Cystic adrenal lesions: CT features.

PURPOSE: To define computed tomographic (CT) features of cystic adrenal lesions that differentiate them from similar-appearing adenoma. MATERIALS AND METHODS: CT scans of 13 cystic adrenal lesions (four endothelial cysts, three benign pseudocysts, one nonspecific benign cyst, one carcinoma, one pheochromocytoma, and three stable lesions with no histologic diagnosis) were analyzed retrospectively. Reports in the literature of 26 benign adrenal cysts were also reviewed. RESULTS: Mean lesion diameter was 6.2 cm, and six lesions were less than 5.0 cm. Mean attenuation values was 21 HU, and in eight cases it was less than 15 HU. Partial adrenal involvement was noted in six cases. Ten lesions contained wall or septal calcification. Wall thickness was 3 mm or less in nine and exceeded 6 mm in three lesions; one of the latter was cystic carcinoma. Wall enhancement (but no intralesional enhancement) was found in two of six lesions. Of 37 reviewed benign cysts, 19 had mural and seven had central calcification, 28 were unilocular, and seven had high attenuation value. Wall thickness was 3 mm or less in 31 lesions. CONCLUSION: CT findings of a nonenhancing mass with or without wall calcification allow differentiation of adrenal cyst from adenoma. A small adrenal cyst with near-water attenuation and a thin (< or = 3-mm) wall is likely to be benign.

MR imaging artifacts that simulate disease: how to recognize and eliminate them.

Occasionally, artifacts may simulate pathologic conditions on magnetic resonance (MR) images. Motion artifacts especially affect images of the chest and abdomen. There are a number of techniques for reducing motion artifacts, including respiratory and cardiac gating, k-space phase reordering, gradient moment nulling, even echo rephasing, and physical restraints. Aliasing occurs when the field of view does not include all of the anatomic structures present in the imaged section. Aliasing artifacts can be eliminated by increasing the field of view, oversampling, and use of saturation pulses or surface coils. Truncation artifacts represent the difference between the original and the reconstructed image and can be reduced with data extrapolation algorithms or image filtering. Chemical shift artifacts and magnetic susceptibility artifacts are due to a local deformity of the magnetic field, resulting in spatial misregistration. Chemical shift artifacts are more severe in images acquired with a narrow-bandwidth technique; magnetic susceptibility artifacts are more severe in images acquired with a long echo time. Pitfalls in the interpretation of MR images can be avoided by becoming familiar with the appearances and causes of common MR imaging artifacts.

MRI anatomy of the rat kidney at 1.5 T in different states of hydration.

The objective of this study was to determine correlation between structural anatomy and surface coil spin-echo MR imaging of the rat kidney and the effect of hydration state on MR signal intensities of the cortex and medulla. Twelve rats were studied in a pilot study with a 3-inch surface coil in a 1.5 T magnet under five different states of hydration. Serum and urine osmolality measurements were obtained immediately prior to each scan. Signal intensity measurements were made from both T1- and T2-weighted images of the cortex and medulla of both kidneys in each state of hydration. Gross and histological anatomy of the rat kidneys was correlated with the MR images. Four distinct layers were detected in vivo on MRI images of the rat kidney; these correlated with the histological layers. T1-weighted cortico-medullary differentiation was most pronounced at 48 h dehydration; T2 cortico-medullary differentiation was greatest at 72 h of dehydration. We concluded that different parts of the mammalian nephron can be identified by MR imaging and that cortico-medullary differentiation is affected by the hydration state of the animal.

Radiographic techniques in renal parenchymal disease.

In his or her practice, the nephrologist usually has a substantial number of patients on dialysis for chronic renal failure. The longer a patient remains on either peritoneal dialysis or hemodialysis, the more at risk he or she is of developing acquired cystic disease of the kidney and renal cell carcinoma. Due to recent developments such as lower osmolar intravenous contrast media, sonography, and magnetic resonance imaging, the radiologist has the ability to assess the kidney in chronic renal failure with a growing number of less-invasive modalities. The lower osmolar agents appear to be less toxic to the kidney. Thus, they can be used when the benefit of the information obtained from a necessary procedure, eg, computed tomography or coronary arteriography, surpasses the risk. Duplex Doppler sonography can assess the pressure of flow in the arcuate vessels of the kidney with measurements of the resistive index. The resistive index is a proven tool for assessing rejection of the renal allograft--another newer application is in the diagnosis of obstruction. An elevated resistive index found in a kidney with a dilated collecting system confirms the diagnosis of obstruction. Studies are being made on its application in other renal disease processes as well.

