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Biomedical subjects

M A Christensen

Publications and source records attributed to M A Christensen.

At least 19 recordsLinked to original sources
PubMed1992

Rare pelvic floor hernias. Report of a case and review of the literature.

The case of a 64-year-old female who presented with difficult evacuation of stool is reported. A posterior perineal hernia was diagnosed by dynamic proctography. The patient had an unusual herniation of the upper rectum through the perineal defect. At surgery, there was no peritoneal sac, since the herniation occurred extraperitoneally. The patient was treated with repair of the pelvic floor using Marlex mesh and rectopexy. Pelvic floor hernias are rare and often difficult to diagnose. The three types, in order of decreasing frequency, are obturator, perineal, and sciatic. The etiology, diagnosis, and treatment of each is discussed.

Buttocks↗
PubMed1992

"House" advancement pedicle flap for anal stenosis.

Long strictures of the anal canal, extending from the dentate line to the perianal skin, have challenged surgeons for many years. Numerous techniques have been devised to treat anal strictures. A technique to relieve an anal stenosis that involves the entire circumference and the length of the anal canal from the dentate line onto the perianal skin is described. It has two principal advantages: 1) it provides a broad skin flap for the entire length of the involved anal canal; and 2) it provides primary closure of the donor site. In addition, it avoids extensive mobilization of tissue, the flap maintains good blood supply with minimal tension, and there is no small tip prone to necrosis.

Anal Canal↗
PubMed1992

Normal variation in anorectal manometry.

A study was performed to define the normal range of values for anorectal manometry. Normal volunteers were divided according to gender and parity. There were 20 males, 21 nulliparous females, and 18 multiparous females among the 59 subjects. Anorectal manometry using a radial eight-port catheter was performed during resting and squeezing maneuvers of the anal sphincter. Computerized data analysis and three-dimensional imaging were used to calculate sphincter length at rest and squeeze, mean maximum resting and squeeze pressures, and vector symmetry index. The sphincter length at rest and with squeezing in males was significantly greater compared with the two female groups (P < 0.007). Mean maximum squeeze pressures were also significantly elevated in the male group compared with the female groups (P = 0). Mean maximum resting pressures were significantly higher in nulliparous women than in multiparous women (P = 0.04). However, no difference in resting pressures was found between males and nulliparous females. A comparison of the symmetry of the anal canal revealed no differences among the three groups. Ranges for normal anorectal manometry are definable. Normal ranges are distinct for subgroups of patients, particularly with regard to gender and parity. Patients must be compared with their normal subgroups to correctly identify manometric abnormalities.

Adult↗
PubMed1990

Increased expression of the retinoblastoma gene in human colorectal carcinomas relative to normal colonic mucosa.

We report the first evidence of increased levels of the retinoblastoma (Rb) message in a majority of colorectal cancers when compared with normal mucosa. Southern blot analysis showed an increase in Rb gene copy number in at least 28% of colorectal carcinomas relative to normal mucosa. These results plus previous reports of nonrandom chromosome 13 gains in approximately 50% of colorectal cancers suggest that an increase in Rb gene copy number occurs frequently in these tumors. Possible mechanisms pertaining to overexpression of the Rb gene are discussed in relation to its role as a recessive cancer gene.

Blotting, Northern↗
PubMed1990

Manometric diagnosis of anal sphincter injuries.

A manometric technique of anal pressure vectography has been developed for the detection of anal sphincter injuries. Manometric symmetry of the anal sphincter can be visualized on the pressure vectorgram and quantified as a vector symmetry index. The mean vector symmetry index in asymptomatic women was 0.76, compared with 0.33 in incontinent women with a known sphincter injury (p = 0.0001). Among women who were incontinent without having a recognized sphincter injury, nearly half of those who had a previous episiotomy had subnormal (less than 0.60) vector symmetry indices (p = 0.0003). The values were in the same range as those from known injuries, suggesting the presence of an occult sphincter injury. In contrast, normal symmetry indices were found in all those who had never had an episiotomy or who presented with outlet constipation. We conclude that the vector symmetry index can expose occult anal sphincter injuries and may have a role in the selection of patients for sphincter repair.

