What’s new in Gastrointestinal Imaging – April 2021

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Trends in Use of Diagnostic Imaging for Abdominal Pain in U.S. Emergency Departments 

Wang RC, Kornblith AE, Grupp-Phelan J, Smith-Bindman R, Kao LS, Fahimi J.  

AJR Am J Roentgenol. 2021 Jan;216(1):200-208. doi: 10.2214/AJR.19.22667. Epub 2020 Nov 19. PMID: 33211574. 

This article discusses the epidemiology of abdominal pain, which may be due to a large number of etiologies, and accounts for 7% of all visits to the emergency room in the US, approximately 208 million annually, the third most frequent reason. The authors then examine trends in emergency department imaging for children presenting with abdominal pain, and specifically with concerns for appendicitis. The authors retrospectively analyzed the National Hospital Ambulatory Medical Care Survey to obtain data from 1997-2016. Among emergency room visits for abdominal pain, approximately 2.5% resulted in a diagnosis of appendicitis. In 1997, the first year of data analyzed, 1.2% of children presenting with abdominal pain received a CT scan, and 4.3% underwent ultrasound. The CT percentage increased each year until a peak at 16.6% followed by a slight decrease, with 14.7% in the final year of data, 2016. Ultrasound has gradually increased year over year, to 15.9% in 2016. The authors hypothesize the decrease in CT usage may be related to increased efforts to minimize pediatric radiation, and advancements in diagnostic capabilities of ultrasound. The authors also found that in dedicated pediatric facilities, usage of CT was significantly lower. 

 

Prevalence of Appendicoliths Detected at CT in Adults With Suspected Appendicitis 

Ranieri DM, Enzerra MD, Pickhardt PJ.  

AJR Am J Roentgenol. 2021 Mar;216(3):677-682. doi: 10.2214/AJR.20.23149. Epub 2021 Jan 21. PMID: 33474985. 

This study evaluates the relationship between appendicoliths and patients with appendicitis. The article retrospectively examined 248 patients with surgically proven appendicitis. Appendicoliths have been shown to have an association with complications in appendicitis, such as perforation and abscess formation. While simple appendicitis may sometimes be treated conservatively with antibiotics, the article mentions that some surgeons consider the presence of an appendicolith to be a contraindication to conservative therapy, requiring operative management. In 248 cases of appendicitis, an appendicolith was present in 96, approximately 39%. Appendicoliths were associated with increased inflammatory changes, and statistically significant predictors of perforation. The article mentions that one of the main limitations of their study happened in patients who received oral contrast, which can obscure appendicoliths. In conclusion, the article state that appendicoliths occurred ten times more frequently than in patients without appendicitis. 

 

Abdominal Imaging Manifestations of Recreational Drug Use 

Mansour J, Zulfiqar M, Umer A, Zurcher KS, Heeger A, Menias CO.  

Radiographics. 2020 Nov-Dec;40(7):1895-1915. doi: 10.1148/rg.2020200048. Epub 2020 Oct 16. PMID: 33064622. 

Recreational drug use is a worldwide issue, and patients may seek medical care due to a variety of symptoms or complications. Complications may be due to the toxic effects of the drug, impurities, or nonsterile injection. A diverse range of abdominal complications may be seen with imaging. While none of the imaging findings may be pathognomonic for drug use, they should be considered in otherwise healthy patients presenting with an acute complaint. The article starts by discussing the epidemiology of drug use, and which drugs are the most common, with cannabinoids leading the way. Cannabinoids may cause delayed gastric emptying, acute pancreatitis, and duodenal ulcers, and has been associated with increased risk in germ cell, bladder, and prostate cancers. Cocaine is associated with abdominal organ infarcts due to its vasoconstrictive properties, as well as aortic vasospasm and dissection, priapism, and intraperitoneal hemorrhage. Opiates may result in fecal impaction and acute hepatitis infected pseudoaneurysms, and septic thrombophlebitis from injection. Injection drugs may result in septic emboli, cellulitis, soft tissue abscesses, and retained needle fragments. Amphetamines may result in bowel ischemia, gastric ulcers, renal infarcts, and intraperitoneal hemorrhage. The article also discusses how to identify “body packers,” by recognizing the appearance of drug packets within the GI tract. 

