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Imaging

UROLOGICAL SURVEY

Imaging

High-resolution multidetector CT in the preoperative evaluation of patients with renal cell carcinoma

Catalano C, Fraioli F, Laghi A, Napoli A, Pediconi F, Danti M, Nardis P, Passariello R

From the Department of Radiology, University of Rome "La Sapienza," V. le Regina Elena 324, 00161 Rome, Italy

AJR Am J Roent. 2003; 180: 1271-7

PURPOSE: The purpose of our study was to evaluate the accuracy of multidetector CT (MDCT) using a high-resolution protocol in the preoperative assessment of patients with renal cell carcinoma who are possible candidates for nephron-sparing surgery.

MATERIALS AND METHODS: Forty patients with suspected renal cell carcinoma underwent MDCT. Contrast-enhanced acquisitions were obtained during arterial, nephrographic, and urographic phases using a thin-slice protocol. One-millimeter-thick source images were evaluated by two observers on a dedicated workstation for the identification and characterization of the tumor, presence of a pseudocapsule or invasion of perirenal fat, involvement of adrenal glands or surrounding tissues, presence of satellite lesions within Gerota's fascia, infiltration of renal vein and inferior vena cava, involvement of lymph nodes, and presence of distant metastases. Imaging findings were compared with surgical specimens using criteria from the Robson and TNM classification systems.

RESULTS: The presence and size of all lesions were correctly shown in all patients. In evaluating Robson stage I of renal cell carcinoma, we were able to diagnose fat infiltration on 1-mm scans with 96% sensitivity, 93% specificity, and 95% accuracy; the positive and negative predictive values were, respectively, 100% and 93%. One hundred percent accuracy was achieved in staging high-grade lesions.

CONCLUSION: High-resolution MDCT is accurate in the preoperative evaluation of patients with renal cell carcinoma.

Editorial Comment

Robson's Stage I (T1-T2) tumors are defined on spiral CT as a tumor confined within the kidney with an intact renal capsule. This is usually characterized when the perinephric fat and renal fascia adjacent to the lesion are preserved. Until now, the most specific sign of extension of the tumor to these structures has been the presence of a discrete mass measuring at least 1 cm in diameter projecting into the perinephric space. Although this finding is 98% specific for Robson's stage II (T3a) tumors, its sensitivity is too low (only 46%) as this finding is absent in the majority of patients with perinephric extension (1). As the perinephric fat and Gerota's fascia are resected during a radical nephrectomy, the radiological distinction between T1 and T3a has not been very important. More recently, however, renal conservative surgery has been performed with more frequency including the laparoscopic approach; thus, an accurate preoperative radiological staging is essential.

The point of this report is that the use of 1-mm-thick-multidetector CT images (MDCT) allowed the differentiation between Robson stage I (T1-T2) and T3a renal cell carcinoma, with 96% sensitivity, 93% specificity, 95% accuracy, 100% of positive predictive value and with 93% of negative predictive value. These results are very enthusiastic but studies with a larger series of patients are desirable. As we know CT-false positives diagnoses has been described in up to 50% of patients with Robson's Stage I disease. This can be explained because perinephric stranding and fascial thickening can occur due to perinephric edema (very nicely illustrated in one case of this report), fat necrosis and fibrosis from remote inflammation (2). Obviously, these data are related to studies performed with single slice spiral CT that has lower spatial resolution than the new generation of MDCT. Multidetector CT provides substantial improvement in volume coverage over single-slice spiral CT. More rapid image acquisition allows better definition of renal capsule and greater separation of arterial and venous phases, thus facilitating multiphasic acquisition. This improvement was very well shown by the superb high resolution multiplanar reconstruction of the kidneys and renal vessels showed in this interesting manuscript.

REFERENCES

1. Johnson CD, Dunnick NR, Cohan RC, Illescas FF: Renal adenocarcinoma: CT staging of 100 tumors. AJR Am J Roent. 1987: 148: 59-63.

