What’s new in Gastrointestinal Imaging – September 2020

8 months ago

 

Diagnostic Utility of CT and Fluoroscopic Esophagography for Suspected Esophageal Perforation in the Emergency Department

Wei CJ, Levenson RB, Lee KS.

Diagnostic Utility of CT and Fluoroscopic Esophagography for Suspected Esophageal Perforation in the Emergency Department [published online ahead of print, 2020 Jun 9].

AJR Am J Roentgenol. 2020;1-8.

https://doi.org/10.2214/ajr.19.22166

This retrospective study evaluates the utility of CT and fluoroscopic esophagrams in diagnosing esophageal perforation. The article begins by discussing the importance of identifying esophageal perforation, with mortality approaching 60% if treatment is delayed. Clinical symptoms of perforation are nonspecific, which makes imaging an important component in diagnosis. Fluoroscopy is often regarded as the imaging study of choice, however, it has logistic limitations such as requiring appropriate staff, which may be limited overnight, and can be limited by the patient’s inability to follow instructions. Additionally, there is a risk of aspiration, which may lead to additional invasive testing such as bronchoscopy. A fluoroscopic exam may be considered positive for perforation if there is contrast extravasation outside the esophageal lumen.  CT avoids many of these logistic limitations, and has the advantage of providing more information about the mediastinum and thorax. Given its accessibility, CT is often the initial study in a patient presenting with suspected perforation.

The authors looked at all 103 patients over 17 years who had both a CT and esophagram done within one day of presenting to their emergency department with concern of esophageal perforation. CT findings included the presence of any of the following: air in the esophageal wall, esophageal wall defect, and extraluminal oral contrast. Of this population, 9 had confirmed perforations, which demonstrates the rarity of perforations given the study time frame. The study found that CT was 100% sensitive for diagnosing perforation, 80% specific, with  32% PPV and 100% NPV. Fluoroscopy was 78% sensitive, 99% specific, with 88% PPV, with 88% PPV and 98% NPV. The findings suggest CT is more sensitive than fluoroscopy, and if a patient has a negative CT, fluoroscopy is unlikely to demonstrate perforation.

 

Imaging of appendicitis: Tips and tricks

Monsonis B, Mandoul C, Millet I, Taourel P.

Imaging of appendicitis: Tips and tricks [published online ahead of print, 2020 Jul 8].

Eur J Radiol. 2020;130:109165.

https://doi.org/10.1016/j.ejrad.2020.109165

This review article gives an in-depth look at one of the most common worldwide surgical emergencies, acute appendicitis. Clinically and radiologically, acute appendicitis can have various presentations and complications; it is important for the radiologist to be aware of the manifestations of acute appendicitis. Imaging plays an important role in diagnosis, with the authors referencing studies that showed a 3% normal appendectomy rate when 99% of patients with suspected appendicitis were imaged, as opposed to a 21% normal appendectomy rate when only 33% of patients were imaged. Ultrasound is the imaging modality of choice for children, pregnant women, and very thin patients, and the authors give tips for finding the appendix on ultrasound, starting with locating the ileocecal junction and then searching for a blind ending 2-3 cm from the ileocecal valve. The article discusses different CT protocols for evaluating the appendix, including focused CT on the lower abdomen, low-dose CT, and the utility of intravenous contrast. The authors mention that at their home institution, MRI is the second-line imaging after ultrasound for pregnant patients if results are equivocal. The article then reviews common imaging features of appendicitis, including appendiceal inflammatory wall thickening greater than 3 mm, dilation of the appendix, peri-appendicular fat stranding, and enlarged mesenteric lymph nodes. The article briefly mentions complications of acute appendicitis, which are important to identify as they affect patient management. The main complications include perforation, phlegmon, abscess, small bowel obstruction related to inflammation, and pylephlebitis, an infectious thrombophlebitis of the mesenteric vein or portal circulation.

 

Utilization Trends in Abdominal Imaging, 2004–2016

Kramer MR, Levin DC, Rao VM.

Utilization Trends in Abdominal Imaging, 2004-2016.

