Dr. Poullos is a native of Stockton California. He attended Santa Clara University where he earned his BS in Biology. He received his M.D. degree at the University of Texas Medical School at Houston, after which he did Internal Medicine residency at the University of California-San Francisco, finishing in 2002. He stayed at UCSF as a Gastroenterology fellow until 2004. However, after a spinal cord injury, he decided to retrain in Radiology. He did his Radiology residency at Stanford University, where he also completed a fellowship In Body Imaging in 2009. Dr. Poullos is now faculty in both the departments of Radiology and Gastroenterology and Hepatology. His clinical practice is at the Stanford University Medical Center, where he interprets CT, MRI, and ultrasound primarily of the abdomen and pelvis. His interests include radiology of the acute abdomen, hepatobiliary imaging, and colorectal cancer screening.
Dr. Poullos served as Associate Residency Program Director for the Stanford University Radiology Residency from 2009 through 2016. He now serves on the Stanford School of Medicine Faculty Senate, and is a member of the School of Medicine Teaching and Mentoring Academy. He also has a strong interest in medical education, and enjoys the opportunity to teach medical students, residents, and fellows.
- Body Imaging
- Diagnostic Radiology
- virtual colonoscopy
- Gastrointestinal Diseases
- Hepatobiliary Imaging
- Pancreatic imaging
- Imaging of the acute abdomen
- Acute appendicitis imaging
Clinical Associate Professor, Radiology
Clinical Associate Professor, Medicine - Gastroenterology & Hepatology
Associate Residency Program Director, Stanford University Radiology Residency (2009 - 2016)
Honors & Awards
Certificate of Merit, Radiological Society of North America (2010)
Alpha Omega Alpha, University of Texas at Houston (1998)
Boards, Advisory Committees, Professional Organizations
Senator, School of Medicine Faculty Senate (2018 - Present)
Member, Stanford Radiology Diversity Committee (2018 - Present)
Member, Stanford Medicine Teaching and Mentoring Academy (2016 - Present)
Body Division Representative, Radiology Professional Practice Evaluation Committee (PPEC) (2011 - Present)
Member, Society of Abdominal Radiology (2010 - Present)
Member, American College of Radiology (2004 - Present)
Member, Radiological Society of North America (2004 - Present)
Member, Association of Program Directors in Radiology (2010 - 2015)
Member, Association of University Radiologists (2009 - 2015)
Member, Alliance of Clinician Educators in Radiology (2009 - 2015)
Fellowship:Stanford University Medical Center (2009) CA
Residency:Stanford University Hospital (2008) CA
Fellowship:Univ of California San Francisco (2003) CA
Residency:University of California at San Francisco School of Medicine (2002) CA
Medical Education:University of Texas Medical School at Houston Registrar (1999) TX
Board Certification: Diagnostic Radiology, American Board of Radiology (2008)
Board Certification, American Board of Internal Medicine, Internal Medicine (2002)
Prediction of pancreatic cancer surgical outcomes and prognosis based on an objective resectability scoring system
2018 Gastrointestinal Cancers Sysmposium (GI-ASCO)
View details for DOI 10.1200/JCO.2018.36.4_suppl.446
Predicting Pancreatic Cancer Resectability and Outcomes Based on an Objective Quantitative Scoring System.
; 48 (5): 622–28
To quantitatively assess the probability of tumor resection based on measurements of tumor contact with the major peripancreatic vessels.This is a retrospective cohort study of pancreatic cancer patients treated between January 2001 and December 2015 in a single academic comprehensive cancer center. Radiographic measurements of the circumferential degree and length of solid tumor contact with major peripancreatic vessels were obtained from diagnostic pancreatic protocol computed tomography images and tested for correlation with tumor resection and margin status.Of 294 patients analyzed, 113 (38%) were resected, with 71 (63%) with negative margins. Based on the individual measurements of vascular involvement, a resectability scoring system (RSS) was created. The RSS correlated strongly with resection (P < 0.0001) and R0 resection (P < 0.0001) probabilities. Moreover, the RSS correlated with overall survival (P < 0.0001) and metastasis-free survival (P < 0.0001), being able to substratify resectable (P = 0.022) and unresectable patients (P = 0.014) into subgroups with different prognosis based on RSS scores.Based on a comprehensive and systematic quantitative approach, we developed a scoring system that demonstrated excellent accuracy to predict tumor resection, surgical margin status, and prognosis.
