Kidney Anatomy: Function, Shape, Location, Measurement by NursingJobseExam

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Kidney: It is a solid paired, retroperitoneal, vital organ of excretion.

Shape of Kidney

It is bean-shaped.

Situation of Kidney

One on each side of the vertebral column (paravertebral gutter), in the posterior abdominal wall, behind the peritoneum.

Vertebral Level of Kidney

Opposite the level of the upper border of T12-L3 vertebrae (right kidney is 1.5 cm below than the left due to the presence of liver, above the right kidney).

Regions Occupied

Mainly in the lumbar region, also in the hypochondriac, epigastric and umbilical regions.

Color of Kidney

Reddish-brown.

Kidney

Measurements of Kidney

Length: 11 cm.

Breadth: 6 cm.

Thickness (Anteroposterior): 3 cm.

Weight of Kidney

Male: About 150 gm (each kidney).

Female: About 135 gm (each kidney).

Axis of the Kidney

 1. Long axis: Represented from above downwards and laterally, due to which the upper pole is more nearer to the vertebral column than the lower pole.

 2. Transverse axis: Directed from medial to backward and laterally.

Movements of the Kidney

1. Kidney moves with respiration from 1.5 to 2.5 cm due to it is situated below the diaphragm.

 2. Kidney slightly descends from recumbent supine to standing position.

Borders of Kidney

 1. Medial border

 2. Lateral border.

Medial Border

This border is convexo-concavo-convex, where convexity is adjacent to the poles and concave between the poles (on the hilum). It is sloping inferolaterally.

Relations

1. Above the hilum: Suprarenal gland.

 2. Below the hilum: Beginning of ureter.

 3. In the middle: Hilum of the kidney.

Hilum

It is a deep vertical fissure on the anteromedial part of the medial border, through which some structures going in and coming out.

Situation

 i. Hilum of right kidney lies below the transpyloric plane.

 ii. Left kidney if lies above the transpyloric plane, about 5 cm away from the midline.

Structures passing through the hilum

From anterior to posterior

 1. Renal vein

 2. Renal artery

 3. Pelvis of ureter

 4. One of the branches of renal artery with its accompanying tributary

 5. Renal lymphatics (with vein)

 6. Renal nerves (with artery)

 7. Perinephric fat.

Lateral Border

This border is convex and thick and is more at the posterior plane than the medial border.

Relations

Right kidney: Right lobe of liver.

Left kidney

Above: Spleen

Below: Descending colon.

Surfaces of Kidney

 1. Anterior surface

 2. Posterior surface.

Anterior Surface

This surface is convex, directed anterolaterally

Relations

 1. Peritoneal relation

 The anterior surface is covered by the peritoneum, except the following areas:

 i. Suprarenal area

 ii. Duodenal area.

 iii. Colic area.

2. Visceral relations.

Right Kidney

1. Suprarenal area

Situation: A small part of superior pole and upper part of medial border of kidney.

Relation: This area is related to right suprarenal gland.

2. Hepatic area

Situation: It is a large area, about the upper 3/4ths of the anterior surface.

Relation: This area is related to the inferior surface of right lobe of liver.

3. Duodenal area

Situation: It is a narrow area adjoining the medial border.

Relation: It is related to the 2nd part of duodenum.

4. Colic area

Situation: Inferolateral part of the anterior surface.

Relation: This area is related to right colic flexure (hepatic flexure).

5. Jejunal area

Situation: Inferomedial part of the anterior surface.

Relation: This area is related to coils of jejunum.

Left Kidney

 1. Suprarenal area

Situation: It occupies a small medial area of the superior pole.

Relation: This area is related to left suprarenal gland.

 2. Splenic area

Situation: Upper two-thirds of the lateral half of the anterior surface.

Relation: This area is related to renal impression of spleen.

3. Pancreatic areas

Situation: It is the central quadrilateral area across the hilum.

Relation: It is related to the body of pancreas.

4. Gastric area

Situation: It is a triangular area bounded by suprarenal, splenic and pancreatic areas.

Relation: It is related to the posteroinferior surface of the stomach.

5. Colic area

Situation: Laterally and below to the pancreatic area.

Relation: It is related to left colic flexure and beginning of descending colon.

 6. Jejunal area

Situation: Present medially and below the pancreatic area.

Relation: This area is related to coils of jejunum.

Posterior Surface

This surface is flat, directed posteromedially.

