kidney disease | urinary bladder problems | urethral problems
Introduction:Urinary problems are one of the most common reasons that a cat is brought into a veterinary clinic for examination. The term feline urinary tract disease can be used to describe problems occurring in the kidneys, ureters, urinary bladder, or urethra. In general, a catís urine should normally be yellow and clear.
The following pages will discuss the major problems associated with each urinary structure, as well as proper terminology, clinical signs, diagnosis, and treatments. The introduction and terms discussed on page E889 can be very useful for additional information.
Upper Urinary Tract Disease
- Nephritis - Inflammation of the kidney.
- Pyelonephritis - Inflammation of the kidney beginning at the "pelvis." The pelvis is the enlarged, hollow area inside the kidneys where urine pools before entering the ureter. Pyelonephritis is generally due to a bacterial infection.
- Glomerulonephritis - Inflammation of the kidney beginning at the level of the thousands of microscopic glomeruli. The glomeruli are the tiny structures in the kidney which filter water and waste products from the blood. Glomerulonephritis is thought to be due to destruction of the glomeruli by the bodyís own immune system.
- Medullary washout - Loss of the salt concentration gradient inside the kidney. The kidneyís ability to conserve water depends on a difference in saltiness inside the kidney. The outer part of the kidney (cortex) tends to be less salty than the inside (medulla). As diluted urine flows deeper into the center of the kidney, the increasing saltiness pulls water from the urine back into the body. This function allows the body to conserve water and concentrate urine. Medullary washout is, in essence, a loss of the ability to conserve the bodyís water stores by concentrating the urine. This can occur as a complication of various diseases of the kidney.
- Uroliths (stones) - Mineral deposits inside the kidneys or other parts of the urinary tract.
- Renal insufficiency/failure - State or condition where the kidneys are not functioning on an acceptable level. This is usually due to extreme inflammation and/or death of kidney tissue. Toxic compounds which should normally be filtered out of the bloodstream and into the urine begin to accumulate in the body. Death of enough kidney tissue will eventually lead to complete failure of the kidneys and death of the animal.
- Renal neoplasia - Cancer of the kidneys.
Clinical Signs: Clinical signs of kidney disease vary with the condition. Minor inflammation or irritation of the kidneys may not be detected at all.
- Pyelonephritis (bacterial infection of the kidney tissue) will usually result in a listless animal with a high fever and little interest in food. If pyelonephritis continues untreated and involves both kidneys, it can eventually result in kidney failure.
- Small kidney stones may be present for years without causing any obvious problems. Large stones lodged in the kidney may cause blood in the urine (hematuria), abdominal pain, and blockage of the affected kidney. Stones which dislodge from the kidney and pass into the small ureter tube may cause hematuria, abdominal pain, internal bleeding, and urine leakage into the abdomen (a life-threatening situation).
- Cancer of the kidney may cause abdominal pain, abdominal enlargement, vomiting, diarrhea, and hematuria. Cancer in the kidney may also cause pyelonephritis.
When 66-75% of kidney tissue becomes non-functional, the animal usually begins to exhibit classic signs of kidney failure: excessive thirst, increase in the frequency of urination (due to loss of ability to concentrate urine), vomiting (due to buildup of toxic waste products in the bloodstream which cause nausea), weight loss, lethargy, anorexia, and dehydration. Occasionally, certain animals will slow down in urine production rather than produce large quantities of dilute urine. Decreased urine production tends to be worse than increased production.
A clean, fresh urine sample is essential for a diagnosis. Urine specimens may be obtained by catching a sample during normal urination (easiest, but poorest method for diagnostic purposes), insertion of a catheter into the bladder through the urethra, or by cystocentesis. Cystocentesis is the insertion of a sterile needle through the body wall directly into the urinary bladder. Cystocentesis is the method most likely to yield the most accurate results.
- Blood and urine testing are the key tests for the initial detection of kidney insufficiency/failure.
