567 — Canine Bladder Stones: Diagnosis and Treatment

Canine Bladder Stones: Diagnosis and Treatment Dr. Marty Greer, DVM joins host Laura Reeves for a deep dive on bladder stones in dogs, how to diagnose and treat them. The following information is provided by Dr. Greer. Bladder stones are the quintessential “which came first, the chicken or the egg” question. By this, we mean that a dog can have a bladder symptoms that are caused by a bladder stone, or the bladder infection can cause bladder stones to form. Which then becomes a vicious cycle. There are two basic types of bladder stones – the first, struvite stones associated with a bladder infection or second, any of the following other bladder stones, caused by a metabolic disturbance that causes a stone to form in the urinary tract. How do bladder infections cause bladder stones? An undiagnosed, under-treated or recurrent bladder infection can lead to the development of struvite bladder stones. This is the most common type of bladder stone. Or another type of stone can cause irritation to the bladder which can cause a stone to form that is partly any of the types of stone below combined with a struvite stone. These form like a pearl in an oyster – the irritation of the infection or other stone type can cause a struvite coating on an existing bladder stone. Many metabolic stones are associated with a particular breed or disease condition causing minerals to deposit in the bladder, forming stones. These metabolic stones form with long term supersaturated minerals in the urine. With time, the crystals form which develop into a bladder stone. Other factors are the pH of the urine, inhibitors and promotors of stone formation, and macrocrystalline matrix. If something like suture is in the bladder, this can also allow a stone to form. Fortunately, most stones in the urinary tract are in the bladder itself, where they are accessible surgically. Stones in the kidney or ureter (tube from the kidney to the bladder) are not easily managed surgically or by physical removal. Stones that form in the bladder and pack together like sand in a funnel or slip from the bladder into the urethra (tube from the bladder to the outside of the body) cause urinary obstruction. This is a true medical emergency, more common in males that females due to the length and shape of the urethra, the tube from the bladder to the outside. Males have a design flaw – their urethra is more narrow and curved, causing a greater likelihood of urinary obstruction. On the other hand, females have a design flaw, a shorter wider urethra just below the rectum that allows bacteria to ascend into the bladder, increasing the risk that a female will have a bladder infection. That infection can often lead to the formation of struvite stones. Symptoms Symptoms of bladder disease can be virtually non-existent to severe. The symptoms can vary:

1. No signs or very subtle signs of discomfort or urinary accidents.
2. Signs of blood in the urine (often not noted until there is snow on the ground or when the urine is wiped up and blood is seen on a white towel), straining to urinate, frequency of urination, inappropriate urination, +/- fever, pain, and/or urinary incontinence. Dogs are rarely “sick” with a bladder infection – they eat, drink, and act normally other than increased trips outside or urinary accidents on the floor.
3. If obstructed, there will be abdominal pain, vocalizing, vomiting, dehydration, depression, heartbeat irregularities, bladder distension, in advanced cases, bladder rupture, collapse and death.
4. Blood work can show elevated BUN and creatinine, kidney values if obstructed.
5. Blood work may show elevated calcium if calcium oxalate stones are present.
6. Blood work may show liver dysfunction in patients with urate stones.

