Biomedical subjects
C D Johnson
Publications and source records attributed to C D Johnson.
Gallbladder motility, gallstones, and the surgeon.
Cholecystectomy is one of the commonest surgical procedures in the Western world, with more than half a million procedures performed annually in the United States alone. In recent years, studies of gallstone pathogenesis and gallbladder disease have increasingly focused on abnormal gallbladder motility in the pathogenesis of some, if not all, gallbladder conditions. The control of gallbladder motility is complex and depends on an intricate interplay of neural and hormonal factors. An understanding of the control of gallbladder motility is crucial to the understanding of the mechanisms of gallstone formation and may help to explain the failure to cure symptoms after cholecystectomy in up to one third of patients. The purpose of this article is to outline mechanisms controlling gallbladder motility, examine recent developments in our understanding of this complex process, and relate changes in motility to common disease conditions of the gallbladder. The role of altered motility in the pathogenesis of gallstones is discussed and the effects of commonly performed surgical procedures such as truncal vagotomy and cholecystectomy on upper gut physiology are reviewed.
Caenorhabditis elegans mutants resistant to inhibitors of acetylcholinesterase.
We characterized 18 genes from Caenorhabditis elegans that, when mutated, confer recessive resistance to inhibitors of acetylcholinesterase. These include previously described genes as well as newly identified genes; they encode essential as well as nonessential functions. In the absence of acetylcholinesterase inhibitors, the different mutants display a wide range of behavioral deficits, from mild uncoordination to almost complete paralysis. Measurements of acetylcholine levels in these mutants suggest that some of the genes are involved in presynaptic functions.
Abdominal mass in a patient with Crohn's disease.
Explore the source record for details and available documents.
Tuberculosis of the pancreas.
Tuberculosis of the pancreas is extremely rare. We report a case which demonstrates the diagnostic confusion which may arise in this condition. A 55-year-old alcoholic caucasian man presented with loss of weight and obstructive jaundice. Ultrasonography, endoscopic retrograde cholangiopancreatography and computed tomography showed a mass lesion in the head of the pancreas, diagnosed as probably malignant. He underwent a Whipple's pancreatoduodencetomy and made a good recovery. Histological examination showed typical features of tuberculosis. In the absence of other foci of active disease chemotherapy was not given. He remains well 12 months after operation.
MR measurements of mesenteric venous flow: prospective evaluation in healthy volunteers and patients with suspected chronic mesenteric ischemia.
PURPOSE: To quantify portal vein (PV) and superior mesenteric vein (SMV) flow before and after a standardized meal in healthy volunteers and to prospectively evaluate patients with a clinical suspicion of chronic mesenteric ischemia on the basis of magnetic resonance (MR) measurement of flow in the mesenteric venous system in volunteers. MATERIALS AND METHODS: Cine phase-contrast flow measurements were acquired in 10 asymptomatic volunteers and in 10 patients. RESULTS: In volunteers, the difference between the fasting and post-prandial flows in the SMV and PV was significant (P < .001), with a peak flow augmentation of 245% +/- 74 and 70% +/- 29, respectively. Postprandial augmentation of peak flow in the SMV was significantly less in patients with mesenteric ischemia compared with volunteers (64% +/- 28; P = .02). SMV flow augmentation in patients without mesenteric ischemia did not differ significantly from that in volunteers (206% +/- 36; P = .31). CONCLUSION: Measurement of postprandial flow augmentation in the SMV with MR imaging shows promise as a noninvasive screening test for chronic mesenteric ischemia.
Upper abdominal phase-contrast MR angiography: comparison of cine and non-cine techniques.
PURPOSE: To evaluate image quality, vessel conspicuity, and signal-to-noise ratio (S/N) of four two-dimensional magnetic resonance (MR) phase-contrast techniques: cine phase-contrast with respiratory compensation (CPC-R), cine phase-contrast without respiratory compensation (CPC), phase-contrast with two signals acquired (PC-2), and phase-contrast with eight signals acquired (PC-8). MATERIALS AND METHODS: MR angiographic images of the portal vein were obtained in 14 patients. RESULTS: Overall image quality was rated excellent in 10 of 14 patients (CPC-R), in one of 14 patients (CPC), in none of 14 patients (PC-2), and in one of 14 patients (PC-8). Views of 10 upper abdominal vessels were evaluated with each technique. The mean (+/- standard deviation) number of well-imaged vessels was 6 +/- 2 (CPC-R), 3 +/- 2 (CPC), 2 +/- 2 (PC-2), and 3 +/- 2 (PC-8). CPC-R images were significantly better in overall image quality and number of vessels seen (P < .01). Mean S/Ns were 10.8 +/- 3.4 (CPC-R), 6.8 +/- 2.7 (CPC), 4.5 +/- 1.7 (PC-2), and 6.4 +/- 2.1 (PC-8). S/N with CPC-R was significantly greater than with CPC, PC-2, or PC-8. CONCLUSION: CPC-R provided consistently higher quality angiographic images than were obtained with the other sequences studied.
