What’s new in Gastrointestinal Imaging – December 2020

5 months ago

Stump Appendicitis: Clinical and CT Findings

Enzerra et. al AJR

This article reviews stump appendicitis, a rare entity characterized by inflammation or obstruction of the residual appendix after appendectomy. Literature reports of stump appendicitis are relatively rare, thought partially to be due to clinician and radiologist lack of familiarity leading to lack of diagnosis. This case series looks at 14 patients and presents demographics, case vignettes, and imaging features of stump appendicitis. The mean time between initial appendectomy and a diagnosis of stump appendicitis was 5.1 years, with a range of one month to seventeen years after appendectomy. CT findings include the typical features of appendicitis, stranding of the adjacent fat, peri-cecal fluid, and inflammatory changes of the stump. The mean inflamed stump size was 3.2 cm length by 1.1 cm width. Additional clues to diagnosis include an appendicolith, as well as the presence of suture material at the base of the inflamed. Stump perforation was seen in almost one third of cases, and “several” patients underwent abscess drainage, remnant appendectomy or ileocecectomy. The article suggests laparoscopic appendectomy is a predisposing factor, as the technique leads to a decreased field of view, which can make it difficult to properly visualize the appendiceal stump. Additionally, if the initial appendicitis is complicated by perforation, necrosis, or abscess, visualization of the appendiceal base becomes challenging, increasing the risk of subtotal resection and subsequent luminal occlusion leading to stump appendicitis.

 

HCC Screening: Is ultrasound still needed? Point and Counterpoint.

Kamaya A, Rodgers SK. HCC Screening: Is Ultrasound Still Needed at Transplant Centers?—Point: Yes, Ultrasound Remains First Line. AJR August 19, 2020.

Olson MC, Venkatesh SK. HCC Screening: Is Ultrasound Still Needed at Transplant Centers?—Counterpoint: No, CT/MR is the Way to Go. AJR 8/5/2020.

This is an interesting debate on the utility of ultrasound screening or surveillance for patients at high risk for hepatocellular carcinoma. Currently, ultrasound is commonly used as a first-line test, and only patients deemed to be poor ultrasound candidates are recommended to undergo alternative imaging modalities. Some of the arguments for ultrasound include the availability, cost, and ease of the procedure, not requiring the use of contrast or sedation. Sensitivity of ultrasound in screening has been shown to be as high as 80%, with specificity greater than 90%. The author states that cross-sectional imaging may have better accuracy, but that accuracy alone does not make the best screening test, and the author believes ultrasound better fits the definition of an appropriate screening test. Additionally, in surveillance scans after liver transplant, doppler ultrasound has the added ability to confirm patency of hepatic vasculature. The counterpoint argues that CT/MRI is a better test mainly due to the superior ability to diagnosis early HCC, and ultrasound struggles to detect potentially curable early disease. The author provides references with statistics supporting MRI being superior to US in detecting overall and early stage cancers. The authors note that drawbacks of cross sectional imaging include cost and duration, and pose the idea of abbreviated MRI protocols. Another advantage of cross sectional imaging is the ability to fully characterize lesions with one scan, whereas patients with a positive finding on ultrasound will be referred for CT or MRI.

 

Serial MRI Findings After Endoscopic Removal of Button Battery From the Esophagus

Riedesel et. al AJR

This article serves to characterize the natural history of MRI findings in children after endoscopic removal of a button battery from the esophagus. The article looks at 19 patients who met inclusion criteria. On endoscopy, all 19 patients were found to have either mucosal erosion or tissue necrosis. There were no reports of full-thickness injury or perforation. In these 19 patients, 48 MRI examinations were performed with the initial study performed within 48 hours of removal.  Imaging findings within the first two days include extensive edema and enhancement of the regional mediastinal fat, with edema persisting at all studies, including on all four MRIs performed at least 22 days after removal. MRI also demonstrated mucosal irregularity in all cases on the initial scan. Findings concerning for esophageal diverticulum were identified initially in 40% of patients with proximal esophageal injury, defined as between C6 and T3, and 43% of patients with lower esophageal injury. The proximal findings resolved with on follow-up MRI, but persisted in the lower esophageal cases. All patients underwent fluoroscopy, with contained leak seen in 4 of 19 cases, with mucosal irregularity seen on 16 cases, and ulceration on 8 cases. The authors note that CT can be used, but there is the risk of radiation to the patient, and MRI has improved soft tissue resolution and allows for a more detailed evaluation of structures. The authors state at their institution, CT is used for evaluation relating to battery ingestion only when MRI is contraindicated, such as with suspected retained metallic fragments.

