Gadolinium-enhanced MR imaging of renal masses

Development of renal cell carcinoma (RCC) diagnostics and impact on prognosis

OBJECTIVE

To evaluate imaging methods and prognoses between small renal cell carcinomas (RCCs) and larger tumours according to the era of diagnostics.

PATIENTS AND METHODS

In all, 784 consecutive patients diagnosed with RCC between 1964 and 1997 at the Pirkanmaa Hospital District in Finland were included. Patients were divided into two groups: tumours of ≤3.0 and >3.0 cm in diameter. Prognosis was analysed according to the era of diagnostics: (i) pre-computed tomography (CT) and pre-ultrasound (US), (ii) US era and (iii) CT era.

RESULTS

Small tumours became more common: in the pre-CT and pre-US era, only 4.4% of tumours were small; however, in the CT era 16% were small tumours. More diagnostic methods were used in studying small tumours. CT proved to be the most reliable method, although it was actually better at diagnosing large tumours. Relapses occurred less frequently among patients with small tumours; more than half of the tumours that developed distant metastases (16.0%) already evinced them at the time of diagnosis. There were no relapses after 14 years of follow-up among small tumours, whereas large tumours relapsed within that time. RCC was the cause of death in 14.9% of patients with small tumours vs 50.7% with large tumours. The best prognosis was among patients with small tumours diagnosed with CT.

CONCLUSION

Among patients with small tumours, prognosis has improved along with better diagnostics, although some showed relapse during a surveillance period of up to 14 years.

Radiologic evaluation of small renal masses (I): pretreatment management

When characterizing a small renal mass (SRM), the main question to be answered is whether the mass represents a surgical or nonsurgical lesion or, in some cases, if followup studies are a reasonable option. Is this a task for a urologist or a radiologist? It is obvious that in the increasing clinical scenario where this decision has to be made, both specialists ought to work together. This paper will focus on the principles, indications, and limitations of ultrasound, CT, and MRI to characterize an SRM in 2008 with a detailed review of relevant literature. Special emphasis has been placed on aspects regarding the bidirectional information between radiologists and urologists needed to achieve the best radiological approach to an SRM.

Renal lesions: characterization with diffusion-weighted imaging versus contrast-enhanced MR imaging

PURPOSE

To compare the diagnostic performance of diffusion-weighted (DW) magnetic resonance (MR) imaging with that of contrast material-enhanced (CE) MR imaging and to assess the performance of these examinations combined for the characterization of renal lesions, with MR follow-up and histopathologic analysis as the reference standards.

MATERIALS AND METHODS

The institutional review board waived the requirement of informed patient consent for this retrospective HIPAA-compliant study. One hundred nine renal lesions in 64 patients (46 men, 18 women; mean age, 60.7 years) were evaluated with CE MR imaging and breath-hold DW imaging performed with various b values. Renal lesions were characterized with use of CE MR criteria, and apparent diffusion coefficients (ADCs) were measured. The ADCs of benign and malignant lesions were compared at Mann-Whitney testing. Receiver operating characteristic (ROC) analysis was performed to assess the accuracy of DW imaging and CE MR imaging in the diagnosis of renal cell carcinoma (RCC).

RESULTS

The 109 renal lesions--81 benign lesions and 28 RCCs--had a mean diameter of 4.2 cm +/- 2.5 (standard deviation). The mean ADC for RCCs (1.41 x 10(-3) mm(2)/sec +/- 0.61) was significantly lower (P < .0001) than that for benign lesions (2.23 x 10(-3) mm(2)/sec +/- 0.87) at DW imaging performed with b values of 0, 400, and 800 sec/mm(2). At a cutoff ADC of less than or equal to 1.92 x 10(-3) mm(2)/sec, the area under the ROC curve (AUC), sensitivity, and specificity of DW imaging for the diagnosis of RCCs (excluding angiomyolipomas) were 0.856, 86%, and 80%, respectively. The corresponding AUC, sensitivity, and specificity of CE MR imaging were 0.944, 100%, and 89%, respectively. Combined DW and CE MR imaging had 96% specificity. The AUC for the DW imaging-based diagnosis of solid RCC versus oncocytoma was 0.854. Papillary RCCs had lower ADCs than nonpapillary RCCs.

CONCLUSION

DW imaging can be used to characterize renal lesions; however, compared with CE MR imaging, it is less accurate. DW imaging can be used to differentiate solid RCCs from oncocytomas and characterize the histologic subtypes of RCC.

