What’s new in Gastrointestinal Imaging – February 2021

3 months ago

 

Acute cholecystitis: predictive clinico-radiological assessment for conversion of laparoscopic cholecystectomy

Jang YR, Ahn SJ, Choi SJ, Lee KH, Park YH, Kim KK, Kim HS.

Acta Radiol. 2020 Nov;61(11):1452-1462.

Laparoscopic cholecystectomy is the standard of care for gallstone disease, however at times laparoscopic technique can not be completed, and the procedure must be converted to open. This article looks at clinical and radiologic features that can predict the need for open conversion. Some of the intraoperative features requiring open conversion include difficult viewing or dissecting Calot’s triangle, or dense adhesions. This retrospective study looks at 581 patients who underwent cholecystectomy over a 12 month period. Of these 581, 113 required open conversion, approximately 20%. BMI > 30, prior abdominal operation, and prolonged prothrombin time were clinically significant factors associated with requiring open conversion. Radiologic features on CT that predict the need for open conversion include absence of gallbladder wall enhancement, gallstones in the infundibulum, and perihepatic inflammation. Lack of gallbladder enhancement was associated with gangrenous acute cholecystitis. The authors created an equation to calculate probability of open conversion, assigning different values to the different variables.

 

Clinical Implementation of Dual-Energy CT for Gastrointestinal Imaging

Mileto A, Ananthakrishnan L, Morgan DE, Yeh BM, Marin D, Kambadakone AR.

AJR Am J Roentgenol. 2020 Dec 30

This article provides an overview of dual energy CT technology, protocols, and clinical applications, with a focus on gastrointestinal imaging. The article starts by briefly discussing the physics and technical aspects of dual energy CT (DECT), which was FDA approved in 2006. Next, advantages and applications of DECT are discussed. The first advantage mentioned is the ability to create a virtual unenhanced image from a contrast-enhanced sequences. This allows to provide additional information when a noncontrast phase is needed to establish a diagnosis, for example to identify if a hyperattenuating focus is ingested material or bleeding. Additionally, this could be used to work up incidentalomas, such as adrenal adenomas or renal lesions. Iodine maps acquired in DECT can be used to differentiate benign from malignant lesions. In the liver DECT can quantify a hepatic fat fraction, which correlates with the degree of steatosis. The article discusses further applications in the gallbladder, pancreas, and bowel. In conclusion, the authors bring up challenges, limitations, and potential future uses of dual energy CT.

 

Diagnostic performance of CT and the use of GI contrast material for detection of hollow viscus injury after penetrating abdominal trauma. Experience from a level 1 Nordic trauma center

Thorisdottir S, Oladottir GL, Nummela MT, Koskinen SK.

Acta Radiol. 2020 Oct;61(10):1309-1315.

This retrospective analysis evaluates the use of enteric contrast to aid in diagnosis of hollow viscus injury after penetrating trauma, a topic about which the authors say has no consensus opinion. The authors analyzed 177 cases of penetrating abdominal trauma that presented to their Swedish level 1 trauma center over a four year period, including 144 stabs, 26 gunshot wounds, and 7 “other” injuries. In the author’s protocol, the trauma surgery team made the call if the patient was stable for CT, and if oral or rectal contrast were to be given. 47 patients went for emergent laparotomy or laparoscopy after CT imaging. In these patients, CT found 26 hollow viscus injuries, which, when compared to operative findings, revealed 18 true positives, 2 false positives, 19 true negatives, and eight false negatives. The authors note that 8 of these false negatives involved the upper GI tract, five of which were injuries to the stomach. Sensitivity of CT with enteric contrast was 69%, specificity 90%. The article describes different protocols, using any combination of IV, oral, and enteric contrast, given according to patient stability. One of the limitations of this manuscript is the lack of standardization of imaging protocol. In conclusion, the authors state oral and/or rectal contrast should be considered in hemodynamically stable patients undergoing CT for penetrating abdominal trauma, however more standardized studies could provide further information.

 

The implications of missed or misinterpreted cases of pancreatic ductal adenocarcinoma on imaging: a multi-centered population-based study

Kang J, Clarke SE, Abdolell M, Ramjeesingh R, Payne J, Costa AF.

Eur Radiol. 2021 Jan;31(1):212-221.

