Introduction:
The term urinary tract disease can be used to describe problems occurring in the kidneys, ureters, urinary bladder, or urethra. The following pages will discuss the major problems associated with each 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.Kidney 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 body’s own immune system.
- Medullary washout - Loss of the salt concentration gradient inside the kidney. The kidney’s 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 body’s 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.
- 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/or hematuria, and may be complicated with 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.
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- Blood and urine testing are the key tests for the initial detection of kidney insufficiency/failure.
In order to assess the patient’s progress, repeated testing is vital while treating many types of kidney disease. For additional information on many of the above tests, see Section D.
- 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 dogs 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.
Urinary Bladder Problems:
- 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.
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- 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.
- 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. Stones, if small enough, may be removed by various techniques utilizing anesthesia and catheterization. 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 to the outside.)
- Traumatic urethritis - Any trauma to the area of the urethra which may cause inflammation and swelling in the urethral wall.
- Granulomatous urethritis - Chronic inflammation of the urethra, sometimes diagnosed in female dogs. Cause is usually unknown.
- 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 vagina which occurs at birth. Urine pools behind the blockage and causes irritation and sometimes infection of the urethra and/or vagina.
- Urethral neoplasia - Cancer of the urethra.
- 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 removal.