Urinlederne

Urinlederne, known in English as the ureters, are a pair of muscular tubes that transport urine from the kidneys to the urinary bladder. In adults they are typically about 25 to 30 centimeters long and lie in the retroperitoneal space along the posterior abdominal wall. Each ureter runs from the renal pelvis, crosses the psoas major, and descends to enter the bladder at the posterolateral aspect of the trigone through the ureterovesical junction.

Structure and function: The walls of the ureters consist of mucosa lined by transitional epithelium, a connective tissue lamina propria, and a thick muscularis made of an inner circular and an outer longitudinal layer. The outer adventitia anchors the tubes in place. The ureters propel urine by rhythmic peristaltic waves of smooth muscle, starting near the renal pelvis and continuing down to the bladder, aided by gravity and occasional segmental contractions.

Blood supply and innervation: Blood supply along the course comes from a series of arterial branches, including renal arteries proximally and branches from adjacent iliac and vesical arteries distally. Venous drainage mirrors the arterial supply. Innervation is autonomic, with sympathetic and parasympathetic fibers providing motor input for peristalsis and sensory fibers conveying pain, often perceived as flank or groin discomfort in cases of obstruction.

Clinical relevance: Obstruction by kidney stones, strictures, or tumors can cause hydronephrosis and flank pain. The ureterovesical junction acts as a valve to prevent reflux; dysfunction here can contribute to vesicoureteral reflux. Diagnostic imaging and, if needed, interventions such as stenting or surgical correction may be employed to address ureteral disease.