Nephroblastomatosis: clinicopathologic significance and imaging characteristics

Single- and multi-slice spiral computed tomography of the paediatric kidney

Single- and multi-slice computed tomography (CT) is regarded as the primary imaging tool in traumatology, both in adults and children. For complicated infectious disease and renal tumours, these techniques are recommended only as secondary diagnostic tools. Specifically, multi-slice CT (MSCT) provides excellent spatial resolution, which is a particular advantage for the evaluation of small structures as they are typical in children. However, MSCT offers more information than is required for diagnosis. Therefore, low-dose protocols are necessary for paediatric examinations. The CT dose-index (CTDI(vol)) should not exceed 2 mGy for newborns, 4 mGy for toddlers, 5 mGy for elementary school children, and 8 mGy for adolescents.

Clinicopathologic features of nephrogenic rests and nephroblastomatosis

Nephrogenic rests are the consequence of residual metanephric tissue in a fully developed kidney. They usually occur along the perimeter of a mature renal lobe (i.e., perilobar), within the lobe itself (i.e., intralobar), or both (i.e., combined). Nephrogenic rests can be grossly obvious or microscopically discrete. Nephroblastomatosis designates nephrogenic rests that are multifocal or diffuse, and implies more extensive disease. Universal (panlobar) nephroblastomatosis denotes complete replacement of the renal lobe by nephrogenic tissue. The fate of nephrogenic rests and nephroblastomatosis varies and includes obsolescence, sclerosis, dormancy, hyperplasia, or neoplasia. Evidence strongly suggests that neoplastic transformation of nephrogenic rests results in Wilms' tumor (nephroblastoma). Nephrogenic rests almost always occur in the setting of Wilms' tumor; perilobar rests show a strong association with synchronous bilateral Wilms' tumors, whereas intralobar rests are more strongly associated with metachronous tumors. Genetic studies have shown that nephrogenic rests often share many of the same chromosomal defects as Wilms' tumor, which provides further evidence that they are precursors to nephroblastoma. Thus, nephrogenic rests are recognized as clinically significant entities requiring adequate detection and close surveillance. Heightened awareness regarding the clinical relevance of nephrogenic rests and nephroblastomatosis (1) has led to improved detection of these precancerous lesions, (2) fostered more intensive investigation into their biologic behavior, and (3) initiated in-depth discussions about potentially new treatment regimens. The pathologists' ability to identify and detect nephrogenic rests has benefited from the more efficient Beckwith classification. Radiologists have deployed high-resolution radiologic/imaging modalities to improve detection of nephrogenic rests in situ. Clinicians and surgeons are more aware of the impact that nephrogenic rests have upon patient management. Despite this progress, more data is needed to further define these lesions.

Intrarenal cystic mass with pelviureteral junction obstruction

An abdominal mass in the first year after birth most commonly originates from the kidney. Renal masses in this age group are often cystic and may be associated with other abnormalities. We describe an unusual benign unilateral cystic lesion and coexisting pelviureteral junction obstruction in a newborn male with an otherwise morphologically and functionally normal urinary tract. A near normal kidney resulted from subsequent resection of the cyst wall combined with pyeloplasty.

From the archives of the AFIP. Infiltrative renal lesions: radiologic-pathologic correlation. Armed Forces Institute of Pathology

Most renal masses exhibit an expansile growth pattern characterized by radial tumor enlargement that displaces normal renal parenchyma and forms spherical, often exophytic, lesions. These expansile masses have pushing margins that impress adjacent normal renal parenchyma but do not infiltrate it; this behavior results in a well-defined, encapsulated appearance at both radiologic and gross pathologic examination. In contrast, certain disease processes involve the kidney in an infiltrative fashion by using the normal renal architecture as scaffolding for interstitial growth. These infiltrative renal lesions lack a sharp border of demarcation with the normal parenchyma and therefore demonstrate ill-defined zones of transition between the lesion and normal parenchyma. Although infiltrative lesions frequently enlarge the kidney, its reniform shape is usually maintained. Cross-sectional imaging can often help distinguish infiltrative from expansile growth patterns through analysis of the parenchymal interface between the process and the kidney, the effect of the lesion on the collecting system and renal sinus, and the overall renal morphology. A wide variety of neoplastic and inflammatory conditions characteristically involve the kidney by cellular infiltration. Although considerable overlap of the imaging features exists among the various infiltrative processes, the correct diagnosis may be suspected when the clinical data and associated radiologic findings are considered together.

Can MR contribute to the diagnosis of nephroblastomatosis? A report of one case

Presenting one case of nephroblastomatosis (NB) the diagnostic approach by different imaging modalities is discussed. Ultrasound (US) of the kidneys as a basic examination showed one focus of NB but missed two further foci which were clearly shown by contrast enhanced CT and MR. Contrast enhanced CT has been considered to be the most sensitive method in primary diagnosis of NB and follow up. However, in our case contrast enhanced MR examinations showed the foci of NB more clearly than CT. Since the false negative rate of MR is not yet known, we recommend the use of a contrast enhanced MR study parallel to a basic CT examination. If MR findings are consistent with CT findings, no further CT examinations are necessary for follow-up. Since US can miss a considerable amount of foci of NB, basic evaluation of NB and associated lesions by US alone should be avoided.

Benign renal tumors: diagnosis and treatment

Renal tumors both benign and malignant have two basic growth patterns. One pattern is that of appositional growth in which a round mass is shown displacing the normal kidney. The other is that of infiltrative growth. In this situation, the tumor cells grow between the scaffolding of the normal glomerulae and tubules. Thus, in this situation, kidney function appears normal until late in the disease. The kidney thus keeps its reniform shape but does increase in size (bean or orange to grapefruit pattern).

Nephroblastomatosis and Wilms' tumor. Clinical experience and management of seven patients

Nephroblastomatosis is an uncommon abnormality believed to represent the persistence of embryonal renal tissue. Its association with simultaneous or eventual Wilms' tumor has led to the speculation that it is a premalignant lesion. The accumulated clinical experience with this process and its progression to Wilms' tumor in three of seven individuals is discussed. It is concluded that conservative tissue sparing surgery, chemotherapy, and ultrasonographic follow-up are the approaches most appropriate for the management of these difficult patients.

Integrated imaging of neonatal renal masses

Thirty-three neonatal renal masses were evaluated during a 2-year interval. The final diagnoses in these 33 patients were hydronephrosis [14], multicystic dysplastic kidney [10], renal vein thrombosis [3], obstructed upper pole duplication [2], polycystic kidney disease [2], nephroblastomatosis [1], and mesoblastic nephroma [1]. We recommend an integrated imaging approach that utilizes sonography to clarify anatomy and renal scintigraphy or excretory urography to determine renal function.

Multifocal nephroblastomatosis: clinical significance and imaging

The correlation between nephroblastomatosis and Wilms' tumor has been established in the pathology literature. Two cases of multifocal nephroblastomatosis in the kidney contralateral to a Wilms' tumor are presented. The importance of these lesions and their recognition is discussed.