Ahmed R Ahmed

Imperial College Healthcare NHS Trust, Londinium, England, United Kingdom

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Publications (25)116.52 Total impact

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    ABSTRACT: The use of inferior vena cava (IVC) filters for prevention of venous thromboembolism (VTE) in bariatric surgery is a contentious issue. We aim to review the evidence for the use of IVC filters in bariatric surgical patients, describe trends in practice, and discuss challenges in developing evidence-based guidelines. The incidence of VTE in modern bariatric procedures with traditional methods of thromboprophylaxis, such as sequential calf compression devices and perioperative low molecular weight heparin, is approximately 2%. A systematic review of the literature was conducted according to PRISMA guidelines. We searched Medline up until July 2013 with the terms "bariatric filter" and "gastric bypass filter." Two investigators independently screened search results according to an agreed list of eligibility criteria. Eighteen studies were included. There were no randomized controlled trials. Data from controlled cohort studies suggest that those who undergo IVC filter insertion preoperatively may be at higher risk of developing deep vein thrombosis (DVT) and pulmonary embolism (PE). A small cohort of patients with multiple risk factors for VTE benefitted from reduced PE-related mortality after preoperative IVC filter insertion. Data from 12 case series reporting VTE outcomes from a total of 497 patients who underwent preoperative IVC filter insertion demonstrated DVT rates of 0% to 20.8% and PE rates ranging from 0% to 6.4%. Published data reporting the safety and efficacy of IVC filter use in bariatric surgical patients is highly heterogeneous. There is no evidence to suggest that the potential benefits of IVC filters outweigh the significant risks of therapy.
    Annals of surgery. 01/2015; 261(1):35-45.
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    ABSTRACT: There is paucity of data on Enhanced Recovery After Bariatric Surgery (ERABS) protocols. This feasibility study reports outcomes of this protocol utilized within a tertiary-referral bariatric centre. Data on consecutive primary procedures (laparoscopic gastric bypasses, sleeve gastrectomies and gastric bands) performed over 9 months within an ERABS protocol were prospectively recorded. Interventions utilized included shortened preoperative fasts, intra-operative humidification, early mobilization and feeding, avoidance of fluid overload, incentive spirometry, use of prokinetics and laxatives. Data collected included demographics, co-morbidities, morbidity, mortality, length of stay (LOS) and re-admissions. A total of 226 procedures (age [mean ± SD], 45 ± 11 years, median [interquartile range] BMI 44.9 [41.0-49.0] kg/m(2)) were undertaken: 150 (66 %) bypasses, 47 (21 %) sleeves and 29 (13 %) bands. Hypertension, diabetes mellitus, sleep apnea and limited mobility were present in 40 %, 34 %, 24 % and 9 % of patients, respectively. No anastomotic or staple line leaks/bleeds were encountered. Ten (4.4 %) patients developed postoperative morbidity (mainly respiratory complications). One death occurred from massive pulmonary embolus in a high-risk patient (despite insertion of preoperative-IVC filter). Respective mean ± SD LOS for bypasses, sleeves and bands were 1.88 ± 1.12, 2.30 ± 1.69 and 0.69 ± 0.81 days. Successful discharge on the first postoperative day was achieved in 37 % and 28 % of bypasses and sleeves, respectively. Day-case gastric bands were performed in 48 %. Thirty-day hospital re-admission occurred in six (2.7 %) patients. Applying an ERABS protocol was feasible, safe, associated with low morbidity, acceptable LOS and low 30-day re-admission rates. The presence of multiple medical co-morbidities should not preclude use of an ERABS protocol within bariatric patients.
    Obesity Surgery 12/2013; · 3.74 Impact Factor
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    ABSTRACT: Obesity is the new epidemic and is associated with an increased risk of diastolic and systolic heart failure. Effective treatment options with drastic results such as bariatric surgery have raised interest in the possible reversal of some of the cardiovascular sequelae. Many studies have assessed individually the effect of weight loss on specific echocardiographic indices, mostly employing nonhomogeneous groups. The purpose of this narrative review is to summarise the effect of bariatric surgery on echocardiographic indices of biventricular function and to help in the understanding of the expected echocardiographic changes in bariatric patients after weight-loss surgery.
