Nodular renal blastema in the multicystic kidney

Multicystic renal dysplasia: a diagnostic dilemma

A 3-year-old male child had left-sided abdominal lump for 4 months. Radiological examination revealed a cystic mass in the left kidney. A tentative diagnosis of multicystic nephroma was made on clinical and radiological examination. Cytology was inconclusive. Nephrectomy was done. A final diagnosis of multicystic dysplasia was made on histological examination.

Non-surgical management of multicystic dysplastic kidney

OBJECTIVES

To better define the outcome and association of multicystic dysplastic kidney (MCDK) with hypertension, vesico-ureteric reflux (VUR), infection and cancer, as there is no consensus on the management of patients born with MCDK. The risk of cancer has dictated the surgical management of the disease in the past.

METHODS

The Medline database was searched for articles published between 1965 and 2006 and written in the English language, and containing the keywords 'multicystic dysplastic kidney'.

RESULTS

The inclusion criteria were met by 105 reports that were subsequently analysed. Of MCDK, 60% regress or involute within 3 years. About 25% of patients will have VUR into the contralateral kidney, of which 90% is grade <or=3. The risk of urinary tract infection appears to be associated with VUR or coexistent abnormalities rather than the MCDK. The risk of hypertension is no greater than that in the general population and nephrectomy is usually not curative. The overall risk of Wilms' tumour developing in a MCDK is <1 in 2000. All reported Wilms' tumours were identified before 4 years of age and 70% presented as a palpable mass.

CONCLUSIONS

Published reports support the non-surgical management of MCDK. Common practice has been to remove palpable or growing MCDKs, although these represent a very small fraction of MCDKs. In theory, ultrasonographic surveillance until 4 years old might allow the earlier detection of a Wilms' tumour, and decrease the intensity of chemotherapy and improve prognosis. Previous reports do not prove or disprove this concept, and the appropriate frequency of surveillance is not evident.

Histomorphology of renal dysplasia--an autopsy study

A retrospective analysis of pediatric autopsies in the past 18 years was done with the aim of studying the histomorphology of renal dysplasia. Renal dysplasia comprised 150 (3.66%) of the 4,099 pediatric autopsies from 20 weeks of gestation to 1 year of life. Primitive ducts with the fibromuscular collar, the sine qua non of renal dysplasia, was seen in all cases. Lobar disorganization and cysts were seen in all cases except for the 7 cases of hypodysplasia. Other elements were seen in varying proportions: cartilage in 33.7%, bone in 1.08%, thickening of basement membrane of the primitive ducts in 64.13%, extramedullary hematopoiesis in 98.9%, nerve twigs in 72.8%, and nodular renal blastema in 2.17% cases. In unilateral multicystic dysplasia/renal agenesis, the contralateral kidney showed abnormalities in 44.45% and 47.37% of cases, respectively.

Renal and blood pressure phenotype in 18-mo-old bradykinin B2R(-/-)CRD mice

Aberrant gene-environment interactions are implicated in the pathogenesis of congenital renal dysgenesis (CRD), a leading cause of renal failure in infants and children. We have recently developed an animal model of CRD that is caused by gestational salt stress (5% NaCl diet; HS) of bradykinin B2R null mice [B2R(-/-)CRD; El-Dahr SS, Harrison-Bernard LM, Dipp S, Yosipiv IV, and Meleg-Smith S. Physiol Genomics 3: 121-131, 2000.]. Developing B2R(-/-)CRD mice exhibit tubular and glomerular cysts, stromal expansion, and loss of corticomedullary differentiation. In addition, B2R(-/-)CRD mice exhibit transient hypertension from 2 to 4 mo of age. The present study was designed to determine the long-term consequences of CRD on renal morphology and salt sensitivity of blood pressure in B2R(-/-)CRD mice. One-year- and 18-mo-old B2R(-/-)CRD mice exhibited stunted renal growth, glomerular cystic abnormalities, and collecting duct ectasia. Moreover, tumors of mesenchymal cell origin emerged in the dysplastic kidneys of 90% of 1-yr-old and 100% of 18-mo-old B2R(-/-)CRD mice but not in age-matched B2R(-/-) or wild-type mice. When challenged with an HS diet, 18-mo-old B2R(-/-)CRD exhibited a significant rise in systolic and diastolic blood pressures and more pronounced natriuresis and diuresis compared with salt-loaded 18-mo-old wild-type mice. Kidney aquaporin-2 expression was decreased by 50%, whereas renin, ANG type 1 receptor, and Na+-K+-ATPase levels were not different in B2R(-/-)CRD mice compared with controls. In conclusion, this study demonstrates that B2R(-/-)CRD mice exhibit permanent phenotypic and functional abnormalities in renal growth and differentiation. This novel model of human disease links gene-environment interactions with renal development and blood pressure homeostasis.

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.

