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

  • Board Certification: Gastroenterology, American Board of Internal Medicine (2013)
  • Board Certification: Internal Medicine, American Board of 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

  • 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

  • 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

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