AJR Am J Roentgenol. 2020;215(2):420-424.

https://doi.org/10.2214/AJR.19.22524

This healthcare policy article analyzes recent trends in abdominopelvic imaging in the Medicare population. The authors examined publicly available documents published by the Center for Medicare Services to evaluate procedure volume, ordering provider specialty, and other administrative information. The study concluded that in the time period from 2004-2016, the utility of abdominal imaging decreased slightly. While rates of CT, CTA, and MRI increased, this was offset by a decrease in the use of radiographs, fluoroscopy, and nuclear medicine exams. Notably, from 2004 to 2016, the use of abdominal MRI increased from 8.5 to 15.4 studies per  1000 Medicare beneficiaries, an increase of 88%. The biggest decrease was in abdominal radiography, which lowered from 130 to 92 per 1000 Medicare beneficiaries. Ultrasound stayed relatively even, with a 1.5% increase over that same time. CT increased from 226 exams to 278 from 2004 to 2010, and then decreased to 159 per 1000 Medicare beneficiaries. This fluctuation can be attributed to the introduction of code bundling in 2011. Prior to that year, CTs of the abdomen and pelvis performed at the same time could be billed as two separate studies, and with code bundling had to be billed as one exam. Overall, abdominal imaging rates increased from 558 to 601 studies per 1000 Medicare beneficiaries from 2004 to 2010, and then decreased to 442 studies per 1000 beneficiaries in 2016.

 

The Lesser Sac and Foramen of Winslow: Anatomy, Embryology, and CT Appearance of Pathologic Processes

Elmohr MM, Blair KJ, Menias CO, et al.

The Lesser Sac and Foramen of Winslow: Anatomy, Embryology, and CT Appearance of Pathologic Processes [published online ahead of print, 2020 Aug 12].

AJR Am J Roentgenol. 2020;1-9.

https://doi.org/10.2214/AJR.19.22749

This review article details the anatomy, imaging features, and pathology of the lesser sac and the foramen of Winslow. The article begins by discussing the embryology of the lesser sac, arising as the stomach rotates during the fourth week of gestation. The article then describes the anatomy and boundaries of the lesser sac, bordered by multiple organs. The lesser sac is a potential space between the stomach and the pancreas involved in many disease processes and a conduit for the spread of disease within the peritoneal cavity. The article categories pathologies of the lesser sac into categories of fluid collections, space-occupying lesions, and internal hernias. The lesser sac is typically collapsed in healthy patients. Fluid collections may be transudative, such as simple ascites, or may be exudative and the result of an inflammatory or infectious condition of a nearby organ. Acute pancreatitis is the most common cause of fluid collection in the lesser sac, occurring in up to 50% of cases. Peripancreatic fluid collections may develop into pseudocysts over time, which often extends into the lesser sac. Bilomas and hematomas may also be seen, most commonly as the result of trauma. Masses of the lesser sac may be neoplastic. Metastases are more common than primary tumors, and are often associated with peritoneal carcinomatosis, with ovarian and gastrointestinal cancers being the most common source. Primary malignant tumors include liposarcoma, leiomyosarcoma, and GISTs. Benign tumors of the lesser sac include lymphangiomas and teratomas. Nonneoplastic conditions such as duplication cysts, splenic artery aneurysms, and more rarely abscesses and tuberculosis may manifest in the lesser sac. Lastly, internal herniation into the lesser sac may occur, almost always with small intestine herniating through the foramen of Winslow.

 

Multiple Endocrine Neoplasia: Spectrum of Abdominal Manifestations

Davila A, Menias CO, Alhalabi K, et al.

Multiple Endocrine Neoplasia: Spectrum of Abdominal Manifestations [published online ahead of print, 2020 Jul 13].

