After living and training throughout the country, I am excited to be part of the Stanford team. As a result of both my personal experiences and training, I am passionate about ensuring that patients receive appropriate diagnostic testing and treatment options in order to improve people's quality of life. In collaboration with my amazing colleagues, I am confident in the high quality and easily accessible care we are able to provide to patients across northern California.

While my interest is most in inflammatory bowel disease, I am also interested in the interaction between mental health, incentives, and emerging therapies in gastroenterology.

Clinical Focus

  • Gastroenterology
  • Inflammatory Bowel Disease
  • ulcerative colitis
  • Crohn's disease

Academic Appointments

Honors & Awards

  • Pierskalla Award for Best Paper in healthcare Applications, INFORMS (2014)

Boards, Advisory Committees, Professional Organizations

  • Member, American Society of Gastrointestinal Endoscopy (2011 - Present)
  • Member, American Gastroenterology Association (2011 - Present)
  • Member, Crohn's and Colitis Foundation (2016 - Present)
  • Member, Practice Management Committee-American College of Gastroenterology (2013 - Present)

Professional Education

  • Fellowship: Stanford University Gastroenterology Fellowship (2013) CA
  • Residency: University of Texas Southwestern Internal Medicine Residency (2010) TX
  • Internship: University of Texas Southwestern Internal Medicine Residency (2008) TX
  • Medical Education: University of Michigan School of Medicine (2007) MI
  • Board Certification: American Board of Internal Medicine, Gastroenterology (2013)
  • Board Certification: American Board of Internal Medicine, Internal Medicine (2010)
  • Fellowship, Stanford University, Gastroenterology Fellowship (2013)
  • Residency, University of Texas-Southwestern Medical Center at Dallas, Internal Medicine (2010)
  • M.D., University of Michigan, Medical School (2007)
  • B.S., Georgia Tech, Industrial Engineering (2003)

Graduate and Fellowship Programs

  • Gastroenterology & Hepatology (Fellowship Program)

All Publications

  • The Impact of Intermittent Fasting on Patients With Suspected Gastroesophageal Reflux Disease. Journal of clinical gastroenterology Jiang, Y., Sonu, I., Garcia, P., Fernandez-Becker, N. Q., Kamal, A. N., Zikos, T. A., Singh, S., Neshatian, L., Triadafilopoulos, G., Goodman, S. N., Clarke, J. O. 2022


    GOAL: The aim was to investigate the short-term impact of time restricted feeding on patients with suspected gastroesophageal reflux disease (GERD).BACKGROUND: Lifestyle modifications are often suggested, but the role of diet in GERD is unclear. Intermittent fasting is popular in the media and has demonstrated potential benefits with weight loss and inflammatory conditions as well as alterations in gastrointestinal hormones.STUDY: Patients who were referred for 96-hour ambulatory wireless pH monitoring off proton pump inhibitor to investigate GERD symptoms were screened for eligibility. Patients were instructed to maintain their baseline diet for the first 2 days of pH monitoring and switch to an intermittent fasting regimen (16 consecutive hour fast and 8h eating window) for the second 2 days. Objective measures of reflux and GERD symptom severity were collected and analyzed.RESULTS: A total of 25 participants were analyzed. 9/25 (36%) fully adhered to the intermittent fasting regimen, with 21/25 (84%) demonstrating at least partial compliance. Mean acid exposure time on fasting days was 3.5% versus 4.3% on nonfasting days. Intermittent fasting was associated with a 0.64 reduction in acid exposure time (95% CI: -2.32, 1.05). There was a reduction in GERD symptom scores of heartburn and regurgitation during periods of intermittent fasting (14.3 vs. 9.9; difference of -4.46, 95% CI: -7.6,-1.32).CONCLUSIONS: Initial adherence to time restricted eating may be difficult for patients. There is weak statistical evidence to suggest that intermittent fasting mildly reduces acid exposure. Our data show that short-term intermittent fasting improves symptoms of both regurgitation and heartburn.

