Inferior mesenteric artery

Question 1

what is the IMA a major branch of?

Answer 1

a major branch of the abdominal aorta

Question 2

what does the IMA supply?

Answer 2

arterial blood to the organs of the hindgut - the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum

Question 3

where does the inferior mesenteric artery stem from?

Answer 3

The IMA is the last of the three major anterior branches of the abdominal aorta

Question 4

aside from the IMA, what are the 2 other branches of the abdominal aorta?

Answer 4

coeliac trunk and superior mesenteric artery

Question 5

where does the IMA arise from?

Answer 5

It arises at L3, near the inferior border of the duodenum, 3-4 cm above where the aorta bifurcates into the common iliac arteries

Question 6

as the IMA arises from the aorta, where does it descend?

Answer 6

it descends anteriorly to its parent vessel, before moving to the left side

Question 7

what type of structure is the IMA? where is it situated?

Answer 7

It is a retroperitoneal structure – situated behind the peritoneum

Question 8

what do the branches of the IMA supply?

Answer 8

structures of the embryonic hindgut. These include the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum

Question 9

how many major branches arise from the IMA and what are they?

Answer 9

3

left colic artery, sigmoid artery and superior rectal artery

Question 10

what is the first branch of the IMA?

Answer 10

The left colic artery

Question 11

what does the left colic artery supply?

Answer 11

It supplies the distal 1/3 of the transverse colon and the descending colon

Question 12

arising from the parent artery, where does the left colic artery travel?

Answer 12

it travels anteriorly to the psoas major muscle, left ureter and left internal spermatic vessels

Question 13

what happens after the left colic artery has travelled to the left internal spermatic vessel?

Answer 13

it divides into ascending and descending branches

Question 14

what is the course of travel of the ascending branch of the left colic artery?

Answer 14

crosses the left kidney anteriorly, before entering the mesentery of the transverse colon, moving superiorly

Question 15

what does the ascending branch of the left colic artery supply?

Answer 15

the distal 1/3 of the transverse colon, and the upper aspect of the descending colon

Question 16

where does the descending branch of the left colic artery travel? what does it supply?

Answer 16

moves inferiorly to supply the lower part of the descending colon. It anastamoses with the superior sigmoid artery

Question 17

what does the descending branch of the left colic artery anastomose with?

Answer 17

superior sigmoid artery

Question 18

what do the sigmoid arteries supply?

Answer 18

supply the descending colon and the sigmoid colon

Question 19

how many branches are there typically to the sigmoid arteries?

Answer 19

typically 2-4 branches

Question 20

what is the uppermost branch of the sigmoid artery termed?

Answer 20

the superior sigmoid artery

Question 21

where do the sigmoid arteries run?

Answer 21

inferiorly, obliquely and to the left, crossing over the psoas major, left ureter and left internal spermatic vessels

Question 22

what is the superior rectal artery a continuation of?

Answer 22

continuation of the inferior mesenteric artery

Question 23

what does the superior rectal artery supply?

Answer 23

supplying the rectum

Question 24

where does the superior rectal artery descend into?

Answer 24

into the pelvis, crossing the left common iliac artery and vein

Question 25

what happens at the S3 vertebral level to the superior rectal artery?

Answer 25

the artery divides into two terminal branches – one supplying each side of the rectum

Question 26

what happens within the walls of the rectum to the terminal branches of the superior rectal artery?

Answer 26

smaller divisions of these branches eventually communicate with the middle and inferior rectal arteries

Question 27

what is a left hemicolectomy?

Answer 27

the surgical resection (removal) of the descending colon

Question 28

why is a left hemicolectomy performed?

Answer 28

for a variety of reasons such as removal of colon cancer, treatment of diverticulitis, inflammatory bowel disease or trauma

Question 29

what must the surgeon do during a left hemicolectomy?

Answer 29

the surgeon must dissect the branches of the inferior mesenteric artery

Question 30

how do the surgeons dissect the branches of the inferior mesenteric artery?

Answer 30

They do this by shining a light through the mesentery to identify the IMA and inferior mesenteric vein

Question 31

does the IMV follow the same course as the IMA?

Answer 31

NO

Question 32

what do the surgeons do after they have found the IMA?

Answer 32

They then trace the artery back to the aorta and divide it proximally

Question 33

how many major anastomoses is the IMA involved with?

Answer 33

There are two major anastomoses of the IMA

Question 34

what do the 2 major anastomoses of the IMA involve?

Answer 34

both involving a union with branches of the superior mesenteric artery

Question 35

what are the 2 major anastomoses of the IMA?

Answer 35

``` Marginal artery (of Drummond) Arc of Riolan ```

Question 36

what is the marginal artery (of Drummond)?

Answer 36

forms a continuous arterial circle along the inner border of the colon

Question 37

what arises from the marginal artery (of Drummond)?

Answer 37

straight vessels (vasa recta)

Question 38

what do the vasa recta of the marginal artery supply?

Answer 38

the colon

Question 39

what is the marginal artery (of Drummond) formed by?

Answer 39

formed by the union of several branches; the ileocolic, right colic and middle colic of the SMA and left colic and sigmoid branches of the IMA

Question 40

what is the arc of Riolan?

Answer 40

anastomosis between the middle colic branch of SMA and the left colic branch of IMA

Question 41

arc of Riolan - existence?

Answer 41

It is less common than the marginal artery, and indeed its existence has been questioned by some surgeons

Question 42

what can the splenic flexure be described as?

Answer 42

as a watershed area

Question 43

why is the splenic flexure described as a watershed area?

Answer 43

a term used when an area has dual blood supply from the most distal branches of two large arteries

Question 44

what is the advantage of the watershed area of splenic flexure?

Answer 44

Whilst this has the advantage of being more resistant to ischaemia if one of the arteries becomes occluded

Question 45

what is a disadvantage of the watershed area of splenic flexure?

Answer 45

it makes the area more sensitive to systemic hypoperfusion

Question 46

what is horseshoe kidney?

Answer 46

Horseshoe kidney is a congenital disorder where the kidneys fuse together, forming a horseshoe shape

Question 47

how many people does horseshoe kidney affect? common in M/F?

Answer 47

It affects 1/400, and is more common in males

Question 48

what happens during embryonic development of normal kidneys?

Answer 48

the kidneys ascend from the pelvis to their position in the abdomen

Question 49

what happens to a patient with horseshoe kidney?

Answer 49

In a patient with horseshoe kidney, the fused kidney becomes hooked underneath the inferior mesenteric artery, and is stuck in the lower abdomen

Question 50

what does horseshoe kidney require in terms of treatment?

Answer 50

It does not require any treatment, and is often asymptomatic

Question 51

what are the complications that can occur from horseshoe kidney?

Answer 51

complications can occur from the poor drainage of the kidney, such as hydronephrosis, renal stones, and infection