 

Infected versus sterile abdominal fluid collections in postoperative CT: a scoring system based on clinical and imaging findings

Radosa et al Abdominal Radiology

This article was created with the objective of using a scoring system to characterize intra-abdominal fluid collections in post-operative patients. The article begins by discussing the different types of fluid collections after surgery, including seromas, hematomas, abscesses, etc. Infection occurs in up to 5% of clean wounds, and 27% of septic wounds, with mortality of infected collections reaching as high as 80% if left untreated. The authors created a scoring system using the following variables, in order of decreasing weight: Serum CRP ≥150 mg/L (4 points), gas within the collection (3 points), CT attenuation of the collection ≥ 20 HU (2 points),  and enhancement of the collection (2 points). The authors found a score of ≥5 points was predictive of a fluid collection being infected, with 85% sensitivity and 79% specificity. Samples of drained fluid were sent to the laboratory for proof of infection.  The authors state that a scoring system such as the one they have created will allow improved patient management.

 

Imaging Spectrum of Duodenal Emergencies

Gosangi et al Radiographics

This review article discusses the duodenum and emergencies, including those which arise from the duodenum, and those by which the duodenum is secondarily affected. The article first discusses the four-segment anatomy of the duodenum and how it is uniquely intraperitoneal and retroperitoneal. Peptic ulcer disease is one of the most common duodenal pathologies, commonly affecting the first segment. If ulcers are found in the more distal segments, an underlying cause such as Zollinger-Ellison syndrome should be considered. Direct signs of uncomplicated duodenal ulcers are subtle and may not be visualized, but include discontinuity of normal mucosal enhancement and luminal outpouching. Indirect signs include periduodenal fat stranding, adjacent lymphadenopathy, and submucosal edema. If there is concern for an actively bleeding ulcer, the authors recommend triple phase CT angiography, which may demonstrate high-attenuating intraluminal material on the non-contrast phase, would demonstrate a higher-attenuating intraluminal contrast blush on the arterial phase and, a change in shape of the blush on venous phase. Perforation should be suspected with the presence of extraluminal gas. Pancreatitis is a regional pathology that can affect the duodenum, secondary to inflammation from pancreatic enzymes or compression from an enlarged pancreatic head or peripancreatic fluid collection. Acute cholecystitis can also lead to inflammation of the duodenum, and has the potential for a gallstone to erode through the duodenal wall and lead to gallstone ileus. Duodenal trauma is rare, most commonly due to penetrating trauma, with another common cause being a deceleration injury leading to duodenal compression against the lumbar spine. The article also provides a helpful table presenting pathologic conditions by duodenal segment, including less common conditions such as Bouveret syndrome in the second segment, aortoduodenal fistulas in the third segment, and malrotation of the fourth segment.

 

MR Cholangiopancreatography: What Every Radiology Resident Must Know

Vidal et al Radiographics

This brief article gives a good overview of MRCP. The article begins by discussing advantages of MRCP, a noninvasive method for evaluation of pancreatobiliary disorders, which gives a wider field of view of the entire biliary system when compared to the more selective ERCP, which may not be able to visualize past an obstruction. Some of the disadvantages include cost, worse spatial resolution, requiring patient cooperation, and inability to intervene. Next the article introduces different protocols that can be used with MRCP, including the use of 2D radial and 3D sequences. The manuscript directs readers to the Radiographics website, where a more comprehensive presentation elaborates on techniques, advantages, disadvantages, and pitfalls of MRCP imaging. The presentation details the many normal variants of biliary anatomy before addressing pathology of the biliary tract, both benign and malignant. Covered benign entities included choledocholithiasis, cholangitis, biliary atresia, and traumatic/iatrogenic problems. The covered malignant processes include cholangiocarcinoma, as well as ampullary, pancreatic, and gallbladder carcinoma. Some of the pitfalls addressed include misinterpretation of artifacts, and normal variants which mimic pathology.

 

Pancreatic Ductal Adenocarcinoma and Its Variants: Pearls and Perils

Schawkat et al Radiographics

This extensive review article details the imaging of pancreatic adenocarcinoma, the most common primary pancreatic malignancy, accounting for 90% of solid pancreatic tumors. The article introduces pancreatic adenocarcinoma with epidemiology and the poor 7% five-year survival rate. The article discusses clinical and histologic features before discussing imaging. The article states a thin slice multiphasic CT protocol is optimal for evaluating pancreatic masses. Pancreatic adenocarcinoma typically presents on imaging as an indistinct, poorly enhancing mass that obstructs the adjacent pancreatic and bile ducts. Conventional adenocarcinoma will be hypoenhancing to the normal pancreatic parenchyma because of hypovascularity of the tumoral tissue. 10% of pancreatic adenocarcinoma is isoattenuating to adjacent parenchyma, limiting the diagnostic utility of CT. It is important to note that these isoattenuating lesions are associated with better prognosis, thought to be due to containing less desmoplastic stromal tissue. Indirect signs of a pancreatic mass include upstream ductal dilation and common bile duct dilation.MR imaging of pancreatic adenocarcinoma is typically T1-hypointense, varies in T2-intensity, and restricts diffusion. Pancreatic adenocarcinoma has overlapping imaging features of other focal pancreatic lesions, benign and malignant, and for this reason, a comprehensive assessment of clinical manifestations, imaging, and lab values should be used to make the correct diagnosis. The article then describes features of less common histologic subtypes of pancreatic adenocarcinoma, including adenosquamous, colloid, hepatoid, medullary, signet-ring, and undifferentiated carcinomas.

