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Biomedical subjects

K R McQuaid

Publications and source records attributed to K R McQuaid.

12 recordsLinked to original sources
PubMed2001

Colorectal neoplasia: performance characteristics of CT colonography for detection in 300 patients.

PURPOSE: To determine the sensitivity and specificity of computed tomographic (CT) colonography for colorectal polyp and cancer detection by using colonoscopy as the reference standard. MATERIALS AND METHODS: Three hundred patients underwent CT colonography followed by standard colonoscopy. Bowel preparation consisted of magnesium citrate and polyethylene glycol. After colonic air insufflation, patients underwent scanning in the supine and prone positions with 3-mm collimation during a single breath hold. The transverse CT images, sagittal and coronal reformations, and three-dimensional endoluminal images were interpreted by two radiologists independently, and then a consensus reading was performed. CT colonographic findings were correlated with standard colonoscopic and histologic findings. RESULTS: The overall sensitivity and specificity of CT colonography for polyp detection were 90.1% (164 of 182) and 72.0% (85 of 118), respectively. By using direct polyp matching, the overall sensitivity was 69.7% (365 of 524). The sensitivity was 90% (74 of 82) for the detection of polyps 10 mm or larger, 80.1% (113 of 141) for polyps 5.0-9.9 mm, and 59.1% (178 of 301) for polyps smaller than 5 mm. The sensitivity was 94% (64 of 68) for the detection of adenomas 10 mm or larger, 82% (72 of 88) for adenomas 5.0-9.9 mm, and 66.9% (95 of 142) for adenomas smaller than 5 mm. CT colonography was used to identify all eight carcinomas. CONCLUSION: CT colonography has excellent sensitivity for the detection of clinically important colorectal polyps and cancer.

Adenomatous Polyps↗
PubMed2000

Treatment of uninvestigated dyspepsia with cisapride for patients with negative Helicobacter pylori serologies.

OBJECTIVE: The aim of this study was to compare symptoms for patients with uninvestigated dyspepsia and a negative Helicobacter pylori serology who were treated with cisapride or placebo. METHODS: Helicobacter pylori-seronegative patients with chronic dyspepsia were randomized to receive cisapride 10 mg t.i.d. or placebo t.i.d. for 30 days. Symptom scores were performed 1 month and 3 months after randomization. Outcomes measured were dyspepsia symptom scores and a treatment "success" variable defined as absence of symptoms or decrease in the most severe individual symptom by two grades. RESULTS: A total of 60 patients were randomized; 56 completed the 1-month follow-up and 40 completed the 3-month follow-up interview. The mean score for all patients at the time of entry was 11.0 and declined to 8.3 and 8.2 at 1 and 3 months, respectively, after randomization. At 1 month and 3 months after randomization, there was no significant difference in the number of patients meeting the "success" variable for patients receiving cisapride as compared to placebo. The mean decline in symptom severity scores was not significantly different for patients receiving placebo or cisapride at 1 month (mean, -2.8 vs -3.1; difference = 0.3, p = 0.74) or 3 months (-3.1 vs -2.6, difference = -0.5, p = 0.58) after randomization. CONCLUSIONS: No significant difference in the severity of dyspeptic symptoms was found for patients receiving cisapride as compared to placebo in the setting of uninvestigated dyspepsia and a negative Helicobacter pylori serology.

Administration, Oral↗
PubMed1999

Coordinate up-regulation of low-density lipoprotein receptor and cyclo-oxygenase-2 gene expression in human colorectal cells and in colorectal adenocarcinoma biopsies.

Many colorectal cancers have high levels of cyclo-oxygenase 2 (COX-2), an enzyme that metabolizes the essential fatty acids into prostaglandins. Since the low-density lipoprotein receptor (LDLr) is involved in the uptake of essential fatty acids, we studied the effect of LDL on growth and gene regulation in colorectal cancer cells. DiFi cells grown in lipoprotein-deficient sera (LPDS) grew more slowly than cells with LDL. LDLr antibody caused significant inhibition of tumor cell growth but did not affect controls. In addition, LDL uptake did not change in the presence of excess LDL, suggesting that ldlr mRNA lacks normal feedback regulation in some colorectal cancers. Analysis of the ldlr mRNA showed that excess LDL in the medium did not cause down-regulation of the message even after 24 hr. The second portion of the study examined the mRNA expression of ldlr and its co-regulation with cox-2 in normal and tumor specimens from patients with colorectal adenocarcinomas. The ratio of tumor:paired normal mucosa of mRNA expression of ldlr and of cox-2 was measured in specimens taken during colonoscopy. ldlr and cox-2 transcripts were apparent in 11 of 11 carcinomas. There was significant coordinate up-regulation both of ldlr and of cox-2 in 6 of 11 (55%) tumors compared with normal colonic mucosa. There was no up-regulation of cox-2 without concomitant up-regulation of ldlr. These data suggest that the LDLr is abnormally regulated in some colorectal tumors and may play a role in the up-regulation of cox-2.