Sagittal MR images of the knee: a low-signal band parallel to the posterior cruciate ligament caused by a displaced bucket-handle tear.

A low-signal band parallel and anterior to the posterior cruciate ligament has been noted on sagittal MR images of the knee in some patients with other evidence for medial meniscal tears. It was hypothesized that this low-signal band represented the mesially displaced fragment of a bucket-handle tear. To verify this, we retrospectively reviewed MR and arthroscopic findings in 54 consecutive patients. Arthroscopy showed a bucket-handle tear of the medial meniscus in seven patients and was considered diagnostic. Sagittal MR images were reviewed without knowledge of the arthroscopic results. The presence of a curvilinear low-signal band above the tibial cortex anterior, inferior, and parallel to the posterior cruciate ligament was identified on MR images in all seven of the patients in whom the presence of a bucket-handle medial meniscal tear was confirmed by arthroscopy. Our findings suggest that a low-signal band anterior and parallel to the posterior cruciate ligament on sagittal MR images of the knee is caused by a mesially displaced bucket-handle tear of the medial meniscus.

Sigmoid diverticulitis: diagnostic role of CT--comparison with barium enema studies.

The diagnostic value of computed tomography (CT) and barium enema (BE) studies was evaluated prospectively in hospitalized patients with the presumptive diagnosis of acute sigmoid diverticulitis based on the presence of left-lower-quadrant pain and tenderness, fever, and leukocytosis. Of 56 patients, 11 had sigmoid diverticulitis confirmed at surgery and 16 by clinical response to medical therapy. CT, performed in all diverticulitis patients, had positive results in 93% (25 of 27). These compared favorably with BE study results, of which 80% (20 of 25) were positive. Neither examination had false-positive results. In the 29 patients who did not have diverticulitis, an alternative diagnosis was made by means of CT in 20, but in only three by means of BE studies. Many of the extracolonic abnormalities recognized at CT were clinically unexpected and necessitated emergency surgery. The excellent sensitivity and specificity of CT coupled with its versatility in the detection of extracolonic disease give it an advantage over contrast enema studies for diagnosis of sigmoid diverticulitis. CT should be the initial study in acutely ill patients, especially when the clinical features are atypical for sigmoid diverticulitis.

Comparison of computed tomography and contrast enema evaluation of diverticulitis.

A total of 31 patients with diverticulitis were analyzed who had both computed tomography and contrast enema. There was almost equal sensitivity to abnormality of approximately 90 percent. Contrast enema produced a specific diagnosis of diverticulitis in 61 percent, using stringent positive criteria, and an additional 29 percent with suggestive findings. Comparative computed tomography specific diagnoses in those 31 cases was made in 65 percent, and suggestive in 23 percent. Computed tomography was particularly useful diagnostically in cases of retrograde obstruction on contrast enema. The authors conclude that contrast enema should be the primary mode of approach, while computed tomography can be a valuable follow-up when the diagnosis is still in doubt, or if it is possible that patient management might be altered by additional information.

CT appearance in tuberculous pancreatic abscess.

We report a case of a tuberculous pancreatic abscess in a 47-year-old human immunodeficiency virus positive intravenous drug abuser. She had a prolonged febrile course and persistent abdominal pain. On CT and sonography the lesion lacked the usual ancillary features of an abscess such as diffuse pancreatic enlargement and a peripancreatic fluid collection, and more closely resembled a necrotic neoplasm.

Isodense splenic mass: hamartoma, a case report.

Hamartoma of the spleen is a very rare, benign tumor. A case report of an isodense mass on computed tomography, both before and after intravenous contrast administration is illustrated. The mass was well demonstrated on sonography and nuclear medicine scans. This benign mass may be missed on routine computed tomography.

Adrenal and pseudoadrenal masses: CT and US findings.

