Pelvic incidentalomas

Recent advances in multi-detector computed tomography, magnetic resonance imaging, and ultrasound have led to the detection of incidental ovarian, uterine, vascular and pelvic nodal abnormalities in both the oncology and non-oncology patient population that in the past remained undiscovered. These incidental pelvic lesions have created a management dilemma for both clinicians and radiologists. Depending on the clinical setting, these lesions may require no further evaluation, additional immediate or serial follow-up imaging, or surgical intervention. In this review, guidelines concerning the diagnosis and management of some of the more common pelvic incidentalomas are presented.

Gastrointestinal infection in the immunocompromised (AIDS) patient

In the past two decades acquired immunodeficiency syndrome (AIDS) has become one of the most devastating illnesses in human history. As the epidemic continues to spread increasingly, AIDS patients are no longer confined to a few specialized AIDS hospitals and are now seen in general hospitals and clinics everywhere. Radiologists need to recognize the appearances, to understand how-safely-to care for patients with this disease, and to know enough about the illness to be able to counsel their patients. This article presents a review of current knowledge about the wide range of gastrointestinal hepatic, splenic, biliary, and retroperitoneal manifestations in AIDS, and how the role of modern medical imaging techniques and diagnosis and treatment can be applied. The imaging aspects (conventional double-contrast gastrointestinal studies, ultrasound, CT, and MR) of the diseases of the luminal gastrointestinal tract, liver, spleen, biliary tract, and retroperitoneum will be systematically discussed. Candidiasis, herpes, cytomegalovirus, cryptosporidiosis, histoplasmosis, isosporiasis, salmonellosis, toxoplasmosis, unusual mycobacteria, and viral infections account for the majority of non-neoplastic disorders.

Staging of colorectal cancer

CT, MR, and TRUS play complementary roles in staging CRC. Further improvements in these techniques will improve the accuracy of preoperative staging and thereby help optimize patient treatment and outcome.

Use of single percutaneous endoscopic gastrostomy in management of gastric volvulus in three patients

Gastric volvulus is a rare condition that occurs when the stomach twists either in an organoaxial or mesenteroaxial direction. In patients with recurrent episodes of volvulus, standard therapy is surgical correction. Many patients, however, are not candidates for surgical therapy because of comorbid conditions or advanced age. Our aim was to determine if the insertion of a single percutaneous gastrostomy tube placement would assist in management of gastric volvulus in patients not able to undergo surgical therapy. The alpha-loop maneuver was used to reduce gastric volvulus in three elderly patients. A percutaneous endoscopic gastrostomy tube was then inserted to prevent recurrent volvulus. Single percutaneous gastrostomy tube placement was successful in managing volvulus in these three patients. Single percutaneous endoscopic gastrostomy tube placement is a useful treatment alternative to surgery in patients requiring therapy of gastric volvulus.

Using triphasic helical CT to detect focal hepatic lesions in patients with neoplasms

OBJECTIVE

Our purpose was to determine the value of triphasic helical CT (unenhanced, hepatic arterial, and portal venous phases) in the detection and characterization of focal hepatic lesions due to hepatomas or metastases.

MATERIALS AND METHODS

One hundred two patients with known or suspected hepatomas or liver metastases underwent triphasic CT. The number and conspicuity of lesions were evaluated on each phase.

RESULTS

Five hundred eighty-four lesions were detected in 102 patients. Patients with hypovascular malignancies had more lesions detected on the portal venous phase with increased conspicuity than on the other phases. Patients with hypervascular malignancies had lesions best detected on the hepatic arterial phase, which revealed small lesions that were not seen on the other phases in seven (21%) of the 33 patients with hypervascular metastases and hepatomas. No lesions were detected on the unenhanced phase that were not seen on the other phases. However, arterial phase images introduced new diagnostic dilemmas because not all lesions seen on the arterial phase alone were caused by hepatomas or metastases, even in patients with known malignancies; several lesions represented benign abnormalities that included focal nodular hyperplasia.

CONCLUSION

The unenhanced phase is not routinely necessary for the detection of metastases or hepatomas. Hypovascular malignancies are best evaluated during the portal venous phase. Small lesions due to hypervascular metastases and hepatomas are best evaluated and may be detected only during the hepatic arterial phase, which should be used routinely in these patients. New dilemmas may develop from the increased sensitivity of the hepatic arterial phase for lesions. However, the hepatic arterial phase is of limited value with hypovascular malignancies.

