ANATOMY: URETERS
Embryology
- At the 5th week of gestation, the ureteric bud arises as a diverticulum from the mesonephric (Wolfian) duct.§
- The bud grows laterally and invades the center of the metanephrogenic blastema, the primordial renal tissue. The meeting of these two tissues causes changes in the bud and the metanephros.
- The metanephrogenic blastema forms glomeruli, proximal tubules and distal tubules.§
- The ureteric bud forms the collecting tubules and ducts, calyces, infundibulae, renal pelvis, and ureters.§§
Gross anatomy
- In adults, the ureter is 22-30cm in length with a diameter of 1.5-6mm
- Begins posterior to the renal artery and continues along the edge of the psoas muscle
- Situated just lateral to the tips of the transverse processes of the lumbar vertebrae in the retroperitoneum
- Segments (3):
- Proximal (above the sacrum)
- Middle (over the sacrum)
- Distal (below the sacrum) segments
- Normally, 3 constrictions could be identified radiologically in each ureter
- Ureteropelvic junction
- Where it crosses the iliac vessels
- Ureterovesical junction
- The bifurcation of the common iliac vessels to the external and internal illiacs is used intraoperatively as a landmark to look for the ureter
- The genitofemoral nerve runs on top of the psoas major muscle behind the ureter
- The right ureter begins behind the descending part of the duodenum
- The left ureter is covered at its origin by the initial part of the jejunum
- Proximally, the gonadal vessels are medial to the ureter. The gonadal vessels descend laterally and cross anterior to the ureter, “water under the bridge”, a third of the way to the bladder.
- The gonadal vessels cross the left ureter after running parallel to it for a small distance
- As the left ureter approaches the pelvis, it is crossed by the left colic vessels, the sigmoid colon, and its mesocolon
- In females, the ureter crosses the infundibulopelvic ligament under the ovarian artery and is just medial to the uterine artery. It also passes through the cardinal ligament and lies in close proximity to the cervix.
- Medial displacement
- Of both pelvic ureteral segments might result from (3):
- Retroperitoneal fibrosis
- Pelvic lipomatosis
- Post-abdominoperineal surgery.
- And concavity of a single pelvic ureter may result from:
- Enlarged hypogastric nodes
- Bladder diverticulum
- Aneurysmal dilatation of the hypogastric artery
- May be a normal finding in adult females if only the right ureter is affected because of the uterine tilt to the left.
Vasculature
- Variable arterial supply. Most often,§
- Proximal ureter is supplied medially by branches from the main renal arteries
- Uncommonly, this segment may be supplied by branches arising from the abdominal aorta or gonadal arteries.
- Middle ureter is supplied posteriorly by branches from the common iliac arteries, abdominal aorta, and the gonadal arteries
- CW11 Chapter 33 “The middle ureter is typically supplied by the aorta; however, it may also be supplied by the common iliac, gonadal, uterine, middle rectal, and vaginal arteries”
- Distal ureter is supplied laterally by the superior and inferior (inferior from chapter 33, inferior and uterine from chapter 68) vesical arteries, branches of the internal iliac artery
- The distal ureteral blood supply is variable. It is estimated by cadaver studies that 10% of females carry a disproportionate amount of their distal ureteral blood supply via uterine artery branches. These branches are necessarily severed when the uterine artery is ligated during the course of a normal hysterectomy.
- Therefore, location of endoureterotomy depends on position:
- Proximal ureter: (postero)laterally
- Mid-ureter: anteriorly
- Distal ureter: medially
- The ureters should be handled gently to avoid unnecessary lateral retraction; removing excessive periureteral adventitial tissues containing the blood supply can cause ureteral ischemia and subsequent stricture
- Venous drainage:
- Upper ureter: renal and gonadal veins
- Middle and distal ureters: common and internal iliac veins
Nerve Supply
- The peristalsis of the ureter originates in pacemakers in the minor calyces. The exact role of autonomic input of the ureters is unclear.
Radiology of the ureter
- The entire length of the ureter is rarely seen on a single film of the excretory urography because of peristaltic activity; the diagnosis of ureteral stricture should not be based on a single film of excretory urography with the presence of ureteral dilation proximal to the site of narrowing
- Ureteral duplication may be complete or incomplete (partial)
- In case of duplex ureters, the Weigert-Meyer rules says that the ureter draining the upper pole of the kidney prevalently inserts in the bladder inferiorly and medial to the lower pole of the kidney.
Endoscopic anatomy
- The trigone is the most vascular part of the bladder and is formed by an extension of the longitudinal muscle fibers of the ureters over the detrusor muscle.
- Both ureteric orifices are rarely seen in a single endoscopic view.
- The higher the grade (0-4) of the ureteric orifice, the more lateral the orifice
- The interureteral ridge is more prominent in males than females, and the ureteric orifices are symmetrically located along it, ≈1 to 2 cm from the midline.
- The intramural ureter represents the narrowest part of the ureter, with an average diameter of 3 to 4 mm
- The renal papillae appear endoscopically as protruding discs surrounded by calyceal fornices, paler in color than the pink friable epithelium covering the papillae.
- The extrarenal pelvis is usually larger and has longer major calyceal infundibula than the intrarenal pelvis.
Questions
- What is the blood supply to the ureter?
Answers
- What is the blood supply to the ureter?
References
- Lescay, Hernan A., Jay Jiang, and Faiz Tuma. "Anatomy, abdomen and pelvis, ureter." StatPearls [Internet] (2020).
- Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 21