View details for PubMedID 31091207
Structured Reporting of Multiphasic CT for Hepatocellular Carcinoma: Effect on Staging and Suitability for Transplant.
AJR. American journal of roentgenology
The purpose of this study is to evaluate whether use of a standardized radiology report template would improve the ability of liver transplant surgeons to diagnose stage T2 hepatocellular carcinoma (HCC) and determine patient suitability to undergo orthotopic liver transplant (OLT).In this retrospective study, a standardized template was devised, and its use was mandated for reporting of liver CT findings for patients with cirrhosis and HCC. Two surgeons analyzed 200 reports (100 before and 100 after template implementation) for descriptions of cirrhosis, portal hypertension, lesion enhancement characteristics, tumor thrombus, portal and superior mesenteric vein patency, and Organ Procurement Transplantation Network (OPTN) class. Ability to determine Milan criteria and surgeon satisfaction were also assessed. Data obtained before and after template implementation were statistically analyzed using the Cochran-Mantel-Haenszel test.Template implementation increased the percentage of reports documenting the presence or absence of portal hypertension (74% to 88% for surgeon 1 and 86% to 87% for surgeon 2; p = 0.042); lesion number (76% to 88% for surgeon 2 [no change for surgeon 1]; p = 0.038), size (95% to 96% for surgeon 1 and 82% to 93% for surgeon 2; p = 0.03), and enhancement (93% to 94% for surgeon 1 and 80% to 91% for surgeon 2; p = 0.049); presence of tumor thrombus (10% to 57% for surgeon 1 and 31% to 63% for surgeon 2; p < 0.001); and OPTN class (8% to 82% for surgeon 1 and 2% to 81% for surgeon 2; p < 0.001). The surgeons were significantly more able to determine the presence of T2 disease and qualification for exception points after implementation of the template (increasing from 80% to 94%; p = 0.025). Satisfaction with reports also improved (p < 0.0001).The reporting template improved determination of patient suitability to undergo transplant according to the Milan criteria.
View details for PubMedID 29470153
Assessing local progression after stereotactic body radiation therapy for unresectable pancreatic adenocarcinoma: CT versus PET.
Practical radiation oncology
2017; 7 (2): 120-125
Evaluation of local tumor progression (LP) has typically been defined by contrast-enhanced computed tomography (CT) imaging after stereotactic body radiation therapy (SBRT) for locally advanced pancreatic cancer (PDAC). The purpose of this study is to determine the benefit of adding 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging to CT for LP assessment of PDAC after SBRT.We retrospectively reviewed pretreatment, follow-up images, and outcomes of all patients treated with definitive SBRT for unresectable PDAC between December 2002 and December 2015 at our institution. For each patient, we independently analyzed LP both by CT and by FDG-PET criteria, using the Response Evaluation Criteria In Solid Tumors version 1.1 and the FDG-PET Response Evaluation Criteria In Solid Tumors version 1.0, respectively.Among 206 patients treated with definitive SBRT for unresectable PDAC, we identified 30 with LP on follow-up. Four did not undergo follow-up FDG-PET. Median time to LP after SBRT was 7.5 months (range, 2-25 months). Of the 26 patients with LP who had follow-up FDG-PET, 21 were diagnosed by FDG-PET (80.7%), 14 by CT (53.8%), and 9 by both FDG-PET and CT (34.6%). Use of CT alone revealed only 53.8% of cases of LP detected when FDG-PET and CT were combined. The cumulative incidence of LP, based on competing risk of death, at 1 and 2 years after SBRT was 9.6% and 16.7% by CT and 11% and 29.1% by FDG-PET, respectively.FDG-PET increases the chance of detecting LP of unresectable PDAC after SBRT and can have an important impact on reported outcomes. We recommend obtaining FDG-PET to assess treatment response when evaluating efficacy of SBRT and taking its use into account when comparing clinical data.
