Imaging manifestations of abdominal fat necrosis and its mimics.

Intraabdominal fat is a metabolically active tissue that may undergo necrosis through a number of mechanisms. Fat necrosis is a common finding at abdominal cross-sectional imaging, and it may cause abdominal pain, mimic findings of acute abdomen, or be asymptomatic and accompany other pathophysiologic processes. Common processes that are present in fat necrosis include torsion of an epiploic appendage, infarction of the greater omentum, and fat necrosis related to trauma or pancreatitis. In addition, other pathologic processes that involve fat may be visualized at computed tomography, including focal lipohypertrophy, pathologic fat paucity (lipodystrophies), and malignancies such as liposarcoma, which may mimic benign causes of fat stranding. Because fat necrosis and malignant processes such as liposarcoma and peritoneal carcinomatosis may mimic one another, knowledge of a patient's clinical history and prior imaging studies is essential for accurate diagnosis.

Septic thrombophlebitis of the portal venous system: clinical and imaging findings in thirty-three patients.

AIM: Our purpose was to review the clinical and imaging findings in a series of patients with septic thrombophlebitis of the portal venous system in order to define criteria that might allow more confident and timely diagnosis. MATERIALS AND METHODS: This is a retrospective case series. The clinical and imaging features were analyzed in 33 subjects with septic thrombophlebitis of the portal venous system. RESULTS: All 33 patients with septic thrombophlebitis of the portal venous system had pre-disposing infectious or inflammatory processes. Contrast-enhanced CT studies of patients with septic thrombophlebitis typically demonstrate an infectious gastrointestinal source (82%), thrombosis (70%), and/or gas (21%) of the portal system or its branches, and intrahepatic abnormalities such as a transient hepatic attenuation difference (THAD) (42%) or abscess (61%). CONCLUSIONS: Septic thrombophlebitis of the portal system is often associated with an infectious source in the gastrointestinal tract and sepsis. Contrast-enhanced CT demonstrates an infectious gastrointestinal source, thrombosis or gas within the portal system or its branches, and intrahepatic abnormalities such as abscess in most cases. We report a THAD in several of our patients, an observation that was not made in prior reports of septic thrombophlebitis.

Radiologists' performance in the diagnosis of acute intestinal ischemia, using MDCT and specific CT findings, using a variety of CT protocols.

The aim of this study was to evaluate the performance of radiologists in the diagnosis of acute intestinal ischemia using specific multi-detector CT findings. The abdominal CT scans of 90 patients were retrospectively reviewed by three radiologists: an abdominal imaging specialist, an experienced general radiologist, and a senior resident. Forty-seven patients had surgically proven intestinal ischemia and comprised the case group, while 43 patients had no evidence of intestinal ischemia at surgery and comprised the control group. Images were reviewed in a random and blinded fashion. Radiologists' performance in diagnosing bowel ischemia from other bowel pathologies was evaluated. The sensitivity, specificity, and accuracy for diagnosing bowel ischemia were 89%, 67%, and 79% for the abdominal imager; 83%, 67%, and 76% for the general radiologist; and 66%, 83%, and 74% for the senior resident, respectively. The calculated kappa value for inter-observer agreement regarding the presence of bowel ischemia was 0.79. CT findings that significantly distinguished bowel ischemia from other bowel pathologies were decreased or absent bowel wall enhancement, filling defect in the superior mesenteric artery, small bowel pneumatosis, and gas in the portal veins or superior mesenteric vein. For most of these signs, there was good inter-observer agreement. Radiologists' performance in diagnosing bowel ischemia is good, but lower than previously reported since a significant amount of cases are evaluated using a suboptimal CT technique. Radiologists' experience and expertise have an important impact on their performance.

Chemoembolization for unresectable hepatocellular carcinoma in patients with or without portal vein thrombosis.

BACKGROUND/AIMS: Chemoembolization in the presence of portal vein thrombosis (PVT) is thought to be hazardous and such patients are regarded as prognostically poor. METHODOLOGY: One hundred sixty two patients with biopsy-proven and unresectable HCC were treated with chemoembolization (TACE). We retrospectively analyzed these patients according to presence or absence of PVT. RESULTS: We found the 2 groups were similar with respect to tumor and liver parameters. Survival was 22.3 months in responders and 6.6 months in non-responders, p < or = 0.0001. Patients with PVT who responded had a 24 mo median survival and without PVT who responded had a 30 month median survival. These 2 groups were thus similar, p = 0.817. Patients who did not respond had a survival of only 5 and 7 months, for presence or absence of PVT, respectively. Responders had significantly lower blood AFP and GGTP levels, lower DCP levels and better liver function. CONCLUSIONS: In this series, response was a major determinant of survival, regardless of the presence or absence of PVT. Thus, branch PVT was not a contraindication to chemoembolization.

