Primary cystic peritoneal masses and mimickers: spectrum of diseases with pathologic correlation.

Cystic lesions within the peritoneum have been classified classically according to their lining on histology into four categories-endothelial, epithelial, mesothelial, and others (germ cell tumors, sex cord gonadal stromal tumors, cystic mesenchymal tumors, fibrous wall tumors, and infectious cystic peritoneal lesions). In this article, we will proceed to classify cystic peritoneal lesions focusing on the degree of radiological complexity into three categories-simple cystic, mildly complex, and cystic with solid component lesions. Many intra-abdominal collections within the peritoneal cavity such as abscess, seroma, biloma, urinoma, or lymphocele may mimic primary peritoneal cystic masses and need to be differentiated. Clinical history and imaging features may help differentiate intra-abdominal collections from primary peritoneal masses. Lymphangiomas are benign multilocular cystic masses that can virtually occur in any location within the abdomen and insinuate between structures. Ultrasound may help differentiate enteric duplication cysts from other mesenteric and omental cysts in the abdomen. Double-layered wall along the mesenteric side of bowel may suggest its diagnosis in the proper clinical setting. Characteristic imaging features of hydatid cysts are internal daughter cysts, floating membranes and matrix, peripheral calcifications, and collagenous pericyst. Non-pancreatic psuedocysts usually have a fibrotic thick wall and chylous content may lead to a fat-fluid level. Pseudomyxoma peritonei appears as loculated fluid collections in the peritoneal cavity, omentum, and mesentery and may scallop visceral surfaces. Many of the primary cystic peritoneal masses have specific imaging features which can help in accurate diagnosis and management of these entities. Knowledge of the imaging spectrum of cystic peritoneal masses is necessary to distinguish from other potential cystic abdominal mimicker masses.

Small renal oncocytomas: is segmental enhancement inversion a characteristic finding at biphasic MDCT?

OBJECTIVE: The purpose of this study was to retrospectively determine whether segmental enhancement inversion was a common and characteristic finding in small (≤ 4 cm) renal oncocytomas on biphasic contrast-enhanced CT. MATERIALS AND METHODS: This retrospective case-control study included 16 patients with 16 renal oncocytomas and 15 control patients with 15 renal cell carcinomas (RCCs), matched for age and sex, who underwent biphasic contrast-enhanced MDCT at our institution. Three reviewers independently analyzed each tumor for enhancement patterns on MDCT, including the presence or absence of segmental enhancement inversion, homogeneity, and phase of peak enhancement. RESULTS: The mean and median sizes of the oncocytomas were 2.5 and 2.4 cm, respectively (range, 1.1-3.9 cm), and the mean and median sizes of the RCCs were both 2.6 cm (range, 1.4-3.9 cm). There was no significant difference in the size of the renal masses between the two groups (p = 0.50). For two reviewers, segmental enhancement inversion was not present in any of the renal masses; for one reviewer, segmental enhancement inversion was present in one oncocytoma (6%) and one RCC (7%). For all reviewers, there was no feature or enhancement pattern that was statistically significantly associated with renal oncocytoma or RCC (p < 0.05). CONCLUSION: Segmental enhancement inversion was not a common or characteristic CT finding for renal oncocytoma and was not helpful in differentiating small renal oncocytomas from RCC.

Renal cortical lesions in patients with autoimmune pancreatitis: a clue to differentiation from pancreatic malignancy.

AIM: To describe the occurrence of renal cortical lesions (RCLs) in patients with autoimmune pancreatitis (AIP). METHODS: This retrospective study was approved by our research ethics board; informed consent was waived. Systematic search of CT scan reports in 5-year interval yielded 17 patients with AIP (male:female; 11:6, age 18-80 years). A consecutive group of 22 patients with pancreatic adenocarcinoma was used as control (male:female; 10:12, age 42-76 years). The CT scans of the two groups were mixed and randomized. Two blinded radiologists independently reviewed the kidneys for the presence of wedge-shaped RCLs. Fisher's exact test was used to determine statistical significance. Consensus review of all imaging of positive patients with AIP and RCLs and three additional patients identified anecdotally was performed. RESULTS: Both readers independently identified the same 6/17 (35%) patients in the study group and 0/22 in the control group with two or more RCLs. This difference was statistically significant (p=0.004). The sensitivity, specificity, positive and negative predictive values of RCLs in the differentiation of AIP from pancreatic adenocarcinoma were 35%, 100%, 100%, and 67%, respectively. To the six AIP patients with RCLs, we added three more identified anecdotally. In 7/9, >5 RCLs were seen which were wedge-shaped and cortical-based, ranging from <1 to 4cm. Typical pancreatic findings of AIP were noted in all, with the gland affected focally in 5/9 patients. CONCLUSION: We have shown the presence of multiple renal cortical lesions which occur in approximately 35% of our AIP patient population.

From the RSNA refresher courses: imaging evaluation for acute pain in the right upper quadrant.

