Urinary Tract Obstruction

Urinary Tract Obstruction

  • Restricted flow of urine at any point in the urinary tract, from the kidneys to the external urethral orifice (the opening through which urine passes during urination)
  • The urinary tract consists of the kidneys, the ureters (the tubes running from the kidneys to the bladder), the urinary bladder (that collects urine and stores it until the pet urinates), and the urethra (the tube from the bladder to the outside, through which urine flows out of the body)

Signalment/Description of Pet

Predominant Sex

  • More common in males than in females

Signs/Observed Changes in the Pet

  • Abnormal frequent passage of urine (known as “pollakiuria”)—common
  • Straining with slow, painful discharge of urine (known as “stranguria”)
  • Reduced velocity or caliber of the urine stream or no urine flow during efforts to empty the bladder (voiding efforts)
  • Obvious blood in the urine (known as “gross hematuria”)
  • Signs of excess levels of urea and other nitrogenous waste products in the blood (known as “uremia” or “azotemia”) that develop when urinary tract obstruction is complete (or nearly complete): sluggishness (lethargy), dull attitude, reduced appetite, and vomiting
  • Excessive urine in the bladder (causing an overly large or tense/turgid bladder) or inappropriate retained urine (urine remains after voiding efforts); distension of the urinary bladder can be felt during physical examination
  • Occasionally, an enlarged kidney or kidneys may be felt during physical examination in an pet with long-term (chronic) partial blockage or obstruction of the ureter(s), especially when the lesion involves only one side; the ureter is the tube running from the kidney to the bladder
  • Signs of severely excessive levels of urea and other nitrogenous waste products in the blood (uremia or azotemia)—dehydration; weakness; low body temperature (known as “hypothermia”); low heart rate (known as “bradycardia”) with moderately increased levels of potassium in the blood (known as “hyperkalemia”); high rate of shallow respirations; stupor or coma; seizures occurring terminally; rapid heart rate (known as “tachycardia”) resulting from irregular heartbeats induced by severely increased levels of potassium in the blood (hyperkalemia)
  • Signs of rupture or perforation of the urinary tract—leakage of urine into the abdomen causes abdominal pain and distension; leakage of urine into tissues around the urethra (the tube from the bladder to the outside, through which urine flows out of the body) causes pain and swelling in the pelvis or in the tissue between the anus and vulva in the female or anus and scrotum in the male, depending on the site of the urethral injury; fever

Causes

Intraluminal Causes

  • Blockage or obstruction involving the inner, open space of the tubular ureters and urethra
  • Solid or semisolid structures including urinary tract stones (uroliths); accumulations of minerals and inflammatory materials in a matrix (known as “urethral plugs”) in cats; blood clots; and sloughed tissue fragments
  • Most common site—the urethra (the tube from the bladder to the outside, through which urine flows out of the body)
  • Urinary tract stones (urolithiasis)
  • Accumulations of minerals and inflammatory materials in a matrix (urethral plugs)—most common cause in male cats

Intramural Causes

  • Blockage or obstruction involving the wall of a hollow organ, such as the bladder
  • Tumors or cancer of the bladder neck (the junction between the bladder and the urethra) or urethra (the tube from the bladder to the outside, through which urine flows out of the body)
  • Nodular inflammatory lesions, characterized by the presence of pus (known as “pyogranulomatous inflammatory lesions”) in the urethra
  • Scar tissue (known as “fibrosis”) at a site of prior injury or inflammation can cause narrowing (stricture or stenosis), which may impede urine flow or may be a site where debris becomes lodged within the lumen (the inner open space of the ureter [the tube from the kidney to the bladder] or urethra [the tube from the bladder to the outside, through which urine flows out of the body])
  • Fluid buildup (known as “edema”), bleeding, or spasm of muscular components can occur at sites of blockage or obstruction involving the inner, open space of the tubular ureters or urethra (intraluminal obstruction), and contribute to persistent or recurrent obstruction to urinary flow after removal of the intraluminal blockage; tissue changes might develop because of injury inflicted by the obstructing material, by the manipulations used to remove the obstructing material, or both
  • Ruptures, lacerations, and punctures—usually caused by traumatic incidents

Miscellaneous Causes

  • Displacement of the urinary bladder into a perineal hernia; a perineal hernia develops when the muscles supporting the rectum weaken and separate, allowing the rectum and/or bladder to slide under the skin and causing swelling in the area of the anus
  • Nervous system disorders

Risk Factors

  • Urinary tract stones (urolithiasis), particularly in males
  • Feline lower urinary tract disease (FLUTD), particularly in males

