Dr. Yulia Zak earned her medical degree from SUNY Downstate Medical Center before completing general surgery residency at Stanford University and advanced minimally invasive gastrointestinal and bariatric fellowship training at the Massachusetts General Hospital. Dr. Zak is certified by the American Board of Surgery and American Society for Metabolic and Bariatric Surgery. She has also completed the Stanford Surgical Education and Simulation fellowship and was previously an Assistant Program Director for the general surgery residency program at Mount Sinai Beth Israel. Dr. Zak joined the faculty at Stanford in 2018 and is the current Fellowship Associate Program Director. Her current clinical practice is focused on bariatrics, foregut and abdominal wall procedures. Her academic interests include quality improvement, surgical education, and bariatric outcomes.

Clinical Focus

  • General Surgery
  • Bariatric Surgery
  • Minimally Invasive Surgery

Academic Appointments

Professional Education

  • Board Certification: American Board of Surgery, General Surgery (2015)
  • Fellowship: Massachusetts General Minimally Invasive and Bariatric Surgery Fellowship (2015) MA
  • Residency: Stanford University General Surgery Residency (2014) CA
  • Medical Education: SUNY Downstate College of Medicine (2007) NY

All Publications

  • Experience With Vertical Sleeve Gastrectomy in Adolescent and Young Adult Ehlers-Danlos Syndrome Patients: a Case Series and Review of the Literature Obesity Surgery Herdes, R. E., Abu El Haija, M., Johnson, K., Shepard, W., Zak, Y., Bruzoni, M., Pratt, J. S. 2021
  • Development and Evaluation of a Novel Instrument to Measure Severity of Intraoperative Events Using Video Data. Annals of surgery Jung, J. J., Jüni, P. n., Gee, D. W., Zak, Y. n., Cheverie, J. n., Yoo, J. S., Morton, J. M., Grantcharov, T. n. 2020


    To develop and evaluate a novel instrument to measure SEVERE processes using video data.Surgical video data can serve an important role in understanding the relationship between intraoperative events and postoperative outcomes. However, a standard tool to measure severity of intraoperative events is not yet available.Items to be included in the instrument were identified through literature and video reviews. A committee of experts guided item reduction, including pilot tests and revisions, and determined weighted scores. Content validity was evaluated using a validated sensibility questionnaire. Inter-rater reliability was assessed by calculating intraclass correlation coefficient. Construct validity was evaluated on a sample of 120 patients who underwent laparoscopic Roux-en-Y gastric bypass procedure, in which comprehensive video data was obtained.SEVERE index measures severity of 5 event types using ordinal scales. Each intraoperative event is given a weighted score out of 10. Inter-rater reliability was excellent [0.87 (95%-confidence interval, 0.77-0.92)]. In a sample of consecutive 120 patients undergoing gastric bypass procedures, a median of 12 events [interquartile range (IQR) 9-18] occurred per patient and bleeding was the most frequent type (median 10, IQR 7-14). The median SEVERE score per case was 11.3 (IQR 8.3-16.9). In risk-adjusted multivariable regression models, history of previous abdominal surgery (P = 0.02) and body mass index (P = 0.005) were associated with SEVERE scores, demonstrating construct validity evidence.The SEVERE index may prove to be a useful instrument in identifying patients with high risk of developing postoperative complications.

    View details for DOI 10.1097/SLA.0000000000003897

    View details for PubMedID 32511124

  • Compliance With Gastric Cancer Guidelines is Associated With Improved Outcomes. Journal of the National Comprehensive Cancer Network Worhunsky, D. J., Ma, Y., Zak, Y., Poultsides, G. A., Norton, J. A., Rhoads, K. F., Visser, B. C. 2015; 13 (3): 319-325


    Limited data are available on the implementation and effectiveness of NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Gastric Cancer.We sought to assess rates of compliance with NCCN Guidelines, specifically stage-specific therapy during the initial episode of care, and to determine its impact on outcomes.The California Cancer Registry was used to identify cases of gastric cancer from 2001 to 2006. Logistic regression and Cox proportional hazard models were used to predict guideline compliance and the adjusted hazard ratio for mortality. Patients with TNM staging or summary stage (SS) were also analyzed separately.Compliance with NCCN Guidelines occurred in just 45.5% of patients overall. Patients older than 55 years were less likely to receive guideline-compliant care, and compliance was associated with a median survival of 20 versus 7 months for noncompliant care (P<.001). Compliant care was also associated with a 55% decreased hazard of mortality (P<.001). Further analysis revealed that 50% of patients had complete TNM staging versus an SS, and TNM-staged patients were more likely to receive compliant care (odds ratio, 1.59; P<.001). TNM-staged patients receiving compliant care had a median survival of 25.3 months compared with 15.1 months for compliant SS patients.Compliance with NCCN Guidelines and stage-specific therapy at presentation for the treatment of patients with gastric cancer was poor, which was a significant finding given that compliant care was associated with a 55% reduction in the hazard of death. Additionally, patients with TNM-staged cancer were more likely to receive compliant care, perhaps a result of having received more intensive therapy. Combined with the improved survival among compliant TNM-staged patients, these differences have meaningful implications for health services research.