Relations

Peritoneal relation: It is non-peritoneal.

Other relations

 1. Upper part

From within outwards:

 i. Medial and lateral arcuate ligaments

 ii. Costodiaphragmatic pleural recess.

 iii. 11th and 12th ribs (on the left side)

 iv. 12th rib (on the right side).

2. Lower part

From medial to lateral:

 i. Psoas major

ii. Quadratus lumborum

 iii. Transversus abdominis

From above downwards:

 i. Subcostal vein

 ii. Subcostal artery

 iii. Subcostal nerve

 iv. Iliohypogastric nerve

 v. 4th lumbar artery (on the right side).

Poles

 1. Superior pole/upper pole

 2. Inferior pole/lower pole. 

 1. Superior pole/upper pole: It is thick and round, inclined medially than the lower pole.

Situation

It is about 2.5 cm lateral to the median plane.

Relation

Suprarenal gland.

 2. Inferior pole/lower pole: It is about 7.5 cm lateral to the median plane and 2.5 cm above the highest point of iliac crest.

Vertebral level: Opposite the L3 vertebra.

Coverings of Kidney

From inside outwards:

 1. Fibrous capsule/true capsule

 2. Perinephric fat

 3. Renal fascia or false capsule/fascia of Gerota

 4. Paranephric fat.

Fibrous Capsule (True Capsule)

i. This tissue is derived from the kidney substance (fibrous stroma) and intimately adherent to the kidney

 ii. This capsule covers the entire organ, lines the walls of renal sinus and is reflected as tubular sheath around the minor and major calyces.

Perinephric Fat

Situation

This occupies the interval between the fibrous capsule and the renal fascia (fascia of Gerota).

Features

i. This fat is abundant along the borders of kidney

 ii. It extends into the renal sinuses.

Renal Fascia or Fascia of Gerota

Formation 

It is the covering of the kidney between the perinephric and paranephric pad of fat, formed by the condensation of the extraperitoneal connective tissue. It is also called fascia of Gerota.

Layers

 i. Anterior layer or Toldt’s fascia

 ii. Posterior layer or Zuckerkandl’s fascia.

Paranephric Fat

Situation

This is situated in the lower part of the posterior aspect of kidney, the interval between the renal fascia and the anterior layer of thoraco-lumbar fascia.

Features 

 i. It is not truly the covering of kidney

 ii. It is abundant on the posterior surface of the lower part of the kidney.

Functions

It acts as a packing material and also as shock absorber.

CLINICAL ANATOMY of Kidney

 i. Decapsulation of the kidney is occasionally made easily in case of suppression of urine due to acute nephritis in an attempt to release the pressure on the renal tubules as in renal congestion and edema.

 ii. In nephropexy operation to fix a movable kidney sometimes the fibrous capsule is divided along the lateral border and rolled posterior flap of the capsule is sutured to the last rib or the muscle of the posterior abdominal wall.

Supports of Kidney

The kidney maintains its position in the abdomen by the following supports:

1. Pressure by the surrounding viscera’s

 2. Renal fascia

 3. Renal fat or paranephric fat

 4. Pedicles of the kidney, i.e.

  i. Renal artery

  ii. Renal vein

  iii. Pelvis of ureter.

Arterial Supply

 1. Renal arteries (right and left ): Renal arteries arises from the abdominal aorta of which right one is larger than the left.

2. Accessory renal artery (about 25% cases).

  i. Sometimes it is present arising from the abdominal aorta

  ii. It supplies upper or lower pole of the kidney without passing through hilum.

Renal Circulation.

 1. Each kidney is supplied by a renal artery which is a branch of abdominal aorta.

 2. Right artery is longer than the left one because the abdominal aorta lies on left side of vertebral column.

 3. About one liter of blood circulates through both kidneys per minute.

 4. Sometimes an accessory renal artery are present in 25% of individuals which are arising from the aorta that supplies upper or lower pole of kidney without passing through hilum.

 5. Renal artery before entering into renal sinus divided into segmental branches (end arteries).

 6. Segmental arteries are further subdivided into lobar (usually one for each renal pyramid).

 7. Each lobar artery divides into 2 to 3 interlobar arteries which pass on each side of the renal pyramid.

 8. Interlobar arteries divide into arcuate arteries.

 9. From convex side of arcuate arteries arise interlobular arteries in the cortex pass along the medullary rays. 

 10. These interlobular arteries give afferent arterioles to glomerulus.

 11. Efferent arterioles from the glomerulus away from the medulla from the peritubular plexus which form interlobular veins.

