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Biomedical subjects

R N Gibson

Publications and source records attributed to R N Gibson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Evaluation of ultrasonographic diagnostic criteria for autosomal dominant polycystic kidney disease 1.

Although ultrasound is commonly used for screening subjects at risk of polycystic kidney disease 1 (PKD1), there has been no evaluation of ultrasonographic diagnostic criteria. We used DNA linkage among subjects from 128 sibships within 18 PKD1 families as the basis for an assessment of ultrasound sensitivity. Positive and negative predictive values were calculated to allow assessment of different diagnostic cut-off points in previously undiagnosed cases. Currently used criteria (bilateral cysts with at least two in one kidney) provided good sensitivity (88.5% at age 15-29 years and 100% at 30 years and above) but performance could be improved by less stringent criteria in subjects aged 15-29 years and more stringent criteria in older family members, in whom simple renal cysts are frequent. The presence of at least two renal cysts (unilateral or bilateral) in individuals at risk and younger than 30 years may be regarded as sufficient to establish a diagnosis; among those aged 30-59 years, the presence of at least two cysts in each kidney may be required, and among those aged 60 years and above, at least four cysts in each kidney should be required.

Adolescent↗
PubMed1993

Modified Doppler flowmetry in the splanchnic circulation.

BACKGROUND: Absolute measurements of blood flow by Doppler ultrasonography are subject to substantial error. A simplified method of Doppler flowmetry using conventional duplex Doppler equipment was studied to establish its validity in determining short-term changes in flow in the splanchnic circulation in portal hypertension. METHODS: Two simple indices were measured: peak velocity averaged over two cardiac cycles and vessel diameter. The relationship between peak and mean velocity was studied using a Doppler phantom. The feasibility of studying relevant vessels and the constancy of regional flow was determined by performing Doppler flowmetry in a basal state twice within 2 hours. RESULTS: Constancy of relationship between peak and mean velocities was confirmed (r > 0.98). Examination was successful in the majority of 28 consecutive patients with portal hypertension for superior mesenteric, main portal, right portal, and paraumbilical (when patent) veins, but was successful in only 54% for the hepatic artery. Constancy of basal flow was found in 11 selected patients when group data were considered, but in individuals, substantial and unpredictable variance was found. CONCLUSIONS: Modified Doppler flowmetry appears valid in the assessment of short-term changes in splanchnic blood flow of patients with portal hypertension. Individual variance in baseline flow is identified as a potential problem and is further reason for caution in the interpretation of measurements of Doppler flow.

Hepatic Artery↗
PubMed1993

An ultrasound renal cyst prevalence survey: specificity data for inherited renal cystic diseases.

This study documents the prevalence of simple renal cysts at various ages to produce a table of age-specific specificity values. The specificity of diagnosis for inherited renal cystic conditions depends primarily on the prevalence of simple renal cysts in disease-free subjects. To provide specificity data useful for the ultrasound assessment of individuals at genetic risk of having a renal cyst-forming condition, a prospective ultrasound study was performed. The urinary tract was examined in detail in 729 individuals referred for investigation of symptoms unrelated to the urinary tract and who had normal renal function. The prevalence of individuals with at least one renal cyst was 0% in those aged 15 to 29 years, 1.7% in those aged 30 to 49 years, 11.5% in those aged 50 to 70 years, and 22.1% in those aged 70 years and above. The prevalence of bilateral renal cysts (at least one cyst in each kidney) was 1% in those aged 30 to 49 years, 4% in those aged 50 to 70 years, and 9% in those aged 70 years and above. A table is provided that allows specificity estimates for differing diagnostic criteria together with 95% confidence limits for each estimate. In the younger age groups, bilateral renal cysts, particularly bilateral cysts with one or both kidneys having more than one cyst, are relatively uncommon. A reduced threshold for suspecting inherited renal cystic disease in younger individuals at high genetic risk will continue to have high specificity while improving the sensitivity of ultrasound diagnosis.

Adolescent↗
PubMed1993

Percutaneous transhepatic measurement of the pressure gradient between the portal and hepatic veins.

