Should asymptomatic unilateral multicystic dysplastic kidneys be removed because of the future risk of neoplasia?

Genitourinary imaging techniques

In the current era of pediatric uroradiology, use of nuclear medicine, ultrasonography, CT, and MRI has been valuable in the identification and management of genitourinary diseases. Excellent information about the renal parenchyma and renal function is currently attainable with current cross-sectional imaging techniques that can identify tissue differentiation of lesions, distinguish dilatation of the pelvocalyceal system, and determine margins of the kidney and perirenal space. Invasive angiography is limited in application specifically to vascular diseases, although they are uncommon in childhood. Because of these newer techniques, intravenous urography has lost its position as the "cornerstone" of urinary tract imaging and is used mainly to identify pathologic conditions of the ureters.

Urological anomalies in children with renal agenesis or multicystic dysplastic kidney

This study aimed to determine the frequency of associated urological abnormalities in children with unilateral renal agenesis (RA) or multicystic dysplastic kidney (MCDK). In total, 38 children (10 girls, 28 boys) were studied: 21 with RA and 17 with MCDK. In 14 children (37%) anomalies of the urinary tract were suspected prenatally in ultrasound studies. In the remaining 24 children the diagnosis of RA/MCDK was made postnatally: in 13 (34%) in the first 7 days of life, in 11 (29%) at the age of 8 days to 34 months, mean 10.6+/-8.05 months. Voiding cystourethrography was done in 36 (95%) children, the isotopic 99mTc-EC/DMSA scan of the kidney in 29 (67%), and urography in 8. Urological anomalies were present in 11 (29%) children: in 7 (33%) with RA and in 4 (24%) with MCDK. Vesicoureteral reflux was diagnosed in 8 children: grade II in 4, III in 3, and IV in 1 (in 1 child to duplicated, in 1 to ectopic kidney); ureterovesical junction obstruction in 2 (9.5%); and ureteropelvic junction obstruction in 1 (4.8%). Among them, 2 children demanded surgery on the contralateral urinary tract: pyeloplasty in 1, antireflux procedure in 1; while 9 children were treated conservatively. Compensatory hypertrophy of the contralateral kidney was found in 90% of children. Thus due to an increased risk of pathological changes in the single functioning kidney, lifelong nephrological care is recommended in patients with unilateral RA/MCDK.

Nephrectomy for multicystic dysplastic kidney: if and when?

OBJECTIVES

To evaluate the criteria for conservative versus surgical treatment of multicystic dysplastic kidneys and to attempt to specify the optimal timing for surgery, when considered indicated.

METHODS

The study population comprised 48 antenatally or neonatally detected consecutive patients with unilateral multicystic dysplastic kidney. The fate of the affected renal conglomerate was regularly analyzed by ultrasonography. All cases were primarily followed up conservatively. In the patients who eventually underwent nephrectomy, the decision to operate was made after a minimum of 18 months (median 25).

RESULTS

Ultrasound follow-up showed complete involution in 13 cases (27%); in 35 cases (73%), the renal conglomerate persisted throughout the study period (mean 46 months). Of the 48 patients, 32 (67%) eventually underwent nephrectomy. The size of the affected mass among the involuted cases was significantly smaller throughout the study period than in those requiring nephrectomy. The difference between the two groups continuously increased during follow-up, with a mean involution rate of 2.5 cm/yr versus 0.6 cm/yr (up to 18 months) for the involuted versus noninvoluted cases, respectively (P <0.0001). From 18 months on, no statistically significant involution was observed in those who eventually underwent nephrectomy.

CONCLUSIONS

Patients with antenatally or neonatally detected multicystic dysplastic kidney can primarily be followed up conservatively. Involution occurs in approximately one fourth of the cases, usually within about 14 months. In our experience, no significant involution can be expected to occur after 18 months. If surgery is decided on, we recommend an age of about 2 years. Late complications (eg, Wilms' tumor and renovascular hypertension) are rare.

Unilateral multicystic dysplastic kidney: experience in children

OBJECTIVES

To report a retrospective study of unilateral multicystic dysplastic kidneys (MCDK) in children, assessing the contralateral kidneys and urinary tract, the functional consequences, and the urological and nephrological management and outcome, as unilateral MCDK is the most common cause of renal cystic disease in children, and malformations of the contralateral urinary tract and kidney (pelvi-ureteric obstruction, megaureter, reflux, renal dysplasia) have been reported.

PATIENTS AND METHODS

The study included 97 patients (60 boys, 37 girls) with MCDK seen between 1985 and 1998; 82 were diagnosed in utero by ultrasonography (US). After birth, the diagnosis was verified by US, renal scanning (in 93) or intravenous urography (in four), and 89 (92%) had voiding cysto-urethrography (VCUG). Of the 97 children, 87 (90% had a mean (range) follow-up of 44.3 (15-115) months.