Adenocarcinoma↗
PubMed1998

The outpatient evaluation of hematochezia.

OBJECTIVE: The objective of this study was to determine whether specific clinical symptoms associated with hematochezia are predictive of important GI pathology and whether full colonoscopic examination is necessary. METHODS: A total of 103 outpatients (> or = 45 yr) with hematochezia, defined as the passage of bright red blood per rectum, underwent anoscopy and colonoscopy. Before endoscopy, patients completed a detailed interview, quantitating the amount and frequency of bleeding, weight loss, use of aspirin/NSAIDs, change in bowel habits, family history, and prior GI illnesses. Based on this information, physicians were asked to predict whether the bleeding was from a perianal or more proximal site. At colonoscopy, pathology was stratified as either proximal or distal to the sigmoid/descending junction. Substantial pathology was defined as one or more adenomas > 8 mm, carcinoma, or colitis. RESULTS: Anoscopy demonstrated internal and external hemorrhoids in 78 and 29 patients, respectively. On colonoscopy, 36 patients had 43 substantial lesions. Thirty-seven of these lesions were distal to the junction of the descending and sigmoid colons and six were proximal lesions. Four patients had cancer; all were distal lesions. Patients with substantial lesions were more likely to give a history of blood mixed within their stool (p = 0.03), to have more episodes of hematochezia per month (p = 0.008), and to have a significantly shorter duration of bleeding before medical evaluation (p = 0.02) than did patients without such lesions. However, the physician's clinical assessment did not predict reliably which patients were likely to have substantial pathology. CONCLUSIONS: In patients with hematochezia, clinicians were unable to distinguish between those patients with and those without significant colonic lesions by history alone. Flexible sigmoidoscopy would have demonstrated most (95%) substantial lesions. The lesions that flexible sigmoidoscopy missed were an unlikely cause of bleeding in this small group of patients.

Ambulatory Care↗
PubMed1998

Omeprazole improves peak expiratory flow rate and quality of life in asthmatics with gastroesophageal reflux.

OBJECTIVE: The aim of this study was to determine if omeprazole improves pulmonary function and quality of life in asthmatics with gastroesophageal reflux. METHODS: This was a double blind, randomized, placebo-controlled cross-over trial. After a 4-wk lead-in period, nine patients with documented asthma and gastroesophageal reflux, were prescribed either omeprazole 20 mg, daily or placebo for 8 wk and then crossed over to the alternate treatment. Outcome measurements included: forced expiratory volume at 1 s (FEV1), peak expiratory flow rate (PEFR), and responses on the Asthma Quality of Life Questionnaire, a validated disease specific measure of functional status. RESULTS: After omeprazole treatment, compared with placebo, patients had higher mean morning and evening PEFR, mean absolute difference (95% CI): morning: 37.8 L/min. (10.9-64.6), evening: 31.2 (3.2-59.2). Omeprazole treatment led to higher mean overall scores on the Asthma Quality of Life Questionnaire, and on the subdomains of activity limitation, symptoms, and emotions (p = 0.039, 0.049, 0.024, 0.040). A trend toward higher FEV1 (mean: 15.6% difference) with omeprazole failed to reach statistical significance (p > 0.2). CONCLUSIONS: After taking omeprazole for 8 wk, asthmatics with GER have better PEFR and quality of life than after placebo.

Activities of Daily Living↗
PubMed1994

Hydrocolonic ultrasonography in the detection of colonic polyps and tumors.