This retrospective review assesses the association of misinterpreted imaging findings of pancreatic ductal adenocarcinoma with the diagnostic interval and survival. The authors begin by discussing the epidemiology and poor survival rate of pancreatic cancer, with the only chance for a cure being complete resection, however only 20% of patients present with potentially resectable disease. Early diagnosis is needed to identify this set of patients to avoid the missing the opportunity for surgery. The only factors associated with significantly increased survival time are time to diagnosis and surgery. The authors looked at 257 CT diagnoses of pancreatic ductal adenocarcinoma, and used the RADPEER scoring system to evaluate the reports. Of these 257, 27 were given a RADPEER score of 2 and 39 were given a 3. The RADPEER score 1 group had a mean diagnostic interval of 53 days, with 86 and 192 days for the RADPEER 2 and 3 groups, respectively. The mean surgical interval was not significantly different between groups. Mean survival was 207, 168, and 250 days for the groups, respectively. Major takeaways from these studies include the fact that 66/257 patients had a RADPEER 2 or 3 score, indicative of both the difficulty in diagnosis, and a missed opportunity for early diagnosis. In the RADPEER 2 and 3 groups, there is a significantly longer diagnostic interval, however, diagnostic delays in imaging do not correlate with worse survival, as mean survival was not significantly different.

 

Prognosis of resected intraductal papillary mucinous neoplasm of the pancreas: using revised 2017 international consensus guidelines

Min, J.H., Kim, Y.K., Kim, H. et al.

Abdom Radiol 45, 4290–4301 (2020).

This retrospective study looked to determine preoperative clinical and MRI features predictive of disease-specific death or recurrence in patients undergoing pancreatic resection of intraductal papillary mucinous neoplasms (IPMN). IPMNs are typically considered benign, with malignant potential. MRCP is the preferred method of evaluating IPMN, the T2-weighted image is good for identifying mural nodules within the IPMN. A total of 167 patients with surgically resected IPMNS were evaluated, 86 were found to be benign, 81 malignant. Radiologically significant MRI features associated with malignant IPMNs include mean pancreatic duct size greater than 10 mm, enhancing mural nodules greater than 5 mm, cyst size greater than 3 cm, thickened or enhancing walls. Clinical features predictive of malignancy include obstructive jaundice and elevated CEA 19-9. Mural nodule size and obstructive jaundice were also found to be poor prognostic factors for malignant tumors, with a significantly lower survival rate when compared to malignant IPMNS without mural nodules. One of the major takeaways from this is the importance of identifying mural nodules pre-operatively, and understanding that nodules greater than 5 mm should raise high suspicion for malignancy.

 

Clinical and Radiologic Predictors of Parastomal Hernia Development After End Colostomy

Pennings JP, Kwee TC, Hofman S, Viddeleer AR, Furnée EJB, van Ooijen PMA, de Haas RJ.

AJR Am J Roentgenol. 2021 Jan;216(1):94-103.

This retrospective analysis examines 65 patients who underwent permanent end colostomy to evaluate risk factors for developing a parastomal hernia, which occurred in 30 patients of their case series. Parastomal hernias may be asymptomatic, but can commonly cause pain and problems with the stoma. Additionally, strangulation, perforation, and obstruction are possible serious complications. Identification of preoperative factors that can predict the development of a postoperative hernia could allow for implementation of preventative measures such as mesh placement. Radiologic factors found to be significantly associated with development of a parastomal hernia include preoperative abdominal or inguinal hernia, waist circumference greater than 98 cm, increased abdominal adipose tissue, surgical abdominal wall defect greater than 3.4 cm, and low muscle mass density. Significant clinical factors include COPD, BMI greater than 25, operation time longer than 395 minutes. COPD is thought to be associated due to increased coughing, which results in increased abdominal pressure, as well as glucocorticoid use which may lead to weakening of the abdominal wall. The authors believe more analysis needs to be done to determine efficacy and cost-effectiveness of mesh placement in patients with an end colostomy.

 

Point and Counterpoint: Non-contrast MRI for abdominal pain in the pediatric emergency department

Udayasankar UK, Desoky S. Moore MM, Brian JM.

AJR

Acute abdominal pain is a common complaint for children presenting to the emergency department. While abdominal pain may be due to many etiologies, acute appendicitis is the most common surgical condition. Diagnosis may be challenging due to a nonspecific clinical presentation. The ACR considers ultrasound to be the first line test for children suspected of appendicitis, while MRI and CT may be appropriate in high risk patients. One of the points made in favor of MRI evaluation is lack of ultrasound consistency, which can be technically difficult and operator dependent. Ultrasound also may fail to provide an alternative diagnosis. The authors state that MRI does not require radiation, contrast, or even an IV, which can be difficult to place in small children. They state CT is limited due to low visceral fat content and contrast resolution, as well as involves radiation. The authors mention a rapid noncontrast protocol which can create high-quality diagnostic images of the entire abdomen.