BACKGROUND: Knowledge of the portal pressure may be of value in the assessment of patients with chronic liver disease but its measurement is problematic. AIMS: To evaluate the ease and safety of percutaneous transhepatic measurement of the pressure gradient between the portal and hepatic veins and to determine directly the need for an internal zero. METHODS: Sixty-one patients undergoing liver biopsy for suspected liver disease had pressures in branches of portal and hepatic veins measured using a flexible 22G (Chiba) needle. RESULTS: The procedure was successful in all patients, took less than ten minutes in most, and was associated with minimal discomfort. Post-procedure morbidity was similar to that of liver biopsy. Portal pressure using an external zero (either puncture site or sternal angle) was inaccurate compared with pressures obtained using the generally accepted gold standard internal zero, hepatic venous pressure, and led to incorrect classification of the presence or absence of portal hypertension in at least 10% of patients. Variations in hepatic venous pressure were not predictable on clinical grounds. The only histopathological feature predictive of portal hypertension was cirrhosis, 20 of 25 patients with and four of 36 patients without cirrhosis having portal hypertension. Of routine biochemical and haematological tests, only plasma albumin and platelet count jointly (and negatively) predicted hepatic venous pressure gradient on multiple regression analysis (R2 = 0.40). CONCLUSIONS: The use of an internal zero is essential for accurate measurement of portal pressure and this can be achieved safely using the percutaneous, transhepatic route in patients with well compensated liver disease.

Adolescent↗
PubMed1993

A comparative study of radionuclide venography and contrast venography in the diagnosis of deep venous thrombosis.

BACKGROUND: The value of the radionuclide blood pool venogram in detecting deep venous thrombosis (DVT) has to date been inadequately evaluated. This is despite its lower complication rate than the gold standard of contrast X-ray venography. AIMS: To compare the relative accuracy and inter observer variability of radionuclide blood pool and X-ray contrast venography as well as evaluate previous literature on radionuclide venography. METHODS: Prospective comparison of radionuclide and contrast venography was performed in 39 patients. Sensitivity and specificity of radionuclide venography were compared to contrast venography and confidence intervals were measured using standard error calculations. A meta-analysis of previous studies was also performed. RESULTS: Significant inter observer variation in reports was present in both radionuclide (37%) and contrast (22%) venograms. Using consensus reports sensitivity of radionuclide venography was 87% compared to contrast venography and specificity was 83%. These results are similar to those obtained in previous studies. Furthermore, sensitivity in specificity in the proximal veins were 90% and 92% respectively which were superior to sensitivity and specificity in the distal veins where it was 74% and 90% respectively. CONCLUSION: The radionuclide venogram appears accurate in the proximal veins and in excluding but not diagnosing distal venous thrombosis.

Adult↗
PubMed1993

Intrathecal sufentanil for labor analgesia--sensory changes, side effects, and fetal heart rate changes.

This study was designed to evaluate intrathecal (IT) sufentanil for labor analgesia with respect to sensory changes, side effects, and fetal heart rate (FHR) changes. In Phase I of the study, data regarding duration of analgesia and hemodynamic changes were obtained retrospectively from the labor and anesthetic records of 90 patients who had received IT sufentanil, 10 micrograms in 1 mL of saline, during active labor. In Phase II, an additional 18 parturients who received similar treatment were studied prospectively to document sensory, motor, and hemodynamic changes, as well as the incidence of side effects. In Phase I, analgesia occurred rapidly and lasted 124 +/- 68 min (SD); 19% of patients required no further analgesia before delivery. In Phase II, median time to onset of analgesia was 3 min (range 1-6 min) and mean duration of analgesia was 96 +/- 36 min. Decreased sensation to pinprick and cold occurred within 6 min extending from T4 to L4 (upper and lower median levels) in the majority of patients. All subjects requested additional analgesia within approximately 30 min of recession of sensory changes. Motor strength remained normal throughout. Hypotension (systolic blood pressure [BP] < or = 90 mm Hg or > 20% decrease in systolic BP) occurred in 14% and 11% of patients in Phase I and II, respectively. Perineal itching preceded analgesia in 95% of patients and all subjects experienced mild sedation. FHR changes occurred in 15% of cases but were not associated with adverse neonatal outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Phenotype and genotype heterogeneity in autosomal dominant polycystic kidney disease.

It is now clear that mutations of at least two genetic loci can lead to autosomal dominant polycystic kidney disease (ADPKD). We have compared the clinical features of ADPKD caused by mutations at the PKD1 locus (linked to the alpha-globin complex on chromosome 16) with those of disease not linked to the locus (non-PKD1). We identified 18 families (285 affected members) with mutations at PKD1 and 5 families (49 affected individuals) in which involvement of this locus could be dismissed. Non-PKD1 patients lived longer than PKD1 patients (median survival 71.5 vs 56.0 years), had a lower risk of progressing to renal failure (odds ratio 0.35, 95% CI 0.13-0.92), were less likely to have hypertension (odds ratio adjusted for age and family of origin 0.29, 0.11-0.80), were diagnosed at an older age (median 69.1 vs 44.8 years), and had fewer renal cysts at the time of diagnosis. Although most of the PKD1 families were ascertained through clinics treating patients with renal impairment, no non-PKD1 family was identified through this source. Non-PKD1 ADPKD has a much milder phenotype than that linked to PKD1. Partly as a result of this difference in severity, the reported prevalence of this genotype is probably an underestimate.

