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Dive into the research topics where Roy S. Dwarkasing is active.

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Featured researches published by Roy S. Dwarkasing.


Radiology | 2011

Hepatocellular Adenomas: Correlation of MR Imaging Findings with Pathologic Subtype Classification

Susanna M. van Aalten; Maarten Thomeer; Türkan Terkivatan; Roy S. Dwarkasing; Joanne Verheij; Robert A. de Man; Jan N. M. IJzermans

PURPOSE To investigate the correlation between magnetic resonance (MR) imaging findings and pathologic subtype classification of hepatocellular adenoma (HCA). MATERIALS AND METHODS This retrospective study was approved by the institutional review board, and the requirement for informed consent was waived. MR imaging studies of 61 lesions (48 patients; median age, 36 years) were available and were independently reviewed by two radiologists. Consensus readings on all morphologic and signal-intensity imaging features were obtained. Previously, these lesions had been classified on the basis of pathologic findings and immunohistochemical analysis. Fisher exact and χ² tests were performed to compare the results between the different subtypes. A Bonferroni correction was applied to correct for multiple testing (α < .0033). RESULTS MR imaging signs of diffuse intratumoral fat deposition were present in seven (78%) of nine liver-fatty acid binding protein (L-FABP)-negative HCAs compared with five (17%) of 29 inflammatory HCAs (P = .001). Steatosis within the nontumoral liver was present in 11 (38%) of 29 inflammatory HCAs compared with none of the L-FABP-negative HCAs (P = .038). A characteristic atoll sign was only seen in the inflammatory group (P = .027). Presence of a typical vaguely defined type of scar was seen in five (71%) of seven β-catenin-positive HCAs (P = .003). No specific MR imaging features were identified for the unclassified cases. CONCLUSION L-FABP-negative, inflammatory, and β-catenin-positive HCAs were related to MR imaging signs of diffuse intratumoral fat deposition, an atoll sign, and a typical vaguely defined scar, respectively. Since β-catenin-positive HCAs are considered premalignant, closer follow-up with MR imaging or resection may be preferred.


Surgical Endoscopy and Other Interventional Techniques | 2007

Successful endoscopic treatment of chronic groin pain in athletes.

R. N. van Veen; P. de Baat; M. P. Heijboer; Geert Kazemier; B. J. Punt; Roy S. Dwarkasing; H. J. Bonjer; C.H.J. van Eijck

BackgroundChronic groin pain, especially in professional sportsmen, is a difficult clinical problem.MethodsFrom January 1999 to August 2005, 55 professional and semiprofessional sportsmen (53 males; mean age, 25 ± 4.5 years; range, 17–36 years) with undiagnosed chronic groin pain were followed prospectively. All the patients underwent an endoscopic total extraperitoneal (TEP) mesh placement.ResultsIncipient hernia was diagnosed in the study athletes: 15 on the right side (27%), 12 on the left side (22%), and 9 bilaterally (16%). In 20 patients (36%), an inguinal hernia was found: 3 direct inguinal hernias (5%) and 17 indirect hernias (31%). All the athletes returned to their normal sports level within 3 months after the operation.ConclusionsA TEP repair must be proposed to patients with prolonged groin pain unresponsive to conservative treatment. If no clear pathology is identified, reinforcement of the wall using a mesh offers good clinical results for athletes with idiopathic groin pain.


European Radiology | 2006

Hepatocellular adenoma : findings at state-of-the-art magnetic resonance imaging, ultrasound, computed tomography and pathologic analysis

Shahid M. Hussain; Indra C. van den Bos; Roy S. Dwarkasing; J. W. Kuiper; Jan C. den Hollander

The purpose of this paper is to describe the most recent concepts and pertinent findings of hepatocellular adenomas, including clinical presentation, gross pathology and histology, pathogenesis and transformation into hepatocellular carcinoma (HCC), and imaging findings at ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging.


Journal of Hepatology | 2011

Validation of a liver adenoma classification system in a tertiary referral centre: Implications for clinical practice

Susanna M. van Aalten; J. Verheij; Türkan Terkivatan; Roy S. Dwarkasing; Robert A. de Man; Jan N. M. IJzermans

BACKGROUND & AIMS A molecular and pathological classification system for hepatocellular adenomas (HCA) was recently introduced and four major subgroups were identified. We aimed to validate this adenoma classification system and to determine the clinical relevance of the subtypes for surgical management. METHODS Paraffin fixed liver tissue slides and resection specimens of patients radiologically diagnosed as HCA were retrieved from the department of pathology. Immunostainings included liver-fatty acid binding protein (L-FABP), serum amyloid A (SAA), C-reactive protein (CRP), glutamine synthetase (GS) and β-catenin. RESULTS From 2000 to 2010, 58 cases (71 lesions) were surgically resected. Fourteen lesions were diagnosed as focal nodular hyperplasia with a characteristic map-like staining pattern of GS. Inflammatory HCA expressing CRP and SAA was documented in 36 of 57 adenomas (63%). Three of these inflammatory adenomas were also β-catenin positive as well as GS positive and only one was CRP and SAA and GS positive. We identified eleven L-FABP-negative HCA (19%) and four β-catenin positive HCA (7%), without expression of CRP and SAA and with normal L-FABP staining, one of which was also GS positive. Six HCA were unclassifiable (11%). In three patients multiple adenomas of different subtypes were found. CONCLUSIONS Morphology and additional immunohistochemical markers can discriminate between different types of HCA in>90% of cases and this classification, including the identification of β-catenin positive adenomas may have important implications in the decision for surveillance or treatment. Interpretation of nuclear staining for β-catenin can be difficult due to uneven staining distribution or focal nuclear staining and additional molecular biology may be required.


