Urinary tract anatomy

Question 1

Describe the anatomical location of the kidneys

Answer 1

• Lie retroperitoneally
• They typically extend from T12 to L3- 3 vertebrae in length.
• Right kidney is situated slightly lower due to the presence of the liver.

The adrenal glands sit immediately superior to the kidneys within a separate envelope of the renal fascia.

Question 2

Describe the external coverings kidney from superficial to deep

Answer 2

Renal capsule – tough fibrous capsule.

Perirenal fat – collection of extraperitoneal fat.

Renal fascia (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands.

Pararenal fat – mainly located on the posterolateral aspect of the kidney.

Question 3

Describe the anatomical structure of the kidney going inwards towards the ureter

Answer 3

1. The cortex extends into the medulla, dividing it into pyramids
2. Apex of pyramid = renal papilla.
3. Each renal papilla is associated with the minor calyx, which collects urine from the pyramids.
4. Several minor calices merge to form a major calyx.
5. Urine passes through the major calices into the renal pelvis
6. The renal pelvis drains into the ureter

Question 4

Name the structure into which the renal vessels and ureter enter the kidney

Answer 4

The renal hilum

Question 5

What are the anatomical relations of the left kidney?

Answer 5

Anterior

• Suprarenal gland
• Spleen
• Stomach
• Pancreas
• Left colic (splenic) flexure
• Jejunum

Posterior

• Diaphragm
• 11th and 12th ribs
• Psoas major, quadratus lumborum and transversus abdominis
• Subcostal, iliohypogastric and ilioinguinal nerves

Question 6

What are the anatomical relations of the right kidney?

Answer 6

Anterior

• Suprarenal gland
• Liver
• Duodenum
• Right colic flexure

Posterior

• Diaphragm
• 12th rib
• Psoas major, quadratus lumborum and transversus abdominis
• Subcostal, iliohypogastric and ilioinguinal nerves

Question 7

Describe the arterial supply of the kidneys

Answer 7

Renal arteries

Arise directly from the abdominal aorta, immediately distal to the origin of the superior mesenteric artery.

Due to the anatomical position of the AA (slightly to the left of the midline), the right renal artery is longer, and crosses the vena cava posteriorly.

The renal artery enters the kidney via the renal hilum and forms an anterior (75%) and a posterior (25%) division supplying the kidney

Question 8

What is the name and location of the avascular plane of the kidney and what is its clinical signficance?

Answer 8

Line of Brodel

Imaginary line along the lateral and slightly posterior border of the kidney

Delineates the segments of the kidney supplied by the anterior and posterior divisions.

Important access route for surgical access of the kidney, as it minimises the risk of damage to major arterial branches.

Question 9

What is the importance of the renal arteries being anatomical end arteries?

Answer 9

There is no communication between vessels.

This is of crucial importance; as trauma or obstruction in one arterial branch will eventually lead to ischaemia and necrosis of the renal parenchyma supplied by this vessel.

Question 10

Describe the venous drainage of the kidneys and the anaotmical relation of the veins

Answer 10

The kidneys are drained by left and right renal veins.

They leave the renal hilum anteriorly to the renal arteries, and empty directly into the inferior vena cava.

As the vena cava lies slightly to the right, the LRV is longer, and travels anteriorly to the AA below the origin of the SMA

The right renal artery lies posterior to the IVC

Question 11

Lymph drainage of kidneys?

Answer 11

paraortic lymph nodes

Question 12

What is the clinical relevence of the kidney’s proximity to the AA?

Answer 12

an AAA can block the renal arteries

Question 13

What are the 3 main functions of the kidneys?

Answer 13

1. Filters blood plasma to produce urine
2. Homeostasis
3. Endocrine function – secretes renin, 1a-hydroxylase and erythropoietin.

Question 14

Briefly explain the physiology of blood filtration in the nephron

Answer 14

ULTRAFILTRATION

• Filtering of blood through fenestrated capillaries of the glomerulus
• All plasma proteins and cells remain in blood – everything else passes into Bowman’s capsule of the nephron.

REABSORPTION

• Material is retained from the ultrafiltrate – includes amino acids, ions, glucose, small proteins, water when necessary
• PCT is responsible for 70% reabsorption

LOOP OF HENLE COUNTER CURRENT MECHANISM

• This creates a hyper-osmotic extracellular fluid

CONCENTRATION OF URINE

• Occurs in the collecting tubule
• Controlled by vasopressin