Adolescent↗
PubMed1990

Carbohydrate and energy metabolism during the evolution of hypoxic-ischemic brain damage in the immature rat.

The brain damage that evolves from perinatal cerebral hypoxia-ischemia may involve lingering disturbances in metabolic activity that proceed into the recovery period. To clarify this issue, we determined the carbohydrate and energy status of cerebral tissue using enzymatic, fluorometric techniques in an experimental model of perinatal hypoxic-ischemic brain damage. Seven-day postnatal rats were subjected to unilateral common carotid artery ligation followed by 3 h of hypoxia with 8% oxygen at 37 degrees C. This insult is known to produce tissue injury (selective neuronal necrosis or infarction) predominantly in the cerebral hemisphere ipsilateral to the carotid artery occlusion in 92% of the animals. Rat pups were quick-frozen in liquid nitrogen at 0, 1, 4, 12, 24, or 72 h of recovery; littermate controls underwent neither ligation nor hypoxia. Glucose in both cerebral hemispheres was nearly completely exhausted during hypoxia-ischemia, with concurrent increases in lactate to 10 mmol/kg. During recovery, glucose promptly increased above control values, suggesting an inhibition of glycolytic flux, as documented in the ipsilateral cerebral hemisphere by measurement of glucose utilization (CMRglc) at 24 h. Tissue lactate declined rapidly during recovery but remained slightly elevated in the ipsilateral hemisphere for 12 h. Phosphocreatine (P approximately Cr) and ATP in the ipsilateral cerebral hemisphere were 14 and 26% of control (p less than 0.001) at the end of hypoxia-ischemia; total adenine nucleotides (ATP + ADP + AMP) also were partially depleted (-46%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1990

Cerebral blood flow and edema in perinatal hypoxic-ischemic brain damage.

The relationship between cerebral blood flow (CBF) and the evolution of brain edema was investigated in an experimental model of perinatal hypoxic-ischemic brain damage. Seven-d postnatal rats were subjected to unilateral common carotid artery ligation followed by 3 h of hypoxia with 8% oxygen at 37 degrees C. This insult produces neuronal necrosis and/or infarction only in the cerebral hemisphere ipsilateral to the arterial occlusion in the majority of animals; hypoxia alone produces no damage. CBF, measured by the indicator diffusion technique using iodo[14C]-antipyrine, and tissue water content were determined concurrently in both cerebral hemispheres at specific intervals during recovery from cerebral hypoxia-ischemia. Water contents in the ipsilateral cerebral hemisphere were 89.1, 89.6, 89.7, 91.0, and 88.3% at 30 min, 4 h, 24 h, 3 d, and 6 d, respectively (p less than 0.001); whereas the percent tissue water in the contralateral hemisphere was unchanged from values in nonligated, hypoxic control rats (87.7%). CBF was similar in both cerebral hemispheres at 30 min, 4 h, and 24 h of recovery (50-65 mL/100 g/min) and not different from age-matched controls. At 3 and 6 d, CBF in the ipsilateral cerebral hemisphere was 30 and 26% of the contralateral hemisphere and 23 and 29% of the control animals, respectively (p less than 0.001). No inverse correlation existed between the changes in brain water content and CBF at any interval until 6 d of recovery. Thus, an early hypoperfusion does not follow perinatal cerebral hypoxia-ischemia, as occurs in adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Office colonoscopy--a safe procedure in selected patients.

Colonoscopy is a common procedure, usually performed in a hospital setting. Hospital backup is desirable for high-risk patients, but the cost to benefit ratio may be unnecessarily high for low-risk patients. The demand for colonoscopic examinations is escalating, and cost containment has become an important issue. One way to reduce the cost is to eliminate the hospital component by performing the examination in the office. Over the past two and a half years, colonoscopy was performed on selected patients in the authors' office. Five hundred fifty-four office colonoscopies were performed to date, including biopsy or polypectomy in 348. Basic principles of safe intravenous sedation and colonoscopy were followed strictly. The cecum was reached in 92 percent of cases, and no significant complications were encountered. Office colonoscopy is a safe alternative to hospital colonoscopy. It confers significant cost savings to the patient and allows more efficient use of the physician's time.

