Renal Histo-Pathology (I) - Normal Kidney Light Microscopy - Dr. Gawad

RENAL HISTO-PATHOLOGY (I)
m

NORMAL KIDNEY
LIGHT MICROSCOPY
Mohammed Abdel Gawad

Lecture References
 Text Books:
2
 Fundamental of Renal Pathology
 Handbook of Renal Biopsy Pathology
 Comprehensive Clinical Nephrology

 Websites:
(Links are available on www.nephrotube.blogspot.com):
 Histology at SIU SOM
 WebPath
 Kidney pathology.com
 Virtual Slide
 Blue Histology
 HistoWeb.
 Visual Histology
 Zoomified Histology
 Renal Pathology Tutorial
 Medical histology

OBJECTIVES
3
 Gross Picture
 Specimen Sectioning & Stains
 Where am I ?
 Renal Malipighian Corpuscle (Bowman’s space)
 Renal Malipighian Corpuscle (GBM & Mesangium)
 Renal Tubules (PCT vs DCT)
 Juxtaglomerular Apparatus
 Renal Tubules (Loop of Henle & Collecting Ducts)
 Renal Vasculature
 Self Assessment Quiz

OBJECTIVES
4
 Gross Picture
 Where am I ?

5 In order to understand better kidney histology
we must have in mind that kidney is
three-dimensional structure,
non bi-dimensional as we see it at microscope

Gross Picture
 On the cut surface, the cortex is the pale outer
9 region, approximately 1.5 cm in thickness, which
has a granular appearance because of the
presence of glomeruli and convoluted tubules.

 the medulla, a series of pyramidal structures
with apical papillae, and have a striped or
striated appearance because of the parallel
arrangement of the tubular structures.

 Cortical parenchyma extends into spaces
between adjacent pyramids; this portion of the
cortex is known as the columns of Bertin.

 medullary pyramid with surrounding cortical
parenchyma, which includes both columns of
Bertin as well as the subcapsular cortex,
constitutes a renal lobe.

 A renal lobule is is a part of a renal lobe. It
consists of the nephrons grouped around a
single medullary ray, and draining into a
single collecting duct.

Renal Lobe
10

Medullary pyramid with surrounding cortical parenchyma, which includes both
columns of Bertin as well as the subcapsular cortex, constitutes a renal lobe.

Renal Lobule
11

• A renal lobule is a part of
a renal lobe. It consists of
the nephrons grouped around
a single medullary ray, and
draining into a single collecting
duct.

• Lobules are centered on
medullary rays (see later)

OBJECTIVES
12
 Gross Picture
 Where am I ?

Specimen Sections
13

Very thin sections (2-3µm or less) are much better
(for the definition of glomerular
pathology, especially regarding cellularity, is dependent on sections of
this thickness.
The ability to detect subtle pathologic abnormalities is enhanced
with thinner sections).

Electron microscopy is essential for demonstrating
functional details like capillary fenestrations and
podocyte filtration slits

Stains
14

PAS Trichrome H&E Silver

Stains
 Silver stain accentuates (BLACK) collagenous structures,
15 e.g., in the glomerulus, the mesangial matrix, the glomerular
basement membrane & tubular basement membrane.

 PAS stain also accentuates (RED) matrix and basement
membrane constituents.

 Trichrome also accentuates (BLUE) matrix and basement
membrane constituents.

 In certain circumstances the trichrome stain demonstrates
granular immune (not linear) deposits as bright
fuchsinophilic (orange, red-orange) smooth homogeneous
structures.

 Congo red, elastic tissue, and other stains are employed
when indicated.

OBJECTIVES
17
 Gross Picture
 Where am I ?

Where am I ?
18
Cortex or Medulla !!

Where am I ?
19
Outer or Inner Medulla !!

Renal Cortex
20

 The cortex of the kidney is distinguished by characteristic renal corpuscles, each of which consists of
a glomerulus surrounded by Bowman's capsule.
 Convoluted tubules comprise the bulk of the cortex. Proximal and distal tubules cannot be readily
distinguished at this magnification.
 Little interstitial tissue in comparison to medulla
 Dense fibrous connective tissue forms a tough capsule around the kidney.

Renal Medulla
22

 Note these features of the renal medulla, in contrast with the renal cortex:
 No renal corpuscles are present.
 All tubules are approximately parallel

Medullary Rays
 Lobules are centered on "medullary rays", bundles of
25
straight tubules (collecting ducts and loops of Henle)
which resemble the substance of the medulla but extend
into the cortex.