MR classification of renal masses with pathologic correlation

To perform a feature analysis of malignant renal tumors evaluated with magnetic resonance (MR) imaging and to investigate the correlation between MR imaging features and histopathological findings. MR examinations in 79 malignant renal masses were retrospectively evaluated, and a feature analysis was performed. Each renal mass was assigned to one of eight categories from a proposed MRI classification system. The sensitivity and specificity of the MRI classification system to predict the histologic subtype and nuclear grade was calculated. Subvoxel fat on chemical shift imaging correlated to clear cell type (p < 0.05); sensitivity = 42%, specificity = 100%. Large size, intratumoral necrosis, retroperitoneal vascular collaterals, and renal vein thrombosis predicted high-grade clear cell type (p < 0.05). Small size, peripheral location, low intratumoral SI on T2-weighted images, and low-level enhancement were associated with low-grade papillary carcinomas (p < 0.05). The sensitivity and specificity of the MRI classification system for diagnosing low grade clear cell, high-grade clear cell, all clear cell, all papillary, and transitional carcinomas were 50% and 94%, 93% and 75%, 92% and 83%, 80% and 94%, and 100% and 99%, respectively. The MRI feature analysis and proposed classification system help predict the histological type and nuclear grade of renal masses.

Three-dimensional gadolinium-enhanced magnetic resonance breath-hold FLASH imaging in the diagnosis and staging of renal cell carcinoma

Renal cell carcinoma accounts for 2% of all reported cancers. Its apparent incidence is increasing due to the more widespread use of cross-sectional imaging and as a result, tumours are being detected at an earlier stage. It is hoped that this improvement in early detection will result in a significant increase in survival rates. Radiological diagnosis and staging have a critical role in triaging patients' -treatment. Although computed tomography (CT) and ultrasound are well established in the evaluation of renal cell carcinoma, magnetic resonance (MR) techniques are still rapidly developing. In our institution breath-hold three-dimensional (3D) gadolinium-enhanced fast low-angled single shot (FLASH) spoiled gradient-echo sequence imaging has become an integral part of staging for renal cell carcinoma. In this article, we review our experience of the use of this emerging technique in the diagnosis and staging of renal cancer.

MRI isolation of infected renal cyst in autosomal dominant polycystic kidney disease

The use of gadolinium-enhanced magnetic resonance (MR) to isolate an infected renal cyst in the setting of autosomal dominant polycystic kidney disease (ADPKD) has not been previously described. A case in which T1- and T2-weighted and gadolinium-enhanced MR images were used to identify a single purulent cyst in a patient with ADPKD is herein presented. We suggest that gadolinium-enhanced MR be considered useful in the evaluation of ADPKD patients with suspected infected cyst.

Contrast-enhanced three-dimensional fast spoiled gradient-echo renal MR imaging: evaluation of vascular and nonvascular disease

Breath-hold contrast material enhanced three-dimensional (3D) fast spoiled gradient-echo (FSPGR) sequences are valuable techniques for evaluation of renal arteries and veins and diagnosis of significant renal arterial stenosis at magnetic resonance (MR) imaging. The excellent spatial and contrast resolution with these techniques, combined with the ability to perform studies in multiple vascular phases, also make them attractive for the diagnosis of a wide range of nonvascular processes that affect the kidneys, including renal infections, renal parenchymal diseases, and renal trauma. Particularly when combined with T1- and T2-weighted MR imaging, the contrast-enhanced techniques are highly effective for characterization of renal masses owing to the ability to portray dynamic contrast enhancement. The ability to display venous structures with contrast-enhanced 3D FSPGR techniques helps staging of renal cell carcinoma. This article presents examples of the wide range of vascular and nonvascular renal diseases that may be effectively imaged with contrast material enhanced 3D FSPGR techniques and illustrates the usefulness of the techniques for renal MR imaging.

Safety of approved MR contrast media for intravenous injection

In the last 10 years, the use of intravenous contrast media in magnetic resonance (MR) has become well-established clinical practice. Contrast media provide critical additional diagnostic information in many instances. The gadolinium chelates constitute the largest group of MR contrast media and are considered to be very safe. These agents are thought to be safer than nonionic iodinated contrast agents. Unlike x-ray agents, the gadolinium chelates are not nephrotoxic. Minor adverse reactions, including nausea (1%-2% for all agents) and hives (<1% for all agents), occur in a very low percent of cases. Health care personnel should be aware of the (extremely uncommon) potential for severe anaphylactoid reactions in association with the use of MR contrast media and be prepared should complications arise. The four gadolinium chelates currently available worldwide, gadopentetate dimeglumine, gadoteridol, gadodiamide, and gadoterate meglumine, cannot be differentiated on the basis of adverse reactions. Far fewer patients have been examined to date with the two other agents that have widespread approval, mangafodipir trisodium and ferumoxides. These latter two agents are considered to be very safe but have a higher percentage of associated adverse reactions (7%-17% with mangafodipir trisodium and 15% with ferumoxides). This review discusses the safety issues involved with administration of intravenous contrast media in MR imaging, focusing on the six agents (four gadolinium chelates, one manganese chelate, and the last a large iron particle) with widespread use world-wide.