Computed tomography (CT) is currently the imaging modality of choice for assessing the morphology of the adrenal glands in adult patients. Much useful information can be gained using CT in disease processes which primarily involve one or both of the adrenal glands, such as adenomas, as well as in entities which secondarily affect the adrenals, such as pituitary or metastatic disease. The size and configuration of the glands can be readily determined, and masses may be detected. We discuss CT of normal and abnormal adrenal glands with sonographic (US) and pathological correlation, when available. Entities which may mimic adrenal abnormalities are emphasized. Relative advantages of US over CT in the pediatric patient are discussed.

Prostatic abscess: CT and sonographic findings.

The value of CT and sonography in the diagnosis and follow-up of abscesses of the prostate was studied in six patients with this disease. Five had CT alone, one had CT and sonography, and one had sonography only. CT findings included an enlarged gland with nonenhancing fluid-density collections that sometimes were multiseptated or had enhancing rims. Sonographic findings were similar, showing a hypoechoic mass with thick walls. Follow-up examinations after antibiotic therapy (one CT, one sonogram) showed improvement or resolution. In the patients studied, CT and sonography were useful methods to detect and follow the course of prostatic abscess.

Nodes or no nodes: CT of adenopathy.

Computed tomography (CT) is the diagnostic modality of choice in the staging of abdominal malignancies. Metastatic disease in the lymph nodes is defined on CT as nodal enlargement. The presence of enlarged nodes does not preclude inflammatory involvement. There are clues that will indicate whether enlarged nodes are malignant or not (i.e., associated bony destruction). This paper will delineate normal nodal anatomy of the abdomen and pelvis. Clinical examples will be used to demonstrate normal structures simulating adenopathy and malignant adenopathy will be illustrated in lymphoma, seminoma, carcinoma of the cervix, prostate, and other pelvic malignancies.

Bile duct carcinoma in an adolescent.

Bile duct carcinoma is a relatively uncommon lesion that usually presents in the 6th to 7th decade. The only prior reported cases under the age of 20 were two patients with diseases known to predispose to the development of this tumor. We report a case of a 17-year-old girl with a bile duct tumor without any known predisposing factors.

Right ureteral obstruction associated with pancreatitis.

In a 5-year review of 207 patients with acute pancreatitis examined by computed tomography, 124 (60%) had findings consistent with active (acute or acute superimposed on chronic) pancreatitis. Six patients (3%), in addition to having evidence for pancreatitis, had associated mild to moderate right hydronephrosis and proximal hydroureter. These patients' findings are presented with a discussion of the renal manifestations of pancreatitis.

Imaging in inflammatory disease of the kidney.

The evaluation and management of patients with severe persistent urinary tract infection after appropriate antibiotic therapy can be difficult. The first radiologic examination is usually excretory urography, but the findings often are nonspecific. A group of 40 patients was studied to assess the contribution of cross-sectional imaging and included patients with diffuse and focal pyelonephritis, renal abscess, pyonephrosis, and pararenal abscess. Indications for cross-sectional imaging include persistent symptoms despite antibiotics, predisposing "risk factors," suspicion of flank mass on other imaging methods, and no excretion on urography. Percutaneous aspiration and/or drainage for diagnosis and/or treatment can be guided by the cross-sectional imaging methods.

Spontaneous rupture of a thymic cyst demonstrated by computed tomography.

Thymic cysts are an uncommon cause of mediastinal masses in children. Spontaneous rupture is a rare complication. This is a case report of spontaneous rupture of a thymic cyst diagnosed on computed tomography and corroborated with ultrasound.

Malignant paragangliomas of the retroperitoneum: value of computed tomography and angiography.

Four patients with malignant paragangliomas of the retroperitoneum were examined by computed tomography. Angiography was performed in two patients. Computed tomography guided the surgeon in obtaining a biopsy and in considering the possibility of resection. Angiography demonstrated the vascular supply and vascularity of the tumours. Pathological correlation was made.

Pheochromocytoma invasion of the inferior vena cava: sonographic evaluation.

Two cases of pheochromocytoma that invaded the inferior vena cava are reported. The significance of this finding in regard to the malignant potential of the tumor and the role of sonography in the evaluation of intracaval tumor are discussed.