30

Are Medullary rays in the cortex
or medulla ??

OBJECTIVES
31
 Gross Picture
 Where am I ?

Renal Malpighian Corpuscle
32

( connective tissue matrix)

(pedicles)

lacis cells or cells of Goormaghtigh

Renal Malpighian Corpuscle
Test Yourself
34

Renal Corpuscle, H&E
35

 Renal corpuscles, each of which consists of an outer envelope of simple squamous epithelium (Bowman's
capsule) surrounding a fluid-filled space (Bowman's space) within which is suspended a glomerulus.
 Individual identities as endothelial cells, podocytes, or mesangial cells are difficult to determine reliably on
relatively thick-sectioned specimens such as this.

Renal Corpuscle, thin section
 This 1µm section provides higher resolution.
39

 Podocyte cell bodies nuclei are relatively large and euchromatic.
 Mesangial cell nuclei are relatively small, irregular in shape, and heterochromatic

OBJECTIVES
40
 Gross Picture
 Where am I ?

Glomerular Filtration Membrane
& Mesangium
41


(pedicles)


& Mesangium
42

& Mesangium
43

& Mesangium
44

(pedicles)


& Mesangium
45

46

47 In order to understand better kidney histology
we must have in mind that kidney is
three-dimensional structure,
non bi-dimensional as we see it at microscope

48

49

Stains
50
 Silver stain accentuates (BLACK)
collagenous structures, e.g., in the glomerulus,
the mesangial matrix, the glomerular
basement membrane & tubular basement
membrane.

 PAS stain also accentuates (RED) matrix and
basement membrane constituents.

 Trichrome also accentuates (BLUE) matrix
and basement membrane constituents.

Stains for Membranes & Mesangium
51  The filtration membrane is not apparent on H&E
stained histological specimens but may be demonstrated with PAS,
trichrome or silver stain. Electron microscopy is the best way to
visualize the filtration membrane.

 The mesangial matrix is not apparent on H&E stained histological
specimens, but (like the filtration membrane) it may be visualized
with PAS, trichrome or silver stain.

 It is very important to recognize the mesangial areas to determine
when there is or non mesangial cell hypercellularity: cluster of
three or more nuclei per mesangial area in thin 2 to 3 micron
sections away from the vascular pole.

 Podocyte cell bodies nuclei are relatively large and euchromatic.

 Mesangial cell nuclei are relatively small, irregular in shape, and
heterochromatic

Renal Corpuscle, Silver Stain
57

58

GBM is thin and smooth (green arrows). The blue arrows indicate nuclei of podocytes, the cytoplasm is
flat and it does not allow to delimit itself clearly with the optical microscopy. The red arrows mark some
mesangial areas and nuclei of mesangial cells

59

The GBM is seen perfectly smooth, without perpendicular irregularities nor projections (red arrows).
The flat cytoplasm of the visceral epithelial cell can be seen; and in some points, it is possible also to
see the cytoplasm of the endothelial cells. The nucleus of a podocyte appears pointed with the green
arrow. The nuclei of the endothelial cells usually are found towards the mesangial portion of the
capillary (blue arrow)

60

61

Renal Corpuscle, Trichrome Stain
62

63

the red arrows indicate several mesangial areas in which there are 1 or 2 nuclei. The green arrows
indicate nuclei of endothelial cells

64

In this image the capillary walls, the podocytes (green arrows), nuclei of endothelial cells (blue
arrows), mesangial cells (yellow arrows), and parietal epithelial cells (red arrows) are well evidenced

OBJECTIVES
65
 Gross Picture
 Where am I ?

Renal Tubules, PCT vs DCT
67
PCT DCT
simple cuboidal epithelium
PCTs have nuclei spaced some what DCTs have nuclei less spaced than
farther apart than those of DCTs those of PCTs
more intensely eosinophilic than those less intensely eosinophilic than those
comprising distal tubules comprising proximal tubules
brush border of microvilli not have a brush border, although
(apical ends less distinct than those of there may be scattered microvilli
DCT). (apical ends more distinct than those
of PCT).
may be occluded lumen clearer lumen
Cells are extensively interdigitated → boundaries between adjacent cells are
inconspicuous (i.e., in section the epithelium looks like a continuous band of
cytoplasm with nuclei appearing at irregular intervals).
Because the proximal convoluted tubule is considerably longer than the distal
convoluted tubule, a typical section of the renal cortex includes many more
profiles of proximal tubules than of distal tubules

