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Biomedical subjects

R B Dyer

Publications and source records attributed to R B Dyer.

At least 73 records · Page 4Linked to original sources
PubMed1992

Transurethral laser prostatectomy in the canine model.

A technique for performing transurethral prostatectomy was devised using a Neodymium:Yttrium Aluminum Garnet laser in a canine model. Six dogs underwent transurethral laser prostatectomy following establishment of a perineal urethrostomy. The efficacy of the prostatectomies was judged by retrograde urethrography, transrectal prostate ultrasonography, cystoscopy, and histologic examination. The method of applying laser energy while holding the tip of the fiberoptic light guide 2-3 mm away from the prostate was ineffective; with power ranging from 40 to 70 watts, this technique resulted mainly in coagulation necrosis and removal of only a small amount of tissue. However, placing the tip of the light guide in direct contact with the prostate and using power from 70 to 100 watts produced impressively large prostatectomy defects by tissue vaporization. We conclude that this newly devised technique for transurethral prostatectomy in the canine model can be performed safely and effectively using a Neodymium:Yttrium Aluminum Garnet laser (Neodymium:YAG).

Aluminum Silicates↗
PubMed1992

Intraluminal renal metastasis from colon cancer simulating a fungus ball.

Reports of renal metastasis from colon cancer are unusual, and none have described intraluminal renal metastasis. We describe a patient with a radiolucent filling defect in the renal pelvis that was discovered by percutaneous nephrostomy during prophylactic nephrostomy tube change. Imaging and laboratory results indicated a fungus ball, but pathologic diagnosis of the percutaneously extracted mass was metastatic colonic adenocarcinoma.

Adenocarcinoma↗
PubMed1991

Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase.

Time-resolved electronic absorption, infrared, resonance Raman, and magnetic circular dichroism spectroscopies are applied to characterization of the intermediate that is formed within 20 ps after photodissociation of CO from cytochrome a3 in reduced cytochrome oxidase. This intermediate decays with the same half-life (approximately 1 microseconds) as the post-photodissociation CU+B-CO species previously observed by time-resolved infrared. The transient UV/visible spectra, kinetics, infrared, and Raman evidence suggest that an endogenous ligand is transferred from CuB to Fea3 when CO binds to CuB, forming a cytochrome a3 species with axial ligation that differs from the reduced unliganded enzyme. The time-resolved magnetic circular dichroism results suggest that this transient is high-spin and, therefore, five-coordinate. Thus we infer that the ligand from CuB binds on the distal side of cytochrome a3 and displaces the proximal histidine imidazole. This remarkable mechanistic feature is an additional aspect of the previously proposed "ligand-shuttle" activity of the CuB/Fea3 pair. We speculate as to the identity of the ligand that is transferred between CuB and Fea3 and suggest that the ligand shuttle may play a functional role in redox-linked proton translocation by the enzyme.

Binding Sites↗
PubMed1991

Spontaneous perinephric hemorrhage: imaging and management.

We report on 10 patients with spontaneous perinephric hemorrhage associated with underlying disease, including renal cell carcinoma (5), angiomyolipoma (2), malignant melanoma (1), periarteritis nodosa (1) and severe portal hypertension (1). The etiology could not be identified with computerized tomography (CT) in 5 cases (50%), including 2 renal cell carcinomas, 1 angiomyolipoma, 1 periarteritis nodosa and 1 portal hypertension. Arteriography demonstrated underlying lesions in 4 of these 5 cases (80%) including the case of vasculitis. CT combined with magnetic resonance imaging is accurate for the diagnosis of spontaneous perinephric hemorrhage but the underlying pathological condition is often undetectable in the acute phase due to the perinephric blood. CT should be the first study performed if this diagnosis is suspected. Arteriography is recommended if a renal mass is not detected. If a mass is not identified with these 2 imaging studies and the patient is clinically stable, followup thin slice CT should be performed.

Adult↗
PubMed1991

A comparison of anatrophic nephrolithotomy and percutaneous nephrolithotomy with and without extracorporeal shock wave lithotripsy for management of patients with staghorn calculi.

A retrospective study was conducted comparing anatrophic nephrolithotomy (10 cases), percutaneous nephrolithotomy alone (4 cases) or percutaneous nephrolithotomy combined with extracorporeal shock wave lithotripsy (23 cases) for the treatment of large staghorn calculi. A comparison based on collecting system anatomy demonstrated that anatrophic nephrolithotomy resulted in a greater stone-free rate, shorter hospitalization and lower costs while complication rates were similar. Anatrophic nephrolithotomy should still be considered a viable treatment option, especially for patients with large branched calculi in complex collecting systems.

Adult↗
PubMed1991

Percutaneous management of localized emphysematous pyelonephritis.

The authors report a case of emphysematous pyelonephritis that was successfully treated with radiologically guided percutaneous drainage. This case illustrates that in certain patients with focal abnormalities, functioning renal tissue can be salvaged and emphysematous pyelonephritis can be eradicated with a combination of antibiotics and radiologically guided percutaneous drainage.

Aged↗
PubMed1990

CT features of renal cell carcinoma with emphasis on relation to tumor size.

