Thermal imaging in the detection of bowel ischemia.

PURPOSE: The aim of this study was to introduce thermal imaging in the intraoperative detection of bowel ischemia by comparing thermal imaging with conventional techniques in detecting acutely ischemic bowel, using histologic evidence for intestinal necrosis as the standard. METHODS: A prospective study was performed using a porcine model. Laparotomy was performed on four pigs under general anesthesia. A 25-cm segment of mid jejunum was tagged with proximal and distal sutures, and its mesentery was ligated and divided. Thermal imaging, visual inspection, Doppler ultrasound, and fluorescence with Wood's lamp after fluorescein were used to estimate the extent of bowel ischemia five minutes after ligation of the mesentery. Measurements were taken in reference to both the proximal and distal tags to obtain two data points per animal for each method. After two hours of warm ischemia, the jejunum was harvested and sectioned longitudinally. Comparisons were made between the estimated region of necrosis for each method and microscopic evidence of necrosis. RESULTS: Visual inspection was the only method unable to detect a difference between vascularized and devascularized bowel for each of the eight data points. Fluorescein dye missed 3 cm of ischemic bowel. Doppler ultrasound and thermal imaging were 100 percent sensitive for necrotic bowel, with thermal imaging overestimating necrosis to a greater extent than Doppler ultrasound. The positive predictive value of fluorescein dye, Doppler ultrasound, and thermal imaging for determining nonviable bowel was 91.8, 80.8, and 69.5 percent, respectively. CONCLUSIONS: Thermal imaging has the potential to be a useful adjunct in the intraoperative determination of bowel ischemia. Further studies are indicated to study this technique.

Discontinuous appendiceal involvement in ulcerative colitis: pathology and clinical correlation.

Continuous mucosal involvement from the rectum proximally is one of the hallmarks of ulcerative colitis. However, recent pathologic series report appendiceal ulcerative colitis in the presence of a histologically normal cecum, representing a "skip" lesion. The clinical significance of this finding has not been established. Eighty patients, 54 males and 26 females, average age 37.9 years (range 14 to 82 years) who underwent proctocolectomy for ulcerative colitis from January 1990 to September 1995 were examined to determine the rate of discontinuous appendiceal involvement. Excluded were 12 patients with prior appendectomy and 11 with fibrotic obliteration of the appendiceal lumen. Of the remaining 57 patients, seven (12.3%) had clear appendiceal involvement in the presence of a histologically normal cecum. These seven patients clinically were indistinguishable from the 50 patients without skip involvement of the appendix in terms of age at surgery, pretreatment medications, type of surgery, interval from diagnosis to definitive procedure, complications, functional results, and clinical course. Discontinuous appendiceal involvement was found in 12.3% of patients undergoing proctocolectomy for ulcerative colitis, and clinically these patients behave as those without this feature.

Decreased density, but not number, of N-methyl-D-aspartate, glycine and phencyclidine binding sites in hippocampus of senescent rats.

Aging is associated with reduced rates of kindling and spatial learning. Blockade of N-methyl-D-aspartate (NMDA) receptors in young animals produces effects similar to those of aging. These findings raise the possibility that age-dependent reductions in neuronal plasticity are the consequence of decreased NMDA receptor-mediated neurotransmission. Conceivably this reduction could be due to an alteration in the NMDA receptor itself. To test this idea we quantified ligand binding to 3 distinct sites on the NMDA receptor/channel complex in hippocampal membranes prepared from 3- and 24-month-old Fischer-344 rats. The binding parameters of the NMDA, glycine and non-competitive antagonist (A.K.A. phencyclidine) sites on the NMDA receptor/channel complex were examined using [3H]3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid ([3H]CPP), [3H]glycine and [3H]N-(1-[2-thienyl]cyclohexyl)3,4-piperidine ([3H]TCP), respectively. Aging produced no change in the affinity or stoichiometry of the binding sites. Aging was associated with a 30% reduction in the density of each of the 3 binding sites (when expressed as sites/mg membrane protein). However, this reduction in receptor density was the consequence of increased protein content in the hippocampus of aged animals, not a reduction in the number of binding sites. These findings suggest that a selective alteration in the NMDA receptor/channel complex itself does not account for the age-dependent reductions in neuronal plasticity.