Acute cholecystitis is the most common cause of acute pain in the right upper quadrant (RUQ), and urgent surgical removal of the gallbladder is the treatment of choice for uncomplicated disease. However, cross-sectional imaging is essential because more than one-third of patients with acute RUQ pain do not have acute cholecystitis. In addition, patients with complications of acute cholecystitis, such as perforation, are often best treated with supportive measures initially and elective cholecystectomy at a later date. Ultrasound (US) is the primary imaging modality for assessment of acute RUQ pain; US is both sensitive and specific in demonstrating gallstones, biliary dilatation, and features that suggest acute inflammatory disease. Occasionally, additional imaging modalities are indicated. Computed tomography is valuable, especially for confirming the extent and nature of the complications of acute cholecystitis. Magnetic resonance cholangiopancreatography is helpful in complicated ductal disease (eg, recurrent pyogenic cholangiohepatitis) when more detailed diagnostic information is required for treatment planning, whereas endoscopic retrograde cholangiopancreatography is used when biliary intervention is required (eg, treatment of choledocholithiasis). Successful imaging with all modalities requires familiarity with both the characteristic and the unusual features of a wide variety of pathologic conditions. In addition, potential pitfalls must be recognized and avoided.

US of the peritoneum.

Familiarity with the pathophysiology of peritoneal disease is the basis of successful ultrasound (US) study of the peritoneum. The pouch of Douglas, diaphragmatic surfaces, the paracolic gutters, and the regions of the mesentery and omentum should receive careful scrutiny in the patient at risk for a peritoneal disease process. An optimal US technique requires assessment of the entire peritoneum with a transducer selected to reflect the depth of the region of interest. US may demonstrate minute quantities of free intraperitoneal fluid and is therefore capable of providing sensitive quantitative information about ascites. Qualitative information may also be inferred, as blood, pus, and neoplastic cells demonstrate correlation with particulate ascites on gray-scale US scans. Peritoneal nodules, plaques, and thickening may be detected on the visceral or parietal peritoneal surfaces, especially when high-frequency probes are used. Transvaginal study in women increases the sensitivity of US for detection of peritoneal disease. In women who have unexplained sepsis or are at risk for carcinomatosis, transvaginal scanning should routinely be added to the regular abdominal and pelvic studies regardless of the findings of those studies. Peritoneal carcinomatosis, primary peritoneal neoplasms, pseudomyxoma peritonei, and peritonitis have characteristic appearances at US.

Dropped gallstones post laparoscopic cholecystectomy mimicking peritoneal seeding: CT and ultrasound features.

PURPOSE: The purpose of this work was to investigate the ultrasound (US) and CT features of dropped gallstones mimicking peritoneal seeding in patients after laparoscopic cholecystectomy (LCC). METHOD: We describe the US and CT features of dropped gallstones mimicking peritoneal seeding in eight patients who underwent LCC. We also conducted a retrospective study of consecutive LCC patients who subsequently had CT to determine the prevalence of this condition. RESULTS AND CONCLUSION: The density of dropped gallstones on CT ranged from hypodense to partially or completely calcified nodules. Some stones did not have visible surrounding reaction, whereas others showed an enhancing halo. All stones were echogenic and demonstrated shadowing on US. The stones were located mostly on the right side of the abdomen, and the majority were around the liver. The prevalence of dropped gallstones post laparoscopic cholecystectomy was 4.2%.

Multi-detector row helical CT in preoperative assessment of small (< or = 1.5 cm) liver metastases: is thinner collimation better?

PURPOSE: To determine the value of collimations less than 5 mm in detecting hepatic metastases 1.5 cm or smaller by using multi-detector row helical computed tomography (CT). MATERIALS AND METHODS: Thirty-one patients underwent contrast material-enhanced multi-detector row helical CT before hepatic resection in this prospective study. Images were reconstructed at collimations of 5.00, 3.75, and 2.50 mm with 50% overlap and reviewed independently by three radiologists. Each lesion was characterized as metastatic, benign, or equivocal and graded for conspicuity. Criterion standards were pathologic assessment of the resected liver and follow-up of the nonresected liver. Only lesions 1.5 cm or smaller were analyzed. RESULTS: There were a total of 88 liver lesions 1.5 cm or smaller, and 25 of these were metastases. Pooled sensitivity for all lesions improved with thinner collimation (66% [58 of 88 lesions], 69% [61 of 88], and 82% [72 of 88] at collimations of 5.00, 3.75, and 2.50 mm, respectively), and this was statistically significant (P =.01). However, no significant difference was noted between collimations in the pooled sensitivity for metastatic lesions (80% [20 of 25 lesions] at all collimations) (P >.99). No statistical difference was noted in the conspicuity of lesions at different collimations (P =.18). CONCLUSION: Image reconstruction with multi-detector row helical CT at collimations less than 5 mm may not improve sensitivity in the detection of hepatic metastases 1.5 cm or smaller.

Cancer of the pancreas: the best image for early detection--CT, MRI, PET or US?

Pancreatic cancer has a poor prognosis, and the best chance for survival is to diagnose the tumour at an early stage. Abdominal ultrasound, computed tomography, magnetic resonance imaging and endoscopic retrograde cholangiopancreatography are the most commonly used radiological techniques for imaging the pancreas. The diagnostic evaluation should be tailored to the individual patient. Dual-phase helical computed tomography and magnetic resonance imaging have similar accuracies for detecting and staging pancreatic adenocarcinoma. Sonography results are highly dependent on the skill and persistence of the operator. No radiological examination is very sensitive at visualizing small metastases in the lymph nodes and peritoneum, or on the surface of the liver. Thus, it is difficult to establish with certainty whether a tumour is resectable. Another major challenge is to differentiate cancer from an inflammatory mass in chronic pancreatitis. Functional imaging (using positron emission tomography with fluorodeoxyglucose) may be helpful, especially if the images are fused with those of computed tomography or magnetic resonance imaging. The diagnostic accuracies, applications and limitations of the various modalities are discussed.