 

Gas Where It Shouldn’t Be! Imaging Spectrum of Emphysematous Infections in the Abdomen and Pelvis 

Nepal P, Ojili V, Kaur N, Tirumani SH, Nagar A.  

AJR Am J Roentgenol. 2021 Mar;216(3):812-823. doi: 10.2214/AJR.20.23545. Epub 2021 Jan 13. PMID: 33439049. 

Emphysematous infections of the abdomen and pelvis are associated with high morbidity and mortality, requiring urgent intervention. CT can provide a definitive diagnosis in most cases, and help depict the extent of involvement. The article provides an overview of the most common gas-forming organisms, and discusses epidemiology of emphysematous infections, most commonly in diabetic patients. The article discusses imaging manifestations of emphysematous cholecystitis, which carries an elevated risk of perforation, emphysematous hepatitis, with mortality close to 100%, as well as emphysematous gastritis, pancreatitis, aortitis, pyelonephritis, cystitis, prostate abscesses, soft tissue infections. These are all rapidly progressing infections associated with higher mortality rates when compared to the non-emphysematous pathologies, which enforces the importance of detecting subtle and early findings. 

 

CT Esophagography for Evaluation of Esophageal Perforation 

Norton-Gregory AA, Kulkarni NM, O’Connor SD, Budovec JJ, Zorn AP, Desouches SL.  

Radiographics. 2021 Mar-Apr;41(2):447-461. doi: 10.1148/rg.2021200132. Epub 2021 Feb 12. PMID: 33577418. 

While fluoroscopic esophagography is the imaging study of choice for evaluation of esophagraphic injury, CT esophagraphy is gaining support for evaluation in the emergent setting. This Radiographics article begins by discussing the epidemiology and different types of esophageal injuries, which may carry a mortality of as high as 20%. The article then introduces protocols of a CT esophagram, which includes a precontrast phase, supine post-contrast imaging after the administration of water-soluble oral contrast, and prone postcontrast imaging. The authors state at their institution they mix oral contrast with a thickening agent, with scanning performed immediately after drinking oral contrast. IV contrast may also be used as indicated. Some centers may also give effervescent granules to expand the esophagus. Prone imaging may be used in cases of suspected anterior esophageal perforation. CT esophagram has the advantage of easier availability of CT when compared to fluoroscopy, but is limited by poor demonstration of mucosal detail as opposed to fluoroscopy.  

 

Ligament of Treitz: Anatomy, Relevance of Radiologic Findings, and Radiologic-Pathologic Correlation 

Nassar S, Menias CO, Palmquist S, Nada A, Pickhardt PJ, Shaaban AM, Gaballah AH, Elsayes KM. 

AJR Am J Roentgenol. 2021 Apr;216(4):927-934. doi: 10.2214/AJR.20.23273. Epub 2021 Feb 10. PMID: 33566632. 

This AJR article discusses the importance of the Ligament of Treitz, also known as the suspensory ligament of the duodenum, which serves as the division between duodenum and jejunum, as well as foregut and midgut. The article discusses the anatomic relations and pathologic conditions involving the Ligament of Treitz, which include malrotation and superior mesenteric artery syndrome. Gastrointestinal bleeding is a common presentation in the emergency room setting, and the Ligament of Treitz serves as the anatomic landmark to distinguish upper from lower sources of GI bleeding. Malignancies, both primary and metastatic can also involve the Ligament of Treitz, although rare. 

 

Imaging Features of Neurofibromatosis Type 1 in the Abdomen and Pelvis 

Zulfiqar M, Lin M, Ratkowski K, Gagnon MH, Menias C, Siegel CL.  

AJR Am J Roentgenol. 2021 Jan;216(1):241-251. doi: 10.2214/AJR.19.22283. Epub 2020 Nov 19. PMID: 33211573. 

Neurofibromatosis type 1 is an autosomal dominant condition which involves multiple body systems. This AJR article reviews the abdominopelvic manifestations of NF1. The most common manifestation is the presence of peripheral nerve sheath tumors, while most common on the skin, can occur in any organ. In the abdomen, these mainly occur retroperitoneally, as well as along the distribution of the lumbar plexus. These have the potential to degenerate into malignant peripheral nerve sheath tumors. Gastrointestinal stromal tumors may also be seen in up to 25% of the NF1 population.  Other neoplasms include neuroendocrine tumors such as carcinoid, pancreatic schwannoma, and adenocarcinoma of the gastrointestinal tract. Additionally, pheochromocytomas and paragangliomas have an increased incidence in patients with NF1. There is some data describing an association between testicular and ovarian tumors, however the authors suggest more evaluation into this relationship is necessary. Vascular anomalies may also be seen. 

