European Journal of Cardiovascular Medicine

Micro vasculature of kidney undergoes a continual and mutually dependent developmental changes through which obtains its structural and functional maturity. It is very important to know the normal developmental anatomy of kidney micro vasculature in prenatal diagnosis of renal anomalies, genetic counseling and treatment of prenatal renal disorders like Wilm’s tumor, multicystic renal dysplasia. Present study was undertaken to study the micro vasculature of the kidney at different stages of development during fetal life.

Aims and Objectives-

The aim of the study was to determine the micro vascular development of the human kidneys during the fetal period.

The present study was carried out in the department of Anatomy, Regional Institute of Medical Sciences, Imphal, Manipur. The material for the study consisted of 60 spontaneously aborted and still born human fetal specimens free from any gross congenital anomalies with gestational age between 11th to 38^thweeks were collected from Obstetrics and Gynaecology department, RIMS after taking permission from the Institutional Ethics Committee and categorized into 4 groups as Group-A(11-20 weeks), Group-B(21-27 weeks),Group- C(28-33 week), Group-D(34-38 weeks) .The kidneys were taken out from fetal specimens, fixed, processed, stained with Haematoxylin and Eosin, observed under the Microscope and micro photographed.

Group –A (11-20 weeks)

Cortex of 11-week-old fetal kidney shows few primitive blood vessels within undifferentiated mesenchymal tissue mass. The primitive renal vesicle bends on itself forming ‘Comma’ shaped and ‘S’ shaped body without any network of capillaries adjacent to them. (Fig.1).

At 11 weeks medulla contains the primitive blood vessels lined by simple squamous epithelium containing RBCs were seen, scattered in undifferentiated mesenchymal tissue. (Fig-2)

Capillary tuft are seen in the nephrogenic zone which are now compactly arranged, deeply stained, indicating the increased activity and show decrease of the interstitial tissue. (Fig.3)

Fig. 3: Cortex of kidney at 16 weeks of gestation (H&E, 40X)

Medulla shows mesenchymal tissue with numerous collecting tubules and blood vessels in it. (Fig.4)         

Group – B (21-27 weeks):

 At 21-27 weeks Cortex shows more mature glomeruli and Medulla shows increased vascularity and number of tubules with decreased mesenchymal tissue.

Group – C (28-33 weeks):

At 30 weeks of gestational age the number of the mature glomeruli are increased in cortex and the interstitial connective tissue is reduced in thickness with increased vascularity. Sections of the distal convoluted tubules are observed adjacent to the renal corpuscles indicating the development of the Juxtaglomerular apparatus. (Fig.5)

Fig. 5: Cortex of kidney at 30 weeks of gestation (H&E, 40X) Medulla

Medulla appears more mature, There is much reduced amount of interstitial tissue in the medulla with increased vascularity.

Group- D (34-38 weeks):

At 36 weeks Juxtaglomerular apparatus is well differentiated in the Cortex. (Fig. 6)

There is increase in vascularity in Medulla.

Fig. 6: Cortex of kidney at 36 weeks of gestation (H&E, 40X)

At 38 weeks of gestation Macula Densa, formed by the epithelial cells of distal convoluted tubule and afferent arteriole are well observed in the cortex. (Fig.7).    

Fig. 7: Cortex of Kidney at 38 weeks of gestation (H&E, 40X)

Fig 8: Medulla of Kidney at 37 weeks of gestation (H&E, 10X)

The present study shows primitive vesicle bends on itself forming comma-shaped and ‘S’ shaped body without any network of capillaries at 11 weeks of gestation similar to Hosapatna M et al¹  and Almeida JR et al² who has described the same at 10-12 weeks of gestational age.

In the present study, at 16 weeks many developing glomeruli with proper capillary tuft were seen in the nephrogenic zone which were then compactly arranged, deeply stained, indicating the increased activity and medulla showed mesenchymal tissue with numerous blood vessels, findings are similar to the studies done by Sharma S and Raina S³, Patil S et al⁴, Sunitha V and Rao BN⁵,

In our study at 20 weeks, cortex showed more number of glomeruli and medulla shows increased vascularity. These findings are in agreement with, Patil S et al⁴,

In this study at 27 weeks of gestation cortex and medulla showed increased in thickness with more number of blood capillaries and reduced connective tissues. These findings of the present study are in agreement with the findings of Patil S et al⁴.

In our study between 28-35 weeks of age, the thickness of the cortex and medulla were increased. number of the mature glomeruli was increased in number and present even in the superficial part of the cortex and interstitial connective tissue was reduced in thickness with increased vascularity. The thickness of interstitial tissue in the medulla reduced was very much with increased vascularity, Similar findings were observed by Tank KC et al⁶ and Patil S et al⁴ at 35 weeks of gestational age.

In our study developing juxtra glomerular apparatus was seen at 30 weeks of gestation, in contrast to that Hosapatna M et al¹ observed the same at 28 weeks of Gestation.

Our study showed well differentiated Juxtaglumerular apparatus at 36 weeks. These findings were in agreement with Ukey RK et al⁷.

 In the present study the medulla of 34-38 weeks age group fetuses showed scanty interstitial connective tissues with increased vascularity, which can be noted to be similar to observations of Syed SA et al⁸.

In this study at 38 weeks of gestation, Macula densa formed by the epithelial cells of distal convoluted tubule and afferent arteriole are well observed similar to Rao BN and Padmini MP⁹.

Knowledge on microvascular development on fetal kidney will be helpful for possible intervention in prematurely delivered normal baby with possible prognosis as premature delivery is very common now a days and also in prenatal diagnosis of kidney diseases

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