Imaging approach for evaluation of focal liver lesions.

Focal liver lesions are common in the general population. Radiology (imaging) plays a pivotal role for the diagnosis, staging, treatment planning, and follow-up of focal liver lesions. To maximize lesion detection and characterization, imaging needs to be performed with appropriate equipment by using protocols carefully designed on the basis of the underlying clinical context. In addition, the decision of an imaging modality cannot be based on the diagnostic accuracy of an imaging test solely but must also consider patient safety and cost-effectiveness.

Spontaneous abdominal hemorrhage: causes, CT findings, and clinical implications.

OBJECTIVE: The purpose of this article is to present the most common causes of spontaneous abdominal hemorrhage and to review the CT findings that are important in establishing the correct diagnosis and in guiding appropriate therapy. CONCLUSION: Knowledge of the common CT manifestations of various causes of spontaneous abdominal hemorrhage allows their accurate diagnosis and has a direct impact on clinical decision making.

CT hypotension complex (shock bowel) is not always due to traumatic hypovolemic shock.

OBJECTIVE: The purpose of our study was to review the clinical and CT findings in a substantial series of 41 patients with the shock bowel sign to determine if there is an association between shock bowel (and other CT signs of hypotension) and conditions other than post-traumatic hypovolemic shock. CONCLUSION: The shock bowel sign and the CT hypotension complex are frequently associated with hypotension from causes other than trauma-induced hypovolemic shock, such as severe head or spine injury, cardiac arrest, septic shock, bacterial endocarditis, and diabetic ketoacidosis. Other elements of the CT hypotension complex such as flattening of the inferior vena cava and aorta, abnormal pancreatic enhancement and peripancreatic fluid, and hypoperfusion of the spleen and liver are variably associated with shock bowel whether due to posttraumatic hypovolemia or other causes of hypotension. The CT hypotension complex (shock bowel) has important prognostic and therapeutic implications and can probably be distinguished from bowel trauma and other forms of bowel injury in most cases.

Focal confluent fibrosis in cirrhotic liver: natural history studied with serial CT.

OBJECTIVE: The objective of this study was to assess the long-term natural history of focal confluent fibrosis in cirrhotic liver with CT. MATERIALS AND METHODS: Two radiologists retrospectively reviewed in consensus 118 liver CT examinations in 26 patients (19 men, seven women; age range, 32-68 years; mean age, 50 years) performed over approximately 6 years. Helical CT scans were obtained before and 30-35 and 65-70 seconds after injection of 125-150 mL of contrast medium at a rate of 4-5 mL/s. Proof of cirrhosis was based on liver transplantation (n = 6), biopsy (n = 9), or imaging findings (n = 11). The number, location, and attenuation of fibrotic lesions and presence of trapped vessels were evaluated. Variation of hepatic retraction associated with the development of focal confluent fibrosis lesions was assessed using the ellipsoid volume formula and an arbitrary retraction index. RESULTS: Each radiologist identified 41 focal confluent fibrosis lesions. All lesions were identified by both radiologists. Twelve patients (46%) had a single lesion, 13 (50%) had two lesions, and one (4%) had three lesions. Thirty-four (83%) of 41 lesions were located in segment IV, VII, or VIII. Thirty-two lesions (78%) were hypoattenuating on unenhanced images, 25 lesions (61%) were hypoattenuating on hepatic arterial phase images, and 20 lesions (49%) were isoattenuating on portal venous phase images. Seven lesions (17%) were or became hyperattenuating at follow-up on portal venous phase images. Trapped vessels were found in six lesions (15%). The retraction index showed a significant increase over time (r = 0.423, p < or = 0.0001). CONCLUSION: The degree of capsule retraction associated with focal confluent fibrosis evolves with time and relates to the natural evolution of cirrhosis.

Perforated duodenal diverticulum: clinical and imaging findings in eight patients.

BACKGROUND: Duodenal diverticula are common and are usually asymptomatic. We have studied a substantial number of patients who had perforation of a duodenal diverticulum and found these challenging to diagnose with little guidance from prior publications. METHODS: Retrospective study for the most recent 10-year period of all patients who had a discharge diagnosis of perforated duodenal diverticulum or duodenal diverticulitis and also had relevant imaging studies. RESULTS: Eight patients had CT evaluation and six had upper GI fluoroscopic evaluation. All presented with acute abdominal pain. Duodenal diverticular perforation was spontaneous in 6 patients, and caused by endoscopy or feeding tube placement in one patient each. The diagnosis was made correctly by imaging in only 2 patients, while retrospective review showed clear evidence of a diverticulum and extraluminal gas in all cases. Clinical management included surgery in five patients and nonoperative management in three. Average duration of hospital stay was 32 days and two patients died. CONCLUSION: Perforation of a duodenal diverticulum may cause severe illness or death and is difficult to diagnose. Careful attention to CT findings and appropriate use of upper GI studies may allow more confident diagnosis and management.

