Ahmed Marwan

Dr. Ahmed Marwan

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Research Focus & Metrics

Academic Career Length

21Years (2006-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 May 2006 in Seminars in Pediatric Surgery
Verified
Journal Article
Closed access
AMAhmed Marwan
Ahmed Marwan
TCTimothy M. Crombleholme
Timothy M. Crombleholme

1 January 2017 in Scientifica
Verified
Journal Article
Open access
PDF file
SMSiti W. Mohd-Zin
Siti W. Mohd-Zin
AMAhmed Marwan
Ahmed Marwan
MCMohamad K. Abou Chaar
Mohamad K. Abou Chaar
AAAzlina Ahmad-Annuar
Azlina Ahmad-Annuar
NANoraishah Mydin Abdul-Aziz
Noraishah Mydin Abdul-Aziz
Spina bifida is among the phenotypes of the larger condition known as neural tube defects (NTDs). It is the most common central nervous system malformation compatible with life and the second leading cause of birth defects after congenital heart defects. In this review paper, we define spina bifida and discuss the phenotypes seen in humans as described by both surgeons and embryologists in order to compare and ultimately contrast it to the leading animal model, the mouse. Our understanding of spina bifida is currently limited to the observations we make in mouse models, which reflect complete or targeted knockouts of genes, which perturb the whole gene(s) without taking into account the issue of haploinsufficiency, which is most prominent in the human spina bifida condition. We thus conclude that the need to study spina bifida in all its forms, both aperta and occulta, is more indicative of the spina bifida in surviving humans and that the measure of deterioration arising from caudal neural tube defects, more commonly known as spina bifida, must be determined by the level of the lesion both in mouse and in man.

3 January 2020 in Gastroenterology Research and Practice
Verified
Journal Article
Open access
PDF file
BWBradley Wallace
Bradley Wallace
FSFabia Schuepbach
Fabia Schuepbach
SGStefan Gaukel
Stefan Gaukel
AMAhmed Marwan
Ahmed Marwan
RSRalph F. Staerkle
Ralph F. Staerkle
RVRaphael Vuille-dit-Bille
Raphael Vuille-dit-Bille
Anastomotic leakage reflects a major problem in visceral surgery, leading to increased morbidity, mortality, and costs. This review is aimed at evaluating and summarizing risk factors for colorectal anastomotic leakage. A generalized discussion first introduces risk factors beginning with nonalterable factors. Focus is then brought to alterable impact factors on colorectal anastomoses, utilizing Cochrane systematic reviews assessed via systemic literature search of the Cochrane Central Register of Controlled Trials and Medline until May 2019. Seventeen meta-anaylses covering 20 factors were identified. Thereof, 7 factors were preoperative, 10 intraoperative, and 3 postoperative. Three factors significantly reduced the incidence of anastomotic leaks: high (versus low) surgeon’s operative volume (RR=0.68), stapled (versus handsewn) ileocolic anastomosis (RR=0.41), and a diverting ostomy in anterior resection for rectal carcinoma (RR=0.32). Discussion of all alterable factors is made in the setting of the pre-, intra-, and postoperative influencers, with the only significant preoperative risk modifier being a high colorectal volume surgeon and the only significant intraoperative factors being utilizing staples in ileocolic anastomoses and a diverting ostomy in rectal anastomoses. There were no measured postoperative alterable factors affecting anastomotic integrity.

1 September 2007 in American Journal of Physiology-Gastrointestinal and Liver Physiology
Verified
Journal Article
Open access
PDF file
JPJignesh K. Parvadia
Jignesh K. Parvadia
SKSundeep G. Keswani
Sundeep G. Keswani
SVSachin Vaikunth
Sachin Vaikunth
AMArturo R. Maldonado
Arturo R. Maldonado
AMAhmed Marwan
Ahmed Marwan
TCTimothy M. Crombleholme
Timothy M. Crombleholme
Previous work in our group has demonstrated that mouse salivary gland has the highest concentration of salivary-derived VEGF protein compared with other organs and is essential for normal palatal mucosal wound healing. We hypothesize that salivary VEGF plays an important role in maintaining the integrity of the gastrointestinal mucosa following small bowel resection (SBR). Thirty-five 8- to 10-wk-old C57BL/6 female mice were divided into seven treatment groups: 1) sham (transaction and anastomosis, n = 5); 2) SBR ( n = 8); 3) sialoadenectomy and small bowel resection (SAL+SBR, n = 8); 4) sialoadenectomy and small bowel resection with EGF supplementation (SAL+SBR+EGF, n = 9); 5) sialoadenectomy and small bowel resection with VEGF supplementation (SAL+SBR+VEGF, n = 9); 6) sialoadenectomy and small bowel resection supplemented with EGF and VEGF (SAL+ SBR+VEGF+EGF, n = 6); 7) selective inhibition of VEGF in the submandibular gland by Ad-VEGF-Trap following small bowel resection (Ad-VEGF-Trap+SBR, n = 7). Adaptation was after 3 days by ileal villus height and crypt depth. The microvascular response was evaluated by CD31 immunostaining and for villus-vessel area ratio by FITC-labeled von Willebrand factor immunostaining. The adaptive response after SBR was significantly attenuated in the SAL group in terms of villus height (250.4 ± 8.816 vs. 310 ± 19.35, P = 0.01) and crypt depth (100.021 ± 4.025 vs. 120.541 ± 2.82, P = 0.01). This response was partially corrected by orogastric VEGF or EGF alone. The adaptive response was completely restored when both were administered together, suggesting that salivary VEGF and EGF both contribute to intestinal adaptation. VEGF increases the vascular density (6.4 ± 0.29 vs. 6.1 ± 0.29 vs. 5.96 ± 0.20) and villus-vessel area ratio (0.713 ± 0.01 vs. 0.73 ± 0.01) in the adapting bowel. Supplementation of both EGF and VEGF fully rescues adaptation, suggesting that the adaptive response may be dependent on VEGF-driven angiogenesis. These results support a previously unrecognized role for VEGF in the small bowel adaptive response.

