Retrorectal tumors: A challenge for the surgeons

Retrorectal or presacral tumors are rare lesions located in the presacral area and considered as being derived from multiple embryological remnants. These tumors are classified as congenital, neurogenic, osseous, inflammatory, or miscellaneous. The most common among these are congenital benign lesions that present with non-specific symptoms, such as lower back pain and change in bowel habit. Although congenital and developmental tumors occur in younger patients, the median age of presentation is reported to be 45 years. Magnetic resonance imaging plays a crucial role in treatment management through accurate diagnosis of the lesion, the evaluation of invasion to adjacent structures, and the decision of appropriate surgical approach. The usefulness of preoperative biopsy is still debated; currently, it is only indicated for solid or heterogeneous tumors if it will alter the treatment management. Surgical resection with clear margins is considered the optimal treatment; described approaches are transabdominal, perineal, combined abdominoperineal, and minimally invasive. Benign retrorectal tumors have favorable long-term outcomes with a low incidence of recurrence, whereas malignant tumors have a potential for distant organ metastasis in addition to local recurrence.     

Size effect in resin/glass composite flexure strengths

The objective of this study was to test the hypothesis that composite restorative materials possess an elastic-brittle nature and therefore will exhibit a size effect for flexure strength data. The experimental material consisted of 20 wt% 60:40 BISGMA:TEGDMA, 10 wt% colloidal silica, and 70 wt% Sr glass and was cured by light irradiation. Two sizes of flexure specimens were fabricated: 3.2x1.6x35 mm, and 6.25x3.1x35 mm. Half of the specimens made were soaked to equilibrium weight gain in 50:50 ethanol:water. The fracture strengths were measured in four-point bending tests. The beams under load were modelled by the finite element package ABAQUS. A statistical fracture mechanics methodology embodied in a public domain computer program called CARES/LIFE, developed by NASA, utilized the ABAQUS input and the fracture strengths of the smaller specimens to predict the fracture strengths of the larger specimens. In making the computation it used an approach that combines a Weibull distribution of flaw size with Batdorf's fracture mechanical model for failure at a material flaw. Both the soaked and unsoaked specimens exhibited Weibull behaviour, with shape parameters ranging from 4.04 to 8.15. Soaking had a clearly detrimental effect on the strengths of specimens of both sizes, and produced a comparable percentage reduction in the estimated scale parameter of the fracture strength distribution. Both the soaked and unsoaked specimens also exhibited a clear and comparable size effect, i.e. the larger specimens had a fracture strength that was lower than that of the smaller specimens by roughly the same percentage. Moreover, the magnitude of the size effect was well predicted by the CARES/LIFE methodology for both the soaked and the dry specimens. The elastic-brittle character of both soaked and unsoaked composite specimens was validated by load-deflection data, the magnitude of the Weibull shape parameters of the observed fracture strength data (<10), and the observed effect of specimen size. The accuracy of CARES/LIFE in predicting the magnitude of the observed size effect in beams of two different sizes strongly suggests that CARES/LIFE will be useful for computation of failure probabilities for clinically relevant structures.     

The double-staple technique in colorectal anastomoses: a critical review.

The widespread availability and use of stapling devices have changed colorectal surgery. In 1980, Knight and Griffen developed the "double-staple" technique, using a circular stapler to transect a linear rectal staple line. This eliminated the need for a hand-sewn, distal purse string, which was sometimes difficult or even impossible to accurately place low in the pelvis. To evaluate this procedure, the authors have reviewed their results with the double-staple technique over the past 5 years. One hundred four patients underwent this procedure between 1985 and 1990 at Thomas Jefferson University Hospital (Philadelphia, PA). There were 60 men and 44 women, with a mean age of 62.4 years. Seventy-two patients underwent operation for carcinoma of the rectum or sigmoid. Thirty-five of these had preoperative radiation therapy. Other diagnoses included 1) diverticular disease, 2) rectal prolapse, 3) villous adenoma, 4) endometrial carcinoma, 5) fistula, 6) stricture, 7) Crohn's disease, 8) colonic endometriosis, 9) lymphoma, 10) ovarian carcinoma, and 11) ulcerative colitis. Incomplete "donuts" were observed in 5 patients. Diverting colostomies were performed in 23 patients, ileostomies in 3. Postoperative complications relating to the double-staple technique itself included a rectovaginal fistula in 1 patient. There were 3 clinical leaks (2.8%), all treated nonoperatively. No strictures were observed. As previously observed, the authors believe the double-staple technique offers certain advantages over traditional, hand-sewn and stapled anastomoses, for instance: 1) there is significantly less contamination, 2) the anastomosis is technically easier, and 3) bowel segments of different diameters can be easily anastomosed.     

