Renal pseudotumors due to fat necrosis in acute pancreatitis.

Retroperitoneal fat necrosis is a well-known complication of acute pancreatitis. We describe an unusual case of fat necrosis presenting as multiple, bilateral renal pseudotumors in a patient with acute pancreatitis. The imaging findings on CT and MR are discussed.

Localized cystic disease of the kidney.

OBJECTIVE: Localized cystic disease of the kidney is a benign nonsurgical condition. Its imaging and clinical features are characterized and differentiated from autosomal dominant polycystic kidney disease, multilocular cystic nephroma, and cystic neoplasm. MATERIALS AND METHODS: Localized cystic disease was diagnosed in 18 patients on the basis of a review of imaging studies, clinical histories, and pathologic proof in four of the 18 patients. Average age at diagnosis was 54 years (age range, 24-83 years). Fifteen of the patients (83%) were men. CT was performed on 18 patients, sonography on nine, excretory urography on six, arteriography on four, and MR imaging on two. RESULTS: Localized cystic disease was unilateral in all patients and characterized by multiple cysts of various sizes separated by normal (or atrophic) renal tissue in a conglomerate mass suggestive of cystic neoplasm. In some patients, involvement of the entire kidney, which was suggestive of unilateral autosomal dominant polycystic kidney disease, was seen. No cysts were seen in the contralateral kidney in 14 patients, and only one or two scattered small cysts were present in four patients. Clinical presentations included hematuria, flank pain, palpable abdominal mass, and localized cystic disease as an incidental finding. None of the patients had a family history of autosomal dominant polycystic kidney disease. Ten patients underwent follow-up (follow-up range, 1-12 years); nine patients underwent imaging follow-up and one patient underwent clinical follow-up, which showed stability of disease. Four patients underwent nephrectomy for suspected renal neoplasm. CONCLUSION: Familiarity with localized cystic disease of the kidney and its imaging findings is important to avoid unnecessary surgery and to differentiate the disease from autosomal dominant polycystic kidney disease.

Delayed CT to evaluate renal masses incidentally discovered at contrast-enhanced CT: demonstration of vascularity with deenhancement.

PURPOSE: To determine whether delayed computed tomography (CT) can help confirm vascularity in a neoplasm and differentiate it from a high-density cyst when a well-demarcated homogeneous high-attenuating (> 30-HU) renal mass is incidentally discovered during contrast material-enhanced CT. MATERIALS AND METHODS: In 25 patients, 26 well-demarcated, homogeneous high-attenuating renal masses (mean diameter, 2.5 cm; range, 1-4 cm) detected at initial postcontrast CT were further evaluated with delayed CT (mean, 38 minutes; range, 15-240 minutes) performed with identical parameters. On both the initial postcontrast and delayed CT scans, region-of-interest measurements were obtained in renal masses and in the gallbladder or low-density renal cysts as controls. Correlation with surgical or additional imaging findings was used to determine proof of diagnosis. RESULTS: Nine of the masses demonstrated no change in attenuation between initial postcontrast and delayed CT, indicating that they represented avascular lesions consistent with high-density cysts. These cases were confirmed with prior or follow-up imaging studies that demonstrated stability. Seventeen masses (nine surgically proved neoplasms and eight neoplasms that demonstrated interval growth at follow-up or previous CT) demonstrated decreased attenuation at delayed CT compared with initial postcontrast CT, which indicates vascularity. CONCLUSION: Delayed CT of incidentally discovered well-demarcated homogeneous high-attenuating (> 30-HU) renal masses detected at postcontrast CT enables differentiation of high-density cysts from renal neoplasms by demonstrating deenhancement as a proof of vascularity and, hence, neoplasm.

MR imaging in the evaluation of small (< or =3.0 cm) renal masses.

The use of MR imaging in evaluating renal tumors has expanded beyond the established utility for patients with renal insufficiency and allergy to iodinated contrast. MR imaging is increasingly relied on for the evaluation of small renal lesions. The use of gadolinium chelate contrast agents, high performance MR systems, and optimized techniques is essential. This article details our experience using MR to evaluate small renal tumors and reviews the clinical issues pertinent to the management of these lesions.

Small renal parenchymal neoplasms: further observations on growth.

