aorta had a 2-mm opening through the staple line. Through the left retroperitoneal approach, the infrarenal aorta and left iliac artery could be dissected and controlled. A modified pledgeted technique used for stapling resulted in hemostasis of the staple line and exclusion of flow without injury to adjacent structures. CONCLUSIONS: The diseased human aorta can be occluded using available laparoscopic staplers. These swine experiments demonstrate the feasibility of the retroperitoneal approach for exclusion of infrarenal aortic aneurysms.

Animals↗
PubMed1995

Experience with protocol biopsies after solitary pancreas transplantation.

The early detection of allograft rejection remains elusive after solitary pancreas transplantation (PTX). We have previously described a modified technique of cystoscopic transduodenal PTX biopsy using the Biopty gun under ultrasound guidance. During the last 2 years, we performed 24 solitary PTXs with prospective protocol biopsy monitoring as well as biopsies performed whenever clinically indicated. The study group included 17 pancreas transplants alone, 6 sequential pancreas after kidney transplants, and 1 sequential pancreas after liver transplant. Five patients received pancreas retransplants. A total of 92 cystoscopically directed core PTX biopsies were performed, including 50 protocol biopsies (mean 2.1 per patient). Protocol biopsies were performed at 1 month (19), 2 months (3), 3 months (20), 6 months (7), and 12 months (1) after PTX. Adequate PTX tissue for histopathologic examination was obtained in 49 cases (98%). Biopsy findings included no rejection (34), mild rejection (13), pancreatitis (1), and cytomegalovirus infection (1). Overall, 15 of the 49 evaluable biopsies (31%) had significant histopathologic findings. All but 1 of the cases of mild rejection were treated with bolus steroids. Eight of these patients subsequently developed recurrent biopsy-proven rejection within 2 months; 5 grafts were subsequently lost to rejection between 3 and 13 months after PTX. Three biopsy complications occurred: 1 hematoma, 1 pancreatitis, and 1 ileus. Patient survival is 96% and PTX graft survival (complete insulin independence) is 75% after a mean follow-up of 15 months. In the remaining 42 clinically indicated biopsies, 3 were insufficient, 8 showed no rejection, and 31 (79%) had rejection. In half of these cases, the rejection was graded as moderate to severe. In conclusion, prospective monitoring with protocol PTX biopsies may result in the earlier detection of allograft rejection and have a direct effect on improving results after solitary PTX.

Adolescent↗
PubMed1995

New imaging techniques in colorectal cancer.

The ability to visualize biochemical processes in tumor tissues by PET and correlate these findings with anatomic imaging such as CT and MRI gives new insight into the metabolic and physiologic aspects of the tumor tissue. This may permit discrimination between recurrent colorectal carcinoma and some benign lesions. The potential for its use in pharmacology or in monitoring drug therapy is just beginning to be explored. Improvements in acquisition techniques such as whole body imaging, and in methods of absolute quantitation will be important for standardizing image information and making it more widely applicable. Careful evaluation of the impact on patient outcome and clinical decision making are vital in determining the further use of this technology and the planned multicenter trial evaluating cost-effectiveness is welcome step in this direction.

Clinical Trials as Topic↗
PubMed1992

Transvaginal sonography of cervical width and length during pregnancy.

Transvaginal ultrasonography has been proposed as a reliable method of assessing dimensions of the cervix. The purpose of the current investigation was to establish normative data for cervical width and length during pregnancy. This information may be helpful in predicting patients at risk for preterm birth. A transvaginal 5 or 7.5 MHz transducer was used on 132 consecutive low-risk pregnant women undergoing evaluation for gestational dating purposes. Even in cases of patient obesity or an empty bladder, high resolution was possible and permitted cervical measurement in all but one case. The external cervical width at the vaginal fornices was found to increase with advancing gestation (R = 0.512, P < 0.005). The cervical length from internal os to external os was found not to change with advancing gestation (R = 0.11, P = 0.30). Using these normative data, investigation is recommended to determine whether measuring cervical width and length is useful in predicting preterm labor and delivery.

Anthropometry↗
PubMed1990

Sonography of the musculoskeletal system.

Improved technology and the development of high-resolution transducers have made sonography of the structures of the musculoskeletal system possible. The vast majority of scientific reports on the value of sonography for imaging musculoskeletal abnormalities have been written only in the last decade. Sonography has several inherent advantages: it is relatively inexpensive, allows comparison with the opposite normal side, uses no radiation, and can be performed at bedside or in the operating room if necessary. The advent of MR imaging has revolutionized musculoskeletal imaging and may be used in many instances rather than sonography for evaluating the same abnormalities or anatomic structures. It is important, however, to keep in perspective what the different imaging techniques have to offer, and, if one is just as efficacious as the other, the least invasive and least expensive should be chosen whenever possible. The goal of this article is to review the applications of sonography to the evaluation of musculoskeletal disorders including tendon disease, soft-tissue masses, identification of foreign bodies, osteomyelitis, cellulitis, and certain joint abnormalities.

Aneurysm↗
PubMed1989

Neurosonographic findings in infants treated by extracorporeal membrane oxygenation (ECMO).

Extracorporeal membrane oxygenation (ECMO) is an approved therapy for some neonates who have respiratory failure that is due to hyaline membrane disease, meconium aspiration, persistent pulmonary hypertension, congenital diaphragmatic hernia, or sepsis. The major complication of this therapy is hemorrhage, with intracranial hemorrhage having the highest morbidity and mortality. Seizures, incisional bleeding and bleeding in the pleural space, hypoxic-ischemic encephalopathy, renal failure, and cardiovascular complications account for most of the other complications. Cranial sonography provides an ideal imaging modality for baseline evaluation and daily follow-up; however, computed tomography and magnetic resonance imaging, because of better sensitivity, are important for assessment after ECMO. The changes in intracranial blood flow related to ECMO can be noninvasively evaluated by Doppler ultrasound modalities.

Cerebral Hemorrhage↗