Liver lesions with hepatic capsular retraction.

Retraction of the liver capsule may be associated with a diverse spectrum of benign and malignant etiologies. The more common causes include focal confluent fibrosis in cirrhotic livers, cholangiocarcinoma, and treated liver tumors, such as hepatocellular carcinoma, metastases, and lymphoma. Less common etiologies include primary sclerosing cholangitis, epithelioid hemangioendothelioma, hepatic hemangioma, solitary fibrous tumor of the liver, and hepatic inflammatory pseudotumor. Hepatic capsular retraction may also result from iatrogenic and noniatrogenic trauma. Due to the diversity and different nature of the various etiologies associated with this sign, it is important that radiologists be familiar with the characteristic features of these abnormalities, to avoid misdiagnosis that may adversely affect the therapeutic approach. It is also important to know that, contrary to some reports, hepatic capsular retraction is not a sign of malignant disease. The purpose of this article is to familiarize readers with the spectrum of benign and malignant etiologies of this sign and to point out additional computed tomographic findings that may allow confident diagnosis of the specific hepatic lesion responsible for the capsular retraction. The hepatic capsular and subcapsular regions may be affected by focal or diffuse pathologies affecting the liver. This hepatic area is more prone to be involved in various malignant and benign diseases due to several factors: the negative subdiaphragmatic pressure that may draw infected material and malignant cells toward the diaphragm, the perihepatic ligaments connecting the liver capsule with adjacent viscera, forming a direct root of dissemination, and the systemic blood inflow that supplies this region in addition to the portal and hepatic arterial blood flow. This is the reason for the multiple pathologic conditions and pseudolesions that occur at the hepatic capsular and subcapsular regions.

Acute gastrointestinal bleeding: the potential role of 64 MDCT and 3D imaging in the diagnosis.

Advancements in both CT scanner technology and three-dimensional (3D) imaging software have now made it feasible to image patients with acute GI bleeding in an effort to identify the bleeding source. This pictorial essay will explore the potential role of utilizing 64 MDCT and 3D imaging in patients presenting with acute gastrointestinal bleeding. A discussion of current technology, appropriate CT protocols, and interpretation strategies will be included.

Nonobstructing renal stones on unenhanced CT: a real cause for renal colic?

OBJECTIVE: The purpose of this study was to evaluate the incidence of nonobstructing renal stones on unenhanced CT in patients presenting to the emergency department with renal colic and to determine whether this finding might be the cause of patients' symptoms. CONCLUSION: Nonobstructing renal stones on unenhanced CT are a frequent finding in patients evaluated in the emergency department for suspected renal colic. These stones are usually not recognized as the cause of pain by physicians and may be responsible for multiple clinical and radiologic evaluations. In the absence of other clinical or CT evidence of a separate cause, these stones are likely to be the cause of a patient's acute pain.

Multiple hepatic adenomas associated with liver steatosis at CT and MRI: a case-control study.

OBJECTIVE: The objective of our study was to investigate the relationship between hepatic adenoma and liver steatosis. MATERIALS AND METHODS: Radiology and pathology records from January 1999 to March 2007 were reviewed to identify 24 patients (22 women and two men; mean age, 40 years) with a pathology-proven diagnosis of hepatic adenoma (mean size +/- SD, 7.2 +/- 3.7 cm) who underwent helical contrast-enhanced CT (n = 23) and/or gadolinium-enhanced MRI (n = 8). The control group was composed of 24 patients of similar age and sex (21 women and three men; mean age, 43 years) with hepatic hemangioma who underwent CT or MR evaluation during the same time period. Two radiologists independently interpreted the imaging studies to determine the number of lesions and whether steatosis was present. The difference in prevalence of steatosis between the adenoma group versus the control group and the difference between patients with a single hepatic adenoma versus those with multiple hepatic adenomas were assessed (chi-square test). RESULTS: Hepatic steatosis was present in 14 of 24 patients (58%) with hepatic adenoma versus seven of 24 patients (29%) with hemangioma (p = 0.042). Steatosis was more common in patients with multiple hepatic adenomas (9/11, 82%) than in those with a single hepatic adenoma (5/13, 38%) (p = 0.047). CONCLUSION: Hepatic adenomas occur more frequently and more often are multiple in patients with hepatic steatosis.

CT of nonneoplastic hepatic vascular and perfusion disorders.

The unique dual blood supply of the liver (75% portal venous, 25% hepatic arterial) makes multiphase helical computed tomography (CT) a highly suitable technique for hepatic evaluation with imaging in two (arterial and portal venous) or more phases. Multiphase helical CT has become an important tool in the detection and characterization of hepatic tumors. In some situations, hemodynamic changes might mimic neoplastic or inflammatory lesions and evoke diagnostic uncertainty. To confidently identify hepatic conditions such as venous outflow obstruction (Budd-Chiari syndrome), arterioportal shunts, hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome), peliosis hepatis, passive congestion, and hepatic infarction, radiologists must be familiar with the disease-specific CT appearances and related clinical manifestations.

