Small animal clinical nutrition - lower urinary tract diseases Flashcards
LUTD
lower urinary tract disease
includes both urolithiasis and idiopathic cystitis as well as bacterial infections of the LUT
MOST COMMON CAUSE OF LUTD IN CATS OF AGE UNDER 10 YEARS
idiopathic cystitis
Describe idiopathic cystitis in cats.
- Symptoms of LUTD resolve spontaneously in 3-7 days.
- No obvious cause
- No specific treatment but:
- Pain management, spasmolytic and supportive treatment
- Glycosaminoglycans (N-acetyl glucosamine vs glucosamine
hydrochloride e.g. product Cystaid) - For prevention: enrichment of environment, decrease stress etc.
- In cases of stress, L-tryptophan, hydrolyzed milk protein: casein or alpha-casozepine by mouth.
- +Pheromone based solutions
- Sufficient water intake
Mechanism of action why Glycosaminoglycans (“GAGs”) such as N-acetyl glucosamine help support urinary tract health? (3)
e.g. product Cystaid
GAGs are key components of the bladder’s mucosal lining, forming a protective layer that shields the underlying bladder wall from harmful substances like bacteria, toxins, and crystals.
GAGs prevent the adhesion of harmful bacteria (such as E. coli) to the bladder wall.
By maintaining the integrity of the bladder lining, GAGs help minimize inflammation, irritation, and damage to the bladder wall, which is often seen in conditions like feline idiopathic cystitis (FIC).
Mechanism of action why L-tryptophan helps support urinary tract health? (2)
e.g. product Calmex
through its role in reducing stress and anxiety
L-tryptophan is a precursor to serotonin, a neurotransmitter that helps regulate mood and reduce stress. Higher serotonin levels promote relaxation and decrease anxiety.
Chronic stress activates the sympathetic nervous system, leading to increased bladder muscle tension and decreased urine flow. L-tryptophan, by promoting relaxation, helps alleviate this tension and normalize bladder function.
Mechanism of action why hydrolyzed milk protein: casein or alpha-casozepine helps support urinary tract health? (1)
e.g. product Zylkene, RC Fe Calm
Hydrolyzed milk proteins such as Alpha-casozepine, a peptide derived from casein, has calming properties similar to the neurotransmitter GABA. It interacts with GABA receptors in the brain, promoting relaxation and reducing anxiety without causing sedation.
HOW TO MAKE CAT TO INCREASE WATER INTAKE? (6)
ENSURE, THAT THE DRINKING WATER FOR PETS IS ALWAYS FRESH
WATER TO EVERY ROOM
DIFFERENT VESSELS IN DIFFERENT PLACES AND LEVALS
CAT FOUNTAIN OR FAUCET CONTANTLY OPENED SLIGHTLY
FLAVORED WATER?
PREFER CANNED FOOD TO DRY FOOD
Uroliths form from
crystals that precipitate in the urinary tract.
DIFFERENT MINERALS ARE INVOLVED:
Ca-OXALATE
CYSTINE
AMMONIUM URATE
STRUVITES
MIXED
SILICA
Soluble or insoluble urolith: struvites.
soluble, treat by dissolution
or non-surgical (urohydropropulsion) or surgical removal
Soluble or insoluble urolith: oxalates
insoluble, non-surgical or surgical removal
Soluble or insoluble urolith: phosphates
insoluble, non-surgical or surgical removal
Soluble or insoluble urolith: urates
insoluble, non-surgical or surgical removal
Soluble or insoluble urolith: cystine
soluble, treat by dissolution
or non-surgical (urohydropropulsion) or surgical removal
Struvite urolithiasis is formed when urine is saturated with (3)
magnesium, ammonium and phosphate salts.
(Remember Struvite stones are made of magnesium-ammonium-phosphorus)
Struvite stones are mostly a result of infections particularly those caused by urease-producing bacteria (e.g., Staphylococcus or Proteus species).
struvite crystals thrive in alkaline environments >7.0 pH.
Struvites typical to what age group of cats?
more common in cats age 1-8 years
Struvite urolithiasis may occur in dogs with…?
urease-producing bacterial infection
(e.g., Staphylococcus or Proteus species).
These bacteria produce urease, an enzyme that breaks down urea into ammonia, leading to an increase in urine pH and higher concentrations of ammonia and phosphate.
Struvite urolithiasis in cats is characterized as…?
sterile struvites (without bacterial involvement)
Struvite stones can be dissolved by
feeding the right acidifying diet in cats for 2-4 weeks, for dogs for 2-3 months.