    European Journal of Clinical Investigation 11/2013; 43(11):1224-1230. · 3.37 Impact Factor
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    ABSTRACT: Roux-en-Y gastric bypass (RYGB) has greater efficacy for weight loss in obese patients than gastric banding (BAND) surgery. We hypothesise that this may result from different effects on food hedonics via physiological changes secondary to distinct gut anatomy manipulations. We used functional MRI, eating behaviour and hormonal phenotyping to compare body mass index (BMI)-matched unoperated controls and patients after RYGB and BAND surgery for obesity. Obese patients after RYGB had lower brain-hedonic responses to food than patients after BAND surgery. RYGB patients had lower activation than BAND patients in brain reward systems, particularly to high-calorie foods, including the orbitofrontal cortex, amygdala, caudate nucleus, nucleus accumbens and hippocampus. This was associated with lower palatability and appeal of high-calorie foods and healthier eating behaviour, including less fat intake, in RYGB compared with BAND patients and/or BMI-matched unoperated controls. These differences were not explicable by differences in hunger or psychological traits between the surgical groups, but anorexigenic plasma gut hormones (GLP-1 and PYY), plasma bile acids and symptoms of dumping syndrome were increased in RYGB patients. The identification of these differences in food hedonic responses as a result of altered gut anatomy/physiology provides a novel explanation for the more favourable long-term weight loss seen after RYGB than after BAND surgery, highlighting the importance of the gut-brain axis in the control of reward-based eating behaviour.
    Gut 08/2013; · 13.32 Impact Factor
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    ABSTRACT: Objective. To compare multimedia and standard consent, in respect to patient comprehension, anxiety, and satisfaction, for various surgical/interventional procedures. Data sources. Electronic searches of PubMed, MEDLINE, Ovid, Embase, and Google Scholar were performed. Relevant articles were assessed by 2 independent reviewers. Study selection. Comparative (randomized and nonrandomized control trials) studies of multimedia and standard consent for a variety of surgical/interventional procedures were included. Studies had to report on at least one of the outcome measures. Data extraction. Studies were reviewed by 2 independent investigators. The first investigator extracted all relevant data, and consensus of each extraction was performed by a second investigator to verify the data. Conclusion. Overall, this review suggests that the use of multimedia as an adjunct to conventional consent appears to improve patient comprehension. Multimedia leads to high patient satisfaction in terms of feasibility, ease of use, and availability of information. There is no conclusive evidence demonstrating a significant reduction in preoperative anxiety.
    Surgical Innovation 05/2012; · 1.34 Impact Factor
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    ABSTRACT: The reported remission of type 2 diabetes in patients undergoing Roux-en-Y gastric bypass has brought the role of the gut in glucose metabolism into focus. Our objective was to explore the differential effects on glucose homeostasis after oral versus gastrostomy glucose loading in patients with Roux-en-Y gastric bypass at an academic health science center. A comparative controlled investigation of oral versus gastrostomy glucose loading in 5 patients who had previously undergone gastric bypass and had a gastrostomy tube placed in the gastric remnant for feeding. A standard glucose load was administered either orally (day 1) or by the gastrostomy tube (day 2). The plasma levels of glucose, insulin, glucagon-like peptide 1 and peptide YY were measured before and after glucose loading. Exclusion of the proximal small bowel from glucose passage induced greater plasma insulin, glucagon-like peptide 1, and peptide YY responses compared with glucose loading by way of the gastrostomy tube (P <.05). Exclusion of glucose passage through the proximal small bowel results in enhanced insulin and gut hormone responses in patients after gastric bypass. The gut plays a central role in glucose metabolism and represents a target for future antidiabetes therapies.