Renal Tubules, PCT
68

 More
 Darker

 More villi, less Nuclei

Renal Tubules,
PCT vs DCT (Silver)
69

Renal Tubules,
PCT vs DCT (PAS)
70

Brush border of the proximal tubules has affinity by the reagents used in the periodic acid of
Schiff coloration (arrows). DCT (asterisks)

Renal Tubules,
PCT vs DCT (PAS)
71

Brush border of the proximal tubules has affinity by the reagents used in the periodic acid of
Schiff coloration (arrows). DCT (asterisks)

Renal Tubules, PCT, H&E
73

abundant, eosinophilic cytoplasm and a brush border easy to identify. The cytoplasmic size, the tall
cells and the brush border (arrows) are more prominent in the proximal convoluted portion

Renal Tubules,
PCT vs DCT (H&E)
74

The tall cells of the S1 segment are seen almost occluding the tubular lumen in many of the histologic
sections. This microphotography shows this portion of proximal tubule (from upper left corner to bottom
right corner) surrounded by distal tubules

Renal Tubules,
PCT vs DCT (H&E)
75

Renal Tubules,
PCT vs DCT (H&E)
76

Renal Tubules,
PCT vs DCT (H&E)
77

Renal Tubules, PCT, Trichrome
78

In the proximal tubules is not unusual to find its cytoplasm occupied by droplets of protein
resorption, they are shown here like small green spheres in a tubule.

OBJECTIVES
79
 Gross Picture
 Where am I ?

Juxtaglomerular Apparatus
81


(pedicles)


83

Juxtaglomerular
Apparatus,
Vascular Pole,
H&E

84

Juxtaglomerular
Apparatus,
Vascular Pole,
H&E

85

Juxtaglomerular
Apparatus,
Vascular Pole,
H&E

•The yellow arrows indicate the macula densa, see the apical nuclei.
•Almost in contact with macula densa cells is the extraglomerular mesangium with the Lacis or
Goormaghtigh cells, indicated with the black arrows.
•The green arrow marks the efferent arteriole and the blue arrow the afferent arteriole.
•The Peripolar cells (cells located just at the transition of the parietal to the visceral epithelium) are
located exactly in the angle in which parietal epithelium contacts visceral epithelium

86

Juxtaglomerular
Apparatus,
Vascular Pole,
Trichrome

Other image of the juxtaglomerular apparatus let us see the Lacis
cells (black arrows), the macula densa (yellow arrows), and two
nuclei of peripolar cells, in both angles of the vascular pole.

Macula Densa, Vascular Pole

87

 The macula densa may be seen at the vascular pole of the corpuscle, displaying its characteristic
appearance of several distal tubule nuclei crowded densely together.

Afferent Arteriole, Vascular Pole

88

89

90

91

Macula Densa, Afferent Arteriole

92

 Conspicuous left of center is the macula densa of a distal tubule, presumably close to a renal corpuscle that is
not visible in this plane of section.
 Beside the macula densa is a small afferent arteriole, probably originating from the interlobular artery at lower
left and presumably leading to the glomerulus that is associated with this juxtaglomerular apparatus.

Macula Densa, Afferent Arteriole

93

 Conspicuous left of center is the macula densa of a distal tubule, presumably close to a renal corpuscle that is
not visible in this plane of section.
 Beside the macula densa is a small afferent arteriole, probably originating from the interlobular artery at lower
left and presumably leading to the glomerulus that is associated with this juxtaglomerular apparatus.
 At the left side of the image is another small arteriole, probably afferent to another corpuscle, cut in
longitudinal section.

Juxtaglomerular Cells,
Vascular Pole
94

 This image from a thin (1µm) section shows sufficient detail to resolve secretory
granules within juxtaglomerular cells, found in the wall of an afferent arteriole.

OBJECTIVES
95
 Gross Picture
 Where am I ?

Renal Tubules,
Loop of Henle & Collecting Ducts
96

Where am I ?
97
Cortex or Medulla !!

Where am I ?
98

Where am I ?
99

Renal Medulla
100


Renal Medulla,
Loop of Henle vs Collecting Duct (H&E)
 thin segment of the loop of Henle:
103
 lined by squamous epithelial cells.
 thick segment of the loop of Henle (same as DCT):
 lined by cuboidal epithelial cells.
 having eosinophilic cytoplasm.
 no apparent cell boundaries.
 collecting duct: (less specialized than PCT & DCT):
 lined by cuboidal epithelial cells.
 having relatively clear cytoplasm.
 distinct cell boundaries.

