About

Victoria Lyo, M.D., M.T.M., F.A.C.S. is an Associate Professor of Surgery at UC Davis Health and serves as the Associate Director of Clinical Research for the Center for Alimentary and Metabolic Science. She is also the Director of Surgery at the Foregut & Esophageal Motility Center. Her clinical expertise includes minimally invasive (laparoscopic and robotic) and traditional open techniques to address obesity, foregut diseases such as GERD, achalasia, and hiatal hernias, as well as abdominal wall and groin hernias, and gallbladder disease. Dr. Lyo specializes in procedures like esophageal dilation and stenting, Heller myotomy, anti-reflux surgeries, gastric fundoplications, gastric resection, and bariatric surgeries including gastric bypass and sleeve gastrectomy. She has fellowship training in minimally invasive surgery under Dr. John Hunter, a pioneer in foregut surgery. Her research focuses on understanding the interactions between the gut microbiome and the human host, particularly how the microbiome contributes to obesity and related diseases, aiming to improve management and outcomes of obesity and bariatric surgery. She holds a Master degree in Translational Medicine from UC Berkeley and UCSF and has received numerous awards for her research contributions.

Research topics

• Surgery
• Internal medicine
• Medicine
• General surgery
• Gastroenterology

Selected publications

• Pregnancy after bariatric surgery: persistent obesity and longer time to conception influences peripartum outcomes more than the type of operation

  Surgery for Obesity and Related Diseases · 2026-02-11

  articleSenior author
  PublisherDOI

• Outcomes of hiatal hernia repair after Roux-en-Y gastric bypass: largest retrospective cohort study to date

  Surgery for Obesity and Related Diseases · 2025-06-18 · 1 citations

  articleOpen access1st authorCorresponding
  PublisherOA PDFDOI

• S705 Sex-Specific Differences in Risk of Colorectal Polyps After Bariatric Surgery: Leveraging Machine Learning (ML) Techniques to Identify At-Risk Individuals

  The American Journal of Gastroenterology · 2025-10-01

  article

  Introduction: Obesity doubles colorectal cancer (CRC) risk. Yet, severe weight loss has mixed effects on CRC risk. With the most potent weight loss method, bariatric surgery (BRS), CRC risk is reportedly reduced in women; however, this effect disappears after 10 years, whereas CRC risk is unchanged in men. Scarce data exists on the risk of pre-neoplastic colorectal polyps after BRS. We aim to investigate whether sex differences exist and the potential for predicting these risks using machine learning (ML) methods. Methods: This single-center, retrospective study included patients with a Body Mass Index (BMI) >35 kg/m² who underwent BRS from 2002-2023. Adults aged 18 and older who underwent a colonoscopy after Roux-en-Y gastric bypass or sleeve gastrectomy were compared to controls who had colonoscopies pre-surgery. Subjects with inflammatory bowel disease or personal/familial CRC were excluded. We evaluated the risk of polyps in men and women post-BRS, confirmed in a paired sensitivity analysis that examined the risk of polyps within these subjects. A prediction model employing 6 ML models was also created to identify individuals at risk for polyp development. Results: A colonoscopy was performed on 47% of BRS adults between 2002-2023. In total, 1,735 patients met the inclusion criteria (719 post-BRS and 1016 controls; 22% male). Pre-matching, both groups were similar in age and BMI at the time of surgery. BRS led to an impactful weight loss (mean post-BRS colonoscopy BMI of 35 kg/m² vs 44 kg/m² at baseline). Post-BRS adults trended towards a higher risk of polyps, which remained significantly elevated after propensity score matching (Hazard Ratio = 1.37, 95% CI: 1.10-1.72). Further, men had a higher risk of advanced polyps compared to women after BRS (Hazard Ratio = 2.09, 95% CI: 1.04-4.18). These findings persisted in a paired, propensity-matched analysis. Our ML analysis produced effective predictive models for identifying polyps, with Logistic Regression and Naïve Bayes showing the best discrimination capability—Logistic Regression at 65% sensitivity and Naïve Bayes at 71% specificity. Key predictive factors of polyps post-BRS included colonoscopy indication, age, metabolic markers, and sex. Conclusion: We identified an increased risk for polyps post-BRS and highlight sex-based trends in these risks. ML seems effective in predicting the risk of polyps, which provides an opportunity to enhance CRC screening uptake in at-risk adults post-BRS.

  PublisherDOI

• Quantification of ¹⁸ F-FDG Delivery Rate for Liver Inflammation Using Shortened Dynamic PET Imaging Protocols

  Journal of Nuclear Medicine · 2025-09-18

  article

  F-FDG [Formula: see text].

  PublisherDOI

• Quantifying the Radiotracer Delivery Rate in Immune Organs to Assess Liver Inflammation Using Total-Body PET

  2025-11-01

  article

  Metabolic dysfunction-associated steatotic liver disease (MASLD) is a multisystem disease and may be regulated by multiple extrahepatic factors. The immune system is increasingly recognized to affect MASLD pathophysiology. Previous studies have shown the promise of a parametric PET approach to assess liver inflammation in MASLD using the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${ }^{18} \text{F-FDG}$</tex> delivery rate <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}_{1}$</tex>. As an inflammatory disease, there is potential for crosstalk between the liver and the immune organs. However, no studies have explored the relationship between liver inflammation and multiple immune organs simultaneously. In this work, we investigate the kinetic changes of bone marrow (BM) and spleen (two important immune organs) in the context of liver inflammation using total-body dynamic PET kinetic modeling. The evaluation included 26 MASLD patients and 14 healthy subjects who underwent a full <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1-\mathrm{h}$</tex> dynamic <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${ }^{18}\text{F-FDG}$</tex> PET scan using the uEXPLORER total-body PET scanner. Results show that a two-tissue irreversible model with time delay correction is necessary to model both BM and spleen dynamic data. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}_{1}$</tex> in these two organs was decreased in the high liver inflammation group, while this change was not observed for other parameters, including SUV and FDG influx rate <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}_{\mathrm{i}}$</tex>. When combining with liver <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}_{1}$</tex>, BM and spleen <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}_{1}$</tex> can further increase the performance of differentiating grades of liver inflammation.