    Surgery for Obesity and Related Diseases 03/2012; 8(4):371-4. · 4.94 Impact Factor
  • Susannah M Wyles, Sherif Hakky, Ahmed R Ahmed
    Surgery for Obesity and Related Diseases 07/2011; 7(4):543-5. · 4.94 Impact Factor
  • Andrew Currie, Andrew Chetwood, Ahmed R Ahmed
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    ABSTRACT: Obesity causes a significant healthcare burden and has been shown to be an important risk factor in the development of cardiovascular disease, type 2 diabetes, and increasingly chronic kidney disease. Bariatric surgery is the most effective treatment for obesity and has been shown to drastically improve both blood pressure and diabetic control. However, the interaction of bariatric surgery and renal function is less clear. This review focuses on the effect of bariatric surgery on renal function both in the acute situation, with respect to acute kidney injury, and also on changes in renal function parameters post-bariatric surgery weight loss. The interaction of obesity, bariatric surgery, and nephrolithiasis as a precipitant of acute kidney injury will also be considered. The role of bariatric surgery in pre- and post-renal transplant recipients is discussed as well as possible mechanisms underlying the improvement in renal function.
    Obesity Surgery 02/2011; 21(4):528-39. · 3.74 Impact Factor
  • Gastroenterology 01/2011; 140(5). · 12.82 Impact Factor
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    ABSTRACT: Internal hernia (IH) and Roux limb compression (RC) are recognized complications after retrocolic laparoscopic Roux-en-Y gastric bypass for obesity. The aim of the present study was to systematically identify the surgical technical errors leading to these complications. An observational clinical human reliability assessment approach was used to analyze the operating videos of 3 groups: an IH group (n = 12), a Roux compression group (n = 13), and a control group (no complications, n = 21). Two investigators, unaware of the outcomes, reviewed all videos, using special rating software. All errors were categorized using the external error mode system and further described if a direct consequential error (e.g., bleeding) was found. An analysis of data showed that, on average, more errors occurred in the complication groups than in the control group (IH 5.85, Roux compression 3.54, control .90, P < .001). The strongest differences were found for missing intermesenteric stitches on both sides of the Roux limb. Logistic regression analysis showed that a missed stitch between the mesentery of the Roux limb and the transverse mesocolon was an independent predictor for IH (B = 1.727, P = .025). No technical or consequential errors could be identified as responsible for RC. The observational clinical human reliability analysis is a useful method to identify operative failure. For retrocolic, retrogastric laparoscopic Roux-en-Y gastric bypass, a systematic approach for the closure of the transverse mesenteric window might prevent IH complications.
    Surgery for Obesity and Related Diseases 01/2011; 8(2):158-63. · 4.94 Impact Factor
  • Susannah M Wyles, Sherif Hakky, Ahmed R Ahmed
    Surgery for Obesity and Related Diseases 11/2010; 6(6):718-20. · 4.94 Impact Factor
  • Susannah M. Wyles, Sherif Hakky, Ahmed R. Ahmed
    Surgery for Obesity and Related Diseases 05/2010; 6(3):S82-S83. · 4.94 Impact Factor
  • Surgery for Obesity and Related Diseases 03/2010; 6(2):227-228. · 4.94 Impact Factor
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    ABSTRACT: Internal hernias (IHs) can complicate laparoscopic Roux-en-Y gastric bypass (LRYGB). A number of radiological investigations can be used in the diagnosis. These include plain X-rays, upper gastrointestinal (UGI) series, ultrasound, and computed tomography (CT) scanning. We present radiological findings in our series of 58 symptomatic internal hernias based on our 6-year experience (2000-2006) of 2,572 LRYGB patients. A retrospective chart review was performed of all patients undergoing LRYGB who developed symptomatic internal hernia requiring operative intervention between January 1, 2000 and September 15, 2006. Types of radiological tests performed and their results were recorded. Fifty-eight symptomatic internal hernias were recorded, of which 56/58 (97%) underwent radiological investigation; 2/58 went directly to surgery. Of the 56 patients who underwent diagnostic imaging, 41 plain abdominal X-rays, 37 CT scans, 26 UGI series, and eight ultrasound scans were performed. Sixty-five percent of UGI series and 92% of CT scans had positive features diagnostic of internal hernia. Performing both CT and UGI series successfully diagnosed IH in 100% of cases. Subgroup analysis did not reveal any association between positive result of imaging test and type of internal hernia. CT scanning is the single most effective radiological investigation for diagnosing internal hernias post-LRYGB. In non-diagnostic cases, the addition of an upper GI series increases the diagnostic rate to 100%.