Renal Medulla,
104

Renal Medulla,
105

Renal Medulla,
106

Renal Medulla,
107

Renal Medulla,
Vessels vs Thin Loop of Henle (H&E)
108

 In this image we can see distal tubules at both sides of a thin portion of the thin limb of Henle with a hyaline
cast (arrow). In many cases it is very difficult, with light microscopy, to differentiate if small spaces in the
medulla, like this here observed, are peritubular capillaries or thin portion of the limb of Henle.

Renal Medulla,
Vessels vs Thin Loop of Henle (H&E)
109

 Because both are lined by simple squamous epithelium, vessels and loops can be difficult to distinguish.
 Epithelial cells lining loops are often conspicuously rounded in the vicinity of the nucleus, not as flat as vascular endothelium.
 Medullary blood vessels may sometimes be distinguished by the presence red blood cells as well as by a an endothelial lining
which may be lower (flatter) than the tubular epithelium.

Renal Medulla,
Loop of Henle (H&E)
110

 Note that epithelial cells lining thin segment are distinctly thinner than epithelial cells
lining thick segments of loops of Henle.

Renal Medulla,
111

 Note that epithelial cells lining collecting ducts have more distinct cell boundaries and
clearer cytoplasm than epithelial cells lining thick segments of loops of Henle.

Renal Medulla,
Collecting Ducts (H&E)
112

 This image shows two collecting ducts merging into a larger duct, deep in the medulla.
 The surrounding tissue consists of medullary blood vessels and thin segments of loops
of Henle. (Because both are lined by simple squamous epithelium, vessels and loops
can be difficult to distinguish, except when blood is present in the vessels).

Renal Medulla,
113

Renal Medulla,
114

DCT vs Collecting Duct (H&E)
115

Where am I ?
Cortex or
Medulla !!

 Distal tubule and collecting duct cells have less eosinophilic cytoplasm than proximal
tubule cells. See a clear halo surrounding the nucleus in many cells.

DCT vs Collecting Duct (H&E)
116

Where am I ?
Cortex or
Medulla !!

 In this image we see collecting duct cells. Distal tubule cells gradually change to
collecting duct cells and the histologic aspect, in many cases, do not permit differentiate
between cells of this portions of the nephron with light microscopy.

DCT vs Collecting Duct (Silver)
117

Where am I ?
Cortex or
Medulla !!

Renal Medulla – Which level ?
118

Outer or Inner
Medulla ?


119

Outer or Inner
Medulla ?

•The larger tubules in this image are collecting ducts.
•The smaller tubules are ascending thick segments of loops of Henle.
•Descending thin segments are present but not conspicuous at this magnification.

120

Outer or Inner
Medulla ?

 This image shows collecting ducts deep in the medulla.
 The surrounding tissue consists of medullary blood vessels and thin segments of loops
of Henle. (Because both are lined by simple squamous epithelium, vessels and loops
can be difficult to distinguish, except when blood is present in the vessels).

Renal Medulla
Ducts of Bellini
121

Renal Pelvis
122

 The transitional epithelium of the renal pelvis is continuous with that of the ureters
and bladder

OBJECTIVES
123
 Gross Picture
 Where am I ?

Renal Vasculature,
Angiogram
125

Renal Vasculature,
Vascular dye injection
126

Renal Vasculature,
127

Renal Vasculature,
128

129

 The renal arteries and arterioles have the
same histologic structure that arteries or
arterioles elsewhere in the body.

They are formed by endothelium,
subendothelial connective tissue or intima,
internal elastic lamella (difficult to identify in
the small arteries), muscular media, and
adventitia that fuses with the interstitial tissue.

Interlobular Arteriole (PAS)
131

 Low magnification of cortex with portions of two glomeruli, tubules, and
interstitium and interlobular artery with arteriolar branch

Interlobular Arteriole (Silver)
132

 Low magnification of cortex. An arcuate artery (AA), interlobular artery (IA),
and afferent arteriole (aa) are in continuity

Interlobular Arteriole (Trichrome)
133

 Interlobular artery (IA) with afferent arteriole (aa) extending into glomerulus

Interlobular Arteriole (H&E)
134

Interlobular Arteriole (H&E)
135

Renal Medulla, Vasa Recta (H&E)

136

 Vasa recta appear as tightly packed bundles of vessels.
 In this specimen, most tubules are cut lengthwise, indicating that the plane of section is
perpendicular to the cortex.

