Introduction
Alkaline urine refers to urine that has a higher than normal pH, generally above 7.0. The normal pH range for cat urine is 6.0-6.5 1. Alkaline urine is considered abnormal in cats and may indicate underlying health issues with the urinary tract, kidneys, or metabolism2. Some of the most common causes of alkaline urine in cats include urinary tract infections, bladder stones, metabolic conditions, and certain medications. This article will explore the various causes, diagnosis, and treatments for alkaline urine in cats.
Kidney and Urinary Tract Infections
Urinary tract infections (UTIs) and kidney infections can commonly cause alkaline urine in cats [1]. When bacteria invade the urinary tract or kidneys, they produce urease, an enzyme that breaks down urea in the urine into ammonia and carbon dioxide. This process raises the pH of the urine, making it more alkaline.
The most common bacteria causing UTIs in cats are Escherichia coli, Staphylococcus species, and Proteus species [2]. Feline UTIs lead to symptoms like frequent and painful urination, straining to urinate, blood in the urine, and crying or whining when urinating. In severe cases, kidney infections can also cause vomiting, diarrhea, fever, and lethargy.
Bladder Stones
Certain types of bladder stones can cause alkaline urine in cats. Struvite stones, also known as magnesium ammonium phosphate stones, often form in alkaline urine environments with a pH over 7.0. According to VCA Animal Hospitals, struvite stones make up over 50% of stones in cats [1]. The alkaline environment allows struvite crystals to grow and aggregate into larger stones. Another stone type called urate stones can also raise urine pH.
Bladder stones irritate the bladder wall and urethra, causing various symptoms in cats. Common signs include straining and crying out when urinating, frequent attempts to urinate, blood in the urine, and urinating outside the litter box. Male cats may develop a urethral obstruction if a stone gets stuck, causing inability to urinate, vomiting, lethargy, and even death if left untreated. According to Mooresville Animal Hospital, even small stones can lead to significant irritation, inflammation, and infection [2].
Certain Medications
Certain medications can lead to alkaline urine in cats. For example, glucocorticoids like prednisone and dexamethasone can cause alkaline urine.
These medications work by suppressing the immune system, which reduces inflammation. However, they also affect the kidneys by inhibiting ion transporters that help excrete acids from the body. This leads to less acidic urine.
Another medication that may cause alkaline urine is phenobarbital, an anti-seizure medication. Phenobarbital works by depressing the central nervous system. As a side effect, it can reduce glomerular filtration rate, leading to impaired acid excretion by the kidneys.
Overall, medications like glucocorticoids and phenobarbital affect urine pH by interfering with the kidney’s ability to excrete acids and produce optimally acidic urine. Their mechanisms vary, but the end result of alkaline urine is the same.
Sources:
https://www.merckvetmanual.com/pharmacology/systemic-pharmacotherapeutics-of-the-urinary-system/controlling-urine-ph-in-animals
https://www.petmd.com/pet-medication/dl-methionine-dogs-and-cats
Kidney Tubular Acidosis
Kidney tubular acidosis (KTA) is a condition where the kidneys are unable to adequately acidify the urine (https://www.petmd.com/cat/conditions/urinary/c_ct_renal_tubular_acidosis). This leads to an accumulation of acid in the bloodstream (metabolic acidosis). In KTA, the renal tubules in the kidneys are unable to excrete acids normally.
KTA is often genetic in cats and seems to occur more frequently in Burmese cats. The defective acid secretion of the renal tubules leads to decreased urine acidity (alkaline urine). KTA can lead to the development of bladder stones as well since the alkaline urine allows minerals to precipitate out.
Bacterial Infection
One potential cause of alkaline urine in cats is an overgrowth of bacteria in the intestines. Normally, the digestive tract contains healthy levels of bacteria that aid in digestion. However, sometimes there can be an overgrowth of bacteria, especially Gram-negative bacteria like E. coli and Proteus species. These bacteria produce urease, an enzyme that breaks down urea from protein metabolism into ammonia. Ammonia reacts with water in the body to form ammonium hydroxide, which is a base. This raises the pH and leads to alkaline urine.[1]
Symptoms of intestinal bacterial overgrowth often include diarrhea, increased gas production, and occasional vomiting. The alkaline urine is detected on urinalysis. Diagnosis can be confirmed by culturing bacteria from a urine sample. Treatment involves antibiotics to reduce the bacterial overgrowth in the intestines and return the urine to a normal acidic pH.