    Obesity Surgery 09/2009; 19(11):1530-5. · 3.74 Impact Factor
  • Journal of the American College of Surgeons 09/2009; 209(3):S14. · 4.45 Impact Factor
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    ABSTRACT: Laparoscopic Roux-en-Y gastric bypass (LRYGB) surgery is known to have a significant effect on obesity-related comorbidities such as hypertension curing it in some (50-70%) while improving control in others. Our aim was to observe the changes in blood pressure (BP) in a cohort of 100 patients followed prospectively for 1 year after LRYGB. BP measurements were recorded prospectively in 100 consecutive patients preoperatively and then postoperatively at weeks 1, 5, 9, and months 6 and 12. In order to reduce bias, three BP measurements were made by the same nurse at each office visit and the mean recorded. Pre- and postoperative usage of antihypertensive medication was also noted. Eighty-nine women and 11 men underwent LRYGB and their BP monitored for 1 year. There was an 85% follow-up rate with mean % excess body weight loss of 60. Reductions in systolic (9 mmHg) and diastolic (7 mmHg) BP measurements were seen as early as week 1 postoperatively and maintained for the duration of the observation period (P < 0.05). Furthermore, postoperative usage of antihypertensive medication is reduced to a third of preoperative use. LRYGB is associated with an early reduction in BP and antihypertensive medication usage which is maintained at 1 year after surgery. This early impact on blood pressure occurs before any significant weight loss is achieved thereby suggesting a hormonal mechanism that may be involved for the changes observed.
    Obesity Surgery 09/2008; 19(7):845-9. · 3.74 Impact Factor
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    ABSTRACT: Internal hernias (IHs) can occur after laparoscopic Roux-en-Y gastric bypass (LRYGBP), perhaps because of a lack of adhesion formation at the cut edges of the mesentery and a cutting through of sutures with a decrease in fat from weight loss. In patients undergoing reoperation after LRYGBP, we observed that bioabsorbable glycolide copolymer staple-line reinforcement (SLR) placed to mitigate staple-line bleeding had evoked adhesiogenesis and tissue fusion at the mesentery edges; therefore, we investigated whether use of this material decreases post-LRYGBP IH rates. The records of the 43 patients (3%) in whom an IH developed during a mean follow-up time of 2 years in a series of 1,704 LRYGBP procedures were reviewed retrospectively. The IHs were in the Peterson's space (n = 4), the enteroenterostomy (n = 17), or the transverse mesocolon (n = 22). The IH rate was significantly higher in patients who had suture closure of the mesenteric defects at LRYGBP than in those without formal closure of the defects but in whom SLR was applied to the edges of the cut mesentery (P = 0.01). The suture-closure and SLR groups had similar demographic, operative, and follow-up characteristics. When transverse mesocolic IHs were excluded from analysis, patients given SLR remained less likely to have an IH (P = 0.05). Use of bioabsorbable polymer SLR may decrease the occurrence of IHs after LRYGBP. Additional studies of the effect of mesentery closure method on IH incidence after LRYGBP are warranted.