 

PET/MRI Characterization of Mucinous Versus Nonmucinous Components of Rectal Adenocarcinoma: A Comparison of Tumor Metabolism and Cellularity 

Queiroz MA, Naves A, Dreyer PR, Cerri GG, Buchpiguel CA.  

AJR Am J Roentgenol. 2021 Feb;216(2):376-383. doi: 10.2214/AJR.19.22627. Epub 2020 Dec 9. PMID: 33295813. 

The purpose of this study was to evaluate if PET/MRI could differentiate mucinous from nonmucinous components of primary rectal adenocarcinoma. The article begins by discussing epidemiology of rectal cancer and the different types. Identifying mucin-containing tumors is important, as the article states mucinous tumors have a worse prognosis than nonmucinous, with more advanced T and N categories, poor response to neoadjuvant chemotherapy, and higher rates of metastases. This prospective analysis evaluated 99 patients, of which 17 were found to have mucinous components in their tumors. The article found that FDG uptake is significantly lower in the mucinous components of tumor, but tumor cellularity based on MRI and DWI findings is not significantly changed between the two types. The finding of lower FDG uptake in mucinous components is consistent with that seen on similar studies of other mucinous tumors throughout the abdomen. 

 

Multimodality Imaging of Abdominopelvic Tumors with Venous Invasion 

LeGout JD, Bailey RE, Bolan CW, Bowman AW, Chen F, Cernigliaro JG, Alexander LF.  

Radiographics. 2020 Nov-Dec;40(7):2098-2116. doi: 10.1148/rg.2020200047. Epub 2020 Oct 16. PMID: 33064623. 

It is not uncommon for malignancies of the abdomen and pelvis to invade venous structures, which plays a significant role in tumor staging and treatment options. Venous tumor invasion is commonly seen with hepatocellular and renal cell carcinomas, however, is also characteristically seen in other malignances of the abdomen and pelvis, and generally carries negative prognostic effects. This article reviews imaging diagnosis of tumor thrombus with ultrasound, CT, and MRI, specifically as it relates to the IVC, portal veins, splanchnic veins, and pelvic veins. The article discusses common mimics and pitfalls to help in differentiation. It can be difficult on ultrasound to distinguish between neoplastic and bland thrombus, the article suggests contrast-enhanced ultrasound is effective at demonstrating thrombus enhancement suggestive of neoplasm. MRI and CT features are also discussed, for example the ability to evaluate continuity of the thrombus with the tumor. The article addresses venous invasion in renal, hepatic, adrenal, pancreatic, sarcomatous, pelvic, and primary venous tumors. 

 

Multimodality Imaging of Foreign Bodies: New Insights into Old Challenges 

Carneiro BC, Cruz IAN, Chemin RN, Rizzetto TA, Guimarães JB, Silva FD, Junior CY, Pastore D, Ormond Filho AG, Nico MAC.  

Radiographics. 2020 Nov-Dec;40(7):1965-1986. doi: 10.1148/rg.2020200061. PMID: 33136481. 

This Radiographics article reviews imaging of foreign bodies, throughout the abdomen, pelvis, and entire body. Retained foreign bodies may be seen in up to 15% of traumatic wounds and lacerations, and can result in a granulomatous tissue response. The article mentions that up to approximately 38% of foreign bodies may be missed on physical evaluation. The authors state that conventional radiography is useful to detect around 80% of all foreign bodies and 98% of radiopaque bodies, and should be used as first line modality for detection. If not seen on plain film, ultrasound can be used as the next step for imaging evaluation. This has the advantage of being inexpensive and not delivering radiation, with a foreign body detection sensitivity of 72%. Foreign bodies are echogenic on ultrasound. CT can be used to localize deeper foreign bodies, but is less sensitive for smaller objects. MRI is not commonly used for detecting foreign bodies, but foreign bodies may be seen incidentally as low-intensity structures on all sequences with non-anatomic morphology. The article then discusses specific imaging features for glass, metal, plastic, wood, stones, and animal-related foreign bodies such as teeth or porcupine quills. 

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