    View details for DOI 10.1097/MCG.0000000000001788

    View details for PubMedID 36730832

  • Immune checkpoint inhibitor-mediated colitis is associated with cancer overall survival. World journal of gastroenterology Weingarden, A. R., Gubatan, J., Singh, S., Balabanis, T. C., Patel, A., Sharma, A., Habtezion, A. 2022; 28 (39): 5750-5763


    Immune checkpoint inhibitor-mediated colitis (IMC) is a common adverse event following immune checkpoint inhibitor (ICI) therapy for cancer. IMC has been associated with improved overall survival (OS) and progression-free survival (PFS), but data are limited to a single site and predominantly for melanoma patients.To determine the association of IMC with OS and PFS and identify clinical predictors of IMC.We performed a retrospective case-control study including 64 ICI users who developed IMC matched according to age, sex, ICI class, and malignancy to a cohort of ICI users without IMC, from May 2011 to May 2020. Using univariate and multivariate logistic regression, we determined association of presence of IMC on OS, PFS, and clinical predictors of IMC. Kaplan-Meier curves were generated to compare OS and PFS between ICI users with and without IMC.IMC was significantly associated with a higher OS (mean 24.3 mo vs 17.7 mo, P = 0.05) but not PFS (mean 13.7 mo vs 11.9 mo, P = 0.524). IMC was significantly associated with OS greater than 12 mo [Odds ratio (OR) 2.81, 95% confidence interval (CI) 1.17-6.77]. Vitamin D supplementation was significantly associated with increased risk of IMC (OR 2.48, 95%CI 1.01-6.07).IMC was significantly associated with OS greater than 12 mo. In contrast to prior work, we found that vitamin D use may be a risk factor for IMC.

    View details for DOI 10.3748/wjg.v28.i39.5750

    View details for PubMedID 36338892

    View details for PubMedCentralID PMC9627421

  • The Effects of Intermittent Fasting on Gastroesophageal Reflux Disease Jiang, Y., Goodman, S., Sonu, I., Garcia, P., Fernandez-Becker, N., Kamal, A., Zikos, T., Singh, S., Neshatian, L., Triadafilopoulos, G., Clarke, J. LIPPINCOTT WILLIAMS & WILKINS. 2021: S214
  • Immune Checkpoint Inhibitor-Mediated Colitis Is Associated With Improved Cancer Overall Survival Weingarden, A. R., Gubatan, J., Balabanis, T., Patel, A., Singh, S., Habtezion, A. LIPPINCOTT WILLIAMS & WILKINS. 2021: S1381
  • In the Thick of It: The Many Faces of Collagenous Gastritis. Digestive diseases and sciences Singh, S., Jing, E., Shen, J. 2020

    View details for DOI 10.1007/s10620-019-06003-9

    View details for PubMedID 31919637

  • Changes in alpha-foetoprotein and Gc-globulin in relation to outcomes in non-acetaminophen acute liver failure. Liver international : official journal of the International Association for the Study of the Liver Singh, S. n., Hynan, L. S., Rule, J. A., Lee, W. M. 2019


    Changes in Gc-globulin (Gc) and in alpha-foetoprotein (AFP) have been shown to be related to outcome in patients with acute liver failure (ALF). Gc is a serum protein that complexes with intravascular actin released during cellular necrosis. AFP, also made by hepatocytes, is associated with hepatocellular growth and regeneration. Previously, low absolute levels or decreases over time in either AFP or Gc portended to be a poor outcome.In a retrospective analysis of the double-blind trial of intravenous N-acetylcysteine (NAC) for ALF not because of acetaminophen, sera on days 1 and 3 or days 2 and 4 following admission were available to measure AFP in 70 patients and Gc in 66 patients. Mann-Whitney U tests were performed on the admission values, the absolute change and the fractional change of AFP and Gc to compare TFS (transplant-free survival) and non-TFS (death or transplantation). Logistic regression and receiver operating characteristic (ROC) analyses were performed to evaluate the markers in comparison and in addition to King's College Criteria (KCC).Transplant-free survival patients were characterized by increases in AFP, whereas non-TFS had significantly different (negative) absolute and fractional changes (P < .01). The addition of declining AFP levels to KCC improved the area under the curve in predicting non-TFS (AUC >70%). Gc globulin values did not differ between TFS and non-TFS in the 2-day intervals studied (P> .2).In this comparison of two prognostic markers in patients with non-acetaminophen-induced ALF, rising AFP but not rising Gc levels was associated with number NCT00004467.