Risk factors predisposing to struvite urolithiasis. (4)
- Alkaline urine; struvite crystals thrive in alkaline environments.
- High concentrations of magnesium, ammonium and phosphates.
- One large meal per day (frequent little meals facilitate the production of more acidic urine and reduce the risk of struvite in cats)
- Bacterial pollution
Ideal urine pH for crystal dissolution is
6.0-6.3
An acidifying pet food additive
calcium sulphate dihydrate
Feeding frequency and effect on crystals/urolithiasis.
One large meal per day may predispose to development of uroliths.
Frequent small meals facilitate the production of more acidic urine and reduce the risk of e.g. struvites in cats.
High cereals quantities in food may be responsible for
struvites due to urine alkalizing properties.
Why do moderate quantities of high quality proteins aid in avoiding urolithiasis?
meat proteins acidify urine and struvites don’t like an acidic environment
Risks associated with over-acidification e.g. in struvite dissolution. (5)
- Metabolic acidosis
- Reduces K levels
- Bone demineralization
- Kidney disease
- Risk of calcium oxalate stones
Therefore its not recommended to use additional urine acidifier supplements if already using a specialty diet.
Ideal pH for prophylaxis of struvites?
What 3 minerals should be decreased in the diet?
pH of <6.5 ( but not <6.3)
Less:
magnesium
sodium
phosphorus
(Remember Struvite stones are made of magnesium-ammonium-phosphorus)
Principles of clinical diet for the treatment of struvite urolithiasis. (4)
- Reduce the intake of specific minerals with food
- Produce urine with a pH, that is unfavorable for the deposition of crystals, and encourages the dissolution of struvites in urine. (make the urine acidic because struvites like alkali)
- Reduced protein (urine contains less urea available to urease-positive bacteria)
- Ensure treatment of bacterial infections
Calcium oxalate urolithiasis forms when (2)
there is an excess of calcium and oxalate in the urine, and under the influence of high molecular weight proteins.
Certain HMWPs can e.g. bind calcium ions in urine. When calcium is complexed with these proteins, it can lead to an imbalance in the solubility of calcium and oxalate. They also act as scaffolding for crystals to begin to form.
Calcium oxalate urolithiasis forms in what pH.
Calcium oxalate crystals can form in both acidic and neutral to slightly alkaline urine, but they are more commonly associated with urine that is acidic (pH less than 7.0).
A diet that leads to more acidic urine can promote the crystallization of calcium oxalate.
Risk factors predisposing to Calcium oxalate urolithiasis (9)
- Hypercalcemia – resulting in increased urine calcium excretion
- Hyperadrenocorticism (cortisol promotes renal calcium excretion)
- Metabolic acidosis (calcium removal from bones)
- Eating of diets enriched with urine acidifiers in cats (urine pH <6.2)
- Deficiency of vit B6/pyridoxine (glyoxylate accumulation)
- Genetic predisposition
- Reduction of urine volume and decrease of urine concentration
- Low phosphorus diet (makes for high Ca+)
Elevated oxalate levels in urine (hyperoxaluria) can result from: (2)
Dietary Sources: Some foods are high in oxalates, including spinach, beets, nuts, and certain types of grains.
Metabolic Disorders: Certain conditions can lead to increased oxalate production in the body, such as primary hyperoxaluria.
Why can deficiency of vitamin B6 predispose to calcium oxalate uroliths?
Vitamin B6 is a co-factor for the enzyme glyoxylate aminotransferase, which plays a crucial role in converting glyoxylate (a precursor to oxalate) into other metabolites.
When vitamin B6 is deficient, this conversion is impaired, leading to an accumulation of glyoxylate, which can then be converted into oxalate. This increases the level of oxalate in the urine (hyperoxaluria), promoting calcium oxalate stone formation.
Why can a low phosphorus diet predispose to calcium oxalate uroliths?
When dietary phosphorus is low, the body may attempt to maintain normal serum calcium levels by increasing calcium absorption from the intestine
creating an imbalance in calcium and phosphorus levels, leading to hypercalciuria. Elevated urinary calcium increases the risk of crystallization
+ Inadequate phosphorus can affect the production of certain metabolites that help regulate oxalate levels.
Recurrence of calcium oxalate is how much
36% over the span of a year if precautions aren’t taken.
How to get rid of calcium oxalate uroliths?
should be removed surgically or via flushing (urohydropropulsion)
Nutritional protocol is directed to minimize the recurrence of urinary stones and to prevent the growth of stones that remain in the urinary tract, but not dissolving them.
