Anatomy of the Ureter

Overview

Segments

1. Abdominal segment - from the renal pelvis to the iliac vessels (crosses at the bifurcation of the common iliac artery)
2. Pelvic segment - from the iliac vessels to the bladder; approximately 15 cm long (half the total length)
3. Intramural segment - passes obliquely through the bladder wall; 1.2-2.5 cm long in adults, ~0.5-0.8 cm in neonates

Course

• Lies retroperitoneally, adherent to the posterior abdominal wall
• Descends anterior to the psoas major muscle, crossing ventral to the transverse processes of L3-L5
• The genitofemoral nerve runs behind the ureter on the psoas major
• The right ureter begins behind the descending duodenum and is crossed by gonadal vessels ("water under the bridge")
• The left ureter is covered at its origin by the jejunum; is crossed by the inferior mesenteric artery and left colic vessels as it approaches the pelvis
• Surface anatomy: a line from 5 cm lateral to the L1 spinous process to the posterior superior iliac spine

• Crosses the common iliac vessels near their bifurcation (a key surgical landmark)
• Runs along the lateral pelvic wall toward the ischial spine
• At the ischial spine, turns medially to reach the bladder
• In females, the ureter passes under the uterine artery ("water under the bridge") approximately 1.5 cm lateral to the cervix - a common site of inadvertent surgical injury

• Pierces the bladder wall obliquely
• Enveloped by the Waldeyer sheath (a specialized muscular-fibrous sheath)
• The oblique passage through the detrusor muscle acts as a flap valve, preventing vesicoureteric reflux during micturition

Constrictions (Sites of Stone Impaction)

Blood Supply

• Upper ureter: renal artery
• Middle ureter: gonadal (testicular/ovarian) arteries, aorta, common iliac artery
• Lower/pelvic ureter: internal iliac, superior vesical, uterine, and inferior vesical arteries

Microscopic Anatomy

1. Mucosa (innermost) - transitional epithelium (urothelium) with 4-6 cell layers; contains many longitudinal folds giving the empty ureter a characteristic stellate outline on cross-section. The lamina propria beneath contains blood vessels and nerve fibers.
2. Muscularis (middle) - two longitudinal layers with an intervening circular layer. In the distal ureter, these appear as distinct inner longitudinal and outer circular layers. These smooth muscle fibers are continuous with those of the renal calyces; the pacemaker for peristalsis is located at the minor calyces.
3. Adventitia (outermost) - dense collagen and elastic fibers, blood vessels, and unmyelinated nerve fibers. Continuous with the renal capsule proximally and forms the Waldeyer sheath distally.

Clinical Relevance

• The pelvic brim is one of the most common sites of ureteral injury during surgery
• In females, the ureter is at risk during hysterectomy where the uterine artery crosses it
• The oblique intramural tunnel creates the antireflux mechanism; loss of this angle (e.g., in vesicoureteric reflux) leads to urine backflow into the kidney
• Obstruction at any of the three constrictions by a calculus causes renal colic

Anatomy of the Ureter

Overview

Segments

1. Abdominal segment - from the renal pelvis to the iliac vessels
2. Pelvic segment - from the iliac vessels to the bladder; approximately 15 cm long (half the total length)
3. Intramural segment - passes obliquely through the bladder wall; 1.2-2.5 cm long in adults, ~0.5-0.8 cm in neonates

Course

• Lies retroperitoneally, adherent to the posterior abdominal wall
• Descends anterior to the psoas major muscle, crossing ventral to the transverse processes of L3-L5
• The genitofemoral nerve runs behind the ureter on the psoas major
• The right ureter begins behind the descending duodenum and is crossed by gonadal vessels ("water under the bridge")
• The left ureter is covered at its origin by the jejunum; crossed by the inferior mesenteric artery and left colic vessels as it approaches the pelvis
• Surface anatomy: a line from 5 cm lateral to the L1 spinous process to the posterior superior iliac spine

• Crosses the common iliac vessels near their bifurcation (a key surgical landmark)
• Runs along the lateral pelvic wall toward the ischial spine
• At the ischial spine, turns medially to reach the bladder
• In females, the ureter passes under the uterine artery (~1.5 cm lateral to the cervix) - a common site of inadvertent surgical injury

