Episode 17  ·  11m 34s

No Urine in the Litter Box Is an Emergency — Urinary Blockages in Cats and Dogs

Dr. Michael LoSasso, DVM & Julie Schwenzer Frisco Emergency Pet Care
Urinary blockage Blocked cats Bladder stones UTIs Emergency signs Prevention
"Urinary problems can escalate fast, especially in cats. Today we're unpacking the most common issues, why they happen, and what every pet parent should know before it becomes an emergency."
— Julie Schwenzer

Episode summary

Not every urinary problem is an emergency — but some are, and Dr. LoSasso says the difference comes down to anatomy and sex. Female dogs and cats have short, wide urethras, which makes infections more common (he sees two or three infected females a week) but makes true blockages rare. Males are the opposite story: their anatomy makes infections less common but creates real chokepoints where stones or debris can get stuck and cut off urine flow entirely.

In male dogs, a bone supports the body of the penis, and the urethra runs through a channel in that bone. If a bladder stone is larger than that channel, it simply can't pass — stones stack up and block the flow. In male cats, the mechanism is different: the urethra is wide near the bladder and narrows dramatically toward the tip — Dr. LoSasso compares it to a four-lane highway narrowing to a bike path, a design that lets cats spray urine under pressure to mark territory. A small stone or a crystal-laden mucus plug can travel most of the way down comfortably and then lodge at that narrow point.

"If your stone has a larger diameter than the opening of that channel, that stone's not going anywhere. They're just going to start stacking up in the urethra and cause obstruction — and that can be a life-threatening urinary problem."
— Dr. Michael LoSasso, DVM

A blocked pet can't eliminate the toxins and potassium that urine is supposed to carry out of the body, which is what makes this a true emergency rather than just an uncomfortable inconvenience. Treatment means restoring urine flow — flushing stones back into the bladder under anesthesia, catheter placement or surgery, IV fluids, and close monitoring of electrolytes and kidney values. Cats typically stay hospitalized two to three days, with costs commonly running $3,500 to $8,000 depending on the case and hospital.

Warning signs of a blockage — don't wait

Repeated trips to the litter box, straining or howling while trying to go, blood in the urine, urinating outside the box, or — most tellingly — no urine produced at all despite repeated attempts. Dr. LoSasso says this is not a "wait and see" situation. It needs to be seen right away, and it most often happens to young male cats, around two or three years old, not just older pets.

Prevention is possible, but with limits. In female dogs, stones are usually driven by long-standing untreated infections, so addressing infections early is genuinely preventive. In males, stone formation is more often tied to metabolic factors that diet can help manage but not eliminate — wet food increases water intake and helps acidify urine, and a prescription urinary diet helps further. Even with a perfect diet, though, Dr. LoSasso is honest that there's no guarantee against re-blocking: it can happen again in three weeks, three months, or seven years, with no way to predict when.

Questions answered in this episode

The following questions are answered by Dr. LoSasso in this episode, drawn directly from the conversation. These are real clinical answers from a practicing emergency veterinarian with 30+ years of experience.