- Radiographs of the abdomen are useful in diagnosing many kidney stones (uroliths); however, not all stones will be visible on radiographs. Radiographs may also be helpful in diagnosing cancer of the kidney. Dye may be introduced into the bloodstream and radiographed as it passes through the kidneys. This allows a better view of kidney size, shape, and any possible blockages found therein. This technique is termed Intravenous Pyelography (IVP).
- Ultrasound is useful in discovering kidney stones (uroliths), including those which are not visible on X-rays. Abnormalities in kidney structure, shape, or composition can also be detected through the use of ultrasound. Ultrasound may also be used as a guide in obtaining a biopsy specimen from the kidney.
- Kidney biopsies and subsequent histopathology (microscopic evaluation of the tissue) are important in diagnosing certain types of kidney disease, such as glomerulonephritis or cancer (neoplasia).
In order to assess the patientís progress, repeated testing is vital while treating many types of kidney disease. For additional information on many of the above tests, see Section D.
Treatment: Treatment varies with the condition.
- Nephritis requires correcting the underlying problem. This may include antibiotic therapy for the patient with pyelonephritis, and immune system suppression for the patient with glomerulonephritis.
- Kidney stones (uroliths) often require removal via surgery. Some newer techniques are being explored which can break up stones into smaller fragments and allow them to pass without surgery.
- Kidney insufficiency or failure requires long term diet restrictions in protein and salt, fluid therapy or diuresis (causing the animal to urinate), appetite-stimulating drugs, and a variety of other medications. Kidney transplantation in animals is under study; it may be some time, however, before this option is made available to the general public.
- Cancer of the kidney requires surgical removal, a procedure which may challenge even the most experienced surgeons. Chemotherapy usually follows removal, but this depends on the type of cancer.
Lower Urinary Tract Disease
Risk Factors:Neutered male or spayed female cats that are between the ages of 1-10 years are more at risk for problems. Cats that are obese, eat dry food, use indoor litter boxes, and do not consume adequate amounts of water are also at an increased risk for lower urinary tract disease.
- Cystitis - Inflammation of the urinary bladder. This is a common problem that may be due to any of the following causes:
- Traumatic cystitis - Any trauma to the posterior (back) half of the animal may lead to inflammation of the bladder wall. Bruising and swelling usually occur within minutes to hours of the trauma. Within a couple of days, bacterial infection of the abnormal tissue may become a complication.
- Drug-induced cystitis - Some drugs, notably cyclophosphamide, a chemotherapy drug, can cause severe inflammation of the urinary bladder.
- Infectious cystitis - Bacteria are the most common agents; however, yeast and some fungal infections may occur.
- Polypoid cystitis - Usually the result of chronic infection or bladder stones (uroliths), this type of inflammation is characterized by the presence of polyps (non-cancerous growths) inside the urinary bladder.
- Rupture of the urinary bladder - If traumatized when distended with urine, the urinary bladder may rupture, spilling urine into the abdomen. Peritonitis (inflammation of the inner lining of the abdomen) will result if untreated.
- Neoplasia of the urinary bladder - Cancer of the urinary bladder.
- Uroliths (urinary tract stones) - Mineral deposits found inside the urinary bladder.
- Persistent urachus - Birth defect in which the bladder continues to leak urine out the umbilicus (belly button). The communication is normally present in the unborn fetus, allowing fetal urine to pass into the placenta where it is absorbed and excreted by the mother. If the communication remains after birth, urine will leak out of the umbilicus.
Clinical Signs: Abnormalities in the act of urination or in the appearance or consistency of the urine itself make up the majority of clinical signs of urinary bladder disorders. Increased frequency of urination usually accompanies irritation of the urinary bladder, regardless of the cause. Straining to urinate may simply indicate irritation and discomfort, or may indicate blockage of the outflow of urine, possibly because of a urolith or a polyp. An animal with complete blockage of urine is in need of emergency veterinary care. Blood, mucous, or even pus may be present in the urine of animals with cystitis. The urine may also be thick and carry a foul odor. Rupture of the urinary bladder may lead to distention of the abdomen with urine and abdominal pain. Severe infections and a fever may follow.