MR imaging of the abdomen with a phased-array multicoil: prospective clinical evaluation.
PURPOSE: To prospectively compare use of a phased-array multicoil and a conventional body coil in abdominal MR imaging. MATERIALS AND METHODS: Thirteen patients (seven men, six women; mean age, 55 years) underwent imaging with a phased-array multicoil and with a conventional body coil. Four pulse sequences were used: T2-weighted spin echo (SE), magnetization-prepared gradient-recalled echo (GRE), breath-hold fast SE, and echo planar (EP). RESULTS: Lesion detection improved the most on fast SE, multicoil-acquired images. Signal-to-noise ratio (S/N) increased 64% with fast SE (P = .0005) and EP (P < .0109) sequences. Contrast-to-noise ratio (C/N) doubled (P < .05) with T2-weighted SE sequences. Lesion conspicuity improved on multicoil-acquired images with all fast sequences (magnetization-prepared GRE, P = .015; fast SE, P = .002; EP imaging, P = .013). There was little difference in respiratory and vascular artifact. Depiction of most abdominal structures improved (P < .01). CONCLUSION: Use of the phased-array multicoil provides better MR images of the abdomen than does use of a conventional body coil.
Palliative resection of pancreatic adenocarcinoma. A survey of British surgeons.
A survey was carried out by postal questionnaire of the attitudes of British surgeons to pancreatic resection as palliation for ductal adenocarcinoma of the pancreas. Replies from 24 surgeons related to experience in over 700 resections. The incidence of estimated residual local disease after resection was median 12.5 percent, range 0-35 percent. Half (12) of the surgeons felt that pancreatic resection with residual macroscopic disease was justified. Only 3 (12.5 percent) surgeons accepted that palliative resection in the presence of liver metastases was sometimes justifiable. Further evidence is required of improved quality of life after resection before the majority of surgeons will accept palliative resection in the management of pancreatic ductal adenocarcinoma.
Pancreatic enzyme supplementation in acute pancreatitis.
This study evaluates the effect of oral pancreatic enzyme supplements on pain, analgesic requirement and the incidence of complications in patients with acute pancreatitis. This double blind, prospectively randomised placebo controlled study included 23 patients. Pain was monitored using a visual analogue scale; the analgesic requirement was assessed with a numerical score. No significant differences were noted between the median (range) pain scores of patients who received placebo: 22 (17.1-58) and those who received enzymes: 23 (11.3-63). Hospital stay was 7 (5-10) days in patients on placebo and 8 (6-24) days in the enzyme group (p = 0.069). Analgesic requirements were: placebo 20 (6-60) and enzymes: 16 (0-63) (p = 0.56). This study has shown no beneficial effect of oral pancreatic enzyme supplements in the initial management of patients with acute pancreatitis.
Postprandial alkaline tide: does it exist?
The concept of an alkaline tide which compensates for gastric acid secretion suggests the possibility of indirect measurement of gastric acid secretion. This study was designed to determine whether postprandial changes in renal and respiratory function could be used to assess gastric secretion in healthy adults. Volunteers ate one of three standard (low, medium or high protein) breakfasts on separate days. A fall in urine acid output was observed during 2 h after the high protein meal, but not after the medium or low protein meal. Fasting subjects showed a similar fall in urine acid output over a 2-hour period. Pretreatment with ranitidine 150 mg b.i.d. had no effect on basal or postprandial urine acid output. We conclude that changes in urine acid output are not related to the gastric secretory response to food. In a separate study, treatment with omeprazole 20 mg daily had no effect on postprandial respiratory function (minute ventilation; mixed expired CO2; minute volume of CO2; respiratory exchange ratio; venous blood pH, pCO2 or bicarbonate; and end tidal CO2). Thus we were unable to detect a respiratory alkaline tide after a standard breakfast. These findings suggest that any respiratory or urinary compensation for gastric acid secretion is too small to be of physiological or clinical significance.
Distinction between cavernous hemangiomas of the liver and hepatic metastases on CT: value of contrast enhancement patterns.