Treatment

Health Care

  • Complete urinary tract obstruction is a medical emergency that can be life-threatening; treatment usually should be started immediately
  • Partial urinary tract obstruction—not necessarily an emergency, but these pets may be at risk for developing complete obstruction; may cause irreversible urinary tract damage, if not treated promptly
  • Treat as an inpatient until the pet’s ability to urinate adequately has been restored
  • Treatment has three major components: (1) combating the problems associated with excess levels of urea and other nitrogenous waste products in the blood that build up due to the urinary tract obstruction (known as “post-renal uremia”)—problems include dehydration; low body temperature (hypothermia); accumulation of acidic compounds in the body (known as “acidosis”); increased levels of potassium in the blood (hyperkalemia); (2) restoring and maintaining an open pathway for urine outflow; and (3) implementing specific treatment for the underlying cause of urine retention and urinary tract obstruction
  • Give fluid therapy to pets with dehydration or with excessive levels of urea and other nitrogenous waste products in the blood (uremia or azotemia)
  • When substantial generalized (systemic) problems exist, start fluid administration and other supportive measures first, before relieving the blockage or obstruction; careful decompression by tapping the bladder to remove urine (known as “cystocentesis”) will relieve pressure on the bladder and may be performed before anesthesia and catheterization

Surgery

  • Surgery is required sometimes
  • Urinary diversion by tube cystostomy is useful in selected cases; tube cystostomy is surgical placement of a catheter from the bladder and exiting through the abdominal wall to allow urine to be removed from the body, thus bypassing blockage of the urethra

Medications

  • Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive
  • Procedures for relief of blockage or obstruction often require, or are facilitated by, giving sedatives or anesthetics; generally isoflurane is the anesthetic of choice; however, a variety of other anesthetics or sedatives can give satisfactory results

Follow-Up Care

Patient Monitoring

  • Assess urine production and hydration status frequently, and adjust fluid administration rate accordingly
  • Verify ability to urinate adequately or periodically use urinary catheterization to combat urine retention
  • If catheter insertion requires repeated use of sedatives or anesthetics or is unduly traumatic, indwelling catheterization with closed drainage is appropriate; however, frequent brief urethral catheterization may be a better choice, if the catheter can be inserted easily on a repeated basis
  • When the electrocardiogram (ECG) indicates changes in the heart rhythm that potentially are life-threatening, use continuous monitoring to guide treatment and evaluate response

Possible Complications

  • Death
  • Injury to the urinary tract, while trying to relieve obstruction
  • Low levels of potassium in the blood (hypokalemia) during post-obstruction diuresis (a condition in which the body produces large volumes of urine after a urinary tract blockage has been relieved)
  • Recurrence of obstruction

Expected Course and Prognosis

  • Long-term management and prognosis depend on the cause of the blockage or obstruction

Key Points

  • Urinary tract obstruction is restricted flow of urine at any point in the urinary tract, from the kidneys to the external urethral orifice, the opening through which urine passes during urination
  • Complete urinary tract obstruction is a medical emergency that can be life-threatening; treatment should be started immediately
  • Partial urinary tract obstruction—not necessarily an emergency, but these pets may be at risk for developing complete obstruction; may cause irreversible urinary tract damage, if not treated promptly
  • Long-term management and prognosis depend on the cause of the blockage or obstruction

Kidney Failure

Kidney Failure – Sudden (Acute) Uremia

  • “Uremia” is the medical term for excessive levels of urea and other nitrogenous waste products in the blood (it is also known as “azotemia”)
  • Sudden (acute) uremia is a clinical syndrome characterized by sudden onset of kidney failure; urea and other nitrogenous waste products build up, leading to clinical signs
  • It is potentially reversible, if diagnosed quickly and treated aggressively
  • The kidney filters the blood and removes various waste products from the body as it produces urine; the kidney is involved in maintaining the normal fluid volume of the body; each kidney is composed of thousands of nephrons (the functional units of the kidney, each consisting of the glomerulus [a tuft of blood capillaries—the “blood filter”] and a series of tubes and ducts, through which the filtered fluid flows, as urine is produced)

Signalment/Description of Pet

Mean Age and Range

  • Peak incidence —6–8 years of age
  • Older pets at greater risk

Signs/Observed Changes in the Pet

  • Sudden onset of lack of appetite (known as “anorexia”); listlessness; depression; vomiting (with or without the presence of blood); diarrhea (with or without the presence of blood); bad breath (known as “halitosis”); wobbly, incoordinated or “drunken” appearing gait or movement (known as “ataxia”); seizures; and production of only small amounts of urine (known as “oliguria”)/or no urine (known as “anuria”) or increased volume of urine (known as “polyuria”)
  • Observed poison or drug exposure; recent medical or surgical conditions
  • Normal body condition and hair coat; dehydration (or overhydration due to administration of fluids); ulcers in the mouth; inflammation of the tongue (known as “glossitis”) and death of tissues of the tongue; low body temperature (known as “hypothermia”) or fever; rapid breathing (known as “tachypnea”); slow heart rate (known as “bradycardia”); inability to feel the urinary bladder during physical examination; and enlarged, painful, firm kidneys