  PublisherDOI

• Comment on: Pregnancy and birth complications among women undergoing bariatric surgery: sleeve gastrectomy versus Roux-en-Y gastric bypass

  Surgery for Obesity and Related Diseases · 2025-01-01

  editorialSenior author
  PublisherDOI

• Response to letter to the editor 25-119

  Surgery for Obesity and Related Diseases · 2025-07-05

  article1st authorCorresponding
  PublisherDOI

• Quantitative PET imaging and modeling of molecular blood-brain barrier permeability

  Nature Communications · 2025-03-30 · 24 citations

  articleOpen access

  Neuroimaging of blood-brain barrier permeability has been instrumental in identifying its broad involvement in neurological and systemic diseases. However, current methods evaluate the blood-brain barrier mainly as a structural barrier. Here we developed a non-invasive positron emission tomography method in humans to measure the blood-brain barrier permeability of molecular radiotracers that cross the blood-brain barrier through its molecule-specific transport mechanism. Our method uses high-temporal resolution dynamic imaging and kinetic modeling for multiparametric imaging and quantification of the blood-brain barrier permeability-surface area product of molecular radiotracers. We show, in humans, our method can resolve blood-brain barrier permeability across three radiotracers and demonstrate its utility in studying brain aging and brain-body interactions in metabolic dysfunction-associated steatotic liver inflammation. Our method opens new directions to effectively study the molecular permeability of the human blood-brain barrier in vivo using the large catalogue of available molecular positron emission tomography tracers.

  PublisherOA PDFDOI

• Bias against biologics in bariatric surgery: is it justified?

  Surgical Endoscopy · 2025-08-14

  articleOpen access

  Abstract Background Obesity is a known risk factor for autoimmune disorders. Chronic steroid treatment among these patients poses greater surgical risk, but biological/immunomodulating agents (BIA) have allowed for safer alternatives. The effects of BIA monotherapy on postoperative complications following metabolic/bariatric surgery (MBS) have not been studied. We aimed to evaluate the effects of preoperative BIA use on post-metabolic/bariatric surgery outcomes. Methods We conducted a retrospective matched-pair cohort study of patients who underwent bariatric surgery between 2012 and 2024. Patients were stratified into two groups: those with autoimmune disorders on BIA monotherapy vs matched controls. Patients were matched by age, BMI, and surgery type (Roux-en-Y gastric bypass [RYGB] vs vertical sleeve gastrectomy [VSG]). Paired T-tests were used to compare continuous variables. McNemar’s test was used to compare dichotomous variables. Results Thirty patients (15 per group) were included in the study. Sixty percent of patients underwent VSG. Among biologic monotherapy patients, 46.7% had rheumatoid arthritis, and 66.7% of BIA were TNF inhibitors. BIAs were used within 12 months of surgery, stopped 6 weeks prior to surgery, and resumed 6 weeks after surgery. Although there was no difference in preoperative comorbidities, BIA group had a significantly higher ASA status (100% with ASA 3) compared to controls (60.0% with ASA 3, p = 0.03). Postoperatively, there were no differences in wound complications (6.7% BIA vs. 0% control, p = 1.00) or readmissions (0% BIA vs 6.7% control, p = 1.00). There were no anastomotic leaks, VTE, or death in either group. Six-month postoperative weight loss was equal between groups: (50.7 ± 15.4%EWL BIA vs 53.4 $$\pm$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>±</mml:mo> </mml:math> 19.8%EWL control, p = 0.89; %TWL (19.7 ± 6.1 [15.1–23.8] vs. 21.2 ± 5.9 [16.9–27.6], p = 0.78). Conclusion Despite higher ASA status, patients on BIA did not have increased postoperative complications, and had similar weight loss to control patients after MBS. Our data suggests that when managed appropriately, patients on BIA have similar benefits from MBS without added risk.

  PublisherOA PDFDOI

• The effect of body mass index on breast cancer stage and breast cancer specific survival

  Breast Cancer Research and Treatment · 2025-03-10 · 2 citations

  article
  PublisherDOI

Frequent coauthors

• Nigel W. Bunnett

  17 shared

• Kimberly S. Kirkwood

  University of California, San Francisco

  16 shared

• Fiore Cattaruzza

  Sanofi (United States)

  15 shared

• Mohamed R. Ali

  14 shared

• Shushmita M Ahmed

  University of California, Davis

  14 shared

• Eileen F. Grady

  14 shared

• Matthew Bogyo

  Stanford University

  12 shared

• Hazem Shamseddeen

  University of California, Davis

  11 shared

Labs

• Foregut, Metabolic and General SurgeryPI

Education

• Advance GI/MIS fellow , Surgery

  Oregon Health & Science University

  2019

• General Surgery Residency, Surgery

  UCSF Medical Center

  2018

• Master in Translational Medicine, Bioengineering

  University of California, Berkeley

  2015

• MD with Thesis

  UCSF School of Medicine

  2011

• Bachelor of Arts

  Wellesley College

  2005

Awards & honors

• Society of American Gastrointestinal and Endoscopic Surgeons…
• Pacific Northwest American College of Surgeons Bruce Wolfe B…
• UC San Francisco Lawrence Way Critical Thinking Award (2018)
• UC San Francisco Dean's Prize in Research Award (2011)
• Howard Hughes Medical Institute Medical Research Fellowship…