OBJECTIVE: Differentiating between cavernous hemangiomas of the liver and hepatic metastases on the basis of single-pass, contrast-enhanced CT is a significant and frequently encountered diagnostic challenge. Recognition of characteristic enhancement features of cavernous hemangiomas can aid in effectively distinguishing between these lesions. The purpose of this study was to determine sensitivity and specificity of dense, globular enhancement for differentiating cavernos hemangiomas and metastases during single-pass, contrast-enhanced CT. MATERIALS AND METHODS: CT appearance of 133 lesions in 91 patients with cavernous hemangiomas (44 patients) or metastases (47 patients) was retrospectively evaluated in a blinded review. CT examinations were performed with nonhelical technique following injection of 150 ml of contrast material. All patients with metastases had pathologic proof (n = 47). Patients with cavernous hemangiomas were clinically stable for at least 2 years after CT (n = 43) or had tissue proof (n = 1). All lesions were evaluated based on the following criteria: (1) Type of enhancement: globular, linear, diffuse and homogeneous, or diffuse and heterogeneous. (Globular enhancement was considered to be present when enhancing nodules less than 1 cm in diameter were seen within lesions.) (2) Continuity of enhancing tissue: continuous or noncontinuous. (Uninterrupted collections of contrast material within at least 50% of a lesion were considered continuous. Multiple, separate collections of contrast material were considered noncontinuous.) (3) Degree of enhancement: hypo-, iso-, or hyperdense relative to the aorta. (4) Distribution of enhancement: peripheral, central, or mixed. RESULTS: Seventy-six percent of cavernous hemangiomas had globular enhancement, compared to 10% of metastases (p < .001). Seventy-two percent of cavernous hemangiomas had enhancement isodense with the aorta, and 96% of metastases were hypodense (p < .001). Sixty-seven percent of cavernous hemangiomas had peripheral enhancement, compared to 38% of metastases (p < .001). The combined finding of globular, isodense enhancement was seen in 67% of cavernous hemangiomas and none of the metastases. Only 10% of cavernous hemangiomas had nonglobular, hypodense enhancement, compared with 90% of metastases. Combining all criteria, reviewers correctly classified 122 (92%) of the lesions. Presence of globular enhancement, isodense with the aorta, was 67% sensitive and 100% specific in differentiating cavernous hemangiomas from hepatic metastases. CONCLUSION: In most cases, differentiation of cavernous hemangiomas from hepatic metastases can confidently be made with single-pass, contrast-enhanced CT. Globular enhancement, isodense with the aorta, is 67% sensitive and 100% specific in differentiating cavernous hemangiomas and hepatic metastases.
Fibrolamellar hepatocellular carcinoma: stage at presentation and results of aggressive surgical management.
OBJECTIVE: The purpose of this study was to report the stage of fibrolamellar carcinoma at presentation and the imaging findings of postoperative recurrent tumor in an aggressively managed population and to assess the implications of those findings relative to the patients' management. MATERIALS AND METHODS: Imaging studies in 10 patients with pathologically proved fibrolamellar carcinoma were reviewed. Preoperative studies included CT (n = 10), sonography (n = 8), and MR imaging (n = 2). Postoperative studies included CT (n = 9), sonography (n = 4), and MR imaging (n = 1). Imaging findings were correlated with clinical and surgical follow-up data. Patients were followed up for 2-75 months (median, 26 months). RESULTS: At presentation, seven (70%) of 10 patients had metastatic lymphadenopathy. Seven patients (70%), including four with lymph node metastasis, had tumor resections with intent to cure. Postoperative imaging studies revealed recurrent tumor in all seven of these patients, including six patients (86%) who had intrahepatic recurrence with or without lymph node metastasis after 6-18 months, and one patient (14%) who had distant metastases 66 months postoperatively. Recurrent lesions were subsequently resected in three (43%) of seven patients, who were disease-free at a mean of 8 months after their second resection. Five patients died after 9 months mean survival, and two patients were alive with residual tumor after 3 months mean follow-up. CONCLUSION: Fibrolamellar carcinomas are often of advanced stage at diagnosis. Recurrence after resection with intent to cure is common. Early and frequent follow-up imaging is necessary for optimizing surgical management in patients with fibrolamellar carcinoma.
Gadoteridol-enhanced MR imaging of malignant hepatic tumors: effects of triple versus standard doses on lesion-liver contrast.