View details for DOI 10.1016/j.prro.2016.09.002
View details for PubMedID 28274396
Factitious Disorder Presenting with Attempted Simulation of Fournier's Gangrene.
Journal of radiology case reports
2016; 10 (9): 26-34
Fournier's gangrene is a severe polymicrobial necrotizing fasciitis of the perineal, genital, or perianal regions. The classic presentation is severe pain and swelling with systemic signs. Crepitus and cutaneous necrosis are often seen. Characteristic CT findings include subcutaneous gas and inflammatory stranding. Unless treated aggressively, patients can rapidly become septic and die. Factitious Disorder is the falsification of one's own of medical or psychological signs and symptoms. Many deceptive methods have been described, from falsely reporting physical or psychological symptoms, to manipulating lab tests, or even injecting or ingesting foreign substances in order to induce illness. We present a case of a 35-year-old man with factitious disorder who attempted to simulate Fournier's gangrene by injecting his scrotum with air and fluid. We will review the clinical presentation and diagnosis of Factitious Disorder, as well as Fournier's gangrene.
View details for PubMedID 27761196
Predictors of appendicitis on computed tomography among cases with borderline appendix size.
2015; 22 (4): 385-394
Confident diagnosis of appendicitis when the appendix is borderline (6 to 7 mm) in size can be challenging. This retrospective study assessed computed tomography (CT) findings that are most predictive of appendicitis when the appendix is borderline in diameter. Three radiologists conducted separate, blind retrospective reviews of 105 contrast-enhanced CTs with borderline appendices. Presence or absence of appendicitis was confirmed by chart review of clinical or surgical outcomes. Logistic regression was used to determine the odds ratio (OR) and the receiver operating characteristic for CT features predictive of appendicitis. Absence of intraluminal air (OR = 5.11, p < 0.001), wall hyperemia (OR = 3.92, p = 0.002), wall thickening (OR = 29.7, p < 0.001), and fat stranding (OR = 3.85, p = 0.003) were significant findings in univariate logistic regression. Using a multivariate model, we found that the absence of intraluminal air (OR = 6.04, p = 0.002) and wall thickening (OR = 24.6, p < 0.001) remained statistically significant and were unaffected by adjustment for gender and pediatric age. The area under the curve was significantly greater for the multivariate model than the initial, clinical CT impressions (p = 0.024). The combination of wall thickening and absence of intraluminal air was 92.6 % (95 % CI 75.7-99.1) sensitive and 82.4 % (95 % CI 65.5-93.2) specific for appendicitis. Wall thickening and the absence of intraluminal air are prominent predictors of appendicitis and, if present together, these features may aid in identifying appendicitis on CT when the appendix is borderline in size.
View details for DOI 10.1007/s10140-015-1297-6
View details for PubMedID 25687166
Ischemic colitis due to a mesenteric arteriovenous malformation in a patient with a connective tissue disorder.
Journal of radiology case reports
2014; 8 (12): 9-21
Ischemic colitis is a rare, life-threatening, consequence of mesenteric arteriovenous malformations. Ischemia ensues from a steal phenomenon through shunting, and may be compounded by the resulting portal hypertension. Computed tomographic angiography is the most common first-line test because it is quick, non-invasive, and allows for accurate anatomic characterization. Also, high-resolution three-dimensional images can be created for treatment planning. Magnetic resonance angiography is similarly sensitive for vascular mapping. Conventional angiography remains the gold standard for diagnosis and also allows for therapeutic endovascular embolization. Our patient underwent testing using all three of these modalities. We present the first reported case of this entity in a patient with a vascular connective tissue disorder.
View details for DOI 10.3941/jrcr.v8i12.1843
View details for PubMedID 25926912
View details for PubMedCentralID PMC4394977
Pancreatic neuroendocrine tumours: hypoenhancement on arterial phase computed tomography predicts biological aggressiveness.