 

Imaging Evaluation of Abdominopelvic Gunshot Trauma

Sodagari et al Radiographics

This Radiographics article discusses the importance of imaging when assessing penetrating ballistic trauma, including important findings on initial presentation and follow-up exams. The article addresses the prevalence of firearm injuries, second only to motor vehicle collisions as a leading cause of injury-related deaths. The article also discusses the physics of ballistics, trajectory analysis, and mechanisms of firearm injury. Common patterns of injuries include laceration, cavitation, and shock waves. Imaging should be reserved for patients who are stable enough to tolerate the scan, if hemodynamically unstable the patient should be triaged to the operating room, and once stabilized imaging should be performed to assess extent of injury. The article discusses the different contrast protocols, admitting there are multiple schools of thought when it comes to protocol. The article states ultrasound and MRI have limited roles in evaluation, and CT is usually the first-line study. Evaluation of organ injuries is then discussed, starting with the importance of trajectory analysis and how it is accomplished. Next, solid and organ injuries are presented, briefly discussing the AAST injury scale for each organ. Musculoskeletal, neurologic, and diaphragmatic injuries are briefly presented. The article concludes by discussing follow-up imaging and challenges of imaging gunshot wounds, including limitations in patient positioning and cooperation, metallic streak artifact, and frequent interruptions by the clinical team in an effort to immediately obtain results of the exam.

 

Imaging features, complications and differential diagnoses of abdominal cystic lymphangiomas

Tistet et al Abdominal Radiology

This review article discusses a relatively rare entity, the abdominal cystic lymphangioma (ACL). Cystic lymphangiomas commonly arise in the neck and axilla, but can be seen in any location that contains lymphatic vessels the abdominal type makes up 5% of all cystic lymphangiomas. In the abdomen, they are most commonly seen in the mesentery, followed by the greater omentum, mesocolon, and retroperitoneum. On imaging, ACLs appear as multilocular lesions with homogeneous serous content, with a thin wall and thin septa. The lesions should be anechoic on ultrasound, fluid attenuation on CT, and water signal on MR, low T1-weighted signal, high T2-weighted signal. On post-contrast imaging, the walls and septa can show slight progressive enhancement. Some cysts may become heterogeneous due to hemorrhagic or inflammatory changes, which imaging will reflect. A thin wall, homogeneous fluid content, and absence of mass effect on regional organs are all important characteristics to diagnosing ACL. They are often single, but multiple can appear. Infection is the most common complication, which will show a heterogeneous appearance on both CT and MR. ACLs have also been demonstrated as the site of a lead point of intestinal intussusception. There is an overlap in imaging features of ACL and a wide variety of differential diagnoses. Loculated ascites, cisterna chylii, extra-pancreatic walled off necrosis, duplication cysts, and cystic teratomas area all part of the differential, patient history may assist with diagnosis. ACLs are benign and mostly asymptomatic, however surgical resection may be indicated if the lesion becomes symptomatic. Recurrence has been reported to occur in up to 27% of cases. Percutaneous sclerotherapy may be an alternative to therapy.

 

Diagnostic clues, pitfalls, and imaging characteristics of ‘‐celes’ that arise in abdominal and pelvic structures

Srisajjakul et al Abdominal Radiology

The suffix -cele comes from ancient Greek and translates to tumor or cavity. This article discussed the many different types of -celes encountered in the abdomen and pelvis. The article mentions that most are identified incidentally, but some can cause clinical symptoms. This article discusses imaging features and diagnostic clues for each of the described -celes. This article discusses some of the more commonly seen lesions such as hydroceles, varicoceles, mucoceles, and also includes some less common abnormalities such as santoriniceles, hematoceles, and syringoceles. Briefly, santoriniceles are focal cystic dilatations of the terminal part of the dorsal pancreatic duct (Duct of Santorini) frequently observed in patients with pancreatic divisum. MRCP can accurately identify santoriniceles and their counterpart Wirsungoceles, which arise from the duct of Wirsung. Syringoceles develop from a cyst in the bulbourethral glands adjacent to the prostate. These can be well identified with perineal ultrasound or with their T2-hyperintense signal at the posterior aspect of the bulbomembranous urethra. Additionally, the article discusses choledochoceles, ureteroceles, lymphoceles, spermatoceles, and pyoceles.

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