A urinary obstruction in cats occurs when the urethra becomes blocked—most commonly by crystals, mucus plugs, or inflammation—preventing urine from leaving the body. This is especially dangerous in male cats because their urethra is much narrower, making them more prone to complete blockage. When urine cannot be passed, toxins and potassium quickly build up in the bloodstream, leading to severe electrolyte imbalances, kidney damage, and potentially fatal heart rhythm abnormalities. Without prompt veterinary treatment, a urinary obstruction can become life-threatening within 24–48 hours.