Visiting Vet: Ureter blockage

Sadly, the hoofbeats were those of a zebra.

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Sugar and Spice. — Sugar's family

Sugar and Spice. Two tortoiseshell siblings. When the pair were 5 years old, Spice started gradually losing weight, despite a ravenous appetite. At first I wasn’t too concerned, telling her owner the old adage, “if you hear hoofbeats, don’t look for zebras.” In other words, it was unlikely to be anything unusual in this seemingly healthy, young kitty. Except it was a zebra. We ultimately diagnosed exocrine pancreatic insufficiency, which is rare in cats. Spice has been doing well now for two years with pancreatic enzymes in her food and B-vitamin injections. 

Then this year, Sugar began losing weight gradually. Unlike Spice, Sugar’s appetite was decreased. She was slightly lethargic, but otherwise seemed fine. No coughing, vomiting, or diarrhea. On exam she was still plump, alert, not pained in any way. Again, I wouldn’t have worried … except for what had happened with Spice. “Let’s do basic bloodwork,” I advised. I wasn’t expecting anything major. Maybe she had hyperthyroidism, a common endocrine abnormality in middle-aged cats. In any case, running a few tests would reassure both her owners and me. 

But the lab results were distressing. Sugar had severe kidney disease. Kidney failure in cats can be acute or chronic, and occur for many reasons. The most common is age-related kidney failure. Sugar was far too young for that. I made my differential diagnosis list. Infection, toxins, cancer, congenital abnormalities, obstruction. I called her family to get more history and discuss next steps. Further diagnostics were needed to determine cause, specific treatment, and prognosis. 

Antifreeze ingestion causes renal failure, and is fatal unless caught very early. Lily ingestion can cause acute renal failure in cats, and there had been lilies on their porch a few weeks back, but her owners were fairly sure she had not bothered the bouquets during the short time the flowers were there. What about infection? We should collect a urine specimen for culture. To diagnose obstruction, cancer, or congenital causes of renal failure (such as a condition called amyloidosis) would require radiographs, ultrasound, and possibly biopsy. 

Considering the markedly abnormal lab numbers, despite Sugar’s minimal signs of illness I offered immediate referral to specialists at an emergency/critical care hospital, but we decided to start with a few tests here first. Sugar still looked fine when we admitted her bright and early next morning. We got a urine sample. Urinalysis was consistent with renal failure, but did not help establish the cause. The culture to rule out bacterial infection would take at least three to five days. X-rays were not remarkable, except for one slightly odd thing. Individually, both kidneys were within what is considered normal size range, but comparatively, the right kidney was smaller, the left noticeably larger. 

I consulted an internal medicine specialist by phone. “Whatever is going on has probably been developing gradually,” she said. “Otherwise we would expect vomiting with these lab numbers.” We discussed the size discrepancy of the kidneys. Could it be normal variation? The specialist thought maybe not. It was time for Sugar to get a detailed ultrasound, and start aggressive treatment and round-the-clock monitoring off-Island.

Zebras. I hate zebras. Ultrasound confirmed evidence of chronic disease in both kidneys, and changes in her right kidney consistent with obstruction of the ureter. The ureter is the tiny tube that carries urine from kidney to bladder (not to be confused with the urethra, which carries urine from the bladder out of the body, and often blocks in neutered male cats). If the ureter gets blocked, urine backs up into the kidney, and can lead to renal failure. In cats, the blockage is most often the result of “stones,” technically called ureteroliths, with strictures being the second most common cause. Other causes include tumors and clots of blood or pus associated with infection. Obstruction can be complete or partial, and can affect one or both kidneys. Prognosis depends on all of the above. Clinical signs may include loss of appetite, vomiting, lethargy, weight loss, excessive drinking and urination, difficulty urinating, blood in the urine, dehydration, and abdominal pain, but in some cases a cat may exhibit no symptoms at all.

Diagnosis can be challenging. Blood tests will be consistent with kidney disease, but do not indicate the reason. Ureteroliths are often too small to see on x-rays, and even with ultrasound, one study showed that in almost a quarter of cats with ureteroliths, ultrasound couldn’t visualize them. Ultrasound can, however, usually establish the diagnosis of ureteral blockage, and often determine if something like a tumor is the underlying cause. Urinalysis, including culture, is always warranted, as in one study about one-third of cats with ureteral obstruction had bacterial urinary tract infections.

Treatment requires relieving the blockage or diverting the urine around it. Occasionally ureteroliths will pass spontaneously with fluid therapy and medication, but most often surgical intervention is needed. There are several possible procedures, including traditional surgery and ureteral stenting, but Sugar’s owner did his homework and got me up to speed on the latest state-of-the-art option, called the subcutaneous ureteral bypass device (SUB). For the past two years, Angell Animal Medical Center in Boston has been using the SUB procedure as the best option in cats with ureteral obstruction to reestablish urine flow from kidney to bladder, though long-term survival data are still being collected. 

Poor Sugar. She clearly had chronic kidney disease, but now a ureter obstruction and severe renal failure. Considering Spice’s “zebra” diagnosis, I had to wonder if these littermates were born with some genetic abnormality predisposing them to such uncommon illnesses. Despite 24 hours of aggressive medical treatment, Sugar’s condition was deteriorating. The kidney damage was profound. A SUB procedure was unlikely to help. Her family did not want her to suffer needlessly, so they went to the Cape and said goodbye. Their loss is still fresh, but they wanted me to go ahead with this column, in hopes the information may one day help some other sweet, sweet kitty. Rest in peace, Sugar.