|Year : 2013 | Volume
| Issue : 2 | Page : 106-108
Fetal polycystic kidney disease: Pathological overview
Sunita B Patil, Madhura D Paricharak, Deepak G Paricharak, SS More
Department of Pathology, Dnyandeo Yashwantrao Patil Medical College, Kolhapur, Maharashtra, India
|Date of Web Publication||23-Jul-2013|
Sunita B Patil
Department of Pathology, Dnyandeo Yashwantrao Patil Medical College, Kasaba Bawada, Kolhapur - 416 006, Maharashtra
Source of Support: None, Conflict of Interest: None
Polycystic kidney disease is a rare developmental anomaly inherited as autosomal dominant or autosomal recessive. It is characterized by cystic dilatation of the collecting ducts frequently associated with hepatic involvement and progression to renal failure. It is included in the differential diagnosis of cystic diseases of the kidney. We report a case of polycystic kidney disease, in 22 weeks fetus incidentally detected on routine antenatal ultrasonography and confirmed by fetal autopsy. This report elucidates the importance of early diagnosis and intervention in cystic kidney diseases.
Keywords: Fibrocystin, renal cyst, renal failure, ultrasonography
|How to cite this article:|
Patil SB, Paricharak MD, Paricharak DG, More S S. Fetal polycystic kidney disease: Pathological overview. J Sci Soc 2013;40:106-8
| Introduction|| |
Polycystic kidney disease (PKD), a common genetic cause of chronic renal failure, is characterized by accumulation of fluid filled cysts in the kidney and other organs. PKD can be inherited as an autosomal recessive (ARPKD) or autosomal dominant trait (ADPKD). ARPKD is relatively uncommon and occurs primarily in neonates and children. The incidence range of ARPKD is one in 6,000 to one in 40,000 live births. , It is characterized by cystic dilatation of renal collecting ducts with hepatic abnormalities consisting of bile duct dysgenesis and periportal fibrosis. , ADPKD is common affecting both children and adults. It is reported that in India, 5% of conservative estimate of 0.1 million new cases of end stage renal disease are caused by ADPKD.  There are no studies reporting the problem statement of PKD in India.
| Case Report|| |
A 21-year-old female patient, presented at 22 weeks of gestation for a routine antenatal check up. She was G2 A1. Ultrasound examination revealed a single live fetus with breech presentation. Fetal heart rate was 153 beats/min. Period of gestation estimated was 22 weeks and 2 days. Amniotic fluid was markedly reduced consistent with severe oligohydramnios. Placenta was posterior and fundal. On biophysical profile, fetal movements, fetal tone, and breathing were normal but the amniotic fluid index was inadequate. Crown rump length was 19.4 cm. Bilateral symmetrically enlarged, echogenic kidneys filling the fetal abdomen were seen. The urinary bladder was not visible. There were no other anomalies noted and fetal liver was normal. Umbilical cord blood flow was intact. Gene mapping was not done.
There was no history of consanguinity amongst the parents. On evaluation, there was no family history of renal diseases on the maternal or paternal side. The patient and the family were counseled about the possibility of autosomal recessive polycystic kidney disease and opted for termination of pregnancy. A male fetus with no gross enlargement of abdomen was delivered.
Fetal autopsy was done. Both upper and lower limbs were normal and there were no amniotic bands. The spine was normal. The fetus had a pink color to it and there were no facial deformities. Head circumference was 23 cm and abdominal circumference was 17.5 cm. The fetus did not show any signs of intra uterine growth retardation. The abdomen was opened.
On gross examination, liver and intestines were normal in appearance. Kidneys on both sides were lobulated and enlarged each measuring about 4 × 2 × 1 cm. The cut surface showed numerous cysts in both the kidneys. The cysts were subcortical. The cortico-medullary junction was not distinct due to cystic transformation of medulla causing distortion of renal columns [Figure 1] and [Figure 2]. Microscopy of both kidneys showed numerous cysts lined by a single layer of flattened to low cuboidal epithelial cells with thick peritubular mesenchyme [Figure 3]. No difference was appreciated in the histology of proximal and distal convoluted tubules Occasional glomeruli were seen and appeared normal. Liver showed normal histology.
|Figure 2: Cut section of kidney showing numerous subcortical cysts. No corticomedullary differentiation|
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The gross and microscopic features were in favour of ARPKD with no accompanying hepatic portal fibrosis and pulmonary hypoplasia [Figure 1], [Figure 2] and [Figure 3]. In our case, the polycystic kidney disease was thought to be an autosomal recessive form and the family carries a 25% risk of occurrence with each pregnancy as the polycystic kidney disease has not been observed in the parents and previous generation, the mode of inheritance may be autosomal recessive or may be a new mutation.