Abdominal granulocytic sarcomas: demonstration by MRI

The magnetic resonance imaging findings of histologically-proven renal and pancreatic granulocytic sarcomas are demonstrated in two patients. Granulocytic sarcomas were moderately hypointense on T1-weighted images, mildly hyperintense on T2-weighted images, and enhanced in a diminished fashion on early and late postgadolinium T1-weighted images.

Bacterial urinary tract infections in diabetes

Diabetes mellitus has a number of long-term effects on the genitourinary system. These effects predispose to bacterial urinary tract infections in the patient with diabetes mellitus. Bacteriuria is more common in diabetic women than in nondiabetic women because of a combination of host and local risk factors. Upper tract infection complications are also more common in this group. Diabetic patients are at higher risk for intrarenal abscess, with a spectrum of disease ranging from acute focal bacterial pyelonephritis to renal corticomedullary abscess, to the renal carbuncle. A number of uncommon complicated urinary tract infection complications occur more frequently in diabetics, such as emphysematous pyelonephritis and emphysematous pyelitis. Because of the frequency and severity of urinary tract infection in diabetic patients, prompt diagnosis and early therapy is warranted. A plain abdominal radiograph is recommended as a minimum radiographic screening tool in the patient with diabetes presenting with systemic signs of urinary tract infection. Ultrasonography or further radiographic studies such as CT scanning may also be warranted, depending on the clinical picture, to identify upper urinary tract complications early for appropriate intervention.

Imaging approach to staging of renal cell carcinoma

Current imaging techniques, especially CT and MR imaging, make accurate preoperative staging of renal cell carcinoma possible. Because surgery provides the only effective therapy and because survival depends on local and distant extent, precise staging is critical for preoperative planning and prognosis. This article reviews the advantages, limitations, accuracy, and pitfalls of each of the imaging approaches to staging renal cell carcinoma, concentrating on CT and MR imaging. This information then is summarized in a suggested overall approach to staging renal cell carcinoma.

Renal cell cancer: incidence of hemorrhage on MR images in patients with chronic renal insufficiency

This study describes the occurrence of hemorrhage in renal cancer in patients with chronic renal insufficiency as shown on MR images. Thirteen consecutive patients with chronic renal insufficiency who had histologically proven renal cancer and underwent MRI at 1.5 T were entered in the study. MR examinations included spoiled gradient echo (SGE) and T1-weighted fat-suppressed imaging pre- and postgadolinium administration. All renal cancers were well shown on MR images and were most clearly depicted on postgadolinium T1-weighted fat-suppressed images. Tumors in 12 of 13 patients had regions of high signal intensity on precontrast T1-weighted images. Histology demonstrated intratumoral hemorrhage in all 12 of these patients. Four hemorrhagic tumors were largely cystic on imaging studies. One of these cancers altered in appearance from largely cystic with extensive hemorrhage to largely solid with substantial enhancement after a 2.5-year interval. Renal cancers demonstrated minimal enhancement (11 patients) on early postgadolinium images and were minimally enhanced on delayed images in 10 of 13 tumors. Two renal cancers demonstrated intense enhancement. Renal cancers are well shown on MR images in patients with chronic renal insufficiency. Because of the common occurrence of hemorrhage into renal cancers in patients with renal insufficiency, caution should be exercised when evaluating hemorrhagic cystic lesions in these patients.

Asymptomatic renal abscess: evaluation with gadolinium DTPA-enhanced MRI

Incidental detection of renal mass in a transplant patient is a diagnostic challenge. These patients are at risk for the development of neoplasms and, more commonly, infection with atypical organisms. Symptomatology may be lacking in either, and both conditions may present with similar symptoms. Magnetic resonance imaging (MRI) evaluation with gadolinium DTPA is helpful in the evaluation of asymptomatic renal mass, with enhancement effectively excluding simple and hemorrhagic cysts. Because the MRI appearances of renal cell neoplasm and renal abscess overlap, both must be considered in the differential diagnosis.