    View details for DOI 10.1111/liv.14216

    View details for PubMedID 31421008

  • Data Uncertainty in Markov Chains: Application to Cost-Effectiveness Analyses of Medical Innovations OPERATIONS RESEARCH Goh, J., Bayati, M., Zenios, S. A., Singh, S., Moore, D. 2018; 66 (3): 697–715
  • Self-Limited Sepsis Syndrome Following Fecal Microbiota Therapy for Refractory C. difficile Infection. Digestive diseases and sciences Singh, S., Jing, E., Stollman, N. 2016; 61 (9): 2488-2491

    View details for DOI 10.1007/s10620-015-3955-7

    View details for PubMedID 26541990

  • Improvements in hepatic serological biomarkers are associated with clinical benefit of intravenous N-acetylcysteine in early stage non-acetaminophen acute liver failure. Digestive diseases and sciences Singh, S., Hynan, L. S., Lee, W. M. 2013; 58 (5): 1397-1402


    N-acetylcysteine (NAC) improves transplant-free survival in early coma grade (I-II) patients with non-acetaminophen induced acute liver failure (ALF). We determined whether the clinical benefit was associated with improvements in hepatic function.In a prospective, double blind trial, 173 ALF patients without evidence of acetaminophen overdose were stratified by coma grade (I-II vs. III-IV) and randomly assigned to receive either intravenous NAC or dextrose (placebo) for 72 h, resulting in four patient groups. INR, ALT, bilirubin, creatinine, and AST obtained on admission (day 1) and subsequent days (days 2-4) were used for secondary analysis performed by fitting longitudinal logistic regression models to predict death or transplantation or transplantation alone.Treatment group and day of study in models including bilirubin or ALT were predictors of transplantation or death (maximum p < 0.03). Those patients with early coma grade who were treated with NAC showed significant improvement in bilirubin and ALT levels when compared to the other three groups (maximum p < 0.02 for NAC 1-2 vs. the 3 other treatments) when predicting death or transplantation. Treatment group, day of study, and bilirubin were predictors of transplantation (maximum p < 0.03) in ALF patients.The decreased risk of transplantation or death or of transplantation alone with intravenous NAC in early coma grade patients with non-acetaminophen induced ALF was reflected in improvement in parameters related to hepatocyte necrosis and bile excretion including ALT and bilirubin, but not in INR, creatinine, or AST. Hepatic recovery appears hastened by NAC as measured by several important lab values.

    View details for DOI 10.1007/s10620-012-2512-x

    View details for PubMedID 23325162

    View details for PubMedCentralID PMC3663882

  • Gastrointestinal Manifestations of Henoch-Schoenlein Purpura DIGESTIVE DISEASES AND SCIENCES Menon, P., Singh, S., Ahuja, N., Winter, T. A. 2013; 58 (1): 42-45

    View details for DOI 10.1007/s10620-012-2124-5

    View details for Web of Science ID 000314182900010

    View details for PubMedID 22451115

  • Cancer-Associated Aorto-Enteric Fistula DIGESTIVE DISEASES AND SCIENCES Singh, S., Ladabaum, U., Hovsepian, D. M., Triadafilopoulos, G. 2012; 57 (3): 625-629

    View details for DOI 10.1007/s10620-011-1945-y

    View details for Web of Science ID 000300578200005

    View details for PubMedID 22021052

  • The Clinical Utility and Limitations of Serum Carbohydrate Antigen (CA19-9) as a Diagnostic Tool for Pancreatic Cancer and Cholangiocarcinoma DIGESTIVE DISEASES AND SCIENCES Singh, S., Tang, S., Sreenarasimhaiah, J., Lara, L. F., Siddiqui, A. 2011; 56 (8): 2491-2496


    CA19-9 is a tumor marker for pancreatic cancer, cholangiocarcinoma, and other malignancies. However, its sensitivity and specificity is suboptimal in clinical practice, which we hypothesized limits its clinical utility.To evaluate the clinical utility and limitations of CA19-9 as a tumor marker.We performed a retrospective review of CA19-9 levels (U/ml) in 483 consecutive patients between 2006 and 2008 at two university hospitals. We abstracted clinical, radiographic, and pathological data and final diagnoses. Descriptive and non-parametric analyses were performed.Patients presenting with jaundice had the highest CA19-9 (420) compared to other complaints (<20) (p<0.01). The indications with the highest CA19-9 had evidence of biliary obstruction (71), liver mass (54), and pancreatic head mass (27) compared to other indications (<15) (p<0.01). The diagnoses with the highest CA19-9 (p<0.01) were cholangiocarcinoma (476), pancreatic cancer (161), and choledocholithiasis (138). Using a receiver operator curve to evaluate CA19-9, the area under the curve was 0.7 when evaluating all patients for pancreatic cancer or cholangiocarcinoma or patients with pancreatic head mass for pancreatic cancer.This study found that for pancreatic cancer and cholangiocarcinoma, CA19-9 had poor clinical utility as a tumor marker and did not change patient management. Elevations in CA19-9 were associated with biliary obstruction based on clinical history, laboratory data, and diagnoses.