Adolescent↗
PubMed1992

Duplex Doppler ultrasound signs of portal hypertension: relative diagnostic value of examination of paraumbilical vein, portal vein and spleen.

The sonographic parameters in portal hypertension (PHT) were examined in a consecutive population of 118 patients who had PHT diagnosed using specific endoscopic, sonographic and Doppler signs. A patent or enlarged paraumbilical vein was found in 85.6% of patients overall and 82.5% of patients with varices indicating a relatively high sensitivity. A portal vein diameter greater than or equal to 13mm was found in only 41.1% and greater than or equal to 15mm in only 20% of patients. A thrombosed portal vein and reversed portal vein flow were present in 3.4% and 5.3% of patients respectively. These signs have only been reported in the context of PHT and are felt to be specific for PHT, but both have a very low sensitivity. Portal vein velocities were highly variable suggesting that this is not a useful predictor of PHT. Splenomegaly was found in only 53.5% of patients demonstrating its poor sensitivity as a sign of PHT. Varices were found in 73.3% of patients overall, and in 100% of patients with a patent or enlarged paraumbilical vein combined with ascites. No other statistically significant correlation between varices and sonographic findings was demonstrated. We conclude that the presence of a patent or enlarged paraumbilical vein is a practical, useful and sensitive ultrasound sign to look for in the diagnosis of PHT.

Esophageal and Gastric Varices↗
PubMed1992

Liver CT: a practical approach to dynamic contrast enhancement.

The aim of this study was to establish a practical, simple protocol that reliably produces high quality dynamic incremental computed tomography (CT) of the liver. We reviewed 90 patients randomly allocated into six different protocols. All had preliminary unenhanced scans followed by a dynamic incremental CT of the liver. An initial delay of 30 seconds was used from the commencement of the injection of Iopamiro 370. The groups were: 1. Pump infusion (a) 100 mls at 2 mls/sec scanning inferosuperiorly. (b) 100 mls at 2 mls/sec scanning superoinferiorly. (c) 100 mls at 1 ml/sec scanning inferosuperiorly. (d) 50 mls at 1 ml/sec scanning inferosuperiorly. 2. 40 mls hand injected bolus followed immediately by 60 ml pump infusion at 1.3 mls/sec scanning inferosuperiorly. 3. 50 mls hand injected bolus scanning inferosuperiorly. The parameters recorded were the degree of hepatic parenchymal and hepatic venous enhancement and the aortic--IVC difference at the last slice through the liver, all measured in Hounsfield units. The protocols using 100 mls of contrast produced approximately twice the parenchymal and hepatic venous enhancement compared with those using 50 mls. Approximately 60-90% of examinations using 100 mls produced scans through the entire liver during the bolus or nonequilibrium phase, deemed the most sensitive for the detection of focal lesions, compared with 13-33% of those using 50 mls. Equally satisfactory results were obtained using the relatively inexpensive Biotel power injector preceded by a 40 ml hand injected bolus, compared with using an Angiomat angiography infusion pump.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortography↗
PubMed1992

A comparison of duplex Doppler sonography of the ligamentum teres and portal vein with endoscopic demonstration of gastroesophageal varices in patients with chronic liver disease or portal hypertension, or both.

The ability of duplex Doppler sonography of the ligamentum teres and portal vein to detect specific signs of portal hypertension was compared with the ability of endoscopy to demonstrate gastroesophageal varices in consecutive patients. Among 90 patients with parenchymal liver disease and a high probability of portal hypertension, 70 had varices, 72 had specific sonographic signs, and four had neither. Ultrasonography was comparable to endoscopy irrespective of the clinical severity of the underlying liver disease. Eleven patients had vascular occlusive diseases; nine had varices; and all had at least one sonographic sign. Duplex Doppler ultrasonography may have a clinical role in noninvasive detection of portal hypertension. Further studies correlating the findings with those of portal pressure are needed to define the place of duplex Doppler ultrasonography as a predictor of the presence of portal hypertension.

Adult↗
PubMed1991

Treatable complications in undiagnosed cases of autosomal dominant polycystic kidney disease.