The authors of the counterpoint argue the fact that many community hospitals do not have access to MRI as a first line modality, possible need for sedation for pediatric MRI, and cost as being factors that should limit MRI, and cites a study which mentions ultrasound is the most cost-effective imaging study. Additionally, the authors state that not all community radiologists are equipped to confidently interpret appendicitis on pediatric MRI, and states that radiologists may favor the more commonly utilized ultrasound and CT.

 

Reporting Templates for Magnetic Resonance Imaging and Water Soluble Contrast Enema in Patients with Ileal Pouch Anal Anastomosis: Experience from a Large Referral Center

Huang C, Remzi F, Dane B, Esen E, Ream JM, Grieco M, Megibow AJ.

AJR Am J Roentgenol. 2020 Sep 16.

This article proposes standardized report templates for MRIs and contrast enemas in patients that have undergone ileal pouch anal anastomosis (IPAA), a procedure commonly performed for treatment of ulcerative colitis. The authors begin by discussing indications, epidemiology, and surgical technique of IPAA, followed by an introduction to advantages of structured report templates. The article then discusses different MR protocols used to evaluate IPAA, which may include MRI defecography in addition to traditional MR sequences. The authors propose to include the following fields in the MRI reporting template:

  • Anastomosis assessment, which should mention anastomotic leaks, sinus tracts, fistulas, or structures.
  • Rectal cuff/anal transitional zone, including cuff length and “cuffitis”
  • Pouch body, describing the shape, size, polyps, and presence of “pouchitis”
  • Pouch inlet and outlet: Strictures, inflammation, angulation
  • Peripouch mesentery evaluation
  • Pelvic abscesses and perianal fistulas not related to anastomosis
  • Additional findings to include lymphadenopathy, desmoid tumor, and osseous abnormalities.

For contrast enemas, the authors describe indications, techniques, and complications that can be evaluated. The reporting template for contrast enemas should include:

  • Indication: Asymptomatic or symptomatic pouch evaluation
  • Pouch filling: Complete pouch filling, passage across distal anastomosis,
  • Leak, sinus tract, fistula if present and location
  • Cuff leak
  • Adequacy of evacuation

 

Secretin-Enhanced MRCP: How and Why—AJR Expert Panel Narrative Review

Swensson J, Zaheer A, Conwell D, Sandrasegaran K, Manfredi R, Tirkes T.

AJR Am J Roentgenol. 2020 Dec 2.

This article provides an overview of secretin-enhanced MRCP (S-MRCP), a technique which can provide multiple advantages when compared to conventional MRCP for imaging the pancreaticobiliary tree. Secretin is a hormone secreted by the duodenum with the effect of increased pancreatic secretions. The authors discuss MRI protocols, patient preparation, and secretin administration. The authors state secretin-enhanced images should be interpreted in combination with the standard MRI and MRCP sequences. S-MRCP has been shown to improve diagnostic yield and clinical utility compared to traditional MRCP, as well has all for dynamic evaluation of pancreatic exocrine volume resolve. Reports of S-MRCP should include descriptions of the main pancreatic duct size over time, as well as a change in duodenal fluid volume. The article mentions some of the advantages of S-MRCP are the ability to better evaluate pancreas divisum, anomalous pancreaticobiliary junction, ductal stenosis or dilation, chronic pancreatitis, and post-operative visualization.

 

Pancreatic Trauma: Imaging Review and Management Update

Ayoob AR, Lee JT, Herr K, LeBedis CA, Jain A, Soto JA, Lim J, Joshi G, Graves J, Hoff C, Hanna TN.

Radiographics. 2021 Jan-Feb;41(1):58-74.

Traumatic injuries to the pancreas are relatively rare compared to other abdominal organs, but may have subtle findings with large clinical significance, and it is important for the radiologist to be aware of pancreatic trauma, as delays in diagnosis increase morbidity and mortality. This article gives a discussion into pancreatic trauma, which occurs in only about 2% of patients with trauma, and in 10% of patients with other intra-abdominal injuries. Most commonly, pancreatic trauma is the result of blunt injury as opposed to penetrating. The authors state the most important factor in evaluating pancreatic trauma is the status of the main pancreatic duct, and while multiphasic CT is a good first line study, MRCP or ERCP may be needed to better evaluate the ductal system. Common injuries to the parenchyma include contusion, which manifests on CT as an indistinct area of parenchymal edema, laceration as a discrete linear area of parenchymal tear or injury, and nonsalvageable tissue loss as characterized by loss of identifiable architecture or traumatic displacement from the pancreas. Indirect signs such as peripancreatic fat stranding, thickening of the adjacent renal fascia, or fluid in the lesser sac may be indicators of pancreatic injury. The article gives an overview into AAST pancreatic trauma grading, with any ductal injury automatically graded at least a 3.

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