    View details for DOI 10.1007/s10620-011-1709-8

    View details for Web of Science ID 000293296100040

    View details for PubMedID 21516323

  • Multimedia article. Sphincterotome stricturoplasty for long ampullary stenoses and benign biliary strictures (with video). Surgical endoscopy Tang, S., Singh, S., Singh, S. 2011; 25 (4): 1313-1318


    Long ampullary stenoses and fibrotic distal biliary strictures are not infrequently encountered during endoscopic retrograde cholangiopancreatography (ERCP). Instead of balloon dilation and stenting, we propose that these strictures can be managed with sphincterotome stricturoplasty (SS) during the initial ERCP.To report our clinical experience with SS for benign distal biliary strictures.Review on prospectively collected data.All (consecutive) patients who underwent ERCP and SS performed by the authors in a 12-month period. Long ampullary stenosis and/or distal biliary stricture is defined as significant narrowing of CBD from the level of duodenal wall into the common bile duct (CBD) after initial sphincterotomy. The upstream CBD is dilated. Despite adequate ES, contrast drainage is poor due to the downstream stricture. SS was performed using the same sphincterotome in slightly bowed position under endoscopic and fluoroscopic guidance. The cutting wire was placed parallel to the superior border within the stricture and incising the stenosis. In cases of relatively long strictures, during initial SS the majority of the cutting wire was inside the biliary opening. This differs from ES, where about one-third to one-half of the length of cutting wire is outside the ampulla.Clinical data, hospital course, procedure-related complication rates, and outcomes were prospectively collected in a database.During the study period, 308 ERCPs were performed. Benign and short (≤15 mm in length) distal biliary strictures were observed in 25 patients. Mean ± SD stricture length was 7.4 ± 3.0 mm. The presumed etiologies for these strictures were choledocholithiasis (n = 22) and postsphincterotomy stenosis (n = 3). There was no perforation, post-ERCP pancreatitis, postsphincterotomy bleeding, or cholangitis. To date, none of these patients who had SS have needed follow-up ERCP.Single-operator experience, limited follow-up period.Compared with balloon stricturoplasty ± biliary stenting, SS is a simple and cost-effective alternative option in managing long ampullary stenosis and/or distal fibrotic biliary stricture during the initial ERCP.

    View details for DOI 10.1007/s00464-010-1340-3

    View details for PubMedID 20835718

  • Acute Pancreatitis During Pregnancy CLINICAL GASTROENTEROLOGY AND HEPATOLOGY Tang, S., Rodriguez-Frias, E., Singh, S., Mayo, M. J., Jazrawi, S. F., Sreenarasimhaiah, J., Lara, L. F., Rockey, D. C. 2010; 8 (1): 85-90


    Acute pancreatitis is rare during pregnancy; limited data are available about maternal and fetal outcomes. We investigated the effects of acute pancreatitis during pregnancy on fetal outcome.This retrospective cohort study, performed at a single academic center, included consecutive pregnant women who presented with (n = 96) or developed acute pancreatitis in the hospital (n = 7) in 2000-2006 (mean age, 26 y). Patient histories and clinical data were collected from medical records.Of the 96 patients with spontaneous pancreatitis, 4 had complications: 1 patient in the first trimester had acute peripancreatic fluid collection, and 3 patients in the third trimester developed disseminated vascular coagulation (DIC). None of these patients achieved term pregnancy, and 1 of the patients with DIC died. Endoscopic retrograde cholangiopancreatography (ERCP) was performed in 23 patients with acute pancreatitis; post-ERCP pancreatitis was diagnosed in 4 patients (a total of 11 patients developed ERCP-associated pancreatitis). Term pregnancy was achieved in 73 patients (80.2%). Patients who developed pancreatitis in the first trimester had the lowest percentage of term pregnancy (60%) and highest risks of fetal loss (20%) and preterm delivery (16%). Of the patients with pancreatitis in the second and third trimesters, only one had fetal loss. Fetal malformations were not observed.The majority of pregnant patients with acute pancreatitis did not have complications; most adverse fetal outcomes (fetal loss and preterm delivery) occurred during the first trimester. Acute pancreatitis, complicated by DIC, occurred most frequently in the third trimester and was associated with poor fetal and maternal outcomes.

