Magnetic resonance imaging in staging of renal cell carcinoma

Renal ultrasonography in critically ill patients

Acute renal failure is a sudden and sustained decrease in the glomerular filtration rate associated with a loss of excretory function and the accumulation of metabolic waste products and water. It leads to an increase in serum urea and creatinine, usually with a decrease in urine output. Although routine surveillance of patients by means of laboratory examinations has been well defined, very little is known about renal imaging. Modern technology has provided a large number of sophisticated monitoring systems. Ultrasonography with color-Doppler study of the kidneys may be indicated as a possible monitor of renal perfusion. Ultrasonography is often used as the initial imaging procedure in the examination of patients with renal failure. Aside from excluding hydronephrosis, it is well recognized in characterizing the type of renal disease, especially in an acute setting. This article describes the use of ultrasound to achieve the proper diagnosis of acute renal diseases and to enable the appropriate and early assessment of these patients in intensive care units.

Imaging of renal lesions: evaluation of fast MRI and helical CT

The purpose of this study is to compare triphasic helical CT and fast MRI with respect to detection, characterization and staging of suspected renal masses. To achieve this triphasic helical CT (plain, corticonephrographic and tubulonephrographic phase) and MRI with fast T(1) weighted and T(2) weighted sequences were performed in 29 patients with a suspected renal lesion. Image quality, lesion characterization and lesion extent were assessed for both methods in all patients. The acquisition phase for CT and the image sequence for MRI offering the best image quality and best diagnostic information regarding renal parenchyma, renal vessels, detection of enlarged lymph nodes, and other abdominal organs were determined. Histologically confirmed renal cell carcinomas (n=18) were staged based on the Robson classification. Quantitative data were obtained from operator-defined regions of interest (ROIs) in all acquisition phases (CT) and all image sequences (MRI). For most criteria the rating of image quality for helical CT was generally higher as compared with fast MRI. CT and MRI detected all 24 histologically proven masses, while no false positive solid tumour was diagnosed with both imaging modalities. All three acquisition phases in CT and all applied image sequences in MRI were regarded as necessary in order to gain important diagnostic information. Altogether, 12 of 18 renal cell carcinomas (67%) were correctly staged by CT and MRI. Helical CT and fast MRI allow the correct detection and characterization of suspicious renal lesions. Both imaging modalities can be recommended for clinical routine application. Although the correct histological staging of renal cancer remains difficult for both imaging methods, both are excellent in providing the critical staging information needed before surgery. Helical CT offers a significantly shorter acquisition time to cover the entire abdomen.

Renal neoplasms amenable to partial nephrectomy: MR imaging

PURPOSE

To determine the magnetic resonance (MR) imaging characteristics of renal lesions in patients who undergo technically successful partial nephrectomy.

MATERIALS AND METHODS

Between February 1991 and September 1997, 38 patients (41 lesions) who underwent partial nephrectomy at a single institution were preoperatively evaluated with contrast material-enhanced, multiplanar, surface-coil MR imaging. Imaging findings that could affect the decision to perform partial nephrectomy were retrospectively evaluated: tumor size; tumor location; presence of pseudocapsule; suspected tumor invasion of renal sinus fat, renal collecting system, renal vein, or perinephric fat; and morphologic and physiologic status of the contralateral kidney. Correlation was made with surgical and pathologic findings.

RESULTS

Thirty-three of 41 lesions (80%) were renal cell carcinomas, five were oncocytic neoplasms (12%), two were hemorrhagic cysts (5%), and one was an angiomyolipoma (2%). Twenty-four of 41 (59%) lesions had pseudocapsules. In most cases, the perinephric fat (n = 38 [93%]), the renal sinus fat (n = 31 [76%]), and the renal collecting system (n = 39 [95%]) were correctly interpreted as being uninvolved by tumor.

CONCLUSION

Renal neoplasms amenable to partial nephrectomy can be identified and characterized with contrast-enhanced, multiplanar, surface-coil MR imaging.

Imaging in the staging of renal cell carcinoma

Imaging is extremely important in determining the type of surgery undertaken in patients with proven renal cell carcinoma. In this review, the strength and limitations of each of the relevant techniques are outlined, highlighting particularly the correlation between the imaging findings and the pathological staging. Over the past decade, CT has become the most widely used technique for staging renal cell carcinoma, partly due to the very high overall accuracy of up to 90% that has been achieved. MRI appears to have a similar overall accuracy to CT, whereas ultrasound is less accurate than CT or MRI in the overall staging of tumours. However, ultrasound is extremely accurate in identifying and localising the clinically important tumour extension into the intra-hepatic vena cava and right atrium and if local surgical practice requires only a knowledge of venous invasion, a technically adequate ultrasound examination may suffice. All techniques are unreliable in detecting early perinephric spread.

MRI of multilocular cystic nephroma

We report the magnetic resonance imaging (MRI) findings in 2 patients with multilocular cystic nephromas. Both underwent MRI immediately prior to resection. The images accurately reflected the morphology of the tumors: in each, the capsule was hypointense on all pulse sequences. Varied intensities of signal from the fluid in the visualized locules presumably represented differing concentrations of old hemorrhage and protein. In one case soft tissue elements became hyperintense on T2-weighted images. We speculate that MRI of multilocular cystic nephromas will produce imaging features that are highly suggestive, but not always pathognomonic, of the disease.