Cirrelda Cooper

AIDS-Associated Intussusception in Young Adults

We have examined the changing demographics of adult intussusception and implicate human immunodeficiency virus (HIV)- and acquired immune deficiency syndrome (AIDS)-associated gastrointestinal pathology as risk factors for intussusception in young adults. The clinical index of suspicion for intussusception should be raised for an HIV-positive young adult with intermittent crampy abdominal pain. Over a 10-year period, eight cases of adult intussusception were diagnosed at our institution, and we reviewed the diagnostic computed tomography (CT) scans and records of these patients to correlate them with radiological studies, clinical history, surgical findings, laboratory studies, pathologic analysis, and outcome. Three of the eight patients with adult intussusception had AIDS, all diagnosed by CT scans. Their average age was 41 years, whereas average age of the non-HIV-associated patients was 63. These findings suggest that HIV- and AIDS-associated gastrointestinal pathology provide lead points for intussusception and are significant risk factors for intussusception in young adults. We reviewed the five previously reported cases of AIDS and intussusception and conclude that intussusception should be a diagnostic consideration in an HIV-positive young adult with abdominal complaints. It is clear that AIDS-associated intussusception is a real clinical problem and that CT is an effective method of diagnosing it.

The optimal temporal window for CT of the liver using a time-density analysis: implications for helical (spiral) CT.

Objective Scanning protocols for conventional CT of the liver have been proposed. Current availability of helical CT with a four- to sixfold decrease in scan time requires significant adjustments in these protocols. The present study assesses the implications of time—density curves on the performance of helical liver CT. Materials and Methods Twenty patients without liver lesions were studied for time—density analysis of the aorta, inferior vena cava (IVC), portal vein, and liver. Scans were performed at the level of the portal vein at baseline and every 15 s for 3 min following uniphasic administration of 150 ml (300 mg I/ml) nonionic contrast agent. Regions of interest were used to measure three areas in each anatomic structure over time. Median and mean peak enhancement times were calculated for all 20 patients. Cubic spline interpretation was employed to determine the point of equilibrium. Results Results demonstrated the following average maximum enhancement values and times for peak enhancement: aorta: 227 HU (75 s); liver: 123 HU (105 s); portal vein: 187 HU (90 s); IVC: 142 HU (90 s). Hepatic enhancement achieved 67 HU over baseline. Peak portal enhancement occurred 15 s prior to liver enhancement (p = 0.001). Aortic and hepatic curves became parallel (onset of equilibrium) at a median time of 120 s. Conclusion Helical scanning requires a longer delay (70–80 s) than used for conventional CT. Upon application of these principles, scan initiation occurs higher on the liver enhancement curve, improving liver enhancement without impinging on equilibrium.

CT appearance of diffuse mesenteric edema.

The extent of pathologic processes involving the mesentery is frequently difficult to assess by clinical examination and standard radiography. Contrast studies of the gastrointestinal tract only identify the effect of these processes on adjacent opacified bowel loops and frequently underestimate the extent of mesenteric pathology. Computed tomography has previously been used to characterize various mesenteric abnormalities, most often secondary to malignant or inflammatory disease. We report the characteristic CT appearance of diffuse mesenteric edema in 14 patients. Eleven patients had documented hypoalbuminemia, two patients superior mesenteric vein thrombosis, and one patient cirrhosis. The CT findings that allowed confident diagnosis of this entity include increase in density of the mesenteric fat, poor definition of segmental mesenteric vessels, relative sparing of the retroperitoneal fat, and association with subcutaneous edema.

Venous Thromboembolism After Uterine Fibroid Embolization

Thromboembolic complications after uterine fibroid embolization (UFE) are infrequent. The incidence and predisposing factors of thromboembolism after UFE are unknown. We present eight cases of nonfatal thromboembolic complications after UFE and estimate the frequency of such events as 0.4%.

CT appearance of focal pseudomembranous colitis.

Previous reports of the CT findings of pseudomembranous colitis (PMC) have demonstrated the diffuse form of the disease. Although the focal nature of PMC is well recognized in the gastrointestinal literature, this manifestation has not been stressed in CT reports. We present three cases of focal colonic thickening detected on CT that proved to be PMC.

CT demonstration of myocardial perforation by a pacemaker lead.

We report a case of perforation of the right atrium by a transvenous right atrial appendage pacemaker lead diagnosed by CT. Routine radiologic assessment was unable to demonstrate the perforation. Computed tomography is recommended in cases where pacemaker perforation is clinically suspected but not confirmed by conventional radiographic means.

Imaging of the liver: a survey update of prevailing techniques for conventional CT scanning

BackgroundA survey of the Society of Computed Body Tomography/Magnetic Resonance (SCBT/MR) was performed to assess current techniques in liver CT scanning.MethodsThe study was designed as an update to a study performed in 1987. The survey was distributed to 67 members of the SCBT/MR at 35 institutions.ResultsTwenty-six institutions responded. As in 1987, none relied solely on noncontrast scans. In 1987, only 54% (12/22) of institutions performed contrast-enhanced scans as their primary technique compared with 73% (19/26) in 1993. Ionic contrast was used exclusively in the earlier study, whereas in the present study 58% used nonionic contrast in the majority of cases and 38% used nonionic contrast routinely. In 1987, 41% performed scans with a power injector compared with 85% in the present study. Enhanced scans were performed during the contrast bolus in 36% of institutions in 1987 compared with 76% in this study. No institution relied on noncontrast scans alone. In the previous study the delay between injection and scanning was variable (0–60 s), whereas in the present study 83% specified a delay of 21–45s.ConclusionSignificant refinements in CT technique, wider use of power injectors, utilization of nonionic contrast, and a more critical approach to optimize liver imaging have created a significant impact on the practice of liver CT.

Cluster Scanning in Body CT

Rapid, dynamic computed tomography (CT) is essential in scanning the body in order to maintain adequate contrast enhancement during the entire examination. In the case of the liver, this is most critical in order to complete scanning prior to the equilibrium phase when lesions are less conspicuous or may be missed entirely. This technical note describes the application of “cluster scanning” to conventional scanning in order to optimize body CT by decreasing the total exam time.