In a study to determine the proportion of unrecognised cases and the prevalence of treatable complications of autosomal dominant polycystic kidney disease (ADPKD), 46 probands were identified through genetics and renal clinics in Melbourne, Australia. 321 offspring of the probands who were older than 15 years and had not been previously diagnosed as having ADPKD were identified. 68 (21%) had ultrasound evidence of polycystic kidney disease. Of this previously undiagnosed group, 25 (37%) had one or more treatable complications at the time of diagnosis. The complications included 20 cases of hypertension (diastolic blood pressure 95 mm Hg or above), 7 cases of impaired renal function (serum creatinine 0.12 mmol/l or above), and 4 cases of bacterial urinary tract infection. 8 people had several complications. ADPKD has an important treatable component which is not being treated in a substantial proportion of affected individuals, because the disease is not being diagnosed despite the presence of a positive family history.

Adolescent↗
PubMed1990

Splenomegaly--an insensitive sign of portal hypertension.

The prevalence of splenomegaly associated with portal hypertension was examined in a consecutive population of 111 patients who had portal hypertension diagnosed using specific endoscopic, sonographic, and Doppler signs. Splenic size was measured objectively via its cranio-caudal length on coronal section using ultrasound and by clinical examination. Sonographically, 52% of patients had a definitely large spleen and 35% a spleen less than one standard deviation from the normal mean, while a further 13% had equivocal splenomegaly. Only 52% of patients had splenomegaly on clinical assessment. Splenomegaly was less common in patients with alcoholic (41% definite, 15% equivocal) than in those with non-alcoholic liver disease (66% definite, 17% equivocal, p = 0.02) and splenic length was significantly smaller in alcoholic patients (12.7 +/- 0.5 cm) compared to patients with either non-alcoholic liver disease (15.0 +/- 0.6 cm, p = 0.003) or portal hypertension due to vascular occlusive diseases (16.5 +/- 2.0 cm, p = 0.006). Splenomegaly, whether assessed sonographically or clinically, is an insensitive sign of portal hypertension and its absence cannot be used as a negative predictor of the presence of portal hypertension in patients with chronic liver disease.

Adult↗
PubMed1989

Ovine fetal cardiorespiratory response to nicardipine.

Nicardipine, a calcium antagonist associated with decreased uterine blood flow in near-term pregnant rabbits and fetal asphyxia after maternal administration in the rhesus monkey and sheep, was infused directly to the fetus in six chronically prepared pregnant ewes at 128 days' gestation. Changes in fetal mean arterial and diastolic blood pressure levels at 2 and 30 minutes after bolus injection of 50 micrograms were minimal; by 60 minutes these values had returned to preinfusion levels. No significant changes were observed after infusion of 100 micrograms of nicardipine. Fetal heart rate, fetal arterial blood gas values, and maternal cardiovascular variables did not change at either dose. Fetal plasma concentrations of nicardipine were 78 +/- 28 ng/ml and 114 +/- 48 ng/ml at 30 minutes after infusion of 50 micrograms and 100 micrograms, respectively, well within the range previously reported to be associated with fetal asphyxia. These data suggest that the previously reported fetal acidosis from maternal infusion of nicardipine may be primarily due to a decrease in maternal uterine blood flow rather than a direct fetal effect of the drug.

Animals↗
PubMed1989

Biliary obstruction due to intraductal tumor.

Five unusual cases of bile-duct obstruction are presented. There were three cases of intrabiliary hepatoma, one of intrabiliary colon cancer metastasis, and one cystadenoma of the bile-duct. The importance of an accurate diagnosis is emphasized, as these tumours can be treated by surgery or by biliary stenting, sometimes with prolonged survival.

Aged↗
PubMed1989

Identification of a patent paraumbilical vein by using Doppler sonography: importance in the diagnosis of portal hypertension.

The aim of this study was to determine if the addition of pulsed Doppler imaging to conventional sonography allows discrimination between true paraumbilical veins of portal hypertension and the apparent vein sometimes seen in the ligamentum teres in normal subjects. Conventional sonography and Doppler sonography of the ligamentum teres were performed in 33 normal subjects and in 39 patients with portal hypertension due to chronic liver disease. An apparent ligamentum teres vessel (i.e., hypoechoic channel) was identified on sonograms in 32 (97%) normal subjects (diameter 0.6-1.9 mm) and in 35 (90%) patients with portal hypertension (diameter 1.1-22 mm). In the portal hypertension group, the apparent vessel had a diameter of greater than 3 mm in only 20 patients (51%), but in 32 patients (82%) it was shown on Doppler examination to be a patent paraumbilical vein (i.e., hepatofugal venous signal). A patent paraumbilical vein on duplex Doppler sonography is therefore a specific sign of portal hypertension. The addition of Doppler imaging to conventional sonographic examination significantly increases the sensitivity for the diagnosis of portal hypertension by demonstration of a paraumbilical vein.

Adolescent↗