Renal dysplasia: an autopsy study of associated congenital malformations

A retrospective analysis of infant autopsies in the last 14 years was done with the aim of determining the frequency of associated malformations. Renal dysplasia comprised 36 of 594 autopsies done and was the commonest congenital urologic malformation (6.06% of all infant autopsies). Histologically all cases were characterised by hallmarks of disordered metanephric differentiation and organisation. Extrarenal malformations were seen in all (100%) of the cases of which other urologic anomalies were the commonest (28) followed by those of musculoskeletal (18), gastrointestinal (13), cardiovascular (10) and central nervous system (6). Syndromic association was seen in 5 (14%) cases. There were twenty two percent still births and 47% infants died perinatally. A thorough search for systemic malformations is mandatory in all cases of renal dysplasia as these may influence the survival significantly. Cystic renal dysplasia should be differentiated from other causes of cystic renal diseases.

Multicystic renal dysplasia diagnosed in the antenatal period: a note of caution

OBJECTIVE

To document the urological problems associated with multicystic renal dysplasia (MCRD), to assess the efficacy of radiological methods for following the natural history of MCRD and to review current experience in the light of historical data regarding this condition.

PATIENTS AND METHODS

From January 1982 to December 1992 data were obtained prospectively on 62 patients (41 boys and 21 girls, age range 1-11 years) who had a diagnosis of MCRD suspected on antenatal ultrasonography. All patients had the diagnosis confirmed with radioisotope scans and micturating cystograms. Serum creatinine was measured in each patient and repeated clinically as indicated. Follow-up was from 1 to 11 years, with a clinical review and an annual ultrasonogram. The natural history of these patients was compared with those in other published studies.

RESULTS

Of the 62 patients, 12 had associated vesicoureteric reflux. Four patients developed impaired renal function during the course of observation and 10 patients required urological surgery for other pathologies. In the patients managed conservatively, 38% underwent no resolution on sequential ultrasonograms during the 2-year follow-up, and in four children, where complete resolution of the MCRD had occurred on ultrasonography, significant cellular renal masses were excised at subsequent surgery.

CONCLUSION

Patients with MCRD have significant associated urological malformations and the natural history in such patients is unpredictable. We do not regard MCRD as an entirely benign condition and feel that all patients require appropriate investigation of their urinary tract and long-term follow-up where conservative treatment is instituted. From the natural history of these patients, reviewed in conjunction with the literature, we recommend that decisions for management can only be taken with the full informed consent of the parents and that surgical excision is offered as part of that process.

Panlobar nephroblastomatosis with cystic dysplasia: an unusual case with diffuse renal involvement studied by immunohistochemistry

A unilateral cystic renal process discovered prenatally was removed in a neonate. Dysplastic cysts were associated with diffuse (both intra- and perilobar) nephroblastomatosis. We describe a comprehensive immunohistological study confirming the transition observed on simple histology between the different structures: nephrogenic rests (CD9+, CD24+/-, CD56+/-), glomeruloid bodies (CD10++, CD35++), ducts lined by columnar epithelium (CD9+, CD24+, CD56++), cysts lined by cuboidal or thin epithelium (some cells CD10+, CD26+, others EMA+, CD24+). Although no typical S-shaped bodies are seen, small cysts and ducts with a columnar epithelium are considered similar. The dysplastic primitive ducts are KL1++, vimentin+/-, CD9+, CD24+. With a view to assessing dysplastic preneoplastic potential, the value of CD56 and Ki67 as activation antigens with possible prognostic significance is discussed.

Flow cytometric evaluation of multicystic dysplastic kidneys

The most appropriate management of the multicystic dysplastic kidney remains controversial. At issue is the long-term risk of the development of malignancy in the multicystic dysplastic kidney. The association between renal dysplasia and neoplasia has not been confirmed, with only 6 cases of malignancy reported. Nephroblastomatosis, a probable precursor of Wilms tumor, has been found in 5 to 7% of the cases of multicystic dysplastic kidney when specifically sought. In an attempt to determine whether a relationship exists between renal dysplasia and neoplasia in terms of abnormalities of cellular deoxyribonucleic acid content we performed flow cytometric evaluation on 30 formalin fixed, paraffin embedded archival specimens of multicystic dysplastic kidneys. None of the kidneys had evidence of malignancy. Nuclear deoxyribonucleic acid ploidy studies were performed on single dissociated nuclei prepared by the technique of McLemore and associates and stained with propidium iodide. All specimens demonstrated a diploid pattern of deoxyribonucleic acid, including 3 specimens with nephroblastomatosis or extensive papillary growth, and no specimen demonstrated a tetraploid or aneuploid pattern. The mean G0/G1 fraction was 85.94% (standard deviation 4.59) and the mean S/G2/M fraction was 12.54% (standard deviation 4.72). These findings do not support or negate the potential for neoplasm associated with multicystic dysplastic kidney, since a diploid deoxyribonucleic acid pattern does not eliminate the possibility of the future development of malignancy.