Computed tomography (CT) is the current standard for diagnosing and staging renal cell carcinoma (RCC). Although general diagnostic guidelines exist, no large studies to date have delineated the CT features of RCC. We reviewed the CT appearances of 78 pathologically proven RCCs. Of the 61 RCCs larger than 50 mm (78%) there was imaging evidence of extrarenal spread (87%), intratumoral necrosis (61%) and differential growth rates within the tumor (64%). Tumors 50 mm or smaller often had a "benign" appearance with sharp, rounded margins (88%), homogeneous density (65%), and distinct interface with the kidney (82%). The significance of these lesions should not be underestimated. Although RCCs often showed transient marked enhancement after bolus contrast material injection (41%), during the infusion phase 97% were hypodense compared with the kidney regardless of tumor size. Calcifications were visible in 31% of RCCs. Although 22% of RCCs were predominantly cystic, none fulfilled all CT criteria of simple renal cysts.

Adult↗
PubMed1990

Vicarious contrast material excretion in patients with acute unilateral ureteral obstruction.

Radiographs of 45 patients with evidence of acute unilateral ureteral obstruction at intravenous urography, obtained at least 24 hours after injection of contrast material, were retrospectively studied. Vicarious contrast material excretion (VCME) as evidence by gallbladder opacification on delayed radiographs was seen in 19 patients (42%), 10 of whom also showed extravasation of contrast material. A total of 15 of the 45 patients developed spontaneous extravasation; 10 (67%) showed VCME, while only nine of the 30 patients (30%) who did not have spontaneous extravasation of contrast material showed VCME. The creatinine level was elevated (greater than 1.5 mg/dL [133 mumol/L]) in four patients with VCME and in six patients without. This series indicates that VCME is more common than previously appreciated in patients with acute unilateral ureteral obstruction and occurs with greater frequency when obstruction is associated with contrast material extravasation.

Diatrizoate Meglumine↗
PubMed1990

Radiology in the diagnosis and staging of renal cell carcinoma.

Renal cell carcinoma (RCC), a potentially curable lesion, is the most common primary renal malignancy. Due to the importance of early diagnosis and the lack of specific clinical features of RCC, imaging plays a vital role in the diagnosis and management of RCC. Newer imaging modalities have superseded plain-film radiography in the diagnosis of RCC by offering greater sensitivity and specificity in both diagnosis and staging. RCC can be diagnosed with computed tomography (CT) with greater than 95% accuracy. Once an RCC is detected, tumor staging becomes paramount for treatment planning. Greater than 90% staging accuracy can be accomplished with CT alone using techniques described in this article. Magnetic resonance imaging (MRI) can be used to achieve staging accuracy similar to CT. MRI and ultrasonography (US) should be used to aid the diagnosis and staging of RCC in equivocal CT cases. The appropriate use of additional staging adjuncts including arteriography, phlebography, skeletal and thoracic imaging is described in this article.

Carcinoma, Renal Cell↗
PubMed1989

Percutaneous dislodgement of an impacted cystic duct stone.

An obstructing cystic duct stone was dislodged with an angiographic catheter and guidewire via a percutaneous cholecystostomy tract in a mildly sedated patient. After brief stenting of the cystic duct, the patient remained asymptomatic with internal bile drainage. When endoscopic negotiation of the cystic duct is difficult, an impacted cystic duct stone can sometimes be dislodged with standard angiographic techniques.

Aged↗
PubMed1989

Angiomyolipoma arising in the renal sinus: a difficult radiologic diagnosis.

We report a case of angiomyolipoma (AML) occurring in the renal sinus evaluated by intravenous urography (IVU), renal ultrasound (US), angiography, and computed tomography (CT). Imaging features of this lesion are identical to AMLs elsewhere, but preoperative diagnosis was complicated by the unusual occurrence of the tumor in this location in a patient with abdominal pain. Accurate preoperative diagnosis will allow tumorectomy or conservative management.

Female↗
PubMed1989

False-positive radionuclide hepatobiliary imaging following cystic duct stone removal.

The authors report a case in which a radionuclide hepatobiliary image was falsely indicative of cystic duct obstruction in a patient with an indwelling cholecystostomy tube and an externalized gallbladder-duodenal stent. Cystic duct patency was demonstrated radiographically shortly before and after the radionuclide study. The authors recommend that cystic duct obstruction indicated by a radionuclide hepatobiliary image be confirmed by another means if a cholecystostomy tube is present, or if the patient recently has undergone percutaneous gallbladder or cystic duct manipulations.

Aged↗
PubMed1988

A comparison of the resonance Raman properties of the fast and slow forms of cytochrome oxidase.

Resonance Raman (RR) spectra of the "rapid" and "slow" forms (Baker et al., 1987) of resting cytochrome oxidase obtained with Soret excitation at 413.1 nm are reported. There are a number of conspicuous differences between the two forms in the high-frequency region of the RR spectrum which involve changes in Raman intensity arising from a blue shift in the Soret maximum of cytochrome a3 upon conversion to the slow form. In the low-frequency region a peak present at 223 cm-1 in the rapid form shifts to 220 cm-1 in the slow form; this peak is assigned as the cytochrome a3 Fe(III)-N(His-Im) stretch. The slow form of the enzyme possesses greater intensity in RR peaks near 1620 cm-1 which have been previously attributed by others to partial photoreduction of the enzyme. We have quantitated the amount of laser-induced photoreduction in these RR spectra by comparison with the spectra of mixed-valence derivatives of the enzyme and find that these 1620-cm-1 features are unreliable indicators of photoreduction. The spectra of the fast- and slow-reacting species in H2O and D2O have been compared. The fast-reacting form exhibits a 4-cm-1 shift, from 223 to 219 cm-1, upon transferring to D2O in a peak which we assign as the cytochrome a3 Fe(III)-N(His-Im) stretch. There is a parallel shift in the feature at 1651 cm-1 due to the C = O stretch of the formyl group of cytochrome a. These deuterium shifts are not observed in the slow form.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