Hepatocellular Carcinoma and Intrahepatic Cholangiocarcinoma: Imaging for Diagnosis, Tumor Response to Treatment and Liver Response to Radiation.

Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) comprise the majority of primary liver cancers. Both HCC and ICC have characteristic imaging appearances on multiphase computed tomography (CT) and magnetic resonance imaging (MRI). Several locoregional therapies, including radiation therapy, are used to treat unresectable disease and residual or recurrent tumor. The tumor response following locoregional therapies has variable imaging manifestations. Focal liver reaction, the imaging changes of the liver following radiation treatment, should be recognized and not mistaken for tumor. We review the diagnostic imaging of HCC and ICC, imaging of tumor response to treatment, and imaging of the liver response to radiation.

CT criteria for differentiating abdominal hemorrhage: anticoagulation or aortic aneurysm rupture?

OBJECTIVE: The purpose of our study was to test the hypothesis that CT criteria would allow accurate diagnosis of the specific cause of abdominal hemorrhage in patients with coagulopathy or abdominal aortic aneurysm. CONCLUSION: Attention to specific CT criteria allows accurate diagnosis of the specific cause of spontaneous abdominal hemorrhage even in patients who have both coagulopathy and an abdominal aortic aneurysm.

Budd-Chiari syndrome: spectrum of imaging findings.

OBJECTIVE: The objective of our study was to illustrate the imaging findings of Budd-Chiari syndrome, including CT, MRI, sonographic, and angiographic findings. CONCLUSION: The key imaging findings in Budd-Chiari syndrome are occlusion of the hepatic veins, inferior vena cava, or both; caudate lobe enlargement; inhomogeneous liver enhancement; and the presence of intrahepatic collateral vessels and hypervascular nodules. Awareness of these findings is important for early diagnosis and appropriate treatment.

Cirrhosis: CT and MR imaging evaluation.

In this article, we present the CT and MR imaging characteristics of the cirrhotic liver. We describe the altered liver morphology in different forms of viral, alcoholic and autoimmune end-stage liver disease. We present the spectrum of imaging findings in portal hypertension, such as splenomegaly, ascites and varices. We describe the patchy and lacelike patterns of fibrosis, along with the focal confluent form. The process of hepatocarcinogenesis is detailed, from regenerative to dysplastic nodules to overt hepatocellular carcinoma. Different types of non-neoplastic focal liver lesions occurring in the cirrhotic liver are discussed, including arterially enhancing nodules, hemangiomas and peribiliary cysts. We show different conditions causing liver morphology changes that can mimic cirrhosis, such as congenital hepatic fibrosis, "pseudo-cirrhosis" due to breast metastases treated with chemotherapy, Budd-Chiari syndrome, sarcoidosis and cavernous transformation of the portal vein.

Contrast media for fluoroscopic examinations of the GI and GU tracts: current challenges and recommendations.

One of the significant challenges facing radiologists who perform and interpret studies of the gastrointestinal and genitourinary systems have been periodic interruptions in the availability of barium and iodinated contrast media specially formulated for gastrointestinal (GI) and genitourinary (GU) studies. These interruptions are due to the US Food and Drug Administration's recent requirement for more stringent documentation of the safety and efficacy of contrast media and the consolidation among contrast manufacturers. Therefore, radiologists may be required to recommend an alternative means of evaluation, such as computed tomography, magnetic resonance, or endoscopy, or they may need to substitute a different formulation of a contrast agent not specifically developed for GI or GU use, for example the utilization of an agent designed and marketed for vascular use. This article reviews the current status of fluoroscopic contrast media, and provides suggestions and recommendations for the optimal and alternative use of contrast media formulations.

Positron emission tomography/computed tomography: protocol issues and options.

Combined positron emission tomography/computed tomography (PET/CT) became FDA-approved for clinical use in late 2001. There are several design advantages of combined PET/CT over PET and CT acquired on separate devices, including more accurate CT and PET data co-registration, improved lesion localization, consolidation of imaging studies, and reduced scan times compared to dedicated PET. There are several protocols that can used to scan patients on combined PET/CT devices. Although there is no single "correct" protocol for performing a PET/CT scan, the use of oral and intravenous contrast media may improve the diagnostic value of the CT component. Whether to utilize contrast media depends on important clinical variables, including the specific type of tumor and the likelihood of encountering viable abdominal and pelvic malignancy. This article discusses various protocols pertinent to PET/CT imaging, including how the CT portion of a PET/CT scan can be performed and optimized, as well as PET/CT interpretation and reporting issues.