Acquired immunodeficiency syndrome (AIDS) of the abdominal organs: imaging features

The liver, spleen, biliary tract, pancreas, and kidneys are commonly affected by opportunistic infection, malignancy, and inflammatory disorders during the course of human immunodeficiency virus (HIV) infection. Clinical manifestations of solid abdominal visceral involvement are protean and usually nonspecific, but it is important to establish a specific diagnosis promptly in these often critically ill patients. This presentation reviews the cross-sectional imaging spectrum of HIV-associated lesions of these organs.

Gastric cancer. Radiologic diagnosis

The development and refinement of double-contrast barium techniques over the past two decades have dramatically improved the radiologist's ability to detect gastric cancer and characterize gastric ulcers. This article presents the radiologic findings of both early and advanced gastric cancer and offers guidelines for differentiating benign versus malignant gastric ulcers.

Small bowel cancer. Clinical and pathologic features

Although the small bowel constitutes over 75% of the length and 90% of the mucosal surface of the alimentary tract, it is the site of only 1% of gastrointestinal cancers. Despite their rarity, it is important to diagnose small bowel tumors early to maximize patient survival. This article focuses on the clinical and pathologic findings of small bowel adenocarcinomas and carcinoids.

Colorectal cancer. Clinical and pathologic features

Despite an improved understanding of the pathogenesis of colorectal cancer and the technical ability to alter its natural history in a large proportion of average and high-risk patients, this cancer remains deadly. There has been no significant change in incidence or survival rates over the past 40 years. This indicates a continued need for earlier detection of polyps and cancers, aggressive surgery for the primary tumor, and improved multimodality treatment for metastatic disease.

Esophageal cancer. Clinical and pathologic features

Carcinoma of the esophagus remains one of the most lethal of all cancers. In the past, squamous cell carcinomas accounted for over 95% of esophageal malignancies. Over the past two decades, however, there has been a dramatic increase in the incidence of adenocarcinoma arising in columnar cell-lined Barrett's mucosa, accounting for up to 34% of all esophageal cancers in some areas. This article discusses the different demographic, pathologic, therapeutic, and prognostic features of squamous cell and adenocarcinoma of the esophagus.

Gastric cancer. Radiologic staging

CT scan and EUS play complementary roles in staging gastric cancer. CT scan is initially performed to detect local and distant metastases. Depending on institutional expertise, EUS may be considered for local staging. Laparoscopic staging may also be helpful in select patients. It is hoped that further improvements in these techniques will improve the ability to stage gastric cancer and thereby optimize patient treatment and outcome.

Gastric cancer. Clinical and pathologic features

Gastric cancer is one of the leading causes of cancer mortality worldwide. Very little progress has been made in improving the dismal cure rate of gastric cancer over the last 30 years in the United States. Unless major breakthroughs develop in chemotherapy or radiation therapy, the only way to improve survival rates rests with earlier recognition and prevention.

Pancreaticobiliary manifestations of AIDS

The pancreas and the biliary tract are frequent sites of infectious, Inflammatory, and neoplastic disease in patients with HIV infection. However, the symptoms of pancreaticobiliary involvement may be relatively mild so that the prevalence of these disorders is probably underestimated. An appreciation of the imaging findings of HIV-associated pancreaticobiliary disorders is important because involvement of these organs may be the only criterion that establishes the diagnosis of AIDS (Table 1).

Upper urinary tract abnormalities in multiple sclerosis patients with urinary symptoms

OBJECTIVE

To determine the prevalence of upper urinary tract complications in multiple sclerosis (MS) patients with urinary symptoms, and to determine if an association exists between degree of physical impairment and upper urinary tract complications.

DESIGN AND SETTING

A cohort study of MS patients seeking treatment at a freestanding, university-affiliated rehabilitation hospital.

PARTICIPANTS

A referred sample of 48 patients with MS, exacerbation-free for 6 months with symptoms of neurogenic bladder dysfunction. For each patient, demographic data, disease characteristics, and urologic history was obtained. Using the Kurtzke Expanded Disability Status Scale (EDSS), participants were divided into a control (EDSS < 7) and study (EDSS >/= 7) group.

INTERVENTION

Ultrasound examination of the upper urinary tract.