 12. Interlobular veins end in arcuate veins which unite to form interlobar veins.

13. Interlobar vein form lobar veins which unite to form renal veins.

 14. From concave side of arcuate arteries arise arteriolae recti which enter into the pyramid and form plexus with efferent vessels form juxtamedullary glomerulus.

 15. From this plexus vena recta arise and end in arcuate veins which form interlobar veins and lobar veins and ultimately renal veins.

So two types of circulation in kidneys are present.

Greater Circulation

In glomerulus away from medulla, the filtration pressure is higher because the caliber in the afferent arterioles is larger than the efferent arterioles and urine is also formed in this type of circulation.

 Normally this type of circulation will occur.

Lesser Circulation

 1. Takes place in the juxtamedullary glomerulus

 2. In this case capillary pressure is not so higher because the caliber of both afferent and efferent vessels is same

 3. So the net result is the minimum formation of urine

 4. Normally this type of circulation does not occur.

Venous drainage

Renal veins (right and left ) drain into inferior vena cava.

Lymphatic drainage

The lymphatics are drained into the lateral aortic group of lymph nodes.

Nerve Supply

Sympathetic

Via the renal plexus (T10 to L1 segments of spinal cord).

Parasympathetic

Vagus nerves (right and left ).

Development

Kidneys are developed in embryonic life from 2-sources.

 1. The nephrons developed from the lowest part of the nephrogenic cord.

 2. The collecting part is developed from a diverticulum called ureteric bud which arises from the lower part of the mesonephric duct.

Congenital anomalies of kidney

 i. Some congenital abnormality of the kidneys and ureters occurs in 3 to 4% of newborn infants

 ii. Anomalies in shape and position are most common. 

According to the Number of Kidney

Agenesis of Kidney

Th is is the condition where the kidney fails to develop due to the inability of formation of ureteric bud. 

Unilateral Agenesis

 1. Unilateral renal agenesis occurring about one in every 1000 newborn

 2. Males are more affected than females

 3. The left kidney is usually agenesis one

 4. Unilateral absence of a kidney is usually asymptomatic because the other kidney usually becomes compensatory hypertrophy and maintains the functions of the missing kidney.

Bilateral Renal Agenesis 

 1. It occurs about one in 3000 births

 2. It is incompatible with postnatal life

 3. It is associated with decreased amniotic fluid (oligohydramnios) because little or no urine is excreted in the amniotic cavity

 4. Decreased amniotic fluid volume where other causative factors are absent (like rupture of the fetal membrane) indicating bilateral renal agenesis.

Multiple Kidneys

Condition where more than one kidney are developed either on one or both sides.

According to the Size of Kidney

Lobulated Kidney

Condition where the kidney is much larger than the normal-sized kidney.

According to the Position of Kidney

Pelvic Kidney

When the kidney fails to ascend in the abdomen and remains in the pelvis.

Ectopic/crossed Ectopia

In this case both kidneys may present on the same side.

Lower Lumbar Fused Kidney 

 1. Sometimes the kidney of one side may displace and fused with the kidney of the other side

 2. It is due to partial failure of ascend of kidney.

Thoracic

It is due to too much ascend of the kidney.

According to the Shape of Kidney

Disk Shaped

The two kidneys join at the midline with their ureters hangs respectively.

CLINICAL ANATOMY

Horseshoe Shaped Kidney

 1. The lower poles of the two kidneys are joined by an isthmus. It will lie at the lower level than the normal position

 2. It is occurring about one in about 500 persons

 3. About 7% persons with turner syndrome have horseshoe-shaped kidney

 4. It is usually situated in the hypogastric region 

 5. It is usually asymptomatic 

 6. The Wilm’s tumor may occur by 5 years of age but may also occur in the fetus (it is a cancer of the kidneys usually affects children by 5 years of age but may also occur in the fetus)

 7. It results 2 to 8 times more affected in children with a horseshoe-shaped kidney than in the general population. 

According to Mobility of Kidney

Floating Kidney

Sometimes the kidney remains suspended in the peritoneal fold from the posterior abdominal wall.

Accessory Renal Artery

 1. It presents in 25 percent persons 

 2. Sometimes the lower pole of the kidney is supplied by the accessory renal artery, which causes obstruction to flow of urine producing hydronephrosis.

