Urethral Stone

An abdominal radiograph shows an oval calcification (arrow) in the midline below the pubic symphysis in a male patient with multiple small right renal calculi (arrowhead).

Facts

• Urethral calculi in males are almost always secondary to stone disease elsewhere (bladder or kidneys), these are called "migrant calculi"
• Primary stone formation within the urethra itself is very rare, but can be seen if stricture or urethral diverticulum is present
• Large urethral calculi may lodge at the point of urethral narrowing such as the membranous urethra
• Clinical: pain, bleeding and impaired urine flow, palpable stone in the perineum or underside of the penis
• Treatment: distal stones may be grabbed by stone forceps and extracted via urethral meatus (requiring general anesthesia) or urethrolithotomy. Proximal stones may be pushed back into the bladder endoscopically, then extracted like a bladder stone

Imaging

• Although rare, the case highlights the need to specifically include the portion of urethra in abdominal radiograph performed to evaluate for stone disease and to actively search for stone in this region
• On CT, urethral stone can easily be overlooked either because it is not imaged (the urethra not commonly included in a stone protocol CT) or missed by the reader

Reference:

1. Kawashima A, Sandler CM, Wasserman NF, et al. Imaging of urethral disease: a pictorial review. RadioGraphics 2004;24:S195-S216.
2. Smith P. Urology - Medico-legal practitioner series. 2001