Inferior mesenteric artery Flashcards

1
Q

what is the IMA a major branch of?

A

a major branch of the abdominal aorta

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2
Q

what does the IMA supply?

A

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

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3
Q

where does the inferior mesenteric artery stem from?

A

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

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4
Q

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

A

coeliac trunk and superior mesenteric artery

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5
Q

where does the IMA arise from?

A

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

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6
Q

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

A

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

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7
Q

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

A

It is a retroperitoneal structure – situated behind the peritoneum

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8
Q

what do the branches of the IMA supply?

A

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

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9
Q

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

A

3

left colic artery, sigmoid artery and superior rectal artery

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10
Q

what is the first branch of the IMA?

A

The left colic artery

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11
Q

what does the left colic artery supply?

A

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

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12
Q

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

A

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

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13
Q

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

A

it divides into ascending and descending branches

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14
Q

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

A

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

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15
Q

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

A

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

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16
Q

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

A

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

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17
Q

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

A

superior sigmoid artery

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18
Q

what do the sigmoid arteries supply?

A

supply the descending colon and the sigmoid colon

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19
Q

how many branches are there typically to the sigmoid arteries?

A

typically 2-4 branches

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20
Q

what is the uppermost branch of the sigmoid artery termed?

A

the superior sigmoid artery

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21
Q

where do the sigmoid arteries run?

A

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

22
Q

what is the superior rectal artery a continuation of?

A

continuation of the inferior mesenteric artery

23
Q

what does the superior rectal artery supply?

A

supplying the rectum

24
Q

where does the superior rectal artery descend into?

A

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

25
Q

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

A

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

26
Q

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

A

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

27
Q

what is a left hemicolectomy?

A

the surgical resection (removal) of the descending colon

28
Q

why is a left hemicolectomy performed?

A

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

29
Q

what must the surgeon do during a left hemicolectomy?

A

the surgeon must dissect the branches of the inferior mesenteric artery

30
Q

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

A

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

31
Q

does the IMV follow the same course as the IMA?

A

NO

32
Q

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

A

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

33
Q

how many major anastomoses is the IMA involved with?

A

There are two major anastomoses of the IMA

34
Q

what do the 2 major anastomoses of the IMA involve?

A

both involving a union with branches of the superior mesenteric artery

35
Q

what are the 2 major anastomoses of the IMA?

A
Marginal artery (of Drummond)
Arc of Riolan
36
Q

what is the marginal artery (of Drummond)?

A

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

37
Q

what arises from the marginal artery (of Drummond)?

A

straight vessels (vasa recta)

38
Q

what do the vasa recta of the marginal artery supply?

A

the colon

39
Q

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

A

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

40
Q

what is the arc of Riolan?

A

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

41
Q

arc of Riolan - existence?

A

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

42
Q

what can the splenic flexure be described as?

A

as a watershed area

43
Q

why is the splenic flexure described as a watershed area?

A

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

44
Q

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

A

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

45
Q

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

A

it makes the area more sensitive to systemic hypoperfusion

46
Q

what is horseshoe kidney?

A

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

47
Q

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

A

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

48
Q

what happens during embryonic development of normal kidneys?

A

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

49
Q

what happens to a patient with horseshoe kidney?

A

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

50
Q

what does horseshoe kidney require in terms of treatment?

A

It does not require any treatment, and is often asymptomatic

51
Q

what are the complications that can occur from horseshoe kidney?

A

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