Ureteral smooth muscle (USM)

Ureteral smooth muscle is the muscular layer of the ureter responsible for the rhythmic, myogenic contractions known as peristalsis, which transport urine from the renal pelvis to the urinary bladder (StatPearls, 2023). While not a single molecular target, it is a primary pharmacological site of action for medical expulsive therapy (MET) used to facilitate the passage of urolithiasis. The tissue contains a variety of receptors, most notably alpha-1 adrenergic receptors (particularly the alpha-1A and alpha-1D subtypes), which mediate contraction, and L-type calcium channels that are essential for the action potentials driving peristaltic waves (NCBI, PMC6034608). Pharmacological intervention typically focuses on inducing relaxation of the ureteral wall to decrease intraluminal pressure and increase the rate of stone passage while reducing the associated pain of ureteral colic (PubMed, 29631163). Common therapeutic agents include alpha-adrenergic antagonists and calcium channel blockers, which modulate the tone of the smooth muscle cells to alleviate obstruction-related symptoms.

Other names

Ureteric smooth muscleTunica muscularis of the ureterUreteral muscularis

Drugs targeting this tissue typically act by antagonizing alpha-1 adrenergic receptors to reduce muscle tone, blocking L-type calcium channels to inhibit contraction, or inhibiting phosphodiesterase-5 to increase intracellular cGMP and promote relaxation.