Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Objectives: Multiple human systems are greatly affected by gravity, and many disease symptoms are altered by posture. However, the overall anatomical structure and pathophysiology of the human body while standing has not been thoroughly analyzed due to the limitations of various upright imaging modalities, such as low spatial resolution, low contrast resolution, limited scan range, or long examination time. Recently, we developed an upright computed tomography (CT), which enables whole-torso cross-sectional scanning with 3-dimensional acquisition within 15 seconds. The purpose of this study was to evaluate the performance, workflow efficacy, effects of gravity on a large circulation system and the pelvic floor, and potential clinical impact of upright CT. Materials and Methods: We compared noise characteristics, spatial resolution, and CT numbers in a phantom between supine and upright CT. Thirty-two asymptomatic volunteers (48.4 ± 11.5 years) prospectively underwent both CT examinations with the same scanning protocols on the same day. We conducted a questionnaire survey among these volunteers who underwent the upright CT examination to determine their opinions regarding the stability of using the pole throughout the acquisition (closed question), as well as safety and comfortability throughout each examination (both used 5-point scales). The total access time (sum of entry time and exit time) and gravity effects on a large circulation system and the pelvic floor were evaluated using the Wilcoxon signed-rank test and the Mann-Whitney U test. For a large circulation system, the areas of the vena cava and aorta were evaluated at 3 points (superior vena cava or ascending aorta, at the level of the diaphragm, and inferior vena cava or abdominal aorta). For the pelvic floor, distances were evaluated from the bladder neck to the pubococcygeal line and the anorectal junction to the pubococcygeal line. We also examined the usefulness of the upright CT in patients with functional diseases of spondylolisthesis, pelvic floor prolapse, and inguinal hernia. Results: Noise characteristics, spatial resolution, and CT numbers on upright CT were comparable to those of supine CT. In the volunteer study, all volunteers answered yes regarding the stability of using the pole, and most reported feeling safe (average rating of 4.2) and comfortable (average rating of 3.8) throughout the upright CT examination. The total access time for the upright CT was significantly reduced by 56% in comparison with that of supine CT (upright: 41 ± 9 seconds vs supine: 91 ± 15 seconds, P < 0.001). In the upright position, the area of superior vena cava was 80% smaller than that of the supine position (upright: 39.9 ± 17.4 mm² vs supine: 195.4 ± 52.2 mm², P < 0.001), the area at the level of the diaphragm was similar (upright: 428.3 ± 87.9 mm² vs supine: 426.1 ± 82.0 mm², P = 0.866), and the area of inferior vena cava was 37% larger (upright: 346.6 ± 96.9 mm² vs supine: 252.5 ± 93.1 mm², P < 0.001), whereas the areas of aortas did not significantly differ among the 3 levels. The bladder neck and anorectal junction significantly descended (9.4 ± 6.0 mm and 8.0 ± 5.6 mm, respectively, both P < 0.001) in the standing position, relative to their levels in the supine position. This tendency of the bladder neck to descend was more prominent in women than in men (12.2 ± 5.2 mm in women vs 6.7 ± 5.6 mm in men, P = 0.006). In 3 patients, upright CT revealed lumbar foraminal stenosis, bladder prolapse, and inguinal hernia; moreover, it clarified the grade or clinical significance of the disease in a manner that was not apparent on conventional CT. Conclusions: Upright CT was comparable to supine CT in physical characteristics, and it significantly reduced the access time for examination. Upright CT was useful in clarifying the effect of gravity on the human body: gravity differentially affected the volume and shape of the vena cava, depending on body position. The pelvic floor descended significantly in the standing position, compared with its location in the supine position, and the descent of the bladder neck was more prominent in women than in men. Upright CT could potentially aid in objective diagnosis and determination of the grade or clinical significance of common functional diseases.

OBJECTIVE. The purpose of this study was to compare the accuracy of CT urography and excretory urography for the detection and localization of upper urinary tract urothelial carcinoma.MATERIALS AND METHODS. Of 128 patients at high risk for upper tract urothelial carcinoma who were examined with both CT urography and excretory urography between 2002 and 2007, 24 were undiagnosed and excluded. CT urography and excretory urography results of the remaining 104 patients and 552 urinary tract segments were compared with histopathologic examination or follow-up imaging at 1 year. Two readers independently scored the confidence levels for the presence or absence of upper urinary tract urothelial carcinoma in each of six upper urinary tract segments on both CT urography and excretory urography; differences were resolved by consensus.RESULTS. Upper urinary tract urothelial carcinoma was diagnosed in 77 (14%) segments of 46 (44%) patients. Per-patient sensitivity, specificity, overall accuracy, and area under the re...

With the increasing discovery of small renal masses with cross-sectional imaging, there has been the concomitant rise in their treatment. With the intent of early curative surgery for a presumed renal cell carcinoma, many renal masses are being resected at surgery without a confirmed diagnosis. Many of them are benign, and some are angiomyolipomas. The diagnosis of renal angiomyolipoma using imaging is, therefore, is as important as ever. Although most, if not all angiomyolipomas with abundant fat are diagnosed readily, some have too little fat to be detected with imaging. This article reviews the current classification, imaging pitfalls, and diagnosis of angiomyolipoma with an emphasis on the fat-poor types. Proper imaging technique, a thorough search for fat, and the appropriate use of percutanoeus biopsy are all needed to eliminate the unnecessary treatment of these benign neoplasms.