Adult↗
PubMed1989

Rectopexy without resection for rectal prolapse.

Forty-three patients underwent simple posterior suture rectopexy for repair of rectal prolapse. Follow-up was obtained in 42 patients (mean 28 months). The recurrence rate was 2 percent (one patient). Postoperative morbidity and mortality were 20 percent and 0, respectively. The proportion of continent patients increased from 36 percent preoperatively to 74 percent postoperatively. Constipation increased after suture rectopexy but was managed conservatively. We believe that simple suture rectopexy offers a safe and effective alternative to other, more complex procedures for the treatment of rectal prolapse.

Aged↗
PubMed1989

Regional cerebral blood flow and glucose utilization during hypothermia in newborn dogs.

To ascertain the effect of profound hypothermia on brain function and metabolism, newborn dogs were subjected to surface cooling during which regional cerebral blood flow (rCBF) and glucose utilization (rCGU) were measured with iodo-[14C]-antipyrine and 2-deoxy-[14C]-glucose, respectively. Puppies were anesthetized with nitrous oxide, paralyzed, and their lungs artificially ventilated to maintain arterial normoxia (PaO2 greater than 60 mmHg) and normal acid-base balance (PaCO2 = 35-41 mmHg; pHa = 7.34-7.42). When rectal temperature was decreased from 37 to 20 degrees C, mean arterial blood pressure (MABP) decreased from 75 to 47 mmHg (P less than 0.001) and heart rate from 238 to 64 beats/min (P less than 0.001). Arterial PCO2 was reduced from 38 to 31 mmHg (P less than 0.001) (corrected to 37 degrees C), whereas pHa was unchanged from control (7.40). The electroencephalogram slowed progressively and became isoelectric at 22-25 degrees C. During normothermia (n = 6) blood flow to 16 component structures of brain varied from 17 (occipital white matter) to 65 (medulla) ml.100 g-1.min-1, whereas during hypothermia (n = 6) blood flow was lower in all regions (P less than 0.001) at remarkably uniform levels 8.3-10.3 ml.100 g-1.min-1). Thus, the greatest reductions (range, 16-48% of control) in CBF occurred in those structures with the highest intrinsic flows during normothermia and were proportionately less in low flow structures. Regional CGU also decreased in all brain regions analyzed (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Regional cerebral blood flow and glucose utilization during hypoglycemia in newborn dogs.

To assess alterations in regional cerebral blood flow and glucose utilization during perinatal hypoglycemia, newborn dogs (2-7 days postnatal age) were anesthetized with halothane, tracheostomized, paralyzed, and artificially ventilated with 70% N2O-30% O2 to maintain arterial normoxia and normocapnia (arterial PO2 greater than 60 mmHg; arterial PCO2: 35-42 mmHg; arterial pH: 7.35-7.45). Regional cerebral blood flow (rCBF) and glucose utilization (rCGU) were determined with iodo-[14C]antipyrine and 2-deoxy-[14C]glucose as the radioactive tracers, respectively. Hypoglycemia with blood glucose concentrations averaging 0.9 mmol/l was achieved within 90-120 min in 10 animals using intermittent intravenous injections of regular insulin; 10 control animals received 0.9% saline (blood glucose = 9 mmol/l). During hypoglycemia, mean arterial blood pressure was 81% of control, whereas heart rate was unchanged. Arterial O2 and acid-base balance were well maintained (arterial PO2 = 68 mmHg; PCO2 = 37 mmHg; pH = 7.35). Hypoglycemia was associated with significant increases in rCBF in all of 16 analyzed structures, ranging from 172% (parietal white matter) to 249% (thalamus) of control values (17-65 ml.100 g-1.min-1). During hypoglycemia, rCGU was relatively unchanged from normoglycemic values in 11 of 16 brain structures. Significant reductions in rCGU were seen only in occipital white matter (-31%) and in the cerebellar vermis and hemisphere (-31 and -43%, respectively). CGU actually increased slightly in the pons and medulla (+12 and +19%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Regional cerebral glucose utilization in the immature rat: effect of hypoxia-ischemia.

