Anatomy of the kidneys

Question 1

Where is the kidney situated?

Answer 1

Retroperitoneally in the posterior abdominal wall, at the sides of the vertebral column

Question 2

What is the vertebral extent of the kidney?

Answer 2

T11-L3 (The right kidney is slightly lower than the left)

• Left kidney T11-L2
• Right kidney T12-L3

Question 3

Which kidney is usually palpable?

Answer 3

The right

Question 4

What maintains the position of the kidneys?

Answer 4

1) Intra-abdominal pressure (pressure from neighboring viscera)

2) Their connections with renal fat and fascia

3) Renal vessels (pedicles of the kidney that are attached to the hila)

• The kidneys move in a vertical range of about an inch during:

1) Full respiration

2) Changing from the supine to the erect position

Question 5

What is meant by nephroptosis?

Answer 5

Downward displacement of the kidneys due to significant weight loss over a short period

Question 6

What is the surface anatomy of the anterior surface of the kidney?

Answer 6

1) Hilum: Lies at the transpyloric plane, 5cm from the midline

2) Upper pole: Lies 2.5cm from the midline

3) Lower pole: Lies 7.5cm from the midline

Question 7

What is the surface anatomy of the posterior surface of the kidney?

Answer 7

• Formed by the morrison’s parallelogram:
• Where we mark 2 points at the level of T11 spine, one 2.5cm away and the other 9cm away, we do the same thing at the level of the third lumbar spine
• The upper pole of the right kidney lies 2.5cm away from T12, while the upper pole of the left kidney lies 2.5cm away from T11

Question 8

Describe the axis of the kidneys

Answer 8

• The kidneys are never completely vertical & tend to be ‘inclined’; i.e., the upper pole is more medial, whereas the lower pole is more lateral

Question 9

Describe the renal angle (costovertebral angle)

Answer 9

• It is the angle between the lower margin of the 12th rib and the lateral margin of the erector spinale muscle
• Any periphrenic abscess will cause swelling and tenderness at the renal angle
• Renal pain is usually felt at the renal angle as a dull ache

Question 10

What are the coverings of the kidney?

Answer 10

1) Fibrous/True capsule

2) Periphrenic fat

3) Renal fascia/Gerota

4) Pararenal fat (adipose tissue that is located superficially to the renal fascia)

• Perinephric fat covers the entire kidney, whereas paranephric fat only covers it on its posterior aspect

Question 11

What forms the fibrous/true capsule of the kidney?

Answer 11

The condensation of the fibrous stroms of the kidney

• It covers the entire organ and lines the wall of the renal sinus
• The true capsule goes around the entire kidney & to the central cavity, covering the renal sinus (the space between the vessels and ureters on the medial aspect)

Question 12

What is the periphrenic fat layer?

Answer 12

• It is found between the fibrous capsule and the renal fascia
• It extends into the renal sinus

Question 13

What is the renal fascia/Gerota?

Answer 13

• It is the condensation of the extra-peritoneal connective tissue around the kidney, which merges with the fascia transversalis laterally
• Laterally, it is continuous with the fascia transversalis
• It is formed of two layers (anterior “Fascia of TOLDT”, and the posterior “ZUCKERKANDL”) which encloses the kidney both anteriorly and posteriorly and then joins with the fascia transversalis

Question 14

What is meant by nephropexy?

Answer 14

It is a surgical procedure in which the kidneys are fixed to the lower ribs or nearby viscera posterior to it by cutting part of the true capsule

Question 15

Describe the renal fascia

Answer 15

1) Laterally: Both layers of the renal fascia fuse and they are continuous with the fascia transversalis

2) Medially: The anterior layer covers the front of the kidney and the renal vessels (adventitia), and they merge with the opposite side

3) Superiorly: Both layers fuse at the upper end and enclose the suprarenal gland

• In the case of nephroptosis, the kidney sinks while the suprarenal gland remains secured to the diaphragm

4) Inferiorly: The 2 layers do not fuse, and they extend along the ureters; finally, they are lost into the extra-peritoneal tissue of the iliac fossa

Question 16

Where is the paraphrenic fat layer found?

Answer 16

• Between the renal fascia and the anterior layer of the thoraco-lumbar fascia
• It is found mainly in the infero-posterior part of the kidney

Question 17

What is meant by nephroptosis?