AJR Am J Roentgenol. 2020;1-11.

https://doi.org/10.2214/AJR.19.22542

This review article looks at the various subtypes of multiple endocrine neoplasia (MEN). The MEN syndromes are rare autosomal-dominant disorders that affect two or more endocrine glands. Abdominal manifestations are common to the MEN subtypes covered in this review. The main components of MEN 1 include parathyroid, pancreatic, and pituitary tumors, however, adrenocortical, carcinoid, and facial angiofibromas may also occur with increased frequency. Up to 80% of patients with MEN 1 will have a pancreatic neuroendocrine tumor, which are often highly vascular and seen on imaging as enhancing in the early arterial phase, and may be further categorized as solid or cystic. The article gives further imaging findings of PNETs by classification as gastrinomas, insulinomas, VIPomas, and somatostatinomas. MEN 2A is associated with medullary thyroid cancer, parathyroid glands, and pheochromocytomas, while MEN 2B is distinguished by the lack of parathyroid hyperplasia and the presence of non-endocrine features such as marfanoid habitus and mucosal neuromas. Abdominal imaging findings may additionally manifest with findings related to hormone oversecretion, such as decreased bone density, nephrolithiasis, and peptic ulcers. While radiologists may not make the diagnosis of MEN, delays in diagnosis of complications can affect management and prevent adequate surveillance, leading to significant morbidity and mortality.

 

Pancreatic necrosis volume – A new imaging biomarker of acute pancreatitis severity

Pamies-Guilabert J, Del Val Antoñana A, Collado JJ, Rudenko P, Meseguer A.

Pancreatic necrosis volume – A new imaging biomarker of acute pancreatitis severity [published online ahead of print, 2020 Jul 24].

Eur J Radiol. 2020;130:109193.

https://doi.org/10.1016/j.ejrad.2020.109193

There are several well-known severity scales that evaluate morbidity and mortality risk of acute pancreatitis using clinical data, and a few radiology grading systems that may be unreliable. The authors of this retrospective study show that quantification of pancreatic necrosis volume (PNV), as measured on CT, is a radiologic biomarker highly correlated with acute pancreatic complications. The authors evaluated 163 cases of acute pancreatitis in hospitalized patients over two years, and found PNV has a linear correlation with the time of hospital stay, as well as statistically significant associations with organ failure, infection, admission to ICU, and need for surgical or percutaneous intervention. The study found that when compared to four other severity scales, including the radiologic CT severity index and Balthazar scores, PNV was the most accurate parameter in predicting multiple organ failure, ICU admission, or the need for therapeutic procedure. Pancreatic necrosis was defined as areas of hypoattenuation of pancreatic parenchyma and any associated necrotic collections, and volume was calculated with the use of tools within their PACS system. The authors found a range of 0-1575 cc of necrosis in their cohort, with a mean of 242 cc and median of 64 cc. The threshold value for predicting complications was 75 cc, with this number achieving a sensitivity of 100% and specificity of 78%. Given the results of the study, the authors conclude that pancreatic necrosis volume is a reliable parameter for predicting complications of acute pancreatitis.

 

Evaluation of penetrating abdominal and pelvic trauma

Durso AM, Paes FM, Caban K, et al.

Evaluation of penetrating abdominal and pelvic trauma [published online ahead of print, 2020 Jul 24].

Eur J Radiol. 2020;130:109187.

https://doi.org/10.1016/j.ejrad.2020.109187

This review article begins by discussing the epidemiology behind penetrating trauma, which is the leading cause of deaths for the population younger than 44, and while blunt trauma makes up approximately 70% of those cases, penetrating trauma is still a significant source of morbidity and mortality. The authors categorize penetrating as ballistic, to include gunshot wounds, and non-ballistic, which includes stab and other puncture wounds. The article gives an overview of the science of wound ballistics, studying the behavior of projectiles within living tissue and injuries they can cause, discussing mechanisms of energy transfer leading to tissue injury. The review also mentions injury patterns seen in secondary blast injuries, which are caused by flying debris. The optimal trauma CT protocol is a controversial subject, with some advocates for triple contrast: IV, oral, and rectal, while some studies demonstrate efficacy of IV contrast only. It is important to note that when using enteric contrast, lack of extravasation does not exclude injury. The review then discusses CT findings which require therapy, and include arterial extravasation, contained vascular injuries such as pseudoaneurysms, and other major vascular injuries, intraperitoneal bladder rupture, and left hemi-diaphragmatic injury. The article goes on to give thorough insight on penetrating traumatic injuries of the different solid organs, and includes the American Association for the Surgery of Trauma classification systems for traumatic injuries. The widespread availability of CT has become a triage tool to aid trauma surgeons in selecting which hemodynamically stable patients will require surgery as opposed to non-operative management, confirming the importance of the radiologist as part of the trauma team.