The 2-deoxy-[14C]-glucose (2-DG) method of Sokoloff was used to assess regional cerebral glucose utilization (CGU) in the immature rat. The 7-d postnatal rats received 2.5 muCi 2-DG subcutaneously, after which blood was collected for measurement of plasma glucose and 2-DG activity at intervals up to 90 min. The brains of the 90-min rat pups either were frozen for analysis of glucose concentration and chromatographic separation of 2-DG and 2-DG-6-phosphate or for [14C]-autoradiography. A lumped constant of 0.55 was calculated from plasma and brain glucose levels of 6.4 and 1.62 mmol/L.kg, respectively. Of the [14C] activity in brain, 75.6% was in the 2-DG-6-phosphate fraction; this percent was substituted for K1*, K2*, and K3* in the Sokoloff equation. Cerebral hemispheric CGU (n = 6) averaged 11.4 +/- 1.5 mumol/100 g/min, 1/10 the value of adult rat brain. Rates in 16 brain structures (n = 10) ranged from 7.8 (frontal white matter) to 16.9 (cerebellum) mumol/100 g/min. During hypoxia-ischemia (unilateral common carotid artery ligation combined with exposure to 8% oxygen), the lumped constant increased to 1.04, and 99% of 2-DG was converted to 2-DG-6-phosphate. Increases in CGU occurred in all eight structures of the cerebral hemisphere ipsilateral to the carotid artery occlusion (n = 9), ranging from 287% (frontal white matter) to 445% (striatum) of control values (p less than 0.05). Relatively comparable elevations in CGU (234-435% of control) occurred in the contralateral cerebral hemisphere, which were not significantly different from those of the ipsilateral hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Rectal prolapse: rational therapy without foreign material.

A number of operations are available for the correction of rectal prolapse. Rational judgement is required for the selection of the most appropriate procedure for each patient. Perineal rectosigmoidectomy offers a reasonable alternative to an abdominal procedure in patients who are elderly and debilitated. Simple suture rectopexy is our procedure of choice for an abdominal prolapse repair. We believe that simple rectopexy offers comparable results with less risk than procedures utilizing resection or foreign material. Colon resection should be reserved for those patients who require surveillance for colon polyps or have a history of diverticulitis.

Adult↗
PubMed1986

The role of colonoscopy in the assessment of patients with colorectal cancer.

A retrospective review of 176 patients with adenocarcinoma of the colon who underwent total colonoscopy preoperatively demonstrated synchronous carcinomas in 3.4 percent and synchronous polyps in 55.1 percent. Full-column barium enemas (68 patients) failed to identify cancer in 22 percent of patients and synchronous polyps in 58 percent of patients, a statistically significant (P less than 0.001) number of false-negative examinations. Double-contrast barium enemas (30 patients) failed to identify cancer in 27 percent of patients and synchronous polyps in 42 percent of patients, also a statistically significant (P less than 0.007) number of false-negative examinations. Full column and air contrast barium enemas identified all index cancers with distant metastases. Air-contrast barium enemas failed to identify 40 percent of "early" index cancers (confined to the bowel wall, negative nodes), and full-column barium enemas failed to identify 32 percent. The incidence of synchronous carcinoma and polyps underscores the need for total colon evaluation when a primary carcinoma is detected. Because of the poor accuracy of barium studies, total colonoscopy is the method of choice for this evaluation.

Adenocarcinoma↗
PubMed1986

Metachronous colorectal cancer. Time interval to presentation of a metachronous cancer.

A retrospective review of 1888 colorectal cancer patients demonstrated 37 metachronous cancers in 30 patients for a metachronous cancer rate of 1.6 percent. Evaluation of the index cancers consisted of the traditional single-contrast barium enema and proctoscopic evaluation. Forty percent of the metachronous cancers appeared within two years of the index cancer. If the minimum length of the polyp-cancer sequence is three to five years, then this represents a failure of a traditional preoperative evaluation. A more sensitive evaluation potentially could decrease the metachronous cancer rate. Colonoscopy, which has been found to be more accurate in detecting synchronous neoplasms, should be included in the evaluation of all patients with colorectal cancers.

Adenocarcinoma↗