Inferior mesenteric artery Flashcards
what is the IMA a major branch of?
a major branch of the abdominal aorta
what does the IMA supply?
arterial blood to the organs of the hindgut - the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum
where does the inferior mesenteric artery stem from?
The IMA is the last of the three major anterior branches of the abdominal aorta
aside from the IMA, what are the 2 other branches of the abdominal aorta?
coeliac trunk and superior mesenteric artery
where does the IMA arise from?
It arises at L3, near the inferior border of the duodenum, 3-4 cm above where the aorta bifurcates into the common iliac arteries
as the IMA arises from the aorta, where does it descend?
it descends anteriorly to its parent vessel, before moving to the left side
what type of structure is the IMA? where is it situated?
It is a retroperitoneal structure – situated behind the peritoneum
what do the branches of the IMA supply?
structures of the embryonic hindgut. These include the distal 1/3 of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum
how many major branches arise from the IMA and what are they?
3
left colic artery, sigmoid artery and superior rectal artery
what is the first branch of the IMA?
The left colic artery
what does the left colic artery supply?
It supplies the distal 1/3 of the transverse colon and the descending colon
arising from the parent artery, where does the left colic artery travel?
it travels anteriorly to the psoas major muscle, left ureter and left internal spermatic vessels
what happens after the left colic artery has travelled to the left internal spermatic vessel?
it divides into ascending and descending branches
what is the course of travel of the ascending branch of the left colic artery?
crosses the left kidney anteriorly, before entering the mesentery of the transverse colon, moving superiorly
what does the ascending branch of the left colic artery supply?
the distal 1/3 of the transverse colon, and the upper aspect of the descending colon
where does the descending branch of the left colic artery travel? what does it supply?
moves inferiorly to supply the lower part of the descending colon. It anastamoses with the superior sigmoid artery
what does the descending branch of the left colic artery anastomose with?
superior sigmoid artery
what do the sigmoid arteries supply?
supply the descending colon and the sigmoid colon
how many branches are there typically to the sigmoid arteries?
typically 2-4 branches
what is the uppermost branch of the sigmoid artery termed?
the superior sigmoid artery
where do the sigmoid arteries run?
inferiorly, obliquely and to the left, crossing over the psoas major, left ureter and left internal spermatic vessels
what is the superior rectal artery a continuation of?
continuation of the inferior mesenteric artery
what does the superior rectal artery supply?
supplying the rectum
where does the superior rectal artery descend into?
into the pelvis, crossing the left common iliac artery and vein
what happens at the S3 vertebral level to the superior rectal artery?
the artery divides into two terminal branches – one supplying each side of the rectum
what happens within the walls of the rectum to the terminal branches of the superior rectal artery?
smaller divisions of these branches eventually communicate with the middle and inferior rectal arteries
what is a left hemicolectomy?
the surgical resection (removal) of the descending colon
why is a left hemicolectomy performed?
for a variety of reasons such as removal of colon cancer, treatment of diverticulitis, inflammatory bowel disease or trauma
what must the surgeon do during a left hemicolectomy?
the surgeon must dissect the branches of the inferior mesenteric artery
how do the surgeons dissect the branches of the inferior mesenteric artery?
They do this by shining a light through the mesentery to identify the IMA and inferior mesenteric vein
does the IMV follow the same course as the IMA?
NO
what do the surgeons do after they have found the IMA?
They then trace the artery back to the aorta and divide it proximally
how many major anastomoses is the IMA involved with?
There are two major anastomoses of the IMA
what do the 2 major anastomoses of the IMA involve?
both involving a union with branches of the superior mesenteric artery
what are the 2 major anastomoses of the IMA?
Marginal artery (of Drummond) Arc of Riolan
what is the marginal artery (of Drummond)?
forms a continuous arterial circle along the inner border of the colon
what arises from the marginal artery (of Drummond)?
straight vessels (vasa recta)
what do the vasa recta of the marginal artery supply?
the colon
what is the marginal artery (of Drummond) formed by?
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
what is the arc of Riolan?
anastomosis between the middle colic branch of SMA and the left colic branch of IMA
arc of Riolan - existence?
It is less common than the marginal artery, and indeed its existence has been questioned by some surgeons
what can the splenic flexure be described as?
as a watershed area
why is the splenic flexure described as a watershed area?
a term used when an area has dual blood supply from the most distal branches of two large arteries
what is the advantage of the watershed area of splenic flexure?
Whilst this has the advantage of being more resistant to ischaemia if one of the arteries becomes occluded
what is a disadvantage of the watershed area of splenic flexure?
it makes the area more sensitive to systemic hypoperfusion
what is horseshoe kidney?
Horseshoe kidney is a congenital disorder where the kidneys fuse together, forming a horseshoe shape
how many people does horseshoe kidney affect? common in M/F?
It affects 1/400, and is more common in males
what happens during embryonic development of normal kidneys?
the kidneys ascend from the pelvis to their position in the abdomen
what happens to a patient with horseshoe kidney?
In a patient with horseshoe kidney, the fused kidney becomes hooked underneath the inferior mesenteric artery, and is stuck in the lower abdomen
what does horseshoe kidney require in terms of treatment?
It does not require any treatment, and is often asymptomatic
what are the complications that can occur from horseshoe kidney?
complications can occur from the poor drainage of the kidney, such as hydronephrosis, renal stones, and infection