| Discussion|| |
The kidney develops from two sources, one in the mesoderm of sacral part of nephrogenic cord and other from the ureteric bud, a diverticulum arising from the mesonephric duct. Further, development involves epithelial mesenchymal interaction. Epithelium of ureteric bud interacts with mesenchyme of metanephric blastema. The mesenchyme expresses a transcription factor that makes this tissue competent to respond to the induction of ureteric bud. In the autosomal recessive polycystic kidney disease, cysts occur from collecting ducts, due to deficient or non-responsive cell adhesion molecules, syndecan and E-catherin which are essential for condensation of mesenchyme to epithelium (Sadler, 2006).  The gene PKHD1, on short arm of chromosome 6p21 responsible for ARPKD is linked to ciliary dysfunction. ,, The autosomal recessive polycystic kidney presents as bilateral enlarged kidneys and severe renal failure. In the present case also the kidneys were bilaterally enlarged. Quite et al., (2005) observed that histologically kidney showed simple cysts lined by a single layer of epithelial cells.  The present histological study also confirms the cysts with single layer.
It contains more than 80 exons and codes for a protein called fibrocystin or polyductin but the cellular functions of the gene product remain uncharacterized.  There is no evidence of genetic heterogeneity, suggesting that the marked variability in clinical severity represents differences in phenotypic expression. PHKD1 gene is expressed at high levels in fetal and adult kidneys and at lower levels in the liver and this corresponds to the principal sites of the disease. The characteristic pathologic changes occur in the kidneys and the liver with a reciprocal relationship between the degree of renal and hepatic involvement. 
Consanguinity has been incriminated strongly in the etiology and clinical diagnostic criteria of PKD. , Parents of a child with ARPKD should be informed that each child or new fetus would have a one in four (25%) chance of developing the disease (although the expression of the disease may be different from that in other siblings) and a one in two chance (50%) of being a carrier. 
Perinatal, neonatal, infantile, and juvenile subcategories have been defined, depending on the time of presentation and presence of associated hepatic lesions. The first two are most common; serious manifestations are usually present at birth.  Children born with ARPKD often, but not always, develop kidney failure before reaching adulthood. Severity of the disease varies. Severe cases can be detected after 24 wks of gestation by antenatal ultrasound. The prognosis of these antenataly detected cases is bleak with death occurring within the first two months due to uremia or respiratory failure. The impairment in renal function leads to oligohydramnios leading to pulmonary hypoplasia. Liver scarring occurs in all patients with ARPKD and tends to become more of a medical concern with increasing age. 
Kidneys are increased in size with subcapsular microcysts usually less than 3 mm in diameter, represents ectasia of the collecting tubules.  In the cross-section, these dilated tubules can be seen in a radial arrangement extending from the calyx to the capsule. There is epithelial hyperplasia along the collecting ducts and these hyperplastic cells undergo a functional change from resorption to secretion. The combination of epithelial hyperplasia and fluid secretion results in ductal ectasia. Histological examination of biopsies reveals cystic dilatation, primarily limited to the collecting tubules, with flattening of the epithelium. Depending on the extent of ductal involvement, there is a wide variability of renal dysfunction. 
It should also be recognized that the ultrasonographic finding of enlarged, echogenic kidneys in the fetus is not diagnostic of PKD. Other disorders that can produce these changes include malformation syndromes such as Meckel syndrome, renal dysplasia, congenital nephritic syndrome, and transient nephromegaly in which the ultrasonographic abnormalities return to normal after birth. , The radiological appearance may not distinguish autosomal recessive from autosomal dominant disease. In this setting, a careful family history and examination of the parents is often helpful. Ultrasonography of parents of children with ARPKD will not detect cysts while ADPKD is often first discovered in a parent at the time of diagnosis of the child. Portal fibrosis or signs of portal hypertension, cholangitis or bile duct dysgenesis favor the diagnosis of autosomal recessive disease. However, renal pathology provides the diagnosis of ARPKD with cystic dilatation of the collecting ducts with progressive intestinal fibrosis and glomerular sclerosis. 
| Conclusion|| |
Although the antenatal diagnosis of fetal anomalies has improved largely due to the availability of high resolution ultrasound equipments, still cystic kidneys discovered incidentally during routine antenatal ultrasonography frequently pose significant diagnostic dilemma. There are diverse etiologies with equally variable implications for prognosis in the affected fetus. Correct and timely antenatal diagnosis of polycystic kidney disease with associated fetal anomalies is important so that proper counselling and appropriate obstetric and paediatric management can be extended.
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[Figure 1], [Figure 2], [Figure 3]