- Urine analysis is usually the first diagnostic step, especially if the urine is abnormal in consistency or appearance. Microscopic evaluation of the urine may reveal abnormal cells, crystals, and bacteria.
- Urine culture and sensitivity can detect specific infections.
- Radiographs may aid in the detection of stones (uroliths) in the urinary bladder. Contrast radiography (dye and/or air infused into the lower urinary tract) helps outline the shape and size of the urinary bladder and urethra. It may also reveal conditions unseen on routine X-rays of the area. Urinary stones, neoplasia, polyps, thickening of the bladder wall, and urinary bladder rupture may be viewed better with this technique.
- Cystoscopy (viewing the interior of the urethra and urinary bladder with an endoscope) can be extremely useful in diagnosing diseases of the lower urinary tract. Cystoscopy can also help obtain a biopsy specimen essential for the diagnosis of polyps, neoplasia, or infections. Due to the small diameter of the feline urethra, this is a very difficult procedure.
- Finally, surgery may be necessary to ultimately view and diagnose some conditions. This is particularly true with small tumors or polyps which may be missed when using other techniques.
See section D for additional information on the above tests.
- Cystitis is usually corrected by:
- Removing the underlying cause for the cystitis (used in drug-induced cystitis and urolith-induced polypoid cystitis).
- Antibiotic or antifungal therapy (used in infectious cystitis).
- Anti-inflammatory drugs (used in traumatic cystitis and polypoid cystitis).
* Complicated cases may require a combination of the above therapeutic approaches.
- Rupture of the urinary bladder and a patent urachus must be treated surgically.
- Treatment of urinary bladder cancer (neoplasia) usually requires surgery, often followed by chemotherapy.
- Urinary bladder stones (uroliths) may require surgery, but are often managed more conservatively. Some stones, if small enough, may be removed by utilizing various techniques (catheterization) while the pet is under anesthesia. Diet is a major factor influencing the creation of many types of stones in the urinary tract. Prevention and even treatment of some stones may be accomplished by special prescription diets and/or medications which alter the pH of the urine.
- Urethritis - Inflammation of the urethra. (The urethra is the small tube that carries urine from the bladder out of the body.)
- Traumatic urethritis - Any trauma to the area of the urethra which may cause inflammation and swelling in the urethral wall.
- Crystal-induced urethritis - Small crystals in the urine cause irritation to the urethra as they are excreted.
- Urethral stricture - Scar tissue formation, often resulting in partial to complete blockage of the urethra.
- Urine pooling - Usually due to a partial blockage in the urethra due to stricture formation or inflammation of the urethra. Urine pools behind the blockage and causes further irritation and sometimes infection of the urethra.
- Urethral neoplasia - Cancer of the urethra.
Clinical Signs: Hematuria and straining to urinate are the two classic signs of urethral disorders.
Diagnosis: Tests such as physical examination, urinalysis, bloodwork, radiography, contrast radiography, urethroscopy (viewing of the urethra via insertion of an endoscope), biopsy, and histopathology may be necessary for an accurate diagnosis. If a male cat is straining to urinate, an experienced veterinarian may only require a physical examination under sedation to diagnose a urethral blockage. See Section D for additional information on the above tests.
Treatment: Because it may partially or even completely block the passage of urine, swelling of the urethra can be extremely detrimental to the animal. If the urethra is even partially blocked, straining will be evident. This is particularly a problem in male cats and should be considered a medical emergency.
- If the urethra is completely blocked, emergency insertion of a catheter to allow the obstructed urine to be passed is essential. Treatment of the cause of the blockage may then be addressed.
- Urethritis may be treated with medications to reduce the swelling and antibiotics to treat/prevent urethral infection.
- Urethral strictures and urethral neoplasia usually require surgical