PURPOSE: To determine the growTH rate and behavior of small (< or = 3.5-cm diameter) incidentally detected renal parenchymal neoplasms. MATERIALS AND METHODS: Forty renal parenchymal tumors in 37 adult patients (mean age, 65.5 years) were observed with computed tomography (CT) and ultrasound for 1.75-8.5 years (mean, 3.25 years). Surgical removal was performed of 26 tumors proved and graded at pathologic examination. Fourteen tumors with CT criteria of neoplasm are being followed up. RESULTS: The overall growth rate of neoplasms was 0-1.1 cm/y (mean, 0.36 cm/y). Thirty tumors grew 0.5 cm/y or less and 19 grew very slowly (< or = 0.35 cm/y). No patient developed metastatic disease. Nine (24%) had multiple neoplasms. CONCLUSION: Most small, incidentally discovered, well-marginated renal parenchymal neoplasms grow slowly and are not an immediate threat to a patient's life. Watchful waiting might be appropriate instead of surgical removal, especially in patients who are elderly or may not survive surgery.

Observation of small incidentally detected renal masses.

As more small (< 3.0 cm) incidentally detected renal cell carcinomas are being discovered in elderly patients, a reassessment of the management of these lesions has become an important issue. The use of partial nephrectomy in these small contained renal neoplasms is being more commonly performed, and the use of "watchful waiting" should also be considered as the initial management approach for some of these lesions. This latter approach is based on the experience gained by the observation of the growth rate and behavior of small incidentally detected solid renal masses that have been followed serially over a 2- to 8-year period. This report will review the available data on the growth rate and clinical behavior of small incidentally discovered renal neoplasms, show why a "watchful waiting" approach is reasonable in some of these cases, and outline which patients would benefit from this management approach.

Extension of a secondary adrenal neoplasm into the inferior vena cava.

Adrenal cortical carcinoma is well known to extend into the renal veins and inferior vena cava. It is less known that neoplasms metastatic to the adrenal might also extend into the renal vein and cava. Only a few reports in the literature document this extension. We report a case of metastatic neoplasm to the adrenal extending into the inferior vena cava.

Renal cell carcinoma: correlation of CT findings with nuclear morphologic grading in 100 tumors.

The contrast-enhanced preoperative computed tomographic (CT) scans and microscopic slides of 94 patients with 100 surgically resected renal cell carcinomas (RCCs) were retrospectively and independently reviewed in order to correlate the CT imaging findings of RCC with nuclear grading. As nuclear grade increased, RCCs were more likely to be of higher stage and greater size at presentation, and appeared more heterogeneous and less marginated. Of the features analyzed, tumor margination most closely correlated with nuclear grade. Overlap in the CT appearance of individual tumors limited the potential of CT to differentiate RCCs of varying grade. Small, well-marginated, homogeneous tumors, however, were either grade I or II, and were distinguishable from the more aggressive grade III lesions, which generally displayed irregular margins and greater inhomogeneity.

Problems in the radiologic diagnosis of renal parenchymal tumors.

There has been a great increase in the detection and earlier diagnosis of a host of renal parenchymal tumors because of the continued improvement in imaging studies. Although this change will tend to improve the cure rate of renal cell carcinoma, it also has uncovered many cases that are problematic in both diagnosis and management. It is hoped that performance of high-quality examinations and the experience gained in dealing with these cases have improved our ability to diagnose and manage these problematic cases successfully.

Renal lesion characterization with gadolinium-enhanced MR imaging: efficacy and safety in patients with renal insufficiency.

Five patients with renal insufficiency were studied with T1-weighted magnetic resonance (MR) imaging before and after intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg) to characterize renal lesions that were detected with nonenhanced computed tomography (CT) and were considered indeterminate. Four patients demonstrated renal lesions that enhanced after gadolinium administration. A total of five lesions in these four patients were surgically resected and found to be renal cell carcinoma at pathologic examination. The fifth patient was spared surgery because a hyperattenuated lesion noted at nonenhanced CT did not enhance with intravenous gadolinium, indicating a benign cyst. Five incidentally occurring benign cysts removed at the time of nephrectomy in two of the patients did not demonstrate enhancement with gadolinium on MR images. Serial serum creatine levels were obtained before and after gadolinium administration in all patients; no changes were noted after gadolinium administration. Gadolinium-enhanced MR imaging is an effective method for characterizing renal lesions in patients with renal insufficiency. At the usual dosage, there appears to be no nephrotoxic reaction in these patients.

Asymmetry of the renal nephrograms on CT: significance of the unilateral prolonged cortical nephrogram.

The finding of asymmetry in the renal nephrograms as manifested by a unilateral prolonged cortical nephrogram on dynamic contrast-enhanced CT examinations signifies the presence of an abnormality of renal parenchymal perfusion and/or tubular transit. The differential diagnostic possibilities include stenosis or long-standing occlusion of the renal artery, renal vein thrombosis, and urinary tract obstruction.