Ways to prevent calcium oxalate stone formation. (5)
reduce urine acidity (make more alkaline)
dilute the urine to <1.030 SG
reduce the release of protein metabolic residues
reduce both Ca+ and oxalate concentrations
promote the effect of mediators that inhibit stone formation (citrate, Mg+, pyrophosphate)
What type of food additives could you use for management of calcium oxalate stone?
alkalizing additives such as potassium citrate (also binds Ca+)
you want the urine around pH 7.5 to avoid calcium oxalate precipitation
What composition diet will help prevent calcium oxalate urolithiasis? (6)
decreased protein content (less protein = less acidic and calcium-oxalate likes acidic)
decreased vit D (less GI Ca+ absorption)
increased magnesium (binds oxalate)
increased vit B6 (less oxalate)
increased dietary fiber (makes less acidic and reduces Ca absorption)
don’t limit phosphorus
Who gets Ammonium urate stones? (4)
*„Breed induced” in dalmatians and english bulldogs that have defective uretic acid metabolism.
- Very rare in cats
*Dogs with portosystemic liver shunt, lack of transport of urates to liver cells.
Urate is a product of
purine metabolism, is converted into metabolic intermediate allantonin in normal dogs, but not in e.g. dalmatians with reduced ability to reabsorb urates and
therefore increased excretion of it via urine.
Treatment of ammonium urate stones in dogs. (4)
*Drug Allopurinol: Dogs receiving allopurinol should be fed with a low purine food to avoid the risk of xanthine stones (low offal diets, low protein diets).
*Potassium citrate is an alkalizing substance (NaHCO3 contains Na and this may contribute to urinary excretion of calcium).
*In young dogs, favor surgical approach if necessary (low protein diet is not good during growth period).
For English bulldogs favor surgical approach due to risk of cardiomyopathy, if dietary proteins are restricted.
What drug is used to treat urate stones and how?
Drug Allopurinol is a competitive inhibitor of xanthine oxidase. It works by inhibiting the production of uric acid.
Xanthine oxidase is an enzyme that plays a key role in the purine degradation pathway, converting hypoxanthine to xanthine and then xanthine to uric acid.
By inhibiting xanthine oxidase, allopurinol effectively decreases the conversion of purines into uric acid, leading to reduced uric acid levels in the blood and urine.
(Also treats gout in humans)
Treatment of ammonium urate stones with allopurinol.
- For dissolution 15 mg/kg KM PO q12h
- Prevention 5-10 mg/kg/KM PO q12h
Dogs receiving allopurinol should be fed with a low purine food to avoid the risk of xanthine stones (low offal diets, low protein diets).
Favor surgical approach For English bulldogs and growing dogs due to risk of cardiomyopathy, if dietary proteins are restricted.
Typical patient signalment for cystine stones.
Extremely rare in cats, rare in dogs.
*English bulldogs, newfoundland dogs, dachshunds, Irish terriers, basset hounds
*Almost exclusively males
(except Newfoundland dogs - autosomal recessive mutation in the SLC3A1 gene)
Cystinuria is characterized by
high concentrations of the amino acid cystine in the urine, leading to the formation of cystine stones in the kidneys, ureters, and bladder. It is a type of aminoaciduria. “Cystine”, not “cysteine,” is implicated in this disease; the former is a dimer of the latter.
is an inherited defect in the transport of cystine in the nephrons.
Are cystine crystals soluble?
Ways to treat? (4)
Cystine crystals and stones are soluble to some extent (solubility is inhibited in pH 5,5- 7,0 , but 2x more probable in alkaline pH 7-8).
*Alkalization of urine with potassium citrate (100 mg/kg/BW/DAY)
*Low protein diets and regular and sufficient water consumption
Can be also be Dissolved with drug tiopronin but if unsuccessful then surgical removal is indicated.
What is tiopronin?
is a medication used to control the rate of cystine precipitation and excretion in the disease cystinuria.
tiopronin 20 mg/kg/BW PO q12h
leads to 60% likelihood of successful cystine crystal dissolution but takes 1-3 months.
Describe SILICA urinary STONES.
*Uncommon in dogs, extremely rare in cats
*Diets high in corn gluten or soybean hulls may be contributory
- Bladder and urethra predilection sites.
- German shepherds, old English sheepdogs etc.
- Occasionally reoccur after surgery
*Effect of urine pH on silicate solubility not established.