One Kidney with Two Ureters

Sometimes one kidney may present with two ureters.

Polycystic Kidney

 1. In this condition the collecting ducts failed to meet properly which results in numerous cysts in the kidneys 

 2. It is the most common anomaly found in kidney.

Macroscopic Structures of the Kidney 

On coronal section kidney shows three parts:

Cortex

 1. It is the outer, reddish-brown color and granular in appearance

 2. The cortex consists of two parts: 

 a. Cortical arches: These present between the bases of the renal pyramids and the surface of the kidney

b. These presents between the adjacent renal pyramids extend to the renal sinus through which interlobar blood vessels transmit.

 Each renal pyramid and cortical arch forms a lobe of the kidney.

Renal Medulla

These are conical masses about 10 in number. Th ey are apices form the renal papillae which indent the minor calices.

The Renal Sinuses

These are spaces that extends from the hilus into the kidney.

Contains

 1. A branches of the renal artery

 2. Tributaries of the renal vein

 3. The renal pelvis.

Clinical Anatomy

1. Bloodless line of Brodel:

 i. This line is present along the convex lateral border, which is relatively avascular zone of renal tissue

 ii. It is the most suitable site for the surgical operation of the kidney.

2. Renal angle: 

 i. It is an angle between the 12th rib and the lateral border of the erector spine

 ii. This angle is tender on palpation or by any deep pressure, if kidney is inflamed.

3. Nephroptosis:

  i. Sometimes kidneys may descends or float due to diminution of perinephric and paranephric fats

  ii. Due to more mobility the kidney produces symptoms of renal colic caused by kinking or coiling of the ureter

 iii. Nephroptosis is distinguished from an ectopic kidney by the length of the ureter where in former cases the length of the ureter is normal but in nephrotosis shows coiling or kinking because distance between the kidney and bladder is reduced. 

4. Rupture of the kidney: 

  i. Although kidneys is well protected by the lower ribs and lumbar part of the vertebral column

ii. However kidney may be ruptured by the severe blunt injury on the abdomen. 

 5. i. Blood or pus from the kidney by rupture or pus from the perinephric abscess may descend downwards through the renal fascia, then into the pelvis because anterior and posterior layers of the renal fascia inferiorly loosely attached

  ii. It cannot cross to the opposite side due to the presence of fascial septum and midline attachment of the renal fascia.

6. Varicocele of the left spermatic cord: As left renal vein crosses in front of the abdominal aorta below the origin of superior mesenteric artery so left renal vein may be compressed between the aorta and superior mesenteric artery, as a result varicocele of the left spermatic cord is more common because left testicular vein drains into the left renal vein. 

7. The renal pain and its radiation:

  i. The renal pain is referred from loin to groin, testis, medial side of the thigh or anterior abdominal wall below the umbilicus due to same segmental nerve supply

  ii. The pain is distributed along the distributions of (T10 to L1 segments of the spinal cord), such as- T10, T11, subcostal, ilioinguinal (L1), iliohypogastric (L1) and genitofemoral nerves.

 8. Renal cysts: 

 i. It occurs in 1/5000 births

  ii. In this condition the collecting ducts failed to meet properly which results in numerous cysts in the kidneys. It is the most common anomaly found in kidney

  iii. The kidneys are markedly enlarged and distorted by the cysts

  iv. It is an important cause of renal failure. 

9. Renal transplantation: 

  i. Renal transplantation is indicated for the treatment of selected cases of chronic renal failure

  ii. The site of kidney is transplanted in the iliac fossa of the greater pelvis

  iii. In this operation the renal artery and vein are joined to the external iliac artery and vein respectively

iv. The ureter is sutured into the urinary bladder.

10. Accessory renal vessels (arteries are about twice as common as veins)

  i. Accessory renal vessels are common by occurring about 25% cases

 ii. They enter or exit through the poles of the kidneys

  iii. If accessory renal artery enters through the lower pole of the kidney, it usually passes anterior to the ureter and obstruct it producing hydronephrosis

 iv. As accessory renal arteries are end arteries when an accessory renal artery is damaged or ligated the part of the kidney supplied by it become ischemic.

 11. Wilm’s tumor: It is a cancer of the kidney usually affects children by 5 years of age but may also occur in the fetus.

 12. Renal calculi (kidney stone):

  i. The renal calculi may be located in the renal calices and may pass into the renal pelvis

 ii. The calculi may pass into the ureter producing ureteric colic.

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