Dr. LoSasso explains that female mammals of any species have a much shorter urethra than males, and infection is normally prevented by regularly clearing the urethra with a urine stream. That shorter length makes infections more common in females — he sees two or three infected female dogs or cats a week — but it also makes true blockages from stones rare in females, since the urethra is short and wide.
Dr. LoSasso explains a male cat's urethra narrows dramatically toward the outside — wide near the bladder, narrowing to what he compares to a bike path by the tip, which lets cats spray urine under pressure to mark territory. A small stone, or a mucus plug containing crystals, can travel most of the way down comfortably and then lodge at that narrow point, blocking urine flow completely. This most often happens to young male cats, around two or three years old.
Dr. LoSasso explains that male dogs have a bone supporting the body of the penis, and the urethra runs through a channel in that bone. If a bladder stone is larger than that channel's opening, it cannot pass — stones stack up and cause a blockage. Treatment usually involves anesthesia to flush the stones back into the bladder, then either a catheter or surgery to remove them.
Dr. LoSasso explains that when urine can't leave the body, the bladder fills and the toxins and potassium the body needs to eliminate through urine build up instead. That buildup can cause serious illness and kidney damage. He describes it as a true emergency requiring restored urine flow, IV fluids, and close monitoring of electrolytes and kidney values, typically with two to three days of hospitalization.
Dr. LoSasso says to watch for repeated trips to the litter box with little or no urine produced, straining, vocalizing or howling while trying to go, blood in the urine, or urinating outside the litter box. If you look in the box and there's simply no urine there despite repeated attempts, that's a genuine emergency and the cat needs to be seen immediately.
Dr. LoSasso recommends wet food over dry food for cats in general — it increases water intake, helps acidify urine, and supports weight control. A prescription urinary diet helps even more, and cats that have blocked once are often kept on it long term. Even so, he's clear there's no guarantee against re-blocking — it can happen again in weeks, months, or years, with no way to predict when.
JulieUrinary problems can escalate fast, especially in cats. Today we're unpacking the most common issues, why they happen, and what every pet parent should know before it becomes an emergency. Could we start with the bigger picture? What makes urinary problems such a common and urgent concern in veterinary medicine?
Dr. LoSassoCommon and urgent may be two different descriptors there. Female mammals in general have a much shorter urethra than males of any species, and the way you prevent infection is clearing the urethra with a urine stream. So in females we see a lot more urinary tract infections, in both dogs and cats — lots of females come in with some blood in their urine or urinating very frequently, and those are frequently infections. I see two or three of those a week, more dogs than cats, but it happens in both. The scarier part is an obstruction. Because the female urethra is short and generally fairly wide, we rarely see stones causing obstructions in females. But in male dogs, sometimes a bladder stone gets into the urethra — the tube connecting the bladder to the outside — and travels down it. The dog has a bone that supports the body of the penis, and the urethra runs through a channel in that bone. If your stone has a larger diameter than that channel's opening, it's not going anywhere — stones stack up in the urethra and cause obstruction, and that can be life-threatening, because the bladder fills and the toxins and potassium the body's trying to get rid of can't get out. We use anesthesia and try to flush those stones back up into the bladder, so we can either keep a catheter in and let them urinate, or take them straight to surgery to remove the stones.
Dr. LoSassoCats are a little different because the male cat is designed differently. The urethra in a cat is fairly wide, think of a four-lane highway, and as it moves toward the outside it narrows down to a bike path. They're designed that way so they can urinate under extreme pressure — it's like holding your thumb over a garden hose to make it spray farther, because that's how cats mark territory. Dogs aren't very couth, they'll lift a leg on a tree or fire hydrant. Cats back up to a fence and shoot a little jet of urine to spray it, because they don't want urine all over themselves. That system works great until you introduce a small stone or a mucus plug with some crystals in it — it travels down the four-lane highway just fine, but it's bigger than the bike path at the end, and it gets lodged, typically right at the very end of the urethra, and they can't urinate. These are often young cats, two or three years old. Usually by the time they're older, they've either done it before or they're not going to. They come in and need to be unblocked — we need to reestablish urine flow, get them on fluids to protect their kidneys, and eventually pull the catheter and hope they don't re-block. We generally keep those guys in hospital two or three days, checking electrolytes and making sure the urinary values are normalizing. So they tend to be fairly expensive cats — depending on where you are and which hospital, you're probably looking at somewhere between $3,500 and $8,000 for that stay.
Dr. LoSassoAnd there's no guarantee they won't do it again — three weeks later, three months later, seven years later, there's no way to predict it. There are strategies to lengthen that time frame, mostly putting them on wet food. Honestly, I'd always feed a cat wet food anyway — it helps acidify the urine a bit and increases dietary water so they urinate more, and it's much better for weight control. There's a specific urinary diet that helps even more, and any wet food beats any dry food. Those cats are frequently on it for life. But it's definitely a shock when you've got what you think is a healthy two-year-old cat you love to death, and suddenly you're looking at a $4,000 bill out of nowhere, and all you noticed was he was going to the litter box and sometimes howling — and you look, and there's no production, no urine in the box. That's a problem, and it needs to be seen right away.
JulieIn addition to diet, is there any way to get ahead of this before something happens — how do you even prevent stones or blockages?
Dr. LoSassoThe only time stones are truly preventable is in females, mostly dogs, and that's by not tolerating urinary tract infections, because stones in female dogs generally come from long-standing infections. Just be aware — a dog going out should urinate in one spot, maybe sniff at a second, but if she urinates and urinates and urinates, fifteen times in a row, that's urge incontinence, and it happens in dogs, cats, women, horses, doesn't matter. That feeling of needing to go even though the bladder's empty is a really powerful urge in the brain. That's not normal and needs to be checked out. If they urinate in the house and you see blood, or any abnormal urinary behavior, have it checked out by your general practice.
JulieDo you think senior pets are just more likely to develop something like that?
Dr. LoSassoNot necessarily. In males, stone formation is caused by metabolic abnormalities most of the time — these aren't the same stones females get, which are called struvite. In males we generally see calcium oxalate, and some dogs get cysteine stones, caused by metabolic pathways that tend to occur a little later, though sometimes early. Those are also treated long-term with diet, sometimes successfully, sometimes not, and they can require repeat cystotomies to remove stones.
JulieAre any breeds more prone to these issues, in cats or dogs?
Dr. LoSassoNot that I've seen — there are certain breeds more prone to calcium oxalate versus cysteine stones, I'd honestly have to look it up. Again, that's generally smaller dogs, not really a big dog problem, though it could happen to anybody. Urinary tract infections and struvite stones in females can definitely happen in huge dogs or small dogs.
JulieWe just spoke about congestive heart failure, and you said you see maybe 40 to 50 of those patients a year. What about this issue — is it really common across the board?
Dr. LoSassoUrinary issues across the board are extremely common — I'd say four or five of those a week. And specifically what we call blocked toms, those urethral obstructions, I'd say we see about one of those a week.

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