Below is a table showing the different types of bladder stones, comparing the composition, cause, prevention and treatment options. Type of stone Cause Prevention Treatment Struvite or magnesium ammonium phosphate hexahydrate. Usually located in bladder but can be in renal pelvis. This is the most common stone in dogs at an incidence of  53%. More common in female than male dogs, usually young dogs. Frequently multiple. Secondary to undermanaged bacterial bladder infection incl most commonly Staphylococcus spp., but less commonly seen urease-producing bacteria include Proteus spp. or Enterococcus spp. Rarely Escherichia coli, Pseudomonas spp., Klebsiellaspp., Corynebacterium urealyticum, or Ureaplasma/Mycoplasma spp.  May have a genetic component. Breeds: American cocker spaniel Bernese Mountain dog Bichon frise Dachshund Golden retriever Lhasa apso Miniature poodle Miniature schnauzer Pekingese Poodle Rottweiler Saint Bernard Shih tzu 1. Find and manage cause of recurrent bacterial bladder infection. 2. Preventive diets lower in protein, phosphorus and magnesium including: Royal Canin® Veterinary Diet Urinary SO, Hill’s Prescription Diet c/d™, Hill’s Prescription Diet w/d™, and Purina Pro Plan Veterinary Diets UR Urinary St/Ox. 3. Increased water intake 4. Weekly monitoring of urine pH and intervention if pH rises. 5. Periodic imaging for early detection of recurrence. 1. Dissolution diet combined with appropriate long-term antibiotics. May be dissolved medically unless obstructed. 2. Acidifiers such as D,L-methionine combined with appropriate long-term antibiotics. 3. Surgical removal or Cystoscopic retrieval 4. Physical removal. Calcium oxalate or calcium oxalate combined stones. Usually in the bladder but can be in the renal pelvis. 2nd most common bladder stone seen in dogs. More common in males, middle aged. Patients who have increased urinary excretion of calcium /or oxalate. May include Cushing’s disease, primary hyperparathyroidism, or cancer causing elevated calcium levels. Obesity. Steroid administration. Genetic predisposition. Bichon frise Cairn terrier Chihuahua Lhasa apso Maltese Miniature poodle Miniature schnauzer Pomeranian Shih tzu Yorkshire terrier Calcium oxalate uroliths recur 8-9% after 6 months, 35-36% after one year, and approximately 50% after 3 years. 1.Diet Royal Canin® Veterinary Diet Urinary S/O Lower Urinary Tract Support, Purina Pro Plan Veterinary Diets UR Urinary St/Ox™, Hill’s Prescription Diet w/d™, and Hill’s Prescription Diet u/d™. 2.Potassium citrate orally. 3.Thiazide diuretics. 4.Vitamin B6 There is no known way to dissolve this stone type so must be physically removed. Cystine More common in males, young to middle aged. Occurs secondary to cystinuria, which is caused by increased levels of cystine excreted into urine. Uncommon. Inherited mutation of SLC3A1 gene, which leads to defective amino acid transport, described in the Newfoundland, Labrador retriever, and in the cat. Missense mutation in SLC7A9 is another cause of cystinuria in the dog. Androgen-dependent cystinuria has been described in dogs. Genetic Test: DNA testing for genetic traits is available at vetGen, Penn Gen, Paw Print Genetics, DDC, Animal Genetics, and UC Davis Veterinary Genetics Laboratory in the USA, as well as Animal Genetics-UK, Laboklin, and Animal DNA Diagnostics in Europe. Breeds: American pit bull terrier Australian cattle dog Bullmastiff Chihuahua Dachshund English bulldog French bulldog Labrador retriever Landseer Mastiff, English Miniature pinscher Newfoundland Rottweiler Scottish terrier South African boerboel Staffordshire terrier, American/bull 1. Feed protein-restricted, low-sodium diet. 2. Potassium citrate to maintain alkaline urine. 3. Some patients may also require 2-MPG therapy. 4. Do not breed affected dogs, their parents, or any other offspring. 5. For breeds with androgen-dependent cystinuria, castration can help in controlling cystinuria. 1. Low protein, low sodium, alkalizing diet: Hill’s Prescription Diet u/d™ and Royal Canin® Veterinary Diet UC Low Purine 2. Potassium citrate to alkalinize urine with a pH goal of 7.2 to 7.5 and dilute urine. 3.Physical removal. Xanthine incidence  0.5 to 1% incidence of bladder stones in dogs An uncommon type of purine urolith. Adults 2 to 6 years of age.  No sex predilection. Causes: Allopurinol administration Diet Idiopathic, unknown Genetic, hereditary: Cavalier King Charles spaniel Dachshund English cocker spaniel...