MAIN OUTCOME MEASURE

Significant MS-related abnormalities of the upper respiratory tract.

RESULTS

Ten of 48 patients (21%) had significant MS-related upper urinary tract abnormalities, which were evenly distributed between control and study groups. In the more disabled study group, abnormalities were associated with the symptom of urinary hesitancy (p < .05) and form of bladder management (p < .05).

CONCLUSIONS

Routine screening for upper urinary tract complications appears indicated in a select group of MS patients with urinary symptoms.

Radiologic investigation of acute inflammatory and infectious bowel disease

Definitive diagnosis of infectious or idiopathic inflammatory bowel disease ultimately rests on histologic and bacteriologic documentation. Nevertheless, radiologic studies play an important role in the evaluation and management of patients with acute enterocolitis. Plain abdominal films can give a gross estimate of disease extent in the colon and detect complications, such as perforation or toxic megacolon. Double-contrast barium enema allows visualization of the mucosal pattern and the overall configuration of the bowel, which are important for determining the extent and severity of disease and its most likely cause. Cross-sectional imaging depicts the mural and mesenteric involvement as well as intraperitoneal complications of inflammatory bowel disease, thus providing a critically important perspective that complements the information afforded by endoscopic and conventional radiographic techniques.

Colitis: use of CT findings in differential diagnosis

PURPOSE

To determine whether colitides can be differentiated based on computed tomographic (CT) features.

MATERIALS AND METHODS

The CT scans of 117 patients with documented colitis and colon wall thickening were reviewed. Features evaluated included mural thickness and homogeneity, distribution of bowel involvement, and associated mesenteric and small bowel disease.

RESULTS

The mean colon wall thickness in Crohn colitis (11.0 mm +/- 5.1) was significantly greater than in ulcerative colitis (7.8 mm +/- 1.9) (P < .002). Submucosal fat deposition, not observed in the acute colitides, was present significantly more often in ulcerative (61%) than in Crohn colitis (8%) (P = .0001). Exclusive involvement of the right colon and small bowel was most frequent with Crohn and infectious colitis. Abscess was associated almost exclusively with Crohn colitis (35%) but was seen in one patient with radiation colitis.

CONCLUSION

Although many CT findings in patients with colitis are nonspecific, some features are helpful in suggesting a specific diagnosis.

Passive hepatic congestion: cross-sectional imaging features

Passive hepatic congestion is caused by stasis of blood within the liver parenchyma due to compromise of hepatic venous drainage. It is a common complication of congestive heart failure and constrictive pericarditis, wherein elevated central venous pressure is directly transmitted from the right atrium to the hepatic veins because of their close anatomic relationship (Fig. 1). The liver becomes tensely swollen as the hepatic sinusoids dilate and engorge to accommodate the backflow of blood. A variety of structural and functional hepatic derangements develop that have distinctive appearances on sonograms, CT scans, and MR images.

Renal manifestations of AIDS

The kidneys in patients with acquired immunodeficiency syndrome (AIDS) are subject to a variety of insults. Renal manifestations can be seen with imaging studies of AIDS patients. Computed tomographic (CT) and ultrasound (US) scans of 64 patients with AIDS and renal dysfunction were retrospectively reviewed and compared with clinical, laboratory, and, when available, biopsy results. Imaging abnormalities included increased cortical echogenicity, nephromegaly, pyelonephritis, lobar nephronia, focal masses caused by abscess and lymphoma, parenchymal calcification, hydronephrosis, and infarct. Generally, patients with AIDS as a result of intravenous drug abuse and those with multiple risk factors were more likely to have abnormalities demonstrated at imaging as well as poorer prognosis than were patients in the homosexual transmission group in this series. Although US should be the screening study used in patients with AIDS and suspected renal dysfunction, CT and magnetic resonance imaging may be necessary to identify focal infectious, ischemic, and neoplastic processes.

Appendices epiploicae of the colon: radiologic and pathologic features

Appendices epiploicae are adipose structures protruding from the serosal surface of the colon. They can be seen with abdominal radiography and cross-sectional imaging if the colonic wall is surrounded by intraperitoneal contrast material, ascites, or blood. Normal appendices epiploicae appear as lobulated masses of pericolic fat, usually 2-5 cm long and 1-2 cm thick. Their enlargement, deformity, or altered radiopacity may result from various pathologic processes that can originate locally or extend from adjacent viscera. In a series of 22 cases, appendices epiploicae were affected by spontaneous torsion and hemorrhagic infarct, calcification due to aseptic fat necrosis, primary or secondary inflammation, enlargement by lipomas or metastases, and incarceration in hernias. Disorders of appendices epiploicae are often manifested by nonspecific clinical signs and symptoms (eg, torsion is often mistaken for appendicitis or diverticulitis). These entities should be included in the differential diagnosis of any unexplained abdominal pain or pericolic lesions in adults.

