MRI of Wilms' tumor: promise as the primary imaging method

Survey of water proton longitudinal relaxation in liver in vivo

Objective

To determine the variability, and preferred values, for normal liver longitudinal water proton relaxation rate R₁ in the published literature.

Methods

Values of mean R₁ and between-subject variance were obtained from literature searching. Weighted means were fitted to a heuristic and to a model.

Results

After exclusions, 116 publications (143 studies) remained, representing apparently normal liver in 3392 humans, 99 mice and 249 rats. Seventeen field strengths were included between 0.04 T and 9.4 T. Older studies tended to report higher between-subject coefficients of variation (CoV), but for studies published since 1992, the median between-subject CoV was 7.4%, and in half of those studies, measured R₁ deviated from model by 8.0% or less.

Discussion

The within-study between-subject CoV incorporates repeatability error and true between-subject variation. Between-study variation also incorporates between-population variation, together with bias from interactions between methodology and physiology. While quantitative relaxometry ultimately requires validation with phantoms and analysis of propagation of errors, this survey allows investigators to compare their own R₁ and variability values with the range of existing literature.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10334-021-00928-x.

Inferior vena cava resection with hepatectomy: challenging but justified

OBJECTIVE

The aim of this study was to evaluate the clinical outcome of hepatectomy combined with inferior vena cava (IVC) resection and reconstruction for treatment of invasive liver tumours.

METHODS

From February 1995 to September 2010, 2146 patients underwent liver resections in our hospital's hepatopancreatobiliary unit. Of these, 35 (1.6%) patients underwent hepatectomy with IVC resection. These patients were included in this study. Data were analysed from a prospectively collected database.

RESULTS

Resections were carried out for colorectal liver metastasis (CRLM) (n= 21), hepatocellular carcinoma (n= 6), cholangiocarcinoma (n= 3) and other conditions (n= 5). Resections were carried out with total vascular occlusion in 34 patients and without in one patient. In situ hypothermic perfusion was performed in 13 patients; the ante situm technique was used in three patients, and ex vivo resection was used in six patients. There were four early deaths from multiple organ failure. Postoperative complications occurred in 14 patients, three of whom required re-operation. Median overall survival was 29 months and cumulative 5-year survival was 37.7%. Rates of 1-, 2- and 5-year survival were 75.9%, 58.7% and 19.6%, respectively, in CRLM patients.

CONCLUSIONS

Aggressive surgical management of liver tumours with IVC involvement offers the only hope for cure in selected patients. Resection by specialist teams affords acceptable perioperative morbidity and mortality rates.

Magnetic resonance urography in pediatric urology

PURPOSE OF REVIEW

Magnetic resonance urography (MRU) has emerged as a powerful diagnostic tool in the evaluation of the pediatric genitourinary tract. The purpose of this review is to familiarize the reader with the basic techniques, strengths and limitations, as well as the current and potential future applications of MRU in pediatric urology.

RECENT FINDINGS

MRU can provide detailed anatomical information and assess renal function and drainage in a single study. MRU does not employ ionizing radiation and may be utilized in patients with iodine-based contrast allergy or impaired renal function. MRU has been most often applied to the evaluation of hydronephrosis and provides valuable insight into a wide range of obstructive uropathies. MRU was shown to be superior to renal scintigraphy for the diagnosis of pyelonephritis and renal scarring. The use of MRU for the assessment of urolithiasis and vesicoureteral reflux is limited and technical refinements are required. Potential future applications include fetal MRU, virtual endoscopy, and MRU-guided procedures. The development of new contrast agents and new image-processing software will further enhance the diagnostic potential of MRU in pediatric urology.

SUMMARY

MRU is currently thought of as a problem-solving tool to define anatomy and function when conventional methods fall short. This technique is likely to emerge as the imaging modality of choice for children with complex genitourinary pathology.

Imaging of renal tumours in infancy and childhood

There is a large range of benign and malignant renal neoplasms. This article lists the most benign, indeterminate and malignant renal tumours that occur during infancy and childhood. It briefly describes the most important entities, including their imaging features, and important complications. Differential diagnosis and pitfalls are discussed, and a brief suggestion for a standardised imaging algorithm is proposed. Although modern imaging techniques, including colour Doppler sonography, helical or multidetector CT, and MR have significantly improved imaging potential, the definite diagnosis on tumour entity still is established only by histology.

Renal neoplasms of childhood

Wilms' tumor is the most common childhood renal tumor. This article describes the epidemiology, histopathologic features, and clinical manifestations of Wilms' tumor along with the spectrum of imaging findings using different modalities. The distinguishing features of other renal tumors encountered in children, such as clear cell sarcoma, rhabdoid tumor, congenital mesoblastic nephroma, multilocular cystic renal tumor, renal cell carcinoma, and angiomyolipoma are also reviewed.

Is contralateral exploration of the kidney necessary in patients with Wilms tumor?

PURPOSE

Surgical exploration of the contralateral kidney in patients with Wilms tumor is standard practice. The introduction of modern imaging techniques (ultrasound, computerized tomography and magnetic resonance imaging) in place of excretory urography has led to a more accurate definition of intrarenal pathology. Is contralateral kidney exploration still necessary in patients with Wilms tumor?

MATERIALS AND METHODS

We reviewed the records of 75 patients from 3 medical centers who were evaluated and treated for Wilms tumor in the last 14 years. All children underwent preoperative excretory urography, computerized tomography, ultrasound and/or magnetic resonance imaging.