Answer 17

• Abdormally mobile kidneys (where they descend more than 1-inch)
• It is distinguished from an acute ectopic kidney (congenitally misplaced kidney) via the normal (length) ureter
• Symptoms are intermittent pain in the renal region due to the traction on the renal vessels (it is relieved by lying down)

Question 18

In the case of nephroptosis, why does the suprarenal gland remain in place?

Answer 18

Because the lie in a separate fascial compartment and are firmly attached to the diaphragm

• In the case of a congenital anomaly, the ureter is already short, so the kidney is in its ‘natural’ (ectopic) position in the pelvis or elsewhere
• In case of sudden weight loss, the ureter would be long due to problems with the renal fascia & fat.

Question 19

How is a kidney transplanted?

Answer 19

• Kidneys can be removed from a donor without damaging the suprarenal gland
• Transplanted kidney is situated in the iliac fossa for support (usually the recipient’s kidney is kept in place)
• The renal vessels are joined to the external iliac vein and the internal iliac artery
• The ureter is sutured into the urinary bladder

Question 20

What are the parts of the kidney?

Answer 20

1) 2-Surfaces (Anterior and posterior)

2) 2-Ends (“2.5cm from midline” Upper and lower “7.5cm from midline”)

3) 2-Borders (medial and lateral)

Question 21

What are the posterior relations of the kidneys?

Answer 21

1) Ribs 11-12 on the left, and 12 on the right

2) Transversus abdominis (most lateral)

3) Diaphragm (superiorly)

4) Quadratus lumborum (between the transversus and the psoas major “in the middle”)

5) Psoas major (most Medially)

• Related to the anterior surface of the quadratus lumborum

6) Subcostal vessels

7) Subcostal nerve

8) Iliohypogastric nerve

9) Ilioinguinal nerve

Question 22

What are the anterior relations of the left kidney?

Answer 22

1) Stomach

2) Suprarenal gland

3) Spleen

4) Splenic artery

5) Tail of Pancreas

6) Small intestine (coild of jejunum)

7) Splenic (left colic) flexure

Question 23

Why does the pain of an inflammation in the pararenal areas increase when we extend our thigh?

Answer 23

Due to the close relationship of the kidney and the psoas major muscle (which flexes the thigh)

• Since the psoas major is closely related to the kidney, inflammation in the surrounding (pararenal) areas as in appendicitis will cause a characteristic, severe psoas pain that is aggravated by extending the thigh & relieved upon flexion.

Question 24

What are the anterior relations of the right kidney?

Answer 24

1) Suprarenal gland

2) Liver

3) Second part of duodenum

4) Right colic flexure

5) Coils of jejunum (S.I)

Question 25

Why does the periphrenic abscess extend into the pelvis?

Answer 25

- Due to two reasons: 1) Gravitational pull 2) It has no attachment to any structures in the pelvic region (unlike the holden line, of the fascia)

Question 26

What is the macroscopic structure of the kidney?

Answer 26

- Made of an outer cortex and an inner medulla - There are 8-18 renal pyramids (pale conical masses)

Question 27

What forms a lobe of the kidney?

Answer 27

1 pyramid capped with the adjoining cortex (pyramid + cortical tissue that comprises the lobe)

Question 28

What is the renal pelvis?

Answer 28

- A flattened, funnel-shaped expansion of the superior end of the ureter - It receives 2/3 major calyces - Each major calyx is divided into 2/3 minor calyx - Each mino calyx is indented by the renal papilla (the apex of the renal pyramid from where urine is excreted)

Question 29

What are the structures found at the hilum of the kidney?

Answer 29

1) Renal vein (most ant) 2) Renal artery (middle) 3) Ureter (most pst) - Mnemonic: VAP

Question 30

What is a renal sinus?

Answer 30

- A narrow space which is entered through the renal hilum - It contains the renal pelvis, calicies, vessels, nerves, and fat

Question 31

What are the ureters?

Answer 31

- They are a narrow muscular tube (25cm long) - They are retroperitoneal through their course - It has a dilated upper end (pelvix of the ureter) - It upper part lies at the posterior abdominal wall while the remainder of it lies within the pelvis

Question 32

What are the normal strictures of the ureter?