Renal Medulla, Vasa Recta (H&E)

137

 Vasa recta appear as tightly packed bundles of vessels.
 In this specimen, most tubules are cut lengthwise, indicating that the plane of section is
perpendicular to the cortex.

Renal Medulla,
Vessels vs Thin Loop of Henle
138

 Because both are lined by simple squamous epithelium, vessels and loops can be difficult to distinguish.
 pithelial cells lining loops are often conspicuously rounded in the vicinity of the nucleus, not as flat as vascular endothelium.
 Medullary blood vessels may sometimes be distinguished by the presence red blood cells as well as by a an endothelial lining
which may be lower (flatter) than the tubular epithelium.

OBJECTIVES
139
 Gross Picture
 Where am I ?

142

 Papilla (right) projecting into calyx (left) lined with
transitional epithelium.

144

Cortex of kidney: alternating straight medullary rays and convoluted portions
(with glomeruli). One longitudinally cut interlobular artery (pale pink contents)
can be seen near the extreme left border of the picture, running up the middle
of a convoluted portion, among glomeruli.

146

 Renal corpuscle with connection to proximal tubule at lower border.
This, then, would be a cut through the urinary pole of the corpuscle.

148

 Detail of renal corpuscle. Dark pink epithelium = proximal
tubule. Lighter pink (as at upper top left) = distal tubule.

150

 Dark pink = proximal tubule. Lighter, low cuboidal
epithelium (as at top left) = distal tubule.

152

 Thin segment of Loop of Henle (in the middle), with a
simple squamous lining. Collecting ducts are present.

155

 Medullary region. There are some longitudinal cuts of pale collecting tubules (at left
center) and several blood vessels filled with pale pink fluid (to the right). Epithelium
of collecting tubules is regular, block-like, simple cuboidal, with unusually clear cell
walls. Other tubules in the field are thick and thin limbs of loops of Henle

158

 Cross cuts in medulla. Collecting tubules. Simple squamous lining indicates thin
loops of Henle. Compare these with blood vessels, which contain r.b.c.'s. (Look for
vessels up near top center and to right; also in lower left quadrant of field).

160

 Large pale tubules are collecting tubules, with clear epithelial cell boundaries.
Brighter pink tubules are thick portions of loops of Henle; these are basically like
distal convoluted tubules in their histology, so would be ascending limbs.

162

 Renal corpuscle in trichome stain to show bright orange r.b.c.'s in both the glomerular capillaries
and the peritubular capillaries (among the convoluted tubules). Notice also the clear simple
squamous epithelium of the parietal layer of Bowman's capsule outlining the whole renal
corpuscle.

164

 Long thin artery leading to glomerulus (look in lower mid-picture). (Note long, thin
endothelial nuclei lining the lumen. Circular muscle fibers have been cross-cut and
look almost like a simple cuboidal epithelium outside the endothelium.)

166

 Detail of wall of renal corpuscle. The space is the lumen of Bowman's capsule that receives
glomerular filtrate from the capillary loops. Left wall is simple squamous parietal lining. The
visceral lining of podocytes on the right wall of the space is too irregular to be seen clearly in light
microscopy because it is following the curves of the individual capillaries.

168

 At lower right pole of glomerulus, note a triangular wedge of Polkissen
cells (JG cells) just to the left of the straight row of macula densa cells.
The latter are part of the epithelial wall of the distal tubule.

170

 This one shows the vascular pole of a renal corpuscle. The blood vessel is
presumably an efferent arteriole because no "cuboidal" J-G cells are seen in its wall.
(Note the biconcave shape of the rbc's in the vessel.) Notice also the clear parietal
layer of Bowman's capsule. Surrounding the renal corpuscle are several cuts of the
proximal tubule, with clear brush borders. There is one small distal tubule at bottom
center of the field, slightly to the left.

172

 This renal corpuscle has been sectioned through the urinary pole where the
proximal tubule is continuous with the urinary space containing the urinary
filtrate.

175

 A field of convoluted tubules, some with striated (brush) borders and some without. Notice also
the small peritubular lying between the proximal and distal tubules

177

 glomerulus, juxtaglomerular apparatus (macula densa)

179

 proximal tubule, distal tubule

181

 distal tubule and collecting duct

183

 Thick & Thin Limbs Loop of Henle

184

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