RESULTS

Seven bilateral Wilms tumors were diagnosed preoperatively and confirmed surgically, whereas extensive operative exploration of the contralateral kidney in the other 69 patients revealed no additional pathological condition. This concurred with preoperative radiological findings with 100% sensitivity and specificity. Furthermore, 1 month to 12 years of followup (mean 4.3 years) revealed no tumor in the contralateral kidney. The major postoperative complication was small bowel obstruction in 5 patients 15 to 180 days (mean 77.2) after explorative laparotomy.

CONCLUSIONS

In all patients preoperative radiological investigation was accurate in excluding bilaterality. With modern imaging techniques and effective chemotherapy extensive contralateral renal exploration may no longer be mandatory for managing Wilms tumor.

Abdominal tumors in infancy and childhood

Detection of an abdominal mass in a child is an alarming finding for both parent and practitioner. Diagnostic studies including ultrasonography, computed tomography, and magnetic resonance imaging provide an accurate diagnosis in most cases. The current treatment of Wilms' tumor results in an 85% to 90% survival. Hepatoblastoma and neuroblastoma often present in an advanced stage and require preoperative chemotherapy before resection is attempted. Improved survival for children with these tumors awaits better detection, chemotherapy, and understanding of the biology of their growth.

Intrapelvic Wilms tumor: report of 2 cases and review of the literature

Wilms tumor arising from the renal parenchyma usually presents initially as an abdominal mass. A review of the literature revealed fewer than 10 cases manifesting as a renal pelvic mass occupying primarily the collecting system. We have treated 2 patients with this unusual presentation: 1) a 4-month-old male infant whose initial radiological investigation demonstrated a left renal neoplasm measuring 10 x 7 x 5 cm.; bisection of the kidney showed a tumor completely filling the collecting system to the proximal ureter with extreme attenuation of the renal parenchyma, and 2) a 9-year-old boy who was hospitalized due to hematuria; ultrasonography, computerized tomography and magnetic resonance imaging showed a mass in the right renal pelvis; gross pathology displayed a 7 x 6 x 5 cm. polypoid mass occupying the renal pelvis without parenchymal involvement. Microscopically, both lesions were typical Wilms tumors. We discuss the characteristic clinical manifestations, diagnosis and treatment, and review the literature.

Imaging of Wilms' tumor: what is important!

The imaging of Wilms' tumor needs to be quite focused so that the oncologist and surgeon can most precisely stage the patient before operation. The imager needs to be exact about the extent of the primary tumor and define any invasion into the adjacent soft tissues. The ability to detect nodal disease is quite difficult but clearly influences the preoperative approach and staging. Children with large tumors extending across the midline in whom primary resection may lead to tumor spillage are prime candidates for preoperative chemotherapy, and the imager has significant input in making this decision. The imager must define metastases in the lungs and the liver and evaluate the risk of bilateral tumor (particularly metachronous) by searching the index kidney for multifocal lesions or nephroblastomatosis in either kidney.

A strategy for resection of Wilms' tumor with vena cava or atrial extension

Resection of a Wilms' tumor that extends into the vena cava or right atrium results in excellent survival when combined with adjuvant therapy. Preoperative identification of the presence of intravascular tumor thrombus and the level of vascular involvement is essential. It facilitates safe surgical resection, with cardiopulmonary bypass immediately available for retrohepatic and atrial tumors. Six patients with intracaval or intracardiac tumor thrombus were treated over a 5-year period with no perioperative deaths. Preoperative chemotherapy was useful in two patients with extensive tumors and pulmonary metastases. Our results using an integrated management plan suggest that an aggressive surgical approach is justified for this extensive variant of Wilms' tumor.

MR imaging of adult Wilms' tumor: correlation with US, CT, and pathology

The magnetic resonance (MR) features of an adult nephroblastoma are presented. The MR appearance is correlated with ultrasound (US), computed tomographic (CT) and pathology. The tumor appeared heterogeneous with calcifications and areas of necrosis and hemorrhage. MR correctly staged the tumor.

Metastatic Wilms' tumor to the liver with MR findings simulating cysts: case report emphasizing need for integrated imaging

A case of Wilms' tumor metastatic to the liver with previously undescribed MR findings is presented. Although there is no evidence that there were hepatic metastases at presentation in this case, small lesions with this appearance would be difficult to detect with MRI. This could lead to incorrect staging of Wilms' tumor examined by MRI alone.

Abdominal magnetic resonance imaging

A review of the first five years of experience with pediatric abdominal Magnetic Resonance Imaging (MR) is presented. The abdomen is examined organ by organ with description of normal anatomy and pathological processes. Practical clinical uses of MR are indicated. There is a brief review of motion artifact suppression techniques.

Magnetic resonance imaging in genital anomalies

Magnetic resonance imaging, a new radiographic modality that is not dependent on ionizing radiation or intravenous contrast agents, was used to identify undescended testes in 11 patients. Of 14 undescended testes 13 were identified and the only testis that was not seen was in a patient with surgically proved unilateral anorchism. We also used magnetic resonance imaging in 9 patients with various types of intersex. The anatomy of the corpora cavernosa, vagina, uterus and gonads was well seen in each instance.

Wilms' tumour: ultrasound and changing concepts

This review traces the changes that have occurred in our understanding of the pathology, radiographic diagnosis and prognosis of Wilms' tumour. Ultrasound has replaced intravenous urography as the main method for primary diagnosis. Computed tomography and magnetic resonance have with few exceptions added little to the primary diagnosis. Follow-up should be by ultrasound and examination but computed tomography has advantages in detecting pulmonary metastases. The survival rate has dramatically improved in the last 15 years and this is shown by tabulating the treatment and survival rates during this period.