2014; 16 (4): 304-311
Contrary to pancreatic adenocarcinoma, pancreatic neuroendocrine tumours (PNET) are commonly hyperenhancing on arterial phase computed tomography (APCT). However, a subset of these tumours can be hypoenhancing. The prognostic significance of the CT appearance of these tumors remains unclear.From 2001 to 2012, 146 patients with well-differentiated PNET underwent surgical resection. The degree of tumour enhancement on APCT was recorded and correlated with clinicopathological variables and overall survival.APCT images were available for re-review in 118 patients (81%). The majority had hyperenhancing tumours (n = 80, 68%), 12 (10%) were isoenhancing (including cases where no mass was visualized) and 26 (22%) were hypoenhancing. Hypoenhancing PNET were larger, more commonly intermediate grade, and had higher rates of lymph node and synchronous liver metastases. Hypoenhancing PNET were also associated with significantly worse overall survival after a resection as opposed to isoenhancing and hyperenhancing tumours (5-year, 54% versus 89% versus 93%). On multivariate analysis of factors available pre-operatively, only hypoenhancement (HR 2.32, P = 0.02) was independently associated with survival.Hypoenhancement on APCT was noted in 22% of well-differentiated PNET and was an independent predictor of poor outcome. This information can inform pre-operative decisions in the multidisciplinary treatment of these neoplasms.
View details for DOI 10.1111/hpb.12139
View details for PubMedID 23991643
Taller Haustral Folds in the Proximal Colon: A Potential Factor Contributing to Interval Colorectal Cancer?
78th Annual Scientific Meeting of the American-College-of-Gastroenterology
NATURE PUBLISHING GROUP. 2013: S628–S628
View details for Web of Science ID 000330178102396
Current techniques in the performance, interpretation, and reporting of CT colonography.
Gastrointestinal endoscopy clinics of North America
2010; 20 (2): 169-192
The technical objective of computed tomographic colonography (CTC) is to acquire high-quality computed tomography images of the cleansed, well-distended colon for polyp detection. In this article the authors provide an overview of the technical components of CTC, from preparation of the patient to acquisition of the imaging data and basic methods of interpretation. In each section, the best evidence for current practices and recommendations is reviewed. Each of the technical components must be optimized to achieve high sensitivity in polyp detection.
View details for DOI 10.1016/j.giec.2010.02.007
View details for PubMedID 20451809
MR colonography and MR enterography.
Gastrointestinal endoscopy clinics of North America
2010; 20 (2): 323-346
The bowel is a common site for pathologic processes, including malignancies and inflammatory disease. Colorectal cancer accounts for 10% of all new cancers and 9% of cancer deaths. A significant decrease in the incidence of colorectal cancer and cancer death rates has been attributed to screening measures, earlier detection, and improved therapies. Virtual colonoscopy (VC), also known as computed tomography colonography, is an effective method for detecting polyps. However, in light of increasing concerns about ionizing radiation exposure from medical imaging and potential increased risk of future radiation-induced malignancies, magnetic resonance imaging (MRI) is seen as an increasingly attractive alternative. Improvements in MRI technology now permit three-dimensional volumetric imaging of the entire colon in a single breath hold at high spatial resolution, making VC with MRI possible.
View details for DOI 10.1016/j.giec.2010.02.010
View details for PubMedID 20451820
Gastrointestinal Amyloidosis: Approach to Treatment.
Current treatment options in gastroenterology
2003; 6 (1): 17–25
The main treatment goals in amyloidosis are twofold: 1) to diagnose the underlying disease state accurately to guide effective primary therapy (if available) and 2) to ameliorate symptoms. The correct diagnosis is essential because disease-modifying therapies vary widely according to the underlying primary pathology. Primary treatment options remain limited. The best evidence is for high-dose chemotherapy, followed by autologous stem cell transplantation in patients with primary systemic amyloidosis. High-flux hemodialysis (HD) may prevent HD-related amyloidosis. Liver transplantation may be an option for patients with familial amyloidotic polyneuropathy. Several novel specific therapies are under investigation, including small molecule drugs and vaccines. Their efficacy and safety in humans remain to be demonstrated. In the absence of specific cures, symptom-directed therapy assumes a paramount role and can improve quality of life by mitigating diarrhea or pain, for example.
View details for PubMedID 12521568