Answer 32

- The potential site of obstruction of the ureteric stones 1) The pelvic-ureteric junction (at the lower pole of the kidney) 2) Pelvix brim (sacroiliac joint) 3) Point of entry into the bladder (narrowest of all, and it lies medial to the tip of the ischial spine)

Question 33

What is the lymphatic drainage of the kidney and ureter?

Answer 33

1) Kidneys and proximal ureter: drains into the lumbar set of lymph nodes 2) Distal part of ureter: Iliac lymph nodes

Question 34

Describe the blood supply of the ureter

Answer 34

- It has no specific artery but small branches from the nearby arteries - Branches the supplies the abdominal half of the ureter approaches medially - Branches that supply the pelvic half approach laterally - FYI: During a surgery, the ureters are avoided, and if necessary, traction of the uterus is applied only towards the blood supply to avoid the disruption of the small branches

Question 35

What are the arteries that supply the proximal branch of the ureter?

Answer 35

1) Renal artery 2) Gonadal artery 3) Common iliac artery - Since they arise along its medial aspect, it is preferred during surgery to pull the proximal ureter medially to avoid stretching & potentially snapping the vessels

Question 36

What are the arteries that supply the distal part of the ureter?

Answer 36

1) Internal iliac and its branches - The distal ureter is pulled laterally during surgery

Question 37

What is the innervation of the kidneys?

Answer 37

1) Sympathetic - Derived from the renal plexuses (T10/11 component of the lesser splanchnic and T12 of the least splanchnic), where they will travel to the aorticorenal ganglion to supply the kidney

Question 38

How is the pain reffered from the ureters?

Answer 38

A ureteric colic that arises from a calculus (may arise from renal stones) will lead to a visceral referred pain to the cutaneous segments sharing the spinal cord level of T11-T12 - The pain typically passes from the loin to the groin (lumbar to the inguinal region) as the stone progresses through the ureter - The pain might also extend to the thigh and scrotum/labia major via the genitofemoral nerve (L1 & 2)

Question 39

Which nerve is responsible for transferring the visceral pain to the scrotum, labia, or thigh?

Answer 39

The genitofemoral nerve

Question 40

What is the origin of the renal arteries?

Answer 40

- They arise from the level of the intervertebral disc between L1 and L2, at a right angle with the abdominal aorta - The right renal artery is longer than the left and passes behind the IVC

Question 41

Describe the course of the renal artery

Answer 41

1) Starts at the intervertebral disc between L1 and L2 1) At the hilum, it divides into anterior and posterior, which give rise to 5-segmental arteries - Clamping of any of the segmental vessels can result in renal ischemia (as they are end-arteries, no anastomoses)

Question 42

What is a renal segment?

Answer 42

The kidney has 5 segments, each supplied by one of the segmental artery branches - Anteriorly 1) Apical 2) Superior 3) Middle 4) Lower - Posteriorly 1) Apical 2) Posterior 3) Upper 4) Midlle 5) Lower - Each segment is surgically resectale - The posterior segmental artery is a continuation of the posterior branch of the renal artery (the only branch from the posterior renal artery, the rest "4" are from the anterior branches of the renal artery)

Question 43

What are the different segmental arteries?

Answer 43

- Renal artery at L1/L2, in the hilum it divides into anterior and posterior: - The anterior (4 segmental branches) 1) 2 Apical 2) 1 Antero-superior 3) 1 antero-inferior - The posterior (continuation) 1) Posterior

Question 44

What is meant by the brodel's bloodless line?

Answer 44

Since the renal arteries are end arteries (that is the anterior branches does not anastomose with the posterior branches), at the junction between the posterior lobe (at the posterior surface) and the upper and middle segment (at the anterior surface), found on the lateral border of the kidney there is a line that forms a bloodless region with no anastomoses

Question 45

What are some of the abnormalities that could occur at the renal artery?

Answer 45

1) About 25% of kidneys on this planet receive branches directly from the aorta 2, 3, or sometimes even 4 branches. These branches could enter into the kidney through the renal sinus or even at the lower or upper poles, but they are not accompanied by veins 2) Sometimes, the fetal vessels of the kidney might persist in an adult