Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Richard L. Clark is active.

Publication


Featured researches published by Richard L. Clark.


Cancer | 1991

Mammography and age: are we targeting the wrong women? A community survey of women and physicians.

Russell Harris; Suzanne W. Fletcher; Jorge J. Gonzalez; Donald R. Lannin; Darrah Degnan; Jo Anne Earp; Richard L. Clark

To determine mammography use among women with a broad range of ages, the authors surveyed women aged 30 to 74 years and physicians practicing primary care in two eastern North Carolina counties. Twenty‐five percent of women in their 30s had ever had a mammogram, and 34% intended to have one in the coming year. From 45% to 52% of women in their 40s, 50s, and 60s had ever had a mammogram, and 55% to 57% intended to have one in the next year. Thirty‐seven percent of women aged 70 to 74 years had ever had a mammogram, and 40% intended to have one in the following year. Nineteen percent of physicians reported screening nearly all women aged 30 to 39 years, and 14% screened few women aged 50 to 74 years. Younger women were more worried about breast cancer than older women and assessed their risk as higher, attitudes that were generally associated with higher mammography utilization. These community surveys suggest that mammography use may be excessive among younger women; older women continue to be underscreened.


Urologic Radiology | 1989

Evolving concepts in the diagnosis of xanthogranulomatous pyelonephritis

Michael D. Parker; Richard L. Clark

Xanthogranulomatous pyelonephritis (XGP) is a rare inflammatory process of the kidney that results in focal or diffuse renal enlargement and nonexcretion. In the past, XGP often has been misdiagnosed as renal carcinoma. Newer investigative modalities and an increased awareness of XGP should make preoperative diagnosis possible. Thirty-two cases of XGP are presented, with emphasis on recent advances in radiographic appraoch to diagnosis.


Investigative Radiology | 1988

Needle localization biopsy of occult lesions of the breast. Experience in 199 cases.

Bonnie C. Yankaskas; Mark H. Knelson; Mary Lisa Abernethy; John T. Cuttino; Richard L. Clark

From January 1980 through June 1986, 199 percutaneous needle localizations for clinically occult breast lesions were performed at North Carolina Memorial Hospital. A retrospective analysis of the medical records, mammograms, operative notes, and pathology reports was undertaken to evaluate the success of this procedure. In our series, biopsy was prompted by abnormal calcifications in 27.1% of lesions, occult masses in 37.2%, and by a combination of occult masses and microcalcification in 35.7%. Overall, we had a yield of positive biopsies for cancer of 16.3%, with the yield improving from 12.3% in the earlier years of our study, to 18.7% in the latter years. Of the cancer cases detected, 89.7% were stage I. The localization procedure was successful in 95.9% of the cases. Analysis of our eight failures, along with a review of the literature, shows the major reasons for failure to be incomplete removal of areas with multiple calcifications, dislodgement of the needle, and problems resulting from lack of communication between the radiologist and surgeon. We conclude that the failure rate is low, the yield good, and needle localization a worthwhile procedure for localizing nonpalpable occult lesions.


Journal of The American Society of Nephrology | 2006

Non-contrast-enhanced computerized tomography and analgesic-related kidney disease: report of the national analgesic nephropathy study.

William L. Henrich; Richard L. Clark; Judith P. Kelly; Vardaman M. Buckalew; Andrew Z. Fenves; William F. Finn; Joseph I. Shapiro; Paul L. Kimmel; Paul W. Eggers; Larry E. Agodoa; George A. Porter; Sam Shapiro; Robert D. Toto; Theresa Anderson; L. Adrienne Cupples; David W. Kaufman

