Anatomy of the Kidney Including the Proximal Ureter
The kidney is a bean-shaped organ with the proximal ureter emerging from its medial concave surface at the renal pelvis, forming the initial portion of the urinary collecting system that transports urine to the bladder.
Gross Anatomy of the Kidney
- Location: Retroperitoneal position in the posterior abdomen, typically extending from T12 to L3 vertebral levels
- Size: Approximately 10-12 cm long, 5-7 cm wide, and 3 cm thick
- Weight: 125-170 grams in adults
- Orientation: The long axis is oriented vertically with the upper pole slightly more medial than the lower pole
External Structure
- Capsule: Thin, fibrous layer surrounding the kidney
- Hilum: Medial concave depression where vessels, nerves, and the renal pelvis enter/exit
- Poles: Superior and inferior ends of the kidney
- Surfaces: Anterior (facing forward) and posterior (facing backward)
Internal Structure
- Cortex: Outer layer containing glomeruli and convoluted tubules
- Medulla: Inner region containing the renal pyramids
- Renal pyramids: 8-18 conical structures with bases facing the cortex and apices (papillae) pointing toward the renal pelvis
- Renal columns: Extensions of cortical tissue between adjacent pyramids
- Calyces:
- Minor calyces: Cup-shaped structures that collect urine from the papillae
- Major calyces: Formed by the union of several minor calyces
Renal Pelvis and Proximal Ureter
- Renal pelvis: Funnel-shaped expansion of the upper end of the ureter within the renal sinus
- Ureteropelvic junction (UPJ): Transition point between the renal pelvis and the ureter
- Proximal ureter:
- First portion of the ureter (approximately 5-7 cm in length)
- Extends from the UPJ to the upper border of the sacrum
- Courses downward and medially behind the peritoneum
- Located anterior to the psoas muscle
- Crosses over the iliac vessels at the pelvic brim
Ureteral Wall Structure (Three Layers)
- Inner mucosa: Transitional epithelium (urothelium) with underlying lamina propria
- Middle muscular layer: Smooth muscle arranged in inner longitudinal and outer circular layers
- Outer adventitia: Connective tissue layer that blends with surrounding retroperitoneal tissues
Blood Supply
- Renal artery: Branch of the abdominal aorta that divides into segmental arteries
- Proximal ureter blood supply: Multiple sources including:
- Renal artery branches
- Gonadal artery branches
- Direct branches from the abdominal aorta
Lymphatic Drainage
- Kidney: Drains to para-aortic lymph nodes
- Proximal ureter: Drains to para-aortic and common iliac lymph nodes
Innervation
- Autonomic innervation: Derived from the renal plexus (sympathetic) and vagus nerve (parasympathetic)
- Sensory innervation: Pain fibers travel with sympathetic nerves (T10-L1)
Clinical Significance
- The proximal ureter is a common site for obstructing stones 1
- Ureteral injuries can occur during abdominal or pelvic surgery, requiring prompt diagnosis and management 1
- Severe hydronephrosis due to proximal ureteral obstruction requires urgent decompression, typically via percutaneous nephrostomy or ureteral stenting 2
Understanding the anatomy of the kidney and proximal ureter is essential for diagnosing and managing conditions such as urolithiasis, congenital anomalies, and iatrogenic injuries affecting this region.