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Biomedical subjects

D A Ahlquist

Publications and source records attributed to D A Ahlquist.

At least 37 records · Page 2Linked to original sources
PubMed1997

Pervasive occult gastrointestinal bleeding in an Alaska native population with prevalent iron deficiency. Role of Helicobacter pylori gastritis.

OBJECTIVE: To confirm prevalent iron deficiency among Yupik Eskimos living in Alaska and to explore the frequency of and potential lesions accounting for occult gastrointestinal bleeding. DESIGN: Descriptive survey. SETTING: Rural Arctic community. SUBJECTS: A total of 140 adult volunteers from 3 villages in the Yukon-Kuskokwim Delta region of western Alaska. MAIN OUTCOME MEASURES: Daily iron intake, hematologic and biochemical indexes of iron status, fecal hemoglobin levels, stool parasites, and endoscopic findings. RESULTS: While dietary iron intake by Yupiks was similar to that of a reference population, iron deficiency prevalence was increased 13-fold in Yupik men and 4-fold in Yupik women. Fecal hemoglobin levels were elevated in 90% of subjects contrasted with only 4% of a reference group; median levels were 5.9 and 0.5 mg of hemoglobin per gram of stool, respectively. Among 70 Yupik subjects with elevated fecal hemoglobin levels who had endoscopy performed, 68 (97%) had an abnormal gastric appearance consisting of erythema, mucosal thickening, diffuse mucosal hemorrhages, erosions, or ulcerations. Gastric biopsies revealed chronic active gastritis with associated Helicobacter pylori in 68 (99%) of 69. No other hemorrhagic gastrointestinal disease was detected. CONCLUSIONS: Based on this study sample, occult gastrointestinal bleeding appears to be pervasive in the Yupik population and likely underlies the prevalent iron deficiency. An atypical hemorrhagic gastritis associated with H pylori infection is present almost universally and may represent the bleeding source.

Adult↗
PubMed1997

Fecal occult blood testing for colorectal cancer. Can we afford to do this?

Fecal blood is an inherently insensitive and nonspecific marker for asymptomatic colorectal neoplasia. As such, use of fecal occult blood tests (FOBTs) necessarily limits the effectiveness and efficiency of a screening application. FOBT screening may result in a modest reduction in colorectal cancer-specific mortality, but it alters neither colorectal cancer incidence nor overall mortality. Costs resulting from FOBT screening are substantial, and the extent to which screen-induced mortality offsets any benefits remains unknown. In the absence of a clearly demonstrated net benefit with FOBT screening, affordability of this expensive effort can be legitimately questioned.

Colorectal Neoplasms↗
PubMed1997

Detection of colorectal polyps with CT colography: initial assessment of sensitivity and specificity.

PURPOSE: To estimate the sensitivity and specificity of computed tomographic (CT) colography in detection of colorectal polyps and to compare these findings with those at axial CT. MATERIALS AND METHODS: In 70 consecutive patients, CT colography and colonoscopy were performed. Helical axial CT images and CT colographic images (multiplanar two- and three-dimensional endoluminal images) were evaluated separately by two radiologists blinded to results from colonoscopy and other imaging studies. Findings were compared with those at colonoscopy, which was the standard. RESULTS: The sensitivity and specificity for the two observers with CT colography averaged 75% and 90% in patients with adenomas 10 mm in diameter or larger, 66% and 63% in patients with adenomas 5 mm in diameter or greater, and 45% and 80% for patients with adenomas less than 5 mm in diameter, respectively. Sensitivity and specificity with axial CT were lower than those with CT colography (58% and 74%, respectively) in patients with adenomas 10 mm in diameter or larger. CONCLUSION: Compared with axial CT, CT colography appears to have superior sensitivity and specificity in detection of clinically important colorectal adenomas. Early performance of CT colography seems promising for detection of colorectal polyps 5 mm and larger.

Adenoma↗
PubMed1997

Evidence against flat dysplasia as a regional field defect in small bowel adenocarcinoma associated with celiac sprue.

OBJECTIVE: To determine whether diffuse flat dysplasia, akin to that seen with chronic ulcerative colitis, occurs as a mucosal field defect accompanying small bowel adenocarcinoma in patients with celiac sprue. DESIGN: A pathologic investigation of archival tissue was undertaken. MATERIAL AND METHODS: From the tissue archives at Mayo Clinic Rochester for the period from January 1978 to January 1993, resected sprue-associated adenocarcinomas with adequate adjacent mucosa for study were identified. On the basis of multiple strip biopsy specimens obtained at the tumor margins and within 4 cm distal and proximal to the tumor, histologic maps were created. RESULTS: Among 94 patients with primary adenocarcinoma of the small bowel, 8 had a concurrent diagnosis of celiac sprue. Of these eight cases, six surgically resected specimens (five duodenal and one jejunal adenocarcinoma) were adequate for study. A thin rim of benign dysplasia was demonstrated at the tumor margin in three of the six specimens; however, contiguous fields of flat dysplasia were not present in any of these cases. CONCLUSION: These data support focal dysplasia (for example, adenoma) rather than sheets of flat dysplasia as the premalignant lesion in sprue-associated small bowel adenocarcinoma. Blind endoscopic biopsies of small bowel mucosa are not justified for neoplasia surveillance in patients with celiac sprue.