 

A radiomics model of liver CT to predict risk of hepatic encephalopathy secondary to hepatitis B related cirrhosis

Cao JM, Yang JQ, Ming ZQ, et al.

A radiomics model of liver CT to predict risk of hepatic encephalopathy secondary to hepatitis B related cirrhosis [published online ahead of print, 2020 Jul 26].

Eur J Radiol. 2020;130:109201.

https://doi.org/10.1016/j.ejrad.2020.109201

This retrospective study was conducted with the intent of using radiomic data  from CT scans to build a model capable of predicting hepatic encephalopathy secondary to hepatitis B related cirrhosis. The article begins by discussing the epidemiology of hepatitis B, with 257 million worldwide carriers. Up to 20% of those patients will develop chronic hepatitis, who may then develop cirrhosis and the complications that goes along with it. Hepatic encephalopathy is one of the severe complications of cirrhosis, and has been shown to be a poor prognostic sign, with a negative impact on quality of life. The article then discusses the concept of radiomics, using imaging features to extract data into advanced algorithms in an attempt to characterize cellular features and clinical data. This study used triple-phase abdominal CT scans to extract data such as liver shape, orientation, convexity, roundness, coarseness, presence of ascites, and advanced data extracted by a software system to create their model. When combined with clinical value of serum albumin, the model was found to be up to 93% accurate in predicting the presence of hepatic encephalopathy in the 304 scanned patients. The study demonstrates yet another possibility in the rapidly evolving field of radiomics.

 

Abdominopelvic CT findings in patients with novel coronavirus disease 2019 (COVID‐19)

Goldberg-Stein S, Fink A, Paroder V, Kobi M, Yee J, Chernyak V.

Abdominopelvic CT findings in patients with novel coronavirus disease 2019 (COVID-19).

Abdom Radiol (NY). 2020;45(9):2613-2623.

https://doi.org/10.1007/s00261-020-02669-2

While the COVID-19 virus is most commonly associated with respiratory disease, this article examines abdominopelvic findings in patients with COVID-19. The article mentions that findings on an abdominal CT may be the first sign of COVID-19, as the lung bases are typically a part of the scan, and 57% of imaged patients had findings typical of COVID-19 in the lung bases. The study looked at 141 COVID-19 positive patients who had an abdominopelvic CT within two weeks of their positive test, and found 57% had positive findings. Reported clinical symptoms in COVID-19 positive patients include nausea, vomiting, and loose stools. In this retrospective study, the authors found the most common imaging abnormality to be mural thickening of the colon. Additional common findings were gallbladder distention, nonspecific renal stranding, and bladder wall thickening. Younger age, male gender, and lower hemoglobin levels were independent predictors of having positive CT findings. The authors state additional studies are required for further evaluation of abdominal findings, and acknowledge a limitation of their study that some of these findings may be due to chronic disease or unrelated to COVID-19.

 

Acute Appendicitis During Coronavirus Disease 2019 (COVID-19): Changes in Clinical Presentation and CT Findings

Romero J, Valencia S, Guerrero A.

Acute Appendicitis During Coronavirus Disease 2019 (COVID-19): Changes in Clinical Presentation and CT Findings.

J Am Coll Radiol. 2020;17(8):1011-1013.

https://doi.org/10.1016/j.jacr.2020.06.002

This article begins by noting several studies worldwide have demonstrated a trend of fewer patients presenting to emergency departments since the start of the coronavirus pandemic. with a significant increase in intensive care admission rates. Specifically addressing appendicitis, the authors have noted a similar trend, with fewer overall cases, but more cases with advanced presentations. The authors present a retrospective study comparing the same three month period in pre-pandemic 2019 and during the pandemic 2020. There were 141 CT scans performed in the 2019 period to evaluate for appendicitis, with 30% positive, and 55 scans  in the 2020 period, with 46% positive, a statistically significant increase. Additionally, the authors evaluated the severity of appendicitis by classifying the presentation into five categories, from probable appendicitis to complicated ruptured appendicitis. The intra-pandemic period found a statistically significant increase in proportion of severe cases when compared to before the pandemic. The authors believe the changes in presentation were due to their home country of Colombia issuing a mandatory stay-at-home order.

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