OBJECTIVE: The purpose of this study was to compare liver signal-to-noise ratio (SNR), lesion SNR, and lesion-liver contrast-to-noise-ratio (CNR) in patients with malignant liver lesions after the administration of a standard dose (0.1 mmol/kg of body weight) or a triple dose (0.3 mmol/kg) of a gadolinium chelate (gadoteridol). We hypothesized that the higher dose would produce a higher lesion-liver CNR and therefore increase the conspicuity of hepatic lesions. MATERIALS AND METHODS: A total of 85 patients with malignant hepatic masses (61 metastases, 22 hepatocellular carcinomas, and two lymphomas) proved by histologic or follow-up studies underwent MR imaging at 1.5 T. T1-weighted spin-echo imaging and gradient-echo imaging were done before and within 1 min after (gradient echo) as well as 5 (spin echo) and 15 (spin echo) min after the injection of 0.1 or 0.3 mmol of gadoteridol per kg, randomized before the start of the study (39 patients received the standard dose, and 46 received the triple dose). The signal intensities of the liver and lesions and the SD of background noise were measured by use of regions of interest to calculate the SNR of the liver and malignant lesions and the lesion-liver CNR. RESULTS: The lesion-liver CNR was increased significantly at 5 and 15 min after the administration of gadoteridol. No significant differences in the liver SNR, lesion SNR, and lesion-liver CNR (after 1 min: standard dose, -5 +/- 8, and triple dose, -4 +/- 14; after 5 min: standard dose, -1 +/- 5, and triple dose, 2 +/- 8; and after 15 min: standard dose, 1 +/- 5, and triple dose, 6 +/- 20) were found between the doses at all time points. CONCLUSION: Triple-dose gadoteridol does not improve the lesion-liver contrast of malignant hepatic lesions over that provided by the standard dose and is not warranted for liver MR imaging.
Single-pass CT of hepatic tumors: value of globular enhancement in distinguishing hemangiomas from hypervascular metastases.
OBJECTIVE: The purpose of this study was to evaluate the sensitivity and specificity of globular enhancement for differentiating hepatic hemangiomas from hypervascular metastases on single-pass, contrast-enhanced CT scans. Globular enhancement was defined as enhancing nodules less than 1 cm seen within a lesion. MATERIALS AND METHODS: Fifty CT examinations were retrospectively evaluated in a blinded fashion by two independent reviewers. The CT studies were done with nonhelical technique after the IV injection of 150 ml of contrast material. The series included 25 patients with histologically proven hypervascular hepatic metastases (carcinoid, islet cell carcinoma, and leiomyosarcoma) and 25 patients with clinically proven hepatic hemangiomas. Patients with hemangiomas were clinically stable for at least 2 years after the CT studies. A single lesion was isolated from the first-pass, contrast-enhanced portion of each examination; the remainder of the examination was excluded from the review to minimize reviewer bias. Each lesion was evaluated for (1) the presence or absence of globular enhancement (defined as enhancing nodules less than 1 cm seen within a lesion), (2) the density of globular enhancement relative to that of the aorta, (3) the degree of border definition (well or poorly marginated), and (4) the presence or absence of a hypodense halo. A diagnostic impression was then recorded for each lesion. RESULTS: Globular enhancement was 88% sensitive and 84-100% specific for differentiating hepatic hemangiomas from hypervascular metastases (p < .001). A mean of 62% of hemangiomas showed globular enhancement isodense relative to that of the aorta; none of the metastases showed globular, isodense enhancement. The majority of the metastases showed nonglobular enhancement (mean, 92%). The reviewers showed 84% agreement in the identification of (1) globular enhancement in hemangiomas, (2) lack of globular enhancement in metastases, and (3) globular enhancement in the combined set of all lesions. Neither the presence of a hypodense halo nor the degree of border definition was significant in distinguishing between the two groups of lesions. The reviewers showed 96% agreement in the categorization of metastases and 76% agreement in the categorization of hemangiomas. There was 86% agreement in the categorization of all lesions. Overall, reviewers diagnosed a mean of 89% of lesions correctly. A mean of 98% of metastases and a mean of 80% of hemangiomas were diagnosed correctly. CONCLUSIONS: Globular enhancement is highly sensitive (88%) and specific (84-100%) for differentiating hepatic hemangiomas from hypervascular metastases on single-pass, contrast-enhanced CT scans.
Controversial issues in the management of pancreatic cancer: Part one. A debate held at St Mary's Hospital, London on 18 November 1993.
Explore the source record for details and available documents.
Gastric outlet obstruction malignant until proved otherwise.
Explore the source record for details and available documents.