Adenocarcinoma↗
PubMed1997

Computed tomographic colography and virtual colonoscopy.

CT colography (CTC) is a powerful new approach to imaging the colorectum and a promising screening tool for the detection of colorectal neoplasia. From data generated by a helical CT scan, CTC uses virtual reality technology to produce highly discriminant two- and three-dimensional images that permit a thorough and minimally invasive evaluation of the entire colorectum. A dynamic CTC display technique from the endoluminal perspective, called cf2virtual colonoscopy,cf1 simulates colonoscopy by "flying" through the three-dimensional colon image. CTC offers potential advantages in diagnostic performance, safety, and patient acceptance over current screening approaches. Although early data suggest excellent colorectal polyp detection rates, this nascent technology will require rigorous clinical investigation and further refinements to assess adequately its place in the endoscopist's armamentarium.

Barium Sulfate↗
PubMed1996

Fecal hemoglobin excretion in elderly patients with atrial fibrillation: combined aspirin and low-dose warfarin vs conventional warfarin therapy.

BACKGROUND: Antithrombotic prophylaxis using combined aspirin and low-dose warfarin is under evaluation in several clinical trials. However, therapy may result in increased gastrointestinal blood loss and clinical bleeding vs conventional single-agent antithrombotic therapy. METHODS: To assess differences in gastrointestinal blood loss, we measured quantitative fecal hemoglobin equivalents (HemoQuant, Mayo Medical Laboratory, Rochester, Minn) in 117 patients, mean age 71 years, 1 month after initiation of assigned therapy in the Stroke Prevention in Atrial Fibrillation III Study. Sixty-three of these patients who had characteristics for high risk of stroke were randomly assigned to conventional adjusted-dose warfarin therapy (international normalized ratio, 2.0 to 3.0) or low-dose combined therapy (warfarin [international normalization ratio,<1.5] plus 325 mg/d of enteric-coated aspirin). The remaining 54 patients with low risk of stroke received 325 mg/d of enteric-coated aspirin. RESULTS: Among the 63 at high risk of stroke, abnormal values (>2mg of hemoglobin per gram of stool) were detected in 11% and values greater than 4 mg of hemoglobin per gram of stool were found in 8%. Mean ( +/- SD) values were more for those randomly assigned to receive combined therapy (1.7 +/- 3.3 mg of hemoglobin per gram of stool vs adjusted-dose warfarin therapy, 1.0 +/- 1.9 mg/g; P=.003). The 54 nonrandomized patients with low risk of stroke receiving aspirin alone had a mean (+/- SD) HemoQuant value of 0.8 +/- 0.7mg of hemoglobin per gram of stool 1 month after entry in the study. CONCLUSIONS: Abnormal levels of fecal hemoglobin excretion were common in elderly patients with high risk of atrial fibrillation 1 month after randomization to prophylactic antithrombotic therapy. Combined warfarin and aspirin therapy was associated with greater fecal hemoglobin excretion than standard warfarin therapy, suggesting the potential for increased gastrointestinal hemorrhage.

Aged↗
PubMed1996

Detection of colorectal polyps by computed tomographic colography: feasibility of a novel technique.

BACKGROUND & AIMS: Computed tomographic colography (CTC) represents a novel technique for colorectal polyp detection. A prospective study was undertaken to determine the optimal CTC scanning parameters based on an artificial colon model and to assess the feasibility of CTC to detect clinically significant colorectal polyps. METHODS: A colon model was scanned by helical computed tomography at multiple parameters. Reformatted two-dimensional and three-dimensional images were then graded for polyp detection and image quality. Subsequently, 10 patients with known colon polyps underwent CTC immediately before colonoscopy. The number of polyps detected by two radiologists using CTC were compared with colonoscopy results that served as the gold standard. RESULTS: The optimal scanning parameters in the colon model were 5-mm collimation, 5 mm/s table speed, and 1-mm reconstruction interval. Ten patients had 30 polyps (range, 0.2-2.0 cm) by colonscopy, and all polyps > or = 0.5 cm were adenomas. Polyp detection by CTC for both observers was 100% (5 of 5) > or = 1 cm, 71% (5 of 7) between 0.5 and 0.9 cm, and 11%-28% (2-5 of 18) < 0.5 cm. CONCLUSIONS: Based on this small, unblinded pilot study, CTC is feasible for colorectal polyp detection > or = 0.5 cm in diameter.