    View details for PubMedID 25736009

  • Laparoscopic spleen-preserving distal pancreatectomy: the technique must suit the lesion. Journal of gastrointestinal surgery Worhunsky, D. J., Zak, Y., Dua, M. M., Poultsides, G. A., Norton, J. A., Visser, B. C. 2014; 18 (8): 1445-1451


    Splenic preservation is currently recommended during minimally invasive surgery for benign tumors of the distal pancreas. The aim of this study was to evaluate the outcomes of patients undergoing laparoscopic spleen-preserving distal pancreatectomy, with particular attention paid to the technique used for spleen preservation (splenic vessel ligation vs preservation). A review of consecutive patients who underwent laparoscopic distal pancreatectomy with the intention of splenic preservation was conducted. Patient demographics, operative data, and outcomes were collected and analyzed. Fifty-five consecutive patients underwent laparoscopic distal pancreatectomy with the intention of splenic preservation; 5 required splenectomy (9 %). Of the remaining 50 patients, 31 (62 %) had splenic vessel ligation, and 19 (38 %) had vessel preservation. Patient demographics and tumor size were similar. The vessel ligation group had significantly more pancreas removed (95 vs 52 mm, P < 0.001) and longer operative times (256 vs 201 min, P = 0.008). Postoperative outcomes, complication rates, and splenic viability were similar between groups. Laparoscopic spleen-preserving distal pancreatectomy is a safe operation with a high rate of success (91 %). Vessel ligation was the chosen technical strategy for lesions that required resection of a greater length of pancreas. We found no advantage to either technique with respect to outcomes and splenic preservation. Operative approach should reflect technical considerations including location in the pancreas.

    View details for DOI 10.1007/s11605-014-2561-x

    View details for PubMedID 24939598

  • The Epidemiology of Idiopathic Acute Pancreatitis, Analysis of the Nationwide Inpatient Sample From 1998 to 2007 PANCREAS Chen, Y., Zak, Y., Hernandez-Boussard, T., Park, W., Visser, B. C. 2013; 42 (1): 1-5


    The study aimed to better define the epidemiology of idiopathic acute pancreatitis (IAP).We identified admissions with primary diagnosis of acute pancreatitis (AP) in Nationwide Inpatient Sample between 1998 and 2007. Idiopathic AP was defined as all cases after excluding International Classification of Diseases, Ninth Revision, codes for other causes of AP (including biliary, alcoholic, trauma, iatrogenic, hyperparathyroidism, hyperlipidemia, etc).Among the primary admissions for AP, 26.9% had biliary pancreatitis, 25.1% alcoholic, and 36.5% idiopathic. Idiopathic AP had estimated 81,8025 admissions with a mean hospitalization of 5.6 days. Patients with IAP accounted for almost half of the fatalities among the cases of AP (48.2%) and had a higher mortality rate than both patients with biliary pancreatitis and patients with alcoholic pancreatitis (1.9%, 1.5%, and 1.0%, respectively, P < 0.01). Forty-six percent of patients with biliary pancreatitis underwent cholecystectomy during the index hospitalization, compared with 0.42% of patients with IAP. Patients with IAP had a demographic distribution similar to that of patients with biliary AP (female predominant and older), which was distinct from patients with alcoholic pancreatitis (male predominant and younger). There was a gradual but steady decrease in the incidence of IAP, from 41% in 1998 to 30% in 2007.Despite improving diagnostics, IAP remains a common clinical problem with a significant mortality. Standardization of the clinical management of these patients warrants further investigation.

    View details for DOI 10.1097/MPA.0b013e3182572d3a

    View details for PubMedID 22750972

  • Failure to comply with NCCN guidelines for the management of pancreatic cancer compromises outcomes HPB Visser, B. C., Ma, Y., Zak, Y., Poultsides, G. A., Norton, J. A., Rhoads, K. F. 2012; 14 (8): 539-547