Previous studies suggested that the non-contrast-enhanced computerized tomography (CT) scan is a highly reliable tool for the diagnosis of analgesic-associated renal disease. However, this issue has not been addressed in the US population. A total of 221 incident patients with ESRD from different regions of the United States underwent a helical CT scan and detailed questioning about drug history. Specific renal anatomic criteria were developed to determine whether a constellation of CT findings (small indented calcified kidneys [SICK]) is linked to analgesic ingestion. For approximating use before the onset of renal disease, only analgesic ingestion at least 9 yr before starting dialysis was considered relevant. Fifteen patients met the criteria for SICK. This represented 7% of the enrolled patients and approximately 1% of the total ESRD population. There was a significant increase in the estimated risk among patients with a history of heavy aspirin ingestion (odds ratio [OR] 7.4 [95% confidence interval (CI) 1.2 to 43] for > or =1 kg lifetime; OR 8.8 [95% CI 1.2 to 66] for > or =0.3 kg/yr). Total analgesic ingestion of > or =0.3 kg/yr also was significantly associated with SICK (OR 8.2; 95% CI 1.5 to 45). These findings were accounted for largely by combination products that contained aspirin and phenacetin (used by three patients with SICK), which are no longer available. In addition, the CT finding of SICK was present only in a minority of heavy analgesic users, yielding a sensitivity of 5 to 26%. Findings of SICK are infrequent in the US ESRD population and do not occur among a sufficient proportion of heavy analgesic users to render the non-contrast-enhanced CT scan a sensitive tool to detect analgesic-associated kidney injury.


Academic Radiology | 1995

A microcholangiographic study of liver disease models in rats

Steven N. Lichtman; Jian Wang; Richard L. Clark

RATIONALE AND OBJECTIVES Rats develop hepatobiliary injury due to small bowel bacterial overgrowth (SBBO) that, at specimen, resembles cholangiography sclerosing cholangitis. To better visualize the smaller bile ducts, we used microcholangiography to determine the spectrum of biliary lesions in this and five other models of liver disease. METHODS The models studied were as follows: (1) Surgically created jejunal, self-filling blind loops induce SBBO. (2) Intraperitoneal injection of a bacterial cell wall polymer, peptidoglycan-polysaccharide (PG-PS), causes granulomatous hepatitis. (3) Intraperitoneal injection of endotoxin (lipopolysaccharide) causes sinusoidal congestion and shock. (4) Bile duct ligation induces bile duct proliferation. (5) Alpha-naphthyl-isothiocyanate (ANIT) induces bile duct proliferation. (6) Carbon tetrachloride (CCl4) causes fibrosis and cirrhosis. Warmed barium sulfate, gelatin, and saline were injected in the extrahepatic bile duct. Liver slices (2 mm) underwent microradiographic techniques, and images were correlated with histology. RESULTS Rats with SBBO had irregular and dilated extrahepatic bile ducts with thickened walls. Rats treated with endotoxin and CCl4 had normal microcholangiograms. Bile duct proliferation was identified following ANIT and bile duct ligation. Rats given PG-PS demonstrated irregular intrahepatic bile ducts. Microcholangiograms following SBBO and PG-PS showed similarities including focal ductal dilatation, narrowing, proliferation, and destruction. CONCLUSION Various models of liver injury induce characteristic cholangiographic appearances. Microcholangiography is useful in examining biliary tract lesions and complements histology.


Investigative Radiology | 1981

Experimental renal papillary necrosis in rats: microangiographic and tubular micropuncture injection studies.

John T. Cuttino; Fred U. Goss; Richard L. Clark; Melissa C. Marr

Proposed causes of renal papillary necrosis (RPN) include tubular toxicity due to hyperconcentration of toxins in the renal medulla and vasoconstriction of medullary vessels with ischemic necrosis. The authors studied these mechanisms in bromoethylamine hydrobromide-induced RPN in rats by microvascular and tubular micropuncture injection studies. During early stages of RPN, microvascular studies revealed reduced perfusion of vasa recta, and tubular injection studies showed unobstructed tubules and collecting ducts. In the late stage, medullary vascular obliteration and intratubular debris with tubular obstruction were seen. This evidence suggests that RPN in this model is initiated by vasoconstriction rather than direct tubular toxicity.


Obstetrics & Gynecology | 2003

Oil-soluble contrast during hysterosalpingography in women with proven tubal patency