• Pierces the bladder wall obliquely, enveloped by the Waldeyer sheath
• The oblique passage through the detrusor muscle acts as a flap valve, preventing vesicoureteric reflux during micturition

Constrictions (Sites of Stone Impaction)

Blood Supply

• Upper ureter: renal artery
• Middle ureter: gonadal (testicular/ovarian) arteries, aorta, common iliac artery
• Lower/pelvic ureter: internal iliac, superior vesical, uterine, and inferior vesical arteries

Microscopic Anatomy

1. Mucosa (innermost) - transitional epithelium (urothelium) with 4-6 cell layers; many longitudinal folds give the empty ureter a characteristic stellate outline on cross-section. The lamina propria contains blood vessels and nerve fibers.
2. Muscularis (middle) - two longitudinal layers with an intervening circular layer. In the distal ureter these appear as inner longitudinal and outer circular layers. These smooth muscle fibers are continuous with those of the renal calyces; the pacemaker for peristalsis is located at the minor calyces.
3. Adventitia (outermost) - dense collagen and elastic fibers with blood vessels and unmyelinated nerve fibers. Forms the Waldeyer sheath distally.

Clinical Relevance

Ureteral Injury in Surgery

• The pelvic brim is one of the most common sites of ureteral injury during surgery
• In females, the ureter is at risk during hysterectomy where the uterine artery crosses it
• The oblique intramural tunnel creates the antireflux mechanism; loss of this angle leads to vesicoureteric reflux (VUR)

Renal (Ureteric) Stones

• Pain relief with NSAIDs (first-line), opioids, antiemetics, and hydration
• Hospital admission is indicated for: persistent/relentless pain, intractable vomiting, established infection, or obstruction
• Urgent nephrostomy may be required to relieve obstruction, followed by ESWL, ureteroscopy with laser lithotripsy, or percutaneous lithotripsy

• Alpha-1 adrenergic blockers (e.g., tamsulosin) are the mainstay of MET; they reduce ureteral smooth muscle tone and peristaltic frequency, facilitating stone passage
• Both the AUA and EAU recommend alpha blockers for distal ureteral stones:
  • EAU: stones > 5 mm
  • AUA: stones < 10 mm, with 4-6 weeks of observation
• Tamsulosin has been shown superior to nifedipine (calcium channel blocker)
• A Cochrane review (67 studies, 10,509 participants) confirmed alpha blockers increase stone clearance and shorten expulsion time

• High fluid intake (urine output ~2.5 L/day) is the single most effective measure to reduce stone recurrence
• Stone composition guides dietary modification (e.g., low oxalate for calcium oxalate stones, low purine for uric acid stones)

Phlebotomy - Principles and Clinical Pitfalls

1. Site preparation - Allow the alcohol to dry completely before venipuncture; trace alcohol causes hemolysis. Povidone-iodine (if used) should be wiped off with alcohol before drawing, as it can interfere with several chemistry assays.
2. Tourniquet application (venous occlusion) - Biochemical changes begin in blood as soon as a tourniquet is applied. Serum potassium can increase by 6% within just 3 minutes of tourniquet application. Phlebotomy should ideally be completed within 30 seconds of tourniquet application. Avoid asking patients to pump their fist, as this elevates potassium, lactate, and phosphate levels.
3. Needle gauge and suction - Smaller-gauge needles and excessive suction pressure increase hemolysis rates. Routine phlebotomy causes a hemolysis rate of < 2%, but ED phlebotomy rates can reach 7-15%, often due to drawing via IV catheters or prolonged tourniquet times.
4. Tube order of draw - To prevent cross-contamination of additives between tubes, fill in this order:
   • Blood cultures → Red → Blue → Speckled red → Green → Lavender → Gray
5. Phlebotomy via IV catheter - Drawing through a freshly placed IV catheter significantly increases hemolysis rates. Using larger-bore catheters and drawing small aliquots reduces hemolysis. However, results remain within clinically acceptable margins of error for most tests.
6. Specimen identity - Patient misidentification is a critical pre-analytical error. Confirm patient identity before every draw.

• Falsely elevated WBC: nucleated red blood cells (RBCs)
• Falsely elevated hemoglobin: severe leukocytosis (>30,000), hyperlipemia, giant platelets
• Falsely decreased hemoglobin: in vitro hemolysis