Ureteral Stones

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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

Ureteral stones obstruct the flow of urine from the kidneys to the bladder and left untreated can cause destruction of the kidney.

Surgical removal of the stone is the treatment of choice if medical therapy (intravenous fluids) not effective.

The prognosis is favorable, unless the kidney is no longer functional.


anatomy of the urinary tractAnatomy

  • Urine produced by each kidney passes down a tube called the ureter to a reservoir, the bladder.
  • The ureters have a thick muscular wall that propel urine to the kidneys in concerted waves of contraction.
  • The inner tube (lumen) of a ureter is very narrow and small stones that form in the kidneys can become lodged as they try to pass down into the bladder.

Signs of ureteral stones

  • In humans, the passage of a stone down the ureter is more painful than giving birth to a child. In dogs and cats the passage of a stone down a ureter frequently goes unnoticed until the cat is ill from kidney failure.
  • Clinical signs of kidney failure may include anorexia, vomiting, urination suddenly stops, lethargy, and dehydration.
  • Sometimes a few stones will make their way to the bladder and then become lodged in the urethra thus the pet will not be in a lot of pain and will be able to urinate at all.

Why do stones develop?

  • The most common type of stone in cats is the calcium oxalate stone. The cause of this is largely not understood, but may be a defect in the metabolism of oxalic acid or excessive spill over of calcium into the urine by the kidney. Some Schnauzers are born with a defect that predisposes them to calcium oxalate stone formation.
  • Calcium oxalate stones may form if the pet has a tumor of the parathyroid gland or another type of cancer.
  • Ammonium biurate stones form if the pet has a liver disease such as a portosystemic shunt.
  • Urate stones form in Dalmatians due to a defect in metabolism
  • Some diets encourage stone formation.



  • Radiographs will confirm the presence of stones (place cursor over radiograph). The use of abdominal compression techniques while making the radiograph can make the stones more visible.
  • Ultrasound of the urinary tract will show the distention of the ureter and the pelvis of the kidney. In some cases the stones will also be visible on the ultrasound.
  • Nuclear scintigraphy may help to show if the kidney that is affected by the ureteral obstruction is functional, however, if the ureter is completely obstructed, the kidney will appear to be misdiagnosed as nonfunctional.
  • Blood tests that are routine include a complete blood count and chemistry profile. Urine testing for bacterial infection and chemical analysis is also recommended.


  • Medical therapy includes aggressive fluid therapy. Careful monitoring of such patients is essential as they can become overloaded with fluids and the lungs will become congested to the point of causing breathing difficulties. Radiographs are made intermittently during the treatment to see if the stones will pass into the bladder. If the stones have not moving in a 12 to 24 hour period, surgery will be recommended.
  • Surgical candidates for surgery include
    • patients that have stones in the ureter
    • dilation of the renal pelvis and ureter are noted
    • the kidney on the affected side has visible tissue (not just a bag of fluid due to chronic ureteral obstruction)
  • In order to have a very high success rate, the surgeon should use high magnification that is offered with an operating microscope and use very fine instruments and suture that is finer than human hair.
  • Surgery entails making an incision into the affected ureter very close to the stones (typically the incision is made a bit closer to the kidney) in a dilated region of the ureter. The stones are removed with fine instruments and the ureters are flushed. If the surgeon is uncertain about the patency of the ureters distal to the obvious site of obstruction, the bladder is opened and fluids are flushed down the ureter to the bladder. The surgeon will be able to visualize the flow of fluid at the opening of the ureter in the bladder.
  • After surgery, intravenous fluids will be administered to keep the patient well hydrated. Analgesics are administered to control pain. If infection is present, antibiotics may be continued for 2 to 3 weeks after surgery.

Care at home

  • The incision should be checked daily for signs of infection
  • Make sure that your pet is urinating well at home.
  • Offer canned food instead of dry food, as this will help to prevent stone reformation
  • The stones will be chemically analyzed and the surgeon may make recommendations about the type of diet that should be fed.


  • Generally the prognosis is good for the surgery to relieve the obstruction and for healing of the ureter(s). If the patient has diseased kidneys, the kidney values on the blood work may not normalize, but frequently will stabilize and the patient will have a good quality of life.
  • Stone may reform, therefore radiographs, blood and urine testing should be done every 3 months.

Frequently Asked Questions After Surgery - General Information

When should my cat have the first bowel movement after surgery?

  • Many cats will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a cat will not have regular bowel movements after surgery include:
    • The cat has been fasted prior to surgery
    • Cats do not eat well during the hospital stay
    • They frequently do not eat well when the go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as fentanyl patches, tramadol, morphine) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home a stool softener such as metamucil can be fed
    • Dose of metamucil 1/4 tsp per mixed in with each meal (canned cat food)

My cat had surgery and will not eat.  What can be done?

  • Offer smelly foods that contain fish such as tuna or smelly cat foods
  • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
  • Hand feeding;  place a small amount of food in the mouth so that they get the flavor
  • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature with your finger; it should  be only luke-warm.
  • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
  • Petting and stroking your cat frequently will help to stimulate appetite
  • Remember that most pets will not eat the first day or two after they get home from surgery
  • Appetite stimulants such as cyproheptadine may be helpful
  • If your cat refuses to eat anything for 7 days a stomach tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My cat is vomiting now that he/she is at home.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the cat usually just opens the mouth and fluid or food will be expelled.  Usually the regurgitant will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be happening the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics are a common cause of vomiting after surgery.  In order to see which medication is causing the problem the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • Unusual cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves with holding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then.  In order to decrease the acidity of the stomach Pepcid AC 0.5 mg/kg given by mouth twice daily for 5 days can sooth an upset stomach.  Metoclopramide is a good anti-vomiting medication for cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, which is called esophagitis.  This results in poor motility of the esophagus so water and food will accumulate in this structure.  In most cases esphagitis is self-eliminating and will resolve within two or three days. 
    • Regurgitation also can be caused by a neuromuscular degeneration of the esophagus and this problem will persist.  It is not associated with surgery, rather other underlying diseases.
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus, does not allow passage of food down the esophagus, thus the pet has persistent regurgitation.  This problem should be brought to the attention of your doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent such as sucralfate.  You should consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs as signs can be more subtle and they usually do not vocalize
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs and they should be given only for a few days

Is it okay for my cat to lick or scratch the incision?

  • If a cat licks the incision it will actually delay the healing process because they usually lick too much and traumatize the area.
  • Cats have a barbed tongue, therefore a lot of damage can be done in a short period of time
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Cats will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking/scrtaching the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • If the incision is over the chest an infant tee shirt can be put on your pet and the waist of the shirt fastened in place with an ace bandage or duct tape.
    • If the incision is over the paw or lower limb a bandage or sock could be put on and kept up with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a drugstore...it is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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