Ureter Stones in Dogs

Ureter stones (also known as bladder stones) can form anywhere in the urinary system and are a fairly common condition in both dogs and cats. These stones are made up of microscopic minerals present in the urinary system that have bonded to one other. The large majority of stones found in canines are found in the bladder itself. If these stones travel down into the urethra it can block off the passage of urine out of the bladder, which can quickly turn into an emergency.

When a dog's ureter, or the tube that connects the kidney to the bladder, is blocked by a formation of stones, it's referred to as ureterolithiasis. This condition can be extremely painful depending on the size of the stone. The stone will have a direct correlation to the breed, age, and sex of the dog that it is lodged in.

• Hematuria (blood in urine)
• Straining on urination
• Pain from urination
• Inappropriate urination in housetrained dogs
• Cloudy or foul-smelling urine
• Tenderness or pain in the bladder area
• Swelling or tightness of the bladder
• Loss of appetite
• Nausea
• Lethargy

Palpable tightness in the abdomen or inability to urinate may indicate that a blockage has occurred. This can be a life-threatening situation, and a veterinarian should be consulted as soon as possible.

Types

Canine bladder stones come in several varieties and are divided by the chemical composition of the stone itself. The chemicals which make up canine bladder stones are:

• Ammonium urate (uric acid)
• Calcium oxalate
• Calcium phosphate
• Cystine
• Magnesium ammonium phosphate
• Silica

In some cases, canine bladder stones are made up of a combination of two or more of these chemicals, and the chemical make up of the stone can influence the treatment choices.

Bladder stones are made up of microscopic mineral crystals which have become bonded to one another, at first sight appearing like grains of sand. These small crystals can continue to combine to create stones that can reach 3”- 4” in diameter. There are several causes that could trigger the stones to form.

• Acidity or alkalinity of the urine
• Some types of stones are more likely to form in acidic urine while others are more likely with more alkaline urine
• Bladder infection (Bacterial)
• Bladder infections can influence stone formation by increasing an enzyme called Urease and causing the urine to be more alkaline. This increases the risk of stone formation, in particular, the formation of stones with a high concentration of magnesium ammonium phosphate. Stones with a high concentration of magnesium ammonium phosphate accounts for approximately 50% of canine urinary stones.
• Concentrations of minerals in the urine
• The concentration of minerals can be affected by diet, metabolism, and hydration levels.
• Genetic predisposition
• Although specific types of stones seem to be more common in certain breeds, any breed can be genetically predisposed to forming stones.

Symptoms indicating that a ureter stone is present are likely to prompt your veterinarian to give your dog blood test to get a blood count and chemistry profile. An analysis of the urine will also be done to ensure there is no bacterial infection and to determine the PH of the urine and what types of crystals are present.

Diagnostic imaging is used to determine the size and position of any stones that are present. The most common forms of diagnostic imaging within most veterinarian clinics include radiograph (x-ray) and ultrasound. The ultrasound imaging is particularly useful in evaluating the size and shape of both the bladder and the kidneys. Most stones will show up rather clearly on a radiograph, although there are cases where a contrast agent will need to be introduced into the urinary tract in order to get visual confirmation. A newer non-invasive technology called nuclear scintigraphy may also be used. The nuclear scintigraphy allows for analysis of blood flow and function to the renal area.

Differing types of stones receive different treatments. Magnesium ammonium phosphate stones, also known as struvite stones, can sometimes be reduced in size or eliminated by putting your pet on a specialized prescription diet, such as Hill’s S/D formula. This specialized diet is not designed to be used long-term, and should only be used as long as your veterinarian recommends.

Stones with chemical compositions other than magnesium ammonium phosphate cannot be dissolved this way, and must be removed surgically. There's a high likelihood that your regular veterinarian will make a recommendation to a specialty veterinary surgeon for these procedures. The surgical procedure will vary depending on where the stones are located. Removal of a stone or stones from the bladder is a cystotomy, and if it has traveled down into the urethra, it is a urethrotomy. The surgeon may need to add a small permanent opening using a procedure called a urethrostomy.

An alternative surgical procedure, laser lithotripsy, has proven effective in a certain situation and is minimally invasive. This procedure requires advanced equipment, including a laser fiber that is inserted either through the urethra or through a small incision in the bladder and breaks apart the stones so that they can pass through naturally.

If there are already stones blocking the urethra it can become an emergency rather quickly, and the stones may need to be either forced back into the bladder using a technique called retrograde urohydropulsion, or urine may need to be removed from the bladder using a syringe.

Although the procedures are generally safe and successful reoccurrence is common.

If your canine is treated for struvite stones, you will want to continue feeding the prescription food for as long as your veterinarian recommends, usually between two and four months. After that period, your dog will either be put back on a regular diet or will be moved to specially formulated maintenance diet.

If surgical options were required, you will need to limit your pet’s activity for approximately 2 weeks as well as ensuring that any incisions are checked for infection. It is also imperative that you monitor your pet’s bathroom behavior as well, confirming that urine is flowing properly. It is common to see small amounts of blood in the urine for the first week or two after surgery.

Because reoccurrence is common, your veterinarian might recommend uranalysis and examinations on a regular basis. This ensures that any bladder infections or small crystals are more likely to be caught early and dealt with in a timely manner.