MRI of hepatic iron deposition in patients with renal transplant

Excess hepatic iron deposition was found in five of 15 (33%) renal transplant patients undergoing magnetic resonance (MR) screening for avascular necrosis of the femoral heads. Only one of these patients had overt liver disease. The number of prior blood transfusions was a significant factor for this deposition, whereas the age and sex of the patients, number and type of transplants, histocompatibility alleles (HLA), and years of hemodialysis and of chronic renal failure were not significant etiological factors. Liver/fat intensity ratios of less than 0.29 on T1-weighted images and ratios of less than 0.21 on T2-weighted images and a calculated T2 value of less than 35 ms were the best indicators of iron overload. Renal transplant patients are at great risk for excess hepatic iron deposition and MR imaging is a promising tool for the diagnosis of iron overload in this patient population.

Diverticulitis of the duodenum: clinical and radiological manifestations of seven cases

Seven patients with duodenal diverticulitis were evaluated by computed tomography (CT) and various other abdominal imaging techniques. The series included four men and three women who ranged in age from 47 to 84 yr (mean: 65 yr). They had presented with epigastric or periumbilical pain, low-grade fever, leukocytosis, and loss of appetite and weight due to postprandial cramps or vomiting. In each instance, the abdominal CT examination proved crucial in the diagnosis of duodenal diverticulitis, with contained perforation or inflammatory changes involving the adjacent structures. Five patients underwent laparotomy while two others were treated conservatively with antibiotics and/or percutaneous drainage of peridiverticular abscess. The clinical and radiological features of this uncommon entity are herein described, along with a brief review of the medical literature regarding the current approach to its diagnosis and management.

CT of inflammatory bowel disease

Computed tomography (CT) provides an important perspective in patients with inflammatory bowel disease that often has a profound influence on the therapeutic decision-making process. By virtue of its ability to image the bowel wall, serosa, and mesentery directly and noninvasively, CT can diagnose infectious and inflammatory complications that often can only be inferred indirectly by barium studies and endoscopy.

CT diagnosis of postoperative abdominal complications

Over 3 million abdominal operations are performed in the United States each year, and a significant number of these patients subsequently undergo computed tomography (CT) either for follow-up of resected lesions or evaluation of possible postoperative complications. This article describes the clinical presentations and CT features of commonly encountered postsurgical complications. A wide spectrum of lesions involving the abdominal wall as well as intraperitoneal structures is herein illustrated to emphasize the role of CT in their diagnosis and management.

Acquired malposition of the colon and gallbladder in patients with cirrhosis: CT findings and clinical implications

Topographic relationships among the gallbladder, liver, hepatic flexure of the colon, right hemidiaphragm, and anterolateral peritoneal reflection were evaluated with computed tomography in 75 patients with biopsy-proved cirrhosis and in 200 control subjects to determine the effect of cirrhotic liver morphology on the anatomy of the right upper quadrant of the abdomen. Interposition of the colon between the liver and anterolateral abdominal wall and/or diaphragm was seen in 18 of the 75 (24%) cirrhotic patients and in six of the 200 (3%) control subjects. There was a strong correlation among gallbladder malposition, colonic interposition, and a ratio of transverse caudate lobe width to right lobe width (C/RL) exceeding 0.60. Patients with cirrhosis, colonic interposition, and gallbladder malposition had a mean C/RL of 0.62, compared with a mean of 0.50 for cirrhotic patients without interposition (P less than .0001). The mean C/RL for control subjects without interposition was 0.43, as compared with 0.69 for control subjects with interposition (P less than .01). These acquired malpositions of the colon and gallbladder may pose a diagnostic dilemma and increase the risk of inadvertent injury during percutaneous liver biopsy, interventional biliary tract procedures, and laparotomy.