1 October 2010 in Journal of Trauma: Injury, Infection & Critical Care
Verified
Journal Article
Closed access
AMAhmed Marwan
Ahmed Marwan
CHCarrol M. Harmon
Carrol M. Harmon
KGKeith E. Georgeson
Keith E. Georgeson
GSGeni F. Smith
Geni F. Smith
OMOliver J. Muensterer
Oliver J. Muensterer
Anecdotally, laparoscopy has been used for the diagnosis and therapy of pediatric abdominal trauma, but only few studies have been published. We performed a systematic analysis of our experience concerning indications, procedures, and outcomes using laparoscopy in pediatric abdominal trauma patients. Our trauma database was searched for patients who underwent laparoscopy after being admitted for abdominal trauma. Cases were grouped into diagnostic and therapeutic procedures. Success was defined as attaining the correct diagnosis or as the ability to repair the injury by laparoscopy. Of 4,836 pediatric trauma admissions over a period of 12 years, 92 had open or laparoscopic abdominal explorations for blunt (n = 47) and penetrating (n = 35) injuries. In 21 patients, diagnostic laparoscopic procedures were performed, and 5 of these children also underwent a therapeutic laparoscopy. Nineteen patients were treated in the acute setting and two in a delayed fashion. Overall, 19 of 21 laparoscopies correctly diagnosed the injury, and all the 5 laparoscopic therapeutic procedures were successful. There was a significant difference in success rate of diagnostic laparoscopy between acute and delayed cases (p < 0.01). Retrospectively, laparotomy was avoided in 13 of 21 patients overall and in 10 of 10 patients with penetrating trauma (p = 0.02). Laparoscopy is useful in the management of the hemodynamically stable pediatric patient with abdominal trauma but may be less valuable in cases with delayed presentation. Many intraabdominal injuries are amenable to laparoscopic repair. In patients with penetrating trauma, laparoscopy avoided laparotomy is more likely than in those with blunt abdominal trauma. Laparoscopy is currently underutilized in the management of pediatric abdominal trauma.

6 September 2017 in Fetal Diagnosis and Therapy
Verified
Journal Article
Closed access
PDF file
MZMichael V. Zaretsky
Michael V. Zaretsky
KLKenneth W. Liechty
Kenneth W. Liechty
HGHenry L. Galan
Henry L. Galan
NBNicholas J. Behrendt
Nicholas J. Behrendt
SRShane Reeves
Shane Reeves
TCTimothy M. Crombleholme
Timothy M. Crombleholme
Objective: We reviewed our experience with open fetal surgical myelomeningocele repair to assess the efficacy of a new modification of the hysterotomy closure technique regarding hysterotomy complication rates at the time of cesarean delivery. Methods: A modification of the standard hysterotomy closure was performed on all patients undergoing prenatal myelomeningocele repair. The closure consisted of an interrupted full-thickness #0 polydioxanone (PDS) retention suture as well as a running #0 PDS suture to re-approximate the myometrial edges, and the modification was a third imbricating layer resulting in serosal-to-serosal apposition. A standard omental patch was placed per our routine. Both operative reports and verbal descriptions of hysterotomy from delivering obstetricians were reviewed. Results: A total of 49 patients underwent prenatal repair of myelomeningocele, 43 having adequate follow-up for evaluation. Of those, 95.4% had completely intact hysterotomy closures, with only 1 partial dehiscence (2.3%) and 1 thinned scar (2.3%). There were no instances of uterine rupture. Discussion: In patients undergoing this modified hysterotomy closure technique, a much lower than expected complication rate was observed. This simple modified closure technique may improve hysterotomy healing and reduce obstetric morbidity.