A male cat that squats, strains and produces nothing has roughly 24 hours before the obstruction turns fatal, and most clinics treat it as a 12-hour problem. Go now, not in the morning. On the way, five things are off the table: do not press or squeeze the bladder, do not attempt a catheter at home, do not give a diuretic or a human painkiller, do not force water, and do not apply a heat pack to the abdomen.
Three numbers carry the diagnosis. A bladder that feels larger than 3 cm across and firm like a plum is obstructed until proven otherwise. A potassium above 7 mmol/L puts the heart rhythm at risk. And a cat that has produced nothing for 24 hours is close to the point where the kidneys and the heart fail together.
Why the clock is shorter than owners think
The obstruction is usually at the penile urethra, 1 to 2 mm wide in a male cat, and it blocks with a plug of mucus, crystals and cells rather than a stone. Urine backs up, the bladder distends, and pressure is transmitted back to the kidneys within 12 to 24 hours, cutting filtration. Potassium the kidney can no longer excrete rises fast: 3.5 to 5.5 mmol/L is normal, 6.5 is a warning, 8 can stop the heart.
A cat that is quiet, off food and hiding at hour 18 may already be hyperkalaemic; vomiting at hour 24 makes it critical rather than urgent.
The 3 cm bladder rule
A normal bladder in a 4 to 5 kg cat is soft, pear-sized and about 2 to 3 cm across when partly full. An obstructed one is round, tense, and larger than 3 cm, and it is painful: the cat flinches when you touch the belly and often licks a swollen penis.
Feel, do not press. A tense bladder at 5 to 6 cm can rupture under a firm hand, and a ruptured bladder turns a treatable obstruction into a surgical case with peritonitis.
Potassium above 7: the heart goes first
Hyperkalaemia slows the heart and changes the ECG before it changes the cat's behavior: flattened P waves, a widened QRS, then a sine wave and arrest. That is why a blocked cat is stabilized before it is unblocked, and why the first 15 minutes in the clinic are an ECG, a potassium reading and an intravenous line.
Calcium gluconate protects the heart within minutes without lowering potassium; insulin with dextrose and a fluid bolus move potassium into the cells over 30 to 60 minutes. All of this is by prescription and none of it is a home treatment. A cat at potassium 7 with a heart rate under 120 is not one to drive 40 minutes to a cheaper clinic.
| Hour | Typical signs | Potassium | Action |
|---|---|---|---|
| 0-6 | Straining, nothing passed, licking | 3.5-5.5 mmol/L | Drive now; still fully treatable |
| 6-12 | Restless, then quiet, off food | 5.5-6.5 mmol/L | Urgent; expect hospital admission |
| 12-24 | Vomiting, weak, cold paws | 6.5-8 mmol/L | Critical; ECG and IV fluids first |
| 24-48 | Collapse, slow breathing, seizures | Above 8 mmol/L | Resuscitation; survival drops sharply |
Hour 0 to hour 24
Minute 0: stop offering food and water, note the last time urine was seen, and call ahead so the team has a catheter ready. Minute 30: in the car, keep the cat warm and in a carrier; a blocked cat loses heat fast. Hour 1: at the clinic, weight, bladder palpation, potassium, creatinine and an ECG. Hour 2: after stabilisation, a urinary catheter is placed under sedation and the bladder is drained slowly. Hour 6: fluids run, urine output is measured, and the catheter is stitched or connected to a closed system. Hour 24: most cats stay 24 to 48 hours, and the catheter usually comes out at 24 to 72 hours once the urine is clear of grit.
What the vet does, and why it is not a home job
Unblocking means a soft catheter, lidocaine gel, gentle flushing with sterile saline, and often a 3-way tap to break up the plug. The urethra is 1 to 2 mm wide and a false passage is easy to create with a firm push, which is why it happens under sedation with a catheter made for the job. After unblocking expect 24 to 72 hours of post-obstructive diuresis at 2 to 5 mL/kg per hour, with fluids matched to avoid dehydration and wash out potassium.
Some cats re-obstruct and need a second catheter; a few need a perineal urethrostomy after 2 or 3 episodes, a decision for a repeat offender. Aftercare at home is covered in catheter aftercare, and a cat that stops eating for 2 days after any illness needs a different emergency plan, covered in feeding tube decisions.
The 7 days after: watch the litter box like a job
For 7 days, check every urination: volume, color, and whether the cat strains. A cat that produces a plum-sized clump in 2 visits a day is fine; a cat that visits 6 times and produces nothing is re-blocking and goes back the same hour. Blood-tinged urine for 24 to 72 hours and dribbling for 3 to 5 days are expected.
Keep the cat on wet food from day 1, add water to every meal, and keep 2 water sources in different rooms. Give the prescribed anti-inflammatory and antispasmodic on schedule, and do not stop early because the cat looks bright.
Prevention: 4 levers worth pulling
Water: a 4.5 kg cat needs 180 to 270 mL a day, and a wet diet supplies 70 to 80 percent of it in the food. Weight: fat cats block more; aim for 5 out of 9. Stress: one box per cat plus one, 1.5 times body length, scooped twice a day. Monitoring: weigh monthly and ask for urine pH, gravity and sediment at the annual visit; do not acidify urine with vitamin C on your own, because that advice is 20 years out of date and can cause a different stone.
Three things never to do
- Never squeeze the bladder to help it empty; you can rupture it.
- Never pass a catheter, a straw or a piece of tubing at home.
- Never wait for the cat to pass a little urine on its own as proof it is fine; a partial block can dribble for hours and still be fatal.
If the signs started after a plant or a household product, check the toxic lookup while you drive; some toxins cause straining that looks urinary.
Tonight's checklist
- Note the exact time you last saw urine, and take that number to the clinic.
- Carry the cat in a carrier with a towel; do not let it walk to the car.
- Call ahead and say the words blocked male cat, so a catheter is ready.
- Ask for potassium, creatinine and an ECG on arrival, and ask for the numbers.
- Plan the 7-day litter watch before you leave the clinic.
Terms mentioned in this article
Frequently asked
How long can a blocked male cat survive?
Roughly 24 hours, and many clinics treat it as a 12-hour emergency because potassium rises faster than owners expect. Normal potassium is 3.5 to 5.5 mmol/L, values above 7 threaten the heart rhythm, and above 8 can cause arrest. A cat that has passed nothing for 24 hours is critical, not merely urgent.
Can I express my cat's bladder at home?
No. An obstructed bladder is tense and can rupture under firm pressure, turning a catheter case into peritonitis and surgery. Passing a catheter at home is worse: the male urethra is 1 to 2 mm wide and a false passage is easy to create. Both jobs need sedation and equipment, so the correct home action is a car trip.
What happens after the catheter is removed?
Seven days of litter box watching: volume, color, and whether the cat strains. Blood-tinged urine for 24 to 72 hours and dribbling for 3 to 5 days are expected, but 6 visits with no urine means a re-block and a return the same hour. Wet food, added water and two water sources stay for life.