BACKGROUND: Hydrocolonic ultrasonography--abdominal ultrasonography in conjunction with the retrograde instillation of water into the colon--has been advocated as an alternative to colonoscopy for detecting colorectal polyps and cancer. We conducted a prospective, blinded trial to evaluate the procedure further. METHODS: Fifty-two consecutive patients (50 men and 2 women; average age, 62 years) who were referred for colonoscopy underwent hydrocolonic ultrasonography followed by colonoscopy. The physicians performing colonoscopy were blinded to the ultrasound results. Patients who had a history of colonic polyps or tumors or who had previously undergone flexible sigmoidoscopy or colonoscopy were excluded. RESULTS: Twenty-two patients had normal results on colonoscopy, 26 had polyps, 3 had cancer and polyps, and 1 had cancer alone. Twenty patients had polyps less than 7 mm in diameter, eight had polyps 7 mm or more in diameter, and one had a polyp of unknown size. Hydrocolonic ultrasonography did not detect any cancers and detected only one polyp > or = 7 mm and one polyp < 7 mm in diameter. The overall sensitivity of ultrasonography for identifying any polyp was 6.9 percent, and for identifying a polyp > or = 7 mm, it was 12.5 percent. Ultrasonography suggested the presence of five masses and five polyps that were not confirmed by colonoscopy. Six patients had incomplete ultrasound studies because of discomfort or the inability to retain water. There were two complications: one patient had two vasovagal episodes, and another had diaphoresis. CONCLUSIONS: Hydrocolonic ultrasonography was less useful than colonoscopy for detecting colorectal polyps and cancers. The usefulness of the technique in screening for colonic polyps and tumors appears to be limited.

Colonic Neoplasms↗
PubMed1993

Gastric acid suppression is greater during intravenous ranitidine infusion versus bolus injections of famotidine.

It has been proposed that famotidine may be effective in maintaining intragastric pH > or = 4 for up to 12 h with a single i.v. 20 mg bolus injection and thereby prevent acute stress-related mucosal haemorrhage. The present study was designed to compare a ranitidine continuous i.v. infusion (6.25 mg/h) vs. famotidine bolus injection (20 mg every 12 h) on 24-h intragastric pH and gastric acid secretion. Twenty-eight healthy volunteers (15 males, 13 females; 20-56 years) participated in two 24-h treatment periods; each test was in random order separated by 7-10 days. After an overnight fast, subjects were intubated and gastric pH and acid secretion measured hourly. Whereas ranitidine maintained gastric pH above 4 for the entire 24-h period, mean pH steadily decreased to a nadir of 2.9 and 3.7, respectively, 12 h after each famotidine injection (P < 0.01 vs. ranitidine). Furthermore, gastric acid secretion increased to 4.4 +/- 1.2 mmol/h 12 h after famotidine injection compared to 1.1 +/- 0.3 mmol/h with ranitidine (P < 0.01). We conclude that ranitidine delivered as a continuous i.v. infusion (6.25 mg/h) is superior to bolus famotidine injections (20 mg) at 12-h intervals in suppressing gastric acid secretion and maintaining an intragastric pH > or = 4. More frequent famotidine dosing, or delivery by continuous i.v. infusion, may be required to provide prolonged acid suppression.

Adult↗
PubMed1993

Endoscopy-negative dyspepsia. Hold those forceps!

Nonulcer dyspepsia (NUD) is an enigmatic disorder which likely has heterogeneous etiologies. Helicobacter pylori-associated gastritis has been identified in a large number of patients with NUD, raising speculation that chronic infection with this organism may cause dyspepsia in some patients. Prospective case-control and cohort studies however do not suggest that H. pylori prevalence is greater in NUD than in asymptomatic controls. Limited therapeutic trials of H. pylori-eradication therapy have not shown a convincing symptomatic improvement compared with placebo treatment. Definition of the role of H. pylori in NUD awaits further well-designed, well-controlled epidemiologic and therapeutic studies. Until such information is available, routine endoscopic gastric biopsies looking for H. pylori in patients with NUD should be abandoned.

Biopsy↗
PubMed1992

Medical therapy of peptic ulcer disease.