Anne Z. Steiner; William R. Meyer; Richard L. Clark; Katherine E Hartmann

OBJECTIVE: To determine if there are therapeutic advantages to oil‐soluble contrast medium compared with watersoluble medium during hysterosalpingography. METHODS: A randomized, controlled trial including 56 infertile patients undergoing hysterosalpingography was performed. After a hysterosalpingogram with water‐soluble contrast demonstrated tubal patency, 30 patients were randomized to receive oil‐soluble contrast medium (oil group) and 26 patients received no additional contrast medium (control group). The outcome was pregnancy and timing of pregnancy in relation to hysterosalpingography. RESULTS: There were 18 (64%) pregnancies in the oil group and 14 (56%) pregnancies in the control group. Mean time to achieve pregnancy was shorter in the oil group: 3.8 months in the oil group compared with 6.1 months in the control group (P = .06) There was a clinically meaningful improvement in pregnancy rates between the oil group and the control group at 1 month postprocedure (relative risk [RR] 2.1, 95% confidence interval [CI] 0.6, 7.2). However, at 12 months postprocedure, the advantage was diminished. (RR 1.3, CI 0.8, 2.1) CONCLUSION: Eighteen months after hysterosalpingography, contrast does not appear to influence cumulative pregnancy rates; however, the addition of oil‐soluble contrast medium to water‐soluble contrast medium may have the potential to reduce the time to conception. (Obstet Gynecol 2003;101:109‐13.


Investigative Radiology | 1985

The Effects of Diltiazem and Captopril on Glycerol-Induced Acute Renal Failure in the Rat: Functional, Pathologic, and Microangiographic Studies

Stanley M. Lee; Bruce J. Hillman; Richard L. Clark; Ulrich F. Michael

To evaluate the effects of pharmacologic vasodilatation on glycerol-induced acute renal failure, we studied untreated animals and those given Captopril and Diltiazem at periods ranging from 30 minutes to four weeks after the onset of acute renal failure. At each time frame, comparative coded assessments of renal function, histology, and microangiography were performed. Diltiazem, a calcium channel blocker, significantly reduced the severity of the renal failure, decreased the extent of tubular cell necrosis, and was associated with a more rapid histologic and functional recovery. Captopril, an angiotensin converting enzyme inhibitor, did not influence renal function or pathology throughout the four-week observation period. Microangiography revealed marked differences among the experimental groups. Most notably, there was better visualization of the microvasculature in Diltiazem-treated kidneys at one and two weeks. However, at four weeks, all groups showed similar, severe microangiographic abnormalities. Diltiazem offers significant protection against glycerol-induced acute renal failure in rats. Its mechanism of action in this context remains unknown. Renal function and pathology do not correlate well with microangiographic perfusion patterns in this model of acute renal failure.


Urologic Radiology | 1989

Microradiographic demonstration of human intrarenal microlymphatic pathways

John T. Cuttino; Richard L. Clark; J. Charles Jennette

Renal lymphatics play a prominent role in physiological and pathologic states. However, intrarenal microlymphatic morphology has not been well established in humans.We have developed microangiographic techniques for studying microlymphatic morphology. Lymphatics were identified by location, presence of valves, and histologic characteristics in 4 patients (3 presented here and 1 reported previously), all of whom had congestive cardiac states.The renal lymphatics begin in the cortical interstitium near glomeruli and run adjacent to afferent arterioles and interlobular arteries. They drain into arcuate and interlobar vessels and then into hilar lymphatics. They also originate in and drain the medullary structures in the area of the vasa recta.Our study details the microlymphatic morphology in humans and confirms the similarity of human lymphatics to those studied extensively in pigs and dogs.


Radiology | 1977

Microradiographic studies of renal lymphatics.

Richard L. Clark; John T. Cuttino

Cortical and medullary lymphatics have been observed during micro-angiographic studies of canine renal allograft rejection and retrograde ureteral injection in normal pigs. Lymphatic filling results from microvascular damage in the canine model and forniceal rupture in the pig. Renal lymphatics function as an alternate route for drainage during altered physiological states.

Collaboration


Dive into the Richard L. Clark's collaboration.

Top Co-Authors

Avatar

John T. Cuttino

University of North Carolina at Chapel Hill

View shared research outputs
Top Co-Authors

Avatar

Bonnie C. Yankaskas

University of North Carolina at Chapel Hill

View shared research outputs
Top Co-Authors

Avatar

John H. Schwab

University of North Carolina at Chapel Hill

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Darrah Degnan

University of North Carolina at Chapel Hill

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Etta D. Pisano

Medical University of South Carolina

View shared research outputs
Top Co-Authors

Avatar

Jo Anne Earp

University of North Carolina at Chapel Hill

View shared research outputs
Top Co-Authors

Avatar

Jorge J. Gonzalez

University of North Carolina at Chapel Hill

View shared research outputs
Top Co-Authors

Avatar

Lester Kwock

University of North Carolina at Chapel Hill

View shared research outputs
Researchain Logo
Decentralizing Knowledge