Parathyroid Disorders
Overactive parathyroid glands, a condition known as hyperparathyroidism, is one common cause of alkaline urine in cats. The parathyroid glands regulate calcium levels in the body by secreting parathyroid hormone (PTH). When the parathyroid glands are overactive, they secrete excessive amounts of PTH, causing abnormally high calcium levels in the blood (hypercalcemia).
To counteract the high blood calcium, the kidneys excrete more calcium into the urine. This makes the urine more alkaline. Hyperparathyroidism occurs in up to 77% of hyperthyroid cats, often due to benign tumors of the parathyroid glands.
The abnormally high PTH stimulates increased reabsorption of calcium from bone, increased absorption of calcium from the intestines, and decreased excretion of calcium by the kidneys. All of these processes contribute to elevated blood calcium levels. Treatment involves resolving the underlying cause and may require surgery to remove overactive parathyroid glands.
Renal Tubular Damage
Renal tubular damage can lead to impaired urine acidification, resulting in alkaline urine. The renal tubules are responsible for filtering blood and reabsorbing nutrients while secreting waste products into the urine. Damage to these delicate structures can disrupt the kidney’s ability to excrete acids through the urine.
Renal tubular damage may be caused by toxins, chronic kidney disease, pyelonephritis, amyloidosis, medications, and congenital disorders [1]. The damaged tubules cannot adequately secrete hydrogen ions, leading to decreased urine acidification. This impairs the kidney’s ability to excrete excess acid, resulting in metabolic acidosis. The body tries to compensate by producing more alkaline urine to excrete some of the excess acid.
Because renal tubules are responsible for reabsorbing nutrients like proteins, damage to them can also lead to increased protein levels in the urine (proteinuria). This proteinuria is often seen concurrently with alkaline urine in cats with damaged renal tubules [2].
Diagnosis
To diagnose alkaline urine in cats, vets will typically start with a urinalysis to check the pH and look for signs of infection like bacteria, blood, or crystals. A urine sample is collected, either by cystocentesis (inserting a needle directly into the bladder) or free catch (collecting a mid-stream urine sample as the cat urinates). The urine is then analyzed for its pH level, with normal cat urine ranging from 6.0-6.5 pH. Alkaline urine has a pH over 7.0. The vet will also check the urine for the presence of bacteria, red blood cells, white blood cells, and crystals, which can indicate an infection or inflammation.
In addition to a urinalysis, bloodwork will also be done to evaluate kidney function, check calcium levels, look for diabetes, and identify any other systemic issues. Bloodwork provides important information about kidney function through tests like BUN (blood urea nitrogen) and creatinine. Elevated calcium levels may point to hypercalcemia as a cause of alkaline urine. The vet will also feel for any abnormalities in the kidneys or bladder through palpation.
Medical imaging like x-rays or ultrasound may be used to look for kidney stones or masses in the urinary tract. Cultures can also be done on urine samples to identify any bacterial growth. These diagnostic tests help pinpoint the underlying cause of alkaline urine, guiding the vet’s treatment plan.
Treatment
The treatment for alkaline urine in cats depends on the underlying cause.
If there is an infection present, such as a urinary tract infection or kidney infection, the veterinarian will prescribe antibiotics. Treating the infection should help resolve the alkaline urine.
For recurring alkaline urine not due to infections, vets may prescribe medications or diet changes:
- Ammonium chloride can be given to acidify the urine. This helps prevent crystals and stones from forming in alkaline urine (1).
- Methionine supplements can also help acidify the urine pH (2).
- Prescription urinary foods that promote acidic urine, such as Hills c/d or Royal Canin Urinary SO (3). These foods contain added minerals and salts to lower urinary pH.
- Increased water consumption, through wet food diets or adding water to dry food, helps dilute the urine.
Monitoring the cat’s urine pH at home with test strips helps ensure the treatment is working to acidify the urine. Routine veterinary checkups are also recommended to monitor urinary health.
Sources:
(1) https://www.wikihow.com/Lower-the-pH-of-Cat-Urine
(2) https://wagwalking.com/cat/condition/too-much-acid-body
(3) https://www.justanswer.com/cat-health/ebguo-cat-s-urine-high-alkaline-level-according.html