Lymphadenopathy in chronic active hepatitis: CT observations

CT scans were obtained in 17 patients who had biopsy-proved chronic active hepatitis in order to evaluate deteriorating liver function and clinical status. Lymphadenopathy in the porta hepatis and/or retroperitoneum was found in 11 patients (65%), and this was the only CT indication of significant hepatic disease in six patients (35%). In three of five patients who subsequently underwent immunosuppressive therapy, serial biopsy, and CT scanning, clinical and histologic improvement in the condition of the liver were accompanied by a reduction in lymph-node size on CT. These findings suggest that abdominal adenopathy is a frequent CT finding in patients who have chronic active hepatitis and might be a useful marker in monitoring immunotherapy.

Thrombosis of the splanchnic veins: CT diagnosis

Fourteen patients had mesenteric, portal, or splenic venous thrombosis that was diagnosed primarily by contrast-enhanced CT. The group included five patients with coagulopathy, three with pancreatic carcinoma, two with cirrhosis and portal hypertension, one with pancreatitis, and one with hepatocellular carcinoma. In two patients, no etiology was determined. In all cases, CT easily identified low-density venous thrombosis, which frequently involved more than one vein. In four patients, all three splanchnic veins were involved; five patients had occlusion of two veins. In five patients, only one vein was involved. Additional CT findings included ascites, collateral veins, hepatomegaly, and splenomegaly. No venous wall enhancement was found. CT also was helpful in defining the cause of thrombosis in six of 14 patients. Mesenteric edema and/or bowel wall thickening was not identified. None of the patients had classic clinical evidence of splanchnic venous occlusion, and none died primarily of that disease. The major morbidity suffered by these patients stemmed from complications of splanchnic venous occlusion, and nine patients ultimately required sclerotherapy, splenectomy, and portal decompression. We conclude that CT is useful in the diagnosis of splanchnic venous thrombosis. Our experience suggests that mesenteric, splenic, and/or portal venous thrombosis may occur more commonly than has been previously thought and that the disease in many cases is not life threatening.

A comparative study of computed tomography and ERCP in pancreaticobiliary disease

Fifty-seven patients with suspected pancreaticobiliary pathology constituting a clinical subset in whom the diagnosis was problematic or nonspecific were evaluated with computed tomography and ERCP. The relative sensitivities, specificities, and accuracies of the two tests were compared. Computed tomography was successful in obtaining a diagnostic examination in 100% and ERCP was technically successful in 75%. Both tests were equally accurate in detecting an abnormality (computed tomography 95.7%; ERCP 95.3%) and offering a correct diagnosis (computed tomography 72%; ERCP 70%). Sensitivity and specificity of the two tests for detection of an abnormality was computed tomography 100% and 91.3%; ERCP 91.7% and 100%. Sensitivity and specificity for the correct diagnosis was computed tomography 59% and 91.3%; ERCP 46% and 100%. Computed tomography was also superior to ERCP in making a correct diagnosis in pancreatic carcinoma (80% versus 63%) and pancreatitis (75% versus 50%). Based on these results we conclude that computed tomography utilizing high doses of intravenous contrast material and thin collimation is the preferred screening examination for pancreaticobiliary disease. ERCP should be reserved for those cases where the pancreaticobiliary disease. ERCP should be reserved for those cases where the diagnosis on computed tomography is obscure or uncertain and/or the pancreatic or biliary ductal anatomy requires direct contrast imaging.

Budd-Chiari syndrome: CT observations

The authors describe four patients with Budd-Chiari syndrome in whom contrast material-enhanced computed tomographic (CT) scans demonstrated low-density venous thrombosis in three sites not, to our knowledge, previously described with this modality. Thrombosis was seen in the portal circulation, the hepatic veins, and the intrahepatic inferior vena cava. It is known that concomitant portal vein thrombosis may be seen in 20% of patients with Budd-Chiari syndrome. Three of the four patients in the current study had this finding, one with extensive thrombosis of portal, mesenteric, and splenic veins and the other two with portal vein branch involvement. In one patient hepatic vein thrombosis was demonstrated with CT, and in three inferior vena cava clot was demonstrated. All four patients had the distinctive hepatic parenchymal contrast enhancement pattern seen in this condition, which the authors think may be at least partially caused by associated portal thrombosis. The presence of portal venous thrombosis should prompt the observer to consider the diagnosis of Budd-Chiari syndrome. Detection of hepatic vein clot confirms the diagnosis and may be seen in this condition in association with inferior vena cava thrombus.