    There are little data available regarding compliance with the National Comprehensive Cancer Network (NCCN) guidelines. We investigated variation in the management of pancreatic cancer (PC) among large hospitals in California, USA, specifically to evaluate whether compliance with NCCN guidelines correlates with patient outcomes.The California Cancer Registry was used to identify patients treated for PC from 2001 to 2006. Only hospitals with ≥ 400 beds were included to limit evaluation to centres possessing resources to provide multimodality care (n= 50). Risk-adjusted multivariable models evaluated predictors of adherence to stage-specific NCCN guidelines for PC and mortality.In all, 3706 patients were treated for PC in large hospitals during the study period. Compliance with NCCN guidelines was only 34.5%. Patients were less likely to get recommended therapy with advanced age and low socioeconomic status (SES). Using multilevel analysis, controlling for patient factors (including demographics and comorbidities), hospital factors (e.g. size, academic affiliation and case volume), compliance with NCCN guidelines was associated with a reduced risk of mortality [odds ratio (OR) for death 0.64 (0.53-0.77, P < 0.0001)].There is relatively poor overall compliance with the NCCN PC guidelines in California's large hospitals. Higher compliance rates are correlated with improved survival. Compliance is an important potential measure of the quality of care.

    View details for DOI 10.1111/j.1477-2574.2012.00496.x

    View details for PubMedID 22762402

  • Another Use of the Mobile Device: Warm-up for Laparoscopic Surgery JOURNAL OF SURGICAL RESEARCH Plerhoples, T. A., Zak, Y., Hernandez-Boussard, T., Lau, J. 2011; 170 (2): 185-188


    An important facet of laparoscopic surgery is its psychomotor component. As this aspect of surgery gains attention, lessons from other psychomotor-intense fields such as athletics have led to an investigation of the benefits of "warming up" prior to entering the operating room. Practical implementation of established methods of warm-up is hampered by a reliance on special equipment and instrumentations that are not readily available. In light of emerging evidence of translatability between video-game play and operative performance, we sought to find if laparoscopic task performance improved after warming up on a mobile device balance game.Laparoscopic novices were randomized into either the intervention group (n = 20) or the control group (n = 20). The intervention group played a mobile device balance game for 10 min while the control group did no warm-up whatsoever. Assessment was performed using two tasks on the ProMIS laparoscopic simulation system: "object positioning" (where small beads are transferred between four cups) and "tissue manipulation" (where pieces of plastic are stretched over pegs). Metrics measured were time to task completion, path length, smoothness, hand dominance, and errors.The intervention group made fewer errors: object positioning task 0.20 versus 0.70, P = 0.01, tissue manipulation task 0.15 versus 0.55, P = 0.05, total errors 0.35 versus 1.25, P = 0.002. The two groups performed similarly on the other metrics.Warm-up using a mobile device balance game decreases errors on basic tasks performed on a laparoscopic surgery simulator, suggesting a practical way to warm-up prior to cases in the operating room.

    View details for DOI 10.1016/j.jss.2011.03.015

    View details for Web of Science ID 000295128600013

    View details for PubMedID 21529831

  • Predictors of Surgical Intervention for Hepatocellular Carcinoma ARCHIVES OF SURGERY Zak, Y., Rhoads, K. F., Visser, B. C. 2011; 146 (7): 778-784


    To define current use of surgical therapies for hepatocellular carcinoma (HCC) and evaluate the correlation of various patient and hospital characteristics with the receipt of these interventions.Retrospective cohort.California Cancer Registry data linked to the Office of Statewide Health Planning and Development patient discharge abstracts between 1996 and 2006.Patients with primary HCC.Receipt of liver transplant, hepatic resection, or local ablation.Of 12,148 HCC cases, 2390 (20%) underwent surgical intervention. Three hundred eleven (2.56%) received a liver transplant, 1307 (10.8%) underwent resection, and 772 (6.35%) had local ablation. There were wide variations in treatment by race and hospital type. African American and Hispanic patients were less likely than white patients to undergo transplant (P < .05). African American and Hispanic patients were less likely than white and Asian/Pacific Islander patients to have hepatectomy or ablation (P < .05). In multivariable analysis, the apparent differences in surgical intervention by race/ethnicity were decreased when adjusting for the patients' socioeconomic and insurance statuses. Patients with lower socioeconomic status and no private insurance were less likely to receive any surgery (P < .01). Hospital characteristics also explained some variations. Disproportionate Share Hospitals and public, rural, and nonteaching hospitals were less likely to offer surgical treatment (P < .01).There are significant racial, socioeconomic, and hospital-type disparities in surgical treatment of HCC.

    View details for DOI 10.1001/archsurg.2011.37

    View details for PubMedID 21422327

  • Crossed fused renal ectopia with calculi JOURNAL OF THE AMERICAN COLLEGE OF SURGEONS Ghosh, B. C., DeSantis, M., Kleyner, Y., Zak, Y. 2008; 206 (4): 753
  • Patterns of recurrence of colorectal cancer JOURNAL OF SURGICAL ONCOLOGY Zak, Y., Moore, H. G., Ghosh, B. C. 2008; 97 (1): 1–2

    View details for DOI 10.1002/jso.20882

    View details for Web of Science ID 000252332700001

    View details for PubMedID 17680636