RESULTS

The MCDK was removed in 17 children; the follow-up of 75 children (five lost to follow-up) showed total involution of the MCDK in 25%, shrinkage in 60% and a stable size in 15%. None had any sign of malignancy. The contralateral kidney showed anomalies in 19 of 97 children (20%); 12 had a dilated renal pelvis (two with megaureter), six had a high echogenicity of the contralateral kidney (one had reflux, and two also pelvic dilatation). In only four of the 89 children was reflux found by VCUG; 16 of the 19 anomalies were detected by US. Five children needed surgery on the contralateral urinary tract (three a pyeloplasty, and one each a pyeloplasty plus ureteroneocystostomy, and an antireflux procedure). Of the contralateral kidneys 43% showed compensatory hypertrophy. There was mild renal insufficiency in three children; renal function seemed to be slightly impaired in many. Five infants had hypertension (four with spontaneous resolution) caused by renal scarring after pyelonephritis or inborn dysplasia of the contralateral kidney. There were symptomatic urinary tract infections in seven children.

CONCLUSION

US can be used safely to diagnose unilateral MCDKs and malformations of the contralateral urinary tract and kidney. In cases where US of the dysplastic kidney remains uncertain renal scintigraphy is necessary to detect the lack of renal function. The low rate of reflux makes routine VCUG unnecessary if the contralateral upper urinary tract and kidney appear to be normal on US. Nephrectomy of the dysplastic kidney in typical cases is also unnecessary. A long-term nephro-urological follow-up of children with MCDK is recommended.

Renal cystic neoplasms and renal neoplasms associated with cystic renal diseases: pathogenetic and molecular links

Cystic renal neoplasms represent an isolated cystic mass not accompanied by cystic change of the renal parenchyma. Although cystic change may be seen in any type of renal neoplasm, a few (i.e., cystic renal cell carcinoma, cystic nephroma, cystic partially differentiated nephroblastoma, mixed epithelial and stromal tumor) are characterized by constant cystic change that may involve the entire tumor. Cystic kidney disease is characterized by cystic change, which usually involves the kidneys in a bilateral and diffuse pattern, does not create a discreet mass, and is due to hereditary or developmental conditions. Some of the cystic kidney diseases are not known to give rise to renal neoplasm; others such as autosomal polycystic kidney disease or multicystic dysplastic kidney may fortuitously coexist with renal neoplasms. Three conditions (acquired cystic kidney disease, tuberous sclerosis, and von Hippel-Lindau disease) are associated with renal neoplasms with such a high frequency that they are considered preneoplastic. This article reviews the differential diagnoses among cystic neoplasms. It also focuses on the underlying genetic and molecular mechanisms for the relationship between cystic renal diseases and renal neoplasms.

The importance of accurate diagnosis and early close followup in patients with suspected multicystic dysplastic kidney

PURPOSE

Conservative management of children who have unequivocal multicystic dysplastic kidney with a stable or regressive pattern of disease during close followup is well established. However, a clear diagnosis may prove difficult. We report 3 cases in which the diagnosis was particularly difficult to increase awareness of the importance of applying strict criteria for the diagnosis of multicystic dysplastic kidney.

MATERIALS AND METHODS

Three children in whom a diagnosis of multicystic dysplastic kidney was suspected underwent surgical exploration. One patient who did not comply with followup presented with a large retroperitoneal mass suspicious for neuroblastoma 8 months later. In another patient a growing renal cystic mass was suspicious for a multilocular cyst at 3 months of followup. At 2 months of followup a cystic nephroma was suspected in the remaining patient.

RESULTS

All patients underwent surgical exploration. The patient with suspected neuroblastoma had extensive stage 3 Wilms tumor. In the child with a suspected multilocular cyst segmental multicystic dysplastic kidney of the lower pole of an ipsilateral duplicated system was found. In the patient in whom cystic nephroma was suspected mesoblastic nephroma was confirmed by the National Wilms Tumor Study Pathology Center.

CONCLUSIONS

An unequivocal diagnosis of multicystic dysplastic kidney should be made early in life. The urologist should have an active role in making the initial radiological diagnosis and close followup with renal ultrasound every 3 to 4 months is essential during year 1 of life. Surgical exploration is indicated if the diagnosis becomes equivocal at any point or should concerns exist regarding compliance with followup.

The natural history of the multicystic dysplastic kidney in children

The objective of this study was to examine the natural history of the multicystic dysplastic kidney and the use of sonography for follow-up studies. A retrospective study was performed on 66 children with a radiological diagnosis of multicystic kidney. The change in size demonstrated on sonograms was examined. Adequate follow-up was available on 55 children over a period of 32 months (range 2-69 months). 40/55 of the kidneys underwent a reduction in size, including 22 which were no longer detectable by ultrasound. 10/55 kidneys showed an increase in size and 5/55 showed no change. Reduction in size occurred at a mean age of 84 weeks (range 20-120 weeks). In conclusion, most multicystic kidneys undergo partial or complete involution over the first 2 years of life. The mean size of the multicystic kidney at diagnosis is a poor predictor of eventual outcome.

Unilateral multicystic dysplastic kidney: the case for nephrectomy

Management of unilateral multicystic dysplastic kidneys (MCDK) presents physicians and surgeons with a significant dilemma. Recent studies have indicated that the incidence of short term complications of MCDK is low and many authors have recommended conservative non-operative treatment. Surgery has been proposed by some because of the potential complications of hypertension, infection, and malignant change. Three children with hypertension secondary to MCDK seen at this institution in the past four years, one of whom had been discharged from follow up as a result of 'disappearance' of the cystic kidney on ultrasound examination, are reported. We believe that the risks of hypertension secondary to MCDK have been understated, and that based on the conclusions of these studies, many children may be receiving suboptimal follow up. We currently favour elective nephrectomy as the treatment of choice for this lesion.