Evaluation of ectopic bone by CT

The CT appearance of ectopic bone and its maturation in 25 patients were correlated with the findings on radiographs and bone scans. Ossification progressed from an early appearance of soft-tissue density of lower attenuation than muscle to a calcific density paralleling radiographic and scintigraphic evidence of bone formation. Persistent unossified, low-density soft tissue was detected adjacent to mineralized areas of ectopic bone in 14 patients up to 16 years after neurologic injury, often with bone-scan evidence of maturity of the ectopic bone. This soft tissue most likely corresponds to immature, unossified connective tissue, which may have a potential for ossification. Detection of areas of soft-tissue density by CT and their avoidance during surgical resection of an ankylosing mass of ectopic bone may reduce intraoperative hemorrhage and postoperative ectopic bone recurrence.

Bolus-rapid infusion of contrast medium: simplified technique for optimal computed tomography pancreatography without use of dynamic scanning

Optimal pancreatic computed tomography demands the use of both narrow beam collimation and high levels of intravascular contrast medium. Dynamic scanning with or without table incrementation has been advocated, but not all patients are amenable to prolonged breath holding, and tube cooling requirements may limit the study. In addition, repeat boluses usually must be administered to adequately image the entire pancreas. Enhancement may also be less than uniform. We describe a simple method of pancreatic scanning using bolus injection and pressurized rapid infusion of contrast medium that yields consistently high-quality scans demonstrating both pancreatic parenchymal and peripancreatic vascular enhancement in most patients. The method eliminates the need for dynamic scans in most cases and improves the speed of examination and quality of patient care in a busy computed tomography department.

Cross-sectional imaging of inflammatory bowel disease

The cross-sectional imaging modalities provide an important diagnostic perspective in patients with inflammatory bowel disease that often has a profound influence on the therapeutic decision-making process. They can directly and noninvasively image infectious and inflammatory complications involving the bowel wall, serosa, and mesentery that can only be assessed indirectly by colonoscopy and barium studies. At the present time, CT is superior to ultrasound and MR in diagnosing these extramucosal complications.

Duodenal manifestations of nontropical sprue

Barium studies of the upper gastrointestinal tract and small bowel were performed in 16 adult patients with biopsy-proven nontropical sprue. Commercially available contrast media containing micropulverized barium sulfate, suspending agents, and various other additives were used. Radiographs were analyzed for the incidence and pattern of duodenal vs. small-bowel changes associated with celiac disease. Thirteen of 16 patients (81%) demonstrated abnormalities of the duodenum which ranged from focal erosions to diffusely thickened and nodular folds. A nonspecific, mild dilatation pattern was present on the small-bowel series of 11 patients (69%). The classic radiographic signs of malabsorption, such as flocculation and segmentation, however, occurred in less than 20% of cases, apparently because of the stability of new barium suspensions. The pathogenesis of duodenal changes in sprue and its diagnostic implications are emphasized.

Value of computed tomography in the detection of complications of Crohn's disease

Abdominal and pelvic computed tomography (CT) scans were performed on 17 patients with suspected complications of Crohn's disease. CT was superior to conventional barium studies and colonoscopy in demonstrating mural, serosal, and mesenteric pathology such as bowel wall thickening (100%), abscess (59%) and phlegmon (6%) formation, and fibro-fatty proliferation of the mesentery (41%). While not advocated as the primary means of evaluating Crohn's disease, CT can provide information vital to the management of complications of this disease.

Brain edema: ultrasound examination

Sonographic examination of the brain in 10 patients who had cortical mass lesions was performed. Results were compared with findings of CT. In each case, brain edema surrounded the lesion, and the adjacent white matter had a diffusely echo-genic appearance that corresponded to the area of brain edema seen on CT.

Inferior vena cava CT pseudothrombus produced by rapid arm-vein contrast infusion

Laminar flow within the inferior vena cava can cause artifacts that may simulate thrombus if a foot-vein infusion is used. A "pseudothrombus" artifact within the suprarenal inferior vena cava produced by rapid infusion of contrast material through an arm vein is reported. This artifact was noted in 25 patients in a 6 month period and was believed to be from laminar flow of renal venous effluent of increased opacity around less opacified infrarenal caval contents. Differentiation from true thrombus can be made by the use of delayed scans as well as the increased density and relatively poor margination of the artifact.