2. Parks CM, Kellett MJ: Review: staging renal cell carcinoma. Clin Radiol. 1994; 49: 223-30.

Dr. Adilson Prando

Department of Radiology

Vera Cruz Hospital

Campinas, São Paulo, Brazil

Imaging-guided radiofrequency ablation of solid renal tumors

Farrell MAI, Charboneau WJI, DiMarco DSII, Chow GKII, Zincke HII, Callstrom MRII, Lewis BDI, Lee RAI, Reading CCI

IFrom Department of Radiology, Mayo Clinic, 200 First St., Rochester, MN 55902, and IIDepartment of Urology, Mayo Clinic, Rochester, MN 55902.

AJR Am J Roent. 2003; 180: 1509-13

PURPOSE: We performed a retrospective review of imaging-guided radiofrequency ablation of solid renal tumors.

MATERIALS AND METHODS: Since May 2000, 35 tumors in 20 patients have been treated with radiofrequency ablation. The size range of treated tumors was 0.9 - 3.6 cm (mean, 1.7 cm). Reasons for patient referrals were a prior partial or total nephrectomy (nine patients), a comorbidity excluding nephrectomy or partial nephrectomy (10 patients), or a treatment alterative to nephron-sparing surgery (one patient who refused surgery). Tumors were classified as exophytic, intraparenchymal, or central. Sixteen patients had 31 lesions that showed serial growth on CT or MR imaging. Of these 16 patients, four patients with 10 lesions had a history of renal cell carcinoma, and two patients with 11 lesions had a history of von Hippel-Lindau disease. Four patients had incidental solid masses, two of which were biopsied and shown to represent renal cell carcinoma, and the remaining two masses were presumed malignant on the basis of imaging features. Successful ablation was regarded as any lesion showing less than 10 H of contrast enhancement on CT or no qualitative evidence of enhancement after IV gadolinium contrast-enhanced MR imaging.

RESULTS: Of the 35 tumors, 22 were exophytic and 13 were intraparenchymal. Twenty-seven of the 35 were treated percutaneously using either sonography (n = 22) or CT (n = 5). Two patients had eight tumors treated intraoperatively using sonography. Patients were followed up with contrast-enhanced CT (n = 18), MR imaging (n = 5), or both (n = 5) with a follow-up range of 1 - 23 months (mean, 9 months). No residual or recurrent tumor and no major side effects were seen.

CONCLUSION: Preliminary results with radiofrequency ablation of exophytic and intraparenchymal renal tumors are promising. Radiofrequency ablation is not associated with significant side effects. Further follow-up is necessary to determine the long-term efficacy of radiofrequency ablation.

Editorial Comment

Cryotherapy has been the most frequently thermal ablative technique used for alternative treatment of localized renal cell carcinoma. There are only few reports describing the utilization of radiofrequency ablation (RF) to renal tumors including only small series of patients. Radiofrequency renal tumor ablations can be performed under sonography or computed-tomography-guided percutaneous approach. After treatment, patients are usually followed up with CT scans at 6 weeks and 3, 6, and 12 months, and every 6 months thereafter. Successful ablation has been considered by many authors as a lesion along with a margin of normal parenchyma that no longer enhanced (less than 10 Hounsfield units) on follow-up contrast studies. The point of this report is that 35 tumors, ranging in size from 0.9 to 3.6 cm (mean = 1.7 cm), were treated by RF with no residual or recurrent lesions. The criterion of successful ablation was the same used by other authors and based strictly on radiolologic findings (absence of lesion's enhancement). Radiographic follow-up of radiofrequency ablated small renal tumors, however, may demonstrate little or no residual contrast enhancement depending on tumor size, location within the kidney, and mode of delivering radiofrequency energy. As already pointed out by the authors the absence of postprocedural biopsy can be considered a relative limitation of this study since pathologic examination after RF ablation may show a residual viable tumor in few patients. Another point to be considered is that when performed, adequate histopathologic evaluation of the tumors specimens treated by RF-ablations should include hematoxylin-eosin and a nicotinamide adenine dinucleotide staining in order to determine the presence or absence of tissue viability. This manuscript is recommended because shows very clearly that RF ablation can successfully destroy small peripheral renal tumors with no significant damage to the normal renal parenchyma and more important without significant side effects.

Dr. Adilson Prando

Department of Radiology

Vera Cruz Hospital

Campinas, São Paulo, Brazil

Publication Dates

  • Publication in this collection
    26 Jan 2004
  • Date of issue
    June 2003
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