Aged↗
PubMed1996

Fecal marker variability in colorectal cancer: calprotectin versus hemoglobin.

BACKGROUND: Blood products like hemoglobin are problematic as markers for colorectal neoplasia because bleeding is intermittent. Levels of calprotectin, a leukocyte-derived protein, are increased in stools from colorectal cancer patients. However, this blood constituent may gain luminal access via interstitial leukocyte migration, which could be a less variable mechanism of entry than bleeding. METHODS: To correlate the levels of and to compare the variability of fecal calprotectin and hemoglobin, quantitative assays were performed independently on multiple serially collected stools from 14 patients with colorectal cancer. Marker level association was estimated with Pearson's correlation coefficient, and variation estimated with an analysis of variance model. RESULTS: Fecal calprotectin and hemoglobin levels were discordant in 55 (50%) of 110 matched aliquots, and marker levels failed to correlate. The estimated between-subject correlation was -0.10 (95% CI, -0.60 to 0.46), and mean within-subject correlation -0.27 (95% CI, -0.73 to 0.34). The between-stool coefficient of variation was less for calprotectin (22%) than for hemoglobin (80%). CONCLUSIONS: In patients with colorectal cancer, the mechanism of luminal calprotectin entry appears to be both different from and less erratic than bleeding.

Aged↗
PubMed1994

Endoscopic treatment of major bleeding from advanced gastroduodenal malignant lesions.

OBJECTIVE: To summarize the results of endoscopic therapy for acute hemorrhage from gastroduodenal malignant lesions. DESIGN: The 3-year experience (1989 through 1991) of a specialized gastrointestinal (GI) bleeding team in the endoscopic treatment of acute upper GI bleeding from gastroduodenal malignant tumors was retrospectively reviewed. MATERIAL AND METHODS: Of 1,083 consecutive patients with acute major upper GI hemorrhage, 21 (1.9%) were found to have advanced tumors of the stomach and duodenum, 15 of whom received endoscopic therapy. In this study group of 15 patients, the tumors were gastric in 11 and duodenal in 4. Endoscopic treatment consisted of injection of epinephrine, heater probe coagulation, neodymium:yttrium-aluminum-garnet laser coagulation, or injection of sodium tetradecyl sulfate. RESULTS: Initial endoscopic hemostasis was achieved in 10 of the 15 patients (67%); however, bleeding recurred in 8 of 10 (80%), and all 5 in whom endoscopic hemostasis was not achieved continued to bleed. Mean transfusion requirements for the 30 days before and the 30 days after the first endoscopic treatment were 7.6 and 6.4 units of packed erythrocytes, respectively (P > 0.10). Five major procedure-related complications occurred, two of which were fatal. The median duration of survival after the first endoscopic treatment was 39 days (range, 1 to 1,414). CONCLUSION: In patients with major bleeding from advanced gastroduodenal malignant lesions, endoscopic therapy seems to provide limited benefit.

Acute Disease↗
PubMed1994

Intraluminal measurement of enteric mucosal perfusion: relationship to superior mesenteric artery flow during basal and postprandial states in the dog.

BACKGROUND: Several in vivo techniques that assess mucosal perfusion by intraluminal probes have recently been developed and validated, including laser Doppler flowmetry, reflectance spectrophotometry, and tonometry. METHODS: With these techniques, a canine model where the entire vascular supply to the jejunoileum was isolated as the superior mesenteric artery and vein was used to examine the relationship between enteric mucosal blood perfusion and adjusted decrements in arterial flow under fasting and postprandial conditions. RESULTS: Mucosal perfusion measured by laser Doppler flowmetry and reflectance spectrophotometry correlated linearly with decrements in superior mesenteric artery flow (r2 = 0.96 and 0.98, respectively); estimation of mucosal pH by tonometry decreased only after a critical level of arterial inflow was reached (less than 50% of baseline flow). Mucosal perfusion increased after the meal throughout the jejunoileum with unrestricted superior mesenteric artery flow. However, with restricted superior mesenteric artery flow, nutrient delivery to the jejunum was accompanied by increased mucosal perfusion at that level but by decreased perfusion in the distal ileum not exposed to nutrients. This latter response represents a distal to proximal redistribution of blood, i.e., an intramesenteric steal phenomenon. CONCLUSIONS: In vivo measurements of mucosal perfusion reflected changes in large mesenteric vessel blood flow. These intraluminal techniques discriminated between a normal and an impaired mesenteric circulation in an acute model and may have clinical application.

Animals↗