What is the anatomy of the ureter?

Anatomy of the Ureter

Overview

The ureter is a muscular tube measuring approximately 25-30 cm in length that connects the renal pelvis to the bladder, functioning to transport urine via peristaltic contractions through a non-layered muscular wall surrounding a water-impermeable multilayered urothelium.

Structural Organization

Basic Architecture

• The ureter is a non-layered muscular tube where the anatomical unit consists of muscle bundles containing heterogeneously oriented muscle cells 1
• The wall comprises an inner urothelium (transitional epithelium) that is water-impermeable and multilayered, surrounded by an outer mesenchymal coat of smooth muscle and fibroelastic material 2
• Functional continuity between muscle cells is provided through nexus structures (gap junctions), which are clearly defined anatomical connections 1

Muscular Components

• The muscle bundles contain heterogeneously oriented smooth muscle cells rather than distinct layers 1
• Specialized morphologically distinct muscle cells exist within the ureter and may represent pacemaker cells responsible for initiating peristaltic contractions 1
• The longitudinal ureteral musculature anchors the ureter and outlines the bladder trigone, extending into the dorsal submucosa of the urethra as the urethral crest 3

Anatomical Course and Divisions

Regional Segments

• The ureter can be divided into upper (proximal), middle, and lower (distal) thirds, each with distinct surgical and clinical implications 4
• The upper and middle third injuries typically require ureteroureterostomy for repair 4
• The lower third of the ureter requires direct reimplantation (ureteroneocystostomy) when injured 4

Relationship to Surrounding Structures

• The ureter occupies a posterior position relative to the renal vessels at the renal hilum 5
• This posterior anatomical position makes the ureter less vulnerable to direct injury compared to more anterior vascular structures during renal trauma 5
• On contrast-enhanced CT scans, the ureter can be identified in its posterior position relative to the renal vessels 5

Vesicoureteral Junction

Anatomical Features

• The ureter passes obliquely through the bladder wall, creating a natural valve mechanism 3
• This oblique passage results in compression of the distal ureter during bladder filling, which precludes urine reflux back into the ureter 3
• The ureters are anchored by longitudinal ureteral musculature that outlines the bladder trigone 3

Functional Characteristics

Peristaltic Activity

• The ureter allows unidirectional movement of urine through peristaltically active smooth muscle contractions 2
• Ureters are largely independent of extrinsic innervation for their basic peristaltic function 3
• The morphologic appearance of muscle cells varies depending on their functional status—cells fixed in contraction differ from those fixed in relaxation 1

Blood Supply Considerations

• During surgical procedures involving the upper ureter, preservation of blood supply is essential to prevent ischemic complications 5
• Knowledge of anatomical relationships helps determine viability of ureteral segments for repair 5
• Ureteral devascularization must be kept to a minimum during any surgical anastomosis 4

Clinical Implications

Imaging Characteristics

• CT urography with both nephrographic and excretory phases (5-20 minutes after contrast administration) represents the gold standard for evaluating ureteral anatomy and pathology 4
• A 10-minute delayed-phase CT scan is a valid diagnostic tool for identifying ureteral and ureteropelvic injuries 4
• Understanding the posterior position of the ureter relative to renal vessels is critical when interpreting imaging studies for suspected injuries 5

Surgical Considerations

• Direct visualization of the ureter is mandatory during surgical exploration for suspected ureteral injuries 4, 5
• Complex urinary tract anatomy (including duplicated collecting systems, megaureter, ureterocele, or ureteral strictures) may require additional contrast imaging for adequate definition 4
• The recipient ureter should be mobilized as minimally as possible during reconstruction to avoid disrupting blood supply to any anastomosis 4

Common Anatomical Variations

Congenital Anomalies

• Duplicated collecting systems represent a common anatomical variation requiring special consideration during imaging and surgery 4
• Megaureter and ureterocele are congenital conditions affecting ureteral anatomy 4
• Ureteral strictures may be congenital or acquired and affect the normal caliber and function 4