BMC Surgery | 2011

The CARTS study: Chemoradiation therapy for rectal cancer in the distal rectum followed by organ-sparing transanal endoscopic microsurgery

G.M.J. Bökkerink; Eelco J. R. de Graaf; Cornelis J. A. Punt; Iris D. Nagtegaal; H.J.T. Rutten; Joost J. Nuyttens; Esther van Meerten; Pascal G. Doornebosch; P. J. Tanis; Eric J. Derksen; Roy S. Dwarkasing; Corrie A.M. Marijnen; Annemieke Cats; Rob A. E. M. Tollenaar; Ignace H. de Hingh; Harm Rutten; George P. van der Schelling; Albert J. ten Tije; Jeroen W. A. Leijtens; Guido Lammering; Geerard L. Beets; Theo J. Aufenacker; Apollo Pronk; Eric R. Manusama; Christiaan Hoff; A.J.A. Bremers; Cornelelis Verhoef; Johannes H. W. de Wilt

BackgroundThe CARTS study is a multicenter feasibility study, investigating the role of rectum saving surgery for distal rectal cancer.Methods/DesignPatients with a clinical T1-3 N0 M0 rectal adenocarcinoma below 10 cm from the anal verge will receive neoadjuvant chemoradiation therapy (25 fractions of 2 Gy with concurrent capecitabine). Transanal Endoscopic Microsurgery (TEM) will be performed 8 - 10 weeks after the end of the preoperative treatment depending on the clinical response.Primary objective is to determine the number of patients with a (near) complete pathological response after chemoradiation therapy and TEM. Secondary objectives are the local recurrence rate and quality of life after this combined therapeutic modality. A three-step analysis will be performed after 20, 33 and 55 patients to ensure the feasibility of this treatment protocol.DiscussionThe CARTS-study is one of the first prospective multicentre trials to investigate the role of a rectum saving treatment modality using chemoradiation therapy and local excision. The CARTS study is registered at clinicaltrials.gov (NCT01273051)


Journal of Magnetic Resonance Imaging | 2007

MR imaging of hepatocellular carcinoma: Relationship between lesion size and imaging findings, including signal intensity and dynamic enhancement patterns

Indra C. van den Bos; Shahid M. Hussain; Roy S. Dwarkasing; Wim C. J. Hop; Pieter E. Zondervan; Robert A. de Man; Jan N. M. IJzermans; Craig W. Walker; Gabriel P. Krestin

To assess the relationship between lesion size and MR imaging findings of pathologically‐proven hepatocellular carcinoma (HCC).


Radiology | 2010

Kidney and Urinary Tract Imaging: Triple-Bolus Multidetector CT Urography as a One-Stop Shop—Protocol Design, Opacification, and Image Quality Analysis

Maka Kekelidze; Roy S. Dwarkasing; Marcel L. Dijkshoorn; Karolina Sikorska; Paul C.M.S. Verhagen; Gabriel P. Krestin

PURPOSE To retrospectively evaluate renal, vascular, and urinary tract visualization following a single postcontrast multidetector computed tomographic (CT) urographic sequence performed with three limited-volume bolus injections. MATERIALS AND METHODS The institutional review board approved this retrospective study. Patient informed consent was waived. Triple-bolus multidetector CT urography was performed in 110 patients. Triple-bolus protocol consisted of 30 mL of contrast material at 2 mL/sec at 0 seconds, 50 mL at 1.5 mL/sec at 435 seconds, 65 mL at 3 mL/sec at 488 seconds, with total abdominal scanning time of 510 seconds. Two independent readers rated urinary tract opacification and qualitatively and quantitatively assessed renal parenchymal and vascular contrast enhancement. Upper urinary tract (UUT) distention was measured by one reader. Interobserver agreement was assessed by using kappa statistics. RESULTS Complete opacification of the intrarenal collecting system and proximal ureter was achieved in 91% (184 of 202) (kappa = 0.62) and 82% (166 of 202) (kappa = 0.94) of segments, respectively. The distal ureter was not opacified in 21% of the cases (kappa = 0.92), and the bladder was not opacified in 20% of the cases. Mean distention was higher for proximal (3.9 mm) than for distal (3.7 mm) segments. Image quality of renal parenchymal enhancement was excellent in 76% of cases. Arteries showed better contrast enhancement than veins (excellent rating in 89% vs 59% of the cases). Radiation dose calculated for triple-bolus acquisition was 9.8 mSv. CONCLUSION Triple-bolus multidetector CT urography is a dose-efficient protocol acquiring corticomedullary-nephrographic-excretory and vascular enhancement phases in a single acquisition and provides sufficient opacification and distention of the UUT. Simultaneously, adequate image quality of renal parenchyma and vascular anatomy is achieved.