The central action of pizotifen

The central action of the potential antidepressant drug pizotifen (Sandomigran) was studied in mice, rats and rabbits. Pizotifen in doses up to 10 mg/kg i.p. was ineffective in classic tests for antidepressant activity. It neither antagonized the effects of reserpine in rats (hypothermia, ptosis) nor potentiated the effects of amphetamine (in mice and rats), nialamide or L-dopa (in mice) on locomotor activity. However, its antidepressant activity was found in the despair test in rats.On the other hand, pizotifen inhibited the head twitch reaction induced by L-5-hydroxytryptophan in mice (ED₅₀=0.009 mg/kg, i.p.) and by 5-methoxytryptamine (+tranylcypromine) in rats (ED₅₀=0.45 mg/kg, i.p.). It also antagonized tryptamine-induced clonic convulsions of fore-paws in rats (ED₅₀=0.35 mg/kg, i.p.), and in doses of 5–10 mg/kg s.c. inhibited hyperthermia produced by LSD in rabbits. Finally, pizotifen (0.1–0.3 mg/kg, i.v.) inhibited or abolished LSD- or quipazine-induced stimulation of the hind limb flexor reflex of spinal rats; the above effect was not due to noradrenolytic action of the drug. These results suggest that pizotifen strongly blocks the central postsynaptic serotonin receptors.     

Performing Testicular or Epididymal Sperm Retrieval Prior to the Injection of hCG

Purpose: Our purpose was to determine the feasibility and efficacy of performing testicular or epididymal sperm retrieval prior to the injection of human chorionic gonadotropin (hCG). Methods: This report deals with 87 sperm-positive percutaneous epididymal sperm aspiration (PESA), percutaneous testicular sperm aspiration (PTSA), or testicular sperm extraction (TESE) cycles. All sperm retrieval procedures were performed prior to administration of hCG to the women. Retrieved spermatozoa were cultured in vitro in simple medium for approximately 40 hr prior to intracyto-plasmic sperm injection. Results: In all but one cycle in which TESE was performed for nonobstructive azoospermia, motile sperm were available for ICSI. The overall fertilization rate was 53%. Pregnancy rate per transfer and implantation rate per embryo were 41.2 and 15.7%, respectively. Conclusions: Satisfactory fertilization and pregnancy rates can be achieved when PESA, PTSA, or TESE is performed prior to the injection of hCG followed by in vitro culture of spermatozoa approximately 40 hr before ICSI. Scheduling of testicular or epididymal sperm retrieval cases in this way appears to ease the workload on laboratory and operating room personnel. Furthermore, withholding hCG when sperm is absent may obviate the unnecessary risk of ovarian hyperstimulation when spermatozoa cannot be retrieved.     

Tympanometric changes in an experimental myringosclerosis model after myringotomy.

HYPOTHESIS: The goal of this experimental study was to investigate the specific effect of myringosclerosis on tympanograms in the tympanic membranes of myringotomized rats by using otomicroscopy, tympanometry, and histopathology. BACKGROUND: Myringosclerosis is a common sequela of ventilation tube treatment of otitis media with effusion. The condition involves the hyalinization and calcification of the collagen layer in certain areas of the tympanic membrane. Previous animal experiments suggest an intimate relationship between the formation of myringosclerosis and an increased oxygen concentration in the environment of the wound after myringotomy. The result of a myringotomy therefore is an increased production of free oxygen radicals, initiating irreversible tissue damage involving fibrosis, hyalin degeneration, and finally apoptosis as observed in myringosclerosis. We propose an experimental model specific for creating sclerotic plaques solely on the tympanic membrane and for performing tympanometric measurements on this pure myringosclerosis model without creating any abnormality in the middle ear to test in what proportion myringosclerosis contributes to decrease of amplitude in tympanograms. METHODS: To assess the normal tympanometric values of Wistar albino rats, the pressure and peak admittance of the left middle ears were measured using a semiquantitative computerized clinical admittance meter using a sound frequency of 226 Hz. Twelve animals were randomly selected for the myringotomy group and perforations in the left ears were created. All tympanic membrane perforations in this group had healed and closed prior to the otomicroscopic examination and no pathologic reaction was observed in the external ear canals of rats. Otomicroscopic and tympanometric measurements were carried out on Day 15 and the degree of myringosclerosis was noted before the animals were killed. Twelve specimens in the myringotomy group were histopathologically examined for the presence of myringosclerotic plaques. RESULTS: Under light microscopy, extensive sclerotic lesions were found in the tympanic membranes of the myringotomy group, and these sclerotic deposits were located in the lamina propria. The myringosclerosis occurred predominantly adjacent to the handle of the malleus, but also near the annular region. In all ears with myringosclerosis, the magnitude of the maximum admittance reduced to approximately 50% of the Day-0 values, and this reduction was statistically significant (Z=-3.061, p=0.002). CONCLUSION: The present findings in this study are consistent with the fact that the movement of the tympanic membrane is hampered by lesions of sclerotic material, resulting in a decrease of amplitude in tympanograms (such as Type As) without any effusion or inflammation in the middle ear.