The gastric duodenal mucosa normally is protected from the damaging effects of gastric acid and pepsin by ill-defined mechanisms. Ulcers may arise when there is an imbalance between the aggressive and defensive factors that renders the mucosa susceptible to damage. A variety of factors have been identified that may favor the development of peptic ulcers, but no single pathophysiologic defect applies in all ulcer patients. In duodenal ulcers, gastric acid hypersecretion is observed in as many as one third of patients; however, most patients with duodenal ulcers secrete normal amounts of gastric acid. Decreased mucosal bicarbonate secretion may be important in at least some duodenal ulcer patients. Use of NSAIDs may cause either gastric or duodenal ulcers, probably through the inhibition of mucosal prostaglandin synthesis and disruption of mucosal defenses. Finally, a recently identified bacterium, H. pylori, causes a chronic gastritis that is found in the overwhelming majority of patients with duodenal ulcers and non-NSAID-associated gastric ulcers. This bacterium may play a pivotal role in ulcer pathogenesis and, especially, in ulcer recurrences. A number of drugs of proved efficacy are available for the treatment of acute duodenal and gastric ulcers. The H2 receptor antagonists administered once daily remain the mainstay of ulcer therapy because of their efficacy, ease of use, and excellent safety profile. More thorough and long-lasting acid inhibition is afforded by the H+/K(+)-ATPase inhibitor omeprazole. This agent also promotes more rapid ulcer healing, but in most patients, this minor advantage may not justify the higher cost. It is not known whether more rapid healing will translate into lower ulcer complication rates. Until further data are available, this drug may be preferable in patients with large or complicated ulcers. In patients with refractory ulcers, omeprazole is clearly superior to other available agents. Agents that promote mucosal defense mechanisms are becoming increasingly popular in the treatment of duodenal ulcers but have undergone less testing than in gastric ulcers. Sucralfate 1 g four times daily is equivalent to H2 antagonists in the treatment of duodenal ulcers and, probably, gastric ulcers. Its requirement for multiple daily doses makes it somewhat less attractive at present to most patients. Low- to medium-dose Al-containing antacids are inexpensive and efficacious in duodenal ulcer therapy. They should remain as therapeutic options for the compliant patient in whom cost considerations are important. Colloidal bismuth subcitrate 120 mg four times a day is comparable to other agents in the acute treatment of duodenal ulcers and likely gastric ulcers.(ABSTRACT TRUNCATED AT 400 WORDS)

Antacids↗
PubMed1991

Much ado about gastrin.

The regulation of gastrin secretion from antral G-cells is of major importance in the physiologic control of acid secretion. Gastrin secretion is highly dependent upon gastric intraluminal pH and is inhibited significantly by a pH of less than 3.0. Acute gastric alkalinization greater than pH 6.0 with antisecretory agents such as H2-receptor antagonists or H+/K+ ATPase inhibitors has little impact on fasting serum gastrin levels but promotes an enhanced sustained rise in meal-stimulated gastrin release. Courses of standard therapy with both H2-antagonists and H+/K+ inhibitors cause a significant rise in 24 h integrated plasma gastrin levels that is inversely correlated to the 24-h integrated gastric acidity. The rise in fasting or integrated plasma gastrin levels observed in patients treated with H2-antagonists is small and of unclear clinical significance. Therapy with antisecretory agents leads to earlier ulcer relapse than with other agents. A variety of factors have been proposed to explain the earlier ulcer relapse rate, including secondary hypergastrinemia with rebound acid hypersecretion after discontinuation of the drug. Secondary hypergastrinemia may also lead to tolerance to prolonged courses of H2-antagonists therapy with a decrease in acid inhibition. This may contribute to break-through ulcer recurrence during maintenance H2-antagonist therapy. However, the relative importance of hypergastrinemia and tolerance to H2-antagonists compared with other factors such as baseline gastric acid secretion, smoking status, nonsteroidal anti-inflammatory drug use, and Helicobacter pylori status is difficult to assess.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1987

Extreme dyspnea from unilateral pulmonary venous obstruction. Demonstration of a vagal mechanism and relief by right vagotomy.

A 43-yr-old woman developed severe exertional dyspnea after an unsuccessful attempt to correct a total right anomalous pulmonary venous connection. A clotted anastomosis resulted in unilateral pulmonary venous obstruction. Investigation excluded airway disease, left ventricular failure, and severe pulmonary hypertension as the cause of dyspnea. Exercise studies demonstrated a markedly abnormal ventilatory pattern consistent with excess vagal stimuli to the respiratory center. Temporary and then permanent vagal interruption markedly altered the respiratory pattern and improved her functional status from New York Heart Association Class III to Class I, confirming that vagal afferents were the cause of the dyspnea.

Adult↗