    Obesity Surgery 08/2008; 18(7):797-802. · 3.74 Impact Factor
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    ABSTRACT: Partial small bowel obstruction can occur as a result of circumferential extrinsic compression of the Roux limb as it traverses the transverse mesocolic rent from thickened cicatrix formation in this area. The aim of this study is to examine the incidence of Roux limb compression with particular attention to the timing of presentation and associated weight loss in the setting of a university hospital in the United States. A retrospective chart review was performed of all patients undergoing laparoscopic Roux-en-Y gastric bypass who developed symptomatic small bowel obstruction requiring operative intervention from January 1, 2000 and September 15, 2006. Of 2215 patients, 20 (.9%) developed symptomatic Roux limb compression. The mean time to presentation was 48 days after LRYGB. By this stage, the mean percentage of excess body weight loss was 29%. Of the 20 patients, 19 underwent an upper gastrointestinal contrast study, the results of which confirmed the diagnosis. In all cases, laparoscopic intervention was successful in freeing the constricted Roux limb by dividing the cicatrix formation between the Roux limb and mesocolic window. Switching from continuous to interrupted closure of the space between Roux limb and mesocolic window appeared to reduce the incidence of this complication (P<.05). Narrowing at the transverse mesocolon rent is an uncommon cause of small bowel obstruction after retrocolic laparoscopic Roux-en-Y gastric bypass. Unlike internal hernias, which tend to occur later in the clinical course and are associated with significant weight loss, Roux limb obstruction occurs earlier after gastric bypass and is not associated with significant weight loss. Interrupted closure of the mesocolic window might reduce the risk of Roux compression.
    Surgery for Obesity and Related Diseases 07/2008; 5(2):194-8. · 4.94 Impact Factor
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    ABSTRACT: Investigation of the bypassed stomach in patients with suspected peptic ulcer disease presents a major challenge to bariatric surgeons. Various methods have been suggested for visualization of the duodenum and bypassed stomach. These include endoscopy via percutaneous gastrostomy access, retrograde endoscopy and virtual gastroscopy using CT scan. We present a case of peptic ulcer bleeding diagnosed with the help of conventional CT scan. To the best of our knowledge, this is the second such case reported in the literature and the first in the bariatric population.
    Obesity Surgery 12/2007; 17(11):1520-2. · 3.74 Impact Factor
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    ABSTRACT: Internal hernia is a known complication after gastric bypass, especially when performed laparoscopically. The aim of this study was to see when internal hernias occur in relation to weight loss and time course after surgery. Furthermore, we wish to examine the impact of Roux limb positioning ante- versus retrocolic and whether switching to running versus interrupted closure of the mesenteric defects created at surgery made any difference. A retrospective chart review was performed of all patients undergoing laparoscopic Roux-en-Y gastric bypass surgery (LRYGB) who developed symptomatic internal hernia requiring operative intervention between January 1, 2000 and September 15, 2006. Fifty-four internal hernias occurred in 2,572 patients, an incidence of 2.1%. The site of internal hernias varied: 25 (1%), transverse mesocolon; 22 (0.8%), enteroenterostomy; 7 (0.3%), Peterson's space. The mean time to intervention for an internal hernia repair was 413 +/- 46 days and average % excess body weight loss (%EBWL) in this period was 59 +/- 3.3. Subgroup analysis demonstrates internal hernia incidence to be 2 in 357 (0.6%) in antecolic Roux versus 52 in 2,215 (2.4%) in retrocolic Roux limb (odds ratio = 4, P < 0.05). Continuous closure versus interrupted stitching of mesenteric defects does not seem to alter the incidence of internal hernias. This study demonstrates that the majority of internal hernias occur after a significant (>50%) EBWL. Furthermore, the antecolic approach is associated with a much reduced incidence of internal hernia.
    Obesity Surgery 12/2007; 17(12):1563-6. · 3.74 Impact Factor

Publication Stats

200 Citations
116.52 Total Impact Points


  • 2010–2013
    • Imperial College Healthcare NHS Trust
      Londinium, England, United Kingdom
  • 2009–2012
    • Imperial College London
      • • Section of Investigative Medicine
      • • Department of Surgery and Cancer
      Londinium, England, United Kingdom
  • 2008–2009
    • University Center Rochester
      Rochester, Minnesota, United States
  • 2007–2008
    • University of Rochester
      • Division of Bariatric & GI Surgery
      Rochester, New York, United States
  • 2006–2008
    • Highland Hospital
      Oakland, California, United States