Urethral plugs in the cat: composition and prevention
4-year-old neutered male cat that has been unblocked. During retrohydropulsion a soft, gritty, whitish material comes out of the penile tip. The owner asks if it is 'a stone'.
Which statement about urethral plugs is correct?
chevron_right Show answer and explanation
A. They are calcium oxalate uroliths and require cystotomy to remove residues from the bladder
Plugs are soft and their most common mineral component is struvite, not oxalate. They do not require surgery.
B. They consist of a matrix of proteins, cells and inflammatory debris with variable amounts of minerals, mostly struvite; they are associated with bladder inflammation
Correct. Unlike uroliths, which are almost entirely mineral, plugs contain a large organic matrix from inflammation (often idiopathic cystitis). Prevention combines wet food, more water and MEMO.
C. They are caused by bacterial infection and require three weeks of antibiotics
In young cats, plugs usually form without infection. Antibiotics are only indicated if the urine culture is positive.
D. A struvite dissolution diet on its own eliminates the risk of further obstruction
The diet controls the mineral component but not the inflammatory matrix. Without addressing bladder inflammation, water and environment, the risk persists.
lightbulb Key takeaway
Urethral plug = inflammatory matrix + crystals (usually struvite). It is the most common cause of obstruction in young male cats, and prevention is the same as for idiopathic cystitis.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.