Radiology | 2011

Evaluation of a standardized CT colonography training program for novice readers.

Marjolein H. Liedenbaum; Shandra Bipat; Patrick M. Bossuyt; Roy S. Dwarkasing; Margriet C. de Haan; Roel J. Jansen; Dominique Kauffman; Christiaan van der Leij; Manou S. de Lijster; Cindy C. Lute; Marije P. van der Paardt; Maarten Thomeer; IJsbrand A. Zijlstra; Jaap Stoker

PURPOSE To determine how many computed tomographic (CT) colonography training studies have to be evaluated by novice readers to obtain an adequate level of competence in polyp detection. MATERIALS AND METHODS The study was approved by the Institutional Review Board. Informed consent was obtained from all participants. Six physicians (one radiologist, three radiology residents, two researchers) and three technicians completed a CT colonography training program. Two hundred CT colonographic examinations with colonoscopic verification were selected from a research database, with 100 CT colonographic examinations with at least one polyp 6 mm or larger. After a lecture session and short individual hands-on training, CT colonography training was done individually with immediate feedback of colonoscopy outcome. Per-polyp sensitivity was calculated for four sets of 50 CT colonographic examinations for lesions 6 mm or larger. By using logistic regression analyses, the number of CT colonographic examinations to reach 90% sensitivity for lesions 6 mm or larger was estimated. Reading times were registered. RESULTS The average per-polyp sensitivity for lesions 6 mm or larger was 76% (207 of 270) in the first set of 50 CT colonographic examinations, 77% (262 of 342) in the second (P = .96 vs first set), 80% (310 of 387) in the third (P = .67 vs first set), and 91% (261 of 288) in the fourth (P = .018). The estimated number of CT colonographic examinations for a sufficient sensitivity was 164. Six of nine readers reached this level of competence within 175 CT colonographic examinations. Reading times decreased significantly from the first to the second set of 50 CT colonographic examinations for six readers. CONCLUSION Novice CT colonography readers obtained sensitivity equal to that of experienced readers after practicing on average 164 CT colonographic studies.


British Journal of Surgery | 2009

Abdominosacral resection for locally advanced and recurrent rectal cancer

Floris T. J. Ferenschild; Maarten Vermaas; Cornelis Verhoef; Roy S. Dwarkasing; A.M.M. Eggermont; J.H.W. de Wilt

The results of resection of locally advanced and recurrent rectal cancers, including sacral resection, were analysed critically.


Digestive Surgery | 2010

Diagnosis and Treatment of Hepatocellular Adenoma in the Netherlands: Similarities and Differences

S.M. van Aalten; Türkan Terkivatan; R. A. de Man; D.J. van der Windt; Niels F. M. Kok; Roy S. Dwarkasing; J. IJzermans

Background: The diagnosis of hepatocellular adenoma (HA) has a great impact on the lives of young women and may pose clinical dilemmas to the clinician since there are no standardized protocols to follow. We aimed to establish expert opinions on diagnosis and treatment of HA by collecting data from a nationwide questionnaire in the Netherlands. Methods: A questionnaire was sent to 20 Dutch hospitals known to offer hepatologic and surgical experience on liver tumours. Results: 17 hospitals (85%) responded to the questionnaire. Annually, a median of 52 patients presented with a solid liver tumour. In 15 (88%) hospitals, hepatic adenomas were diagnosed with contrast-enhanced, multiphase spiral CT or MRI. In 2 (12%) hospitals, histology was required as part of a management protocol. Surveillance after withdrawal of oral contraceptives was the initial policy in all clinics. MRI, CT or ultrasound was used for follow-up. Criteria for surgical resection were a tumour size >5 cm and abdominal complaints. In 5 (29%) hospitals, patients were dismissed from follow-up after surgery. In complex cases (e.g. large, multiple or centrally localized lesions, a wish for pregnancy), the treatment policy was highly variable. Pregnancy was not discouraged in 15 hospitals, but in 11 (65%) of these, strictly defined conditions were noted: frequent follow-up, peripheral tumour localization that makes surgery easier if necessary, stable tumour size, and a good informed consent. Conclusion: The management of HAs in the Netherlands is rather uniform, except in complex cases in which multiple factors may influence policy.

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Jan N. M. IJzermans

Erasmus University Rotterdam

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Robert A. de Man

Erasmus University Rotterdam

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Cornelis Verhoef

Erasmus University Rotterdam

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Maarten Thomeer

Erasmus University Rotterdam

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Gabriel P. Krestin

Erasmus University Rotterdam

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F. Willemssen

Erasmus University Rotterdam

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B.J.M. Heijmen

Erasmus University Rotterdam

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J. Verheij

Erasmus University Rotterdam

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Mirelle E.E. Bröker

Erasmus University Rotterdam

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Türkan Terkivatan

Erasmus University Rotterdam

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