    View details for DOI 10.1016/j.cgh.2009.08.035

    View details for Web of Science ID 000277420800019

    View details for PubMedID 19747985

  • Liver test patterns in patients with acute calculous cholecystitis and/or choledocholithiasis ALIMENTARY PHARMACOLOGY & THERAPEUTICS Padda, M. S., Singh, S., Tang, S. J., Rockey, D. C. 2009; 29 (9): 1011-1018


    Liver tests are utilized to determine the presence of biliary obstruction.To examine our hypothesis that liver tests aid in elucidating whether patients have simple calculous cholecystitis (ACC) or choledocholithiasis (CDL).We performed a retrospective study of patients admitted to two University of Texas Southwestern teaching hospitals with a clinical picture consistent with 'acute gallstone disease', i.e. cholecystitis +/- choledocolithiasis. The presence of ACC and CDL was based on defined clinical criteria.The cohort consisted of 154 patients meeting specific entry criteria, primarily with right upper quadrant pain; 62 ACC, 79 both ACC and CDL and 13 CDL alone. Approximately 30% of patients with ACC had abnormal alkaline phosphatase (ALP) and/or bilirubin level and approximately 50% had abnormal aminotransferase levels. Among patients with ACC/CDL, 77% had abnormal ALP, 60% had abnormal bilirubin and 90% had abnormal aminotransferase levels. By multivariate analysis, increasing common bile duct size and an abnormal ALP and alanine aminotransferase (ALT) were excellent predictors of having ACC with CDL.Liver test patterns can aid in elucidating CDL, including in ACC patients. Fundamentally, patients with CDL were more likely to have more abnormal liver tests, whether they had CDL only, or CDL and ACC. A dilated CBD, and abnormal ALP and ALT had modest sensitivity and high specificity for identification of patients with ACC and CDL.

    View details for DOI 10.1111/j.1365-2036.2009.03956.x

    View details for Web of Science ID 000264823000011

    View details for PubMedID 19210291

  • Impact of the hepatitis B virus genotype on pre- and post-liver transplantation outcomes LIVER TRANSPLANTATION Gaglio, P., Singh, S., Degertekin, B., Ishitani, M., Hussain, M., Perrillo, R., Lok, A. S. 2008; 14 (10): 1420-1427


    Emerging data suggest that the hepatitis B virus (HBV) genotype and the precore and core promoter variants impact the outcome of orthotopic liver transplantation (OLT) for hepatitis B. The aim of this study was to determine if there is a correlation between HBV genotype, precore and core promoter variants, and pre- and post-OLT outcomes. Serum samples from patients participating in the National Institutes of Health HBV-OLT study were tested for HBV genotype and precore and core promoter variants. A total of 123 patients were studied: 43% were Asians, 46% were Caucasians, and 8% were African Americans. HBV genotypes A (35%) and C (35%) were the most prevalent, followed by genotypes D and B. Precore and core promoter variants were detectable in 44% and 90% of patients. Patients with genotype C were more likely to have hepatocellular carcinoma (HCC) at listing (P < 0.001). Waitlist mortality was highest among patients with genotype D, while posttransplant mortality was highest among patients with genotype C. Precore or core promoter variants did not correlate with pre- or post-OLT survival. In conclusion, in this US patient population, patients with genotype C were more likely to have HCC at the time of transplant listing and to die after transplant than patients with non-C genotypes. Patients with genotype D had the highest posttransplant survival, but this was offset by higher waitlist mortality. Our study suggests that HBV genotypes but not precore or core promoter variants may have an impact on pre- and post-OLT outcomes of hepatitis B patients.

    View details for DOI 10.1002/lt.21563

    View details for Web of Science ID 000259800300007

    View details for PubMedID 18825703

  • Adolescent salvia substance abuse ADDICTION Singh, S. 2007; 102 (5): 823-824


    Salvia divinorum is a non-water-soluble hallucinogen that is becoming increasingly popular among adolescents. Salvia is a highly selective full agonist of primate and cloned human cerebral kappa-opioid receptors, although its psychotomimetic effects are similar to serotonergic agonists and NMDA glutamate antagonists. Salvia has been associated with depersonalization, laughter, feelings of levitation and self-consciousness. These effects resolve within 30 minutes following use. Salvia has been banned in many countries, although it remains legal and easily assessable over the internet in the United States.A 15-year-old man with a history of salvia and marijuana use presented to psychiatric emergency services with acute onset of mental status changes characterized by paranoia, déjà vu, blunted affect, thought blocking and slow speech of 3 days' duration.There is limited literature discussing the clinical effects of salvia use. Based on this case presentation, salvia use may be associated with many undocumented long-term effects such as déjà vu. The ease of use and increasing popularity of salvia requires further investigation into the clinical effects of salvia use.

    View details for DOI 10.1111/j.1360-0443.2007.01810.x

    View details for Web of Science ID 000245811300022

    View details for PubMedID 17493110