Causes

  • Shock; trauma; blood clots (known as “thromboembolism”); heat stroke; excessive narrowing of the blood vessels (known as “vasoconstriction,” such as following the administration of nonsteroidal anti-inflammatory drugs [NSAIDs]); adrenal gland insufficiency; excessive enlargement or dilation of blood vessels (known as “vasodilation,” such as following the administration of angiotensin-converting enzyme [ACE] inhibitors or medications to decrease blood pressure [known as “antihypertensive drugs”]); prolonged anesthesia; heart failure

Compounds/Medications That Are Toxic to the Kidneys

  • Ethylene glycol (found in antifreeze); antibiotics (aminoglycosides); antifungal medications (amphotericin B); chemotherapeutic agents (such as cisplatin and doxorubicin); nonsteroidal anti-inflammatory drugs; radiographic contrast agents; heavy metals (such as lead, mercury, arsenic, thallium); insect or snake venom; calcium; grape or raisin ingestion; and lily ingestion (cats)

Generalized Disease Affecting the Kidneys

  • Infectious disease (such as leptospirosis or Lyme disease); immune-mediated disease (such as inflammation and accompanying dysfunction of glomeruli [plural of glomerulus] of the kidney [known as “glomerulonephritis”] and inflammation of the arteries [known as “arteritis”]); inflammation of the pancreas (known as “pancreatitis”); generalized disease caused by the spread of bacteria in the blood (known as “septicemia” or “blood poisoning”); blood-clotting disorder (known as “disseminated intravascular coagulopathy” or DIC); liver failure; heat stroke; blood transfusion reactions; bacterial inflammation/infection of the lining of the heart (known as “bacterial endocarditis”); bacterial infection/inflammation of the kidney (known as “pyelonephritis”); and cancer (such as lymphoma; “lymphoma” is a type of cancer that develops from lymphoid tissue, including lymphocytes, a type of white blood cell formed in lymphatic tissues throughout the body)
  • Blockage or obstruction of one or both ureters (the tubes running from the kidneys to the bladder) in cats

 

Risk Factors

  • Preexisting long-term (chronic) kidney disease; dehydration; generalized bacterial infection (known as “sepsis”); low blood volume (known as “hypovolemia”); low blood pressure (known as “hypotension”); advanced age; coexistent disease; low levels of sodium in the blood (known as “hyponatremia”); low levels of potassium in the blood (known as “hypokalemia”); low levels of calcium in the blood (known as “hypocalcemia”); and acidosis (a condition in which levels of acid are increased in the blood)
  • Medications (such as the diuretic, furosemide; nonsteroidal anti-inflammatory drugs; angiotensin-converting enzyme [ACE] inhibitors; antibiotics [aminoglycosides]); prolonged anesthesia; acidifying diets; trauma; multiple organ disease; and high environmental temperature

Treatment

Health Care

  • Inpatient management; eliminate inciting causes; discontinue kidney toxic drugs; establish and maintain circulation and blood flow; treat life-threatening fluid imbalances, biochemical abnormalities, and uremic toxicities
  • If a poison is the likely cause of sudden (acute) uremia and kidney failure, follow appropriate treatment for the specific poison (treatment may include inducing vomiting, flushing of the stomach [known as “gastric lavage”], and administering activated charcoal and specific antidotes); early hemodialysis (procedure to remove waste products from the blood) can eliminate poisons
  • Low blood volume (hypovolemia) or dehydration—correct estimated fluid deficits with normal (0.9%) saline or balanced fluids within 2–4 hours; blood losses may be replaced by blood transfusion; once the pet is hydrated, ongoing fluid requirements are provided; avoid overhydration
  • High blood volume (known as “hypervolemia”) or overhydration—stop fluid administration and eliminate excess fluid by treatment with medications to remove excess fluid from the body (known as “diuretics”) or dialysis (procedure to remove waste products from the body)

Diet

  • Restrict intake of food and water by mouth until vomiting subsides
  • Fat and protein stores will be consumed by the body while pet is not eating (anorexia); resting energy requirements must be provided by 3–5 days, using moderately protein-restricted diets or feeding special solutions formulated to control excessive levels of urea and other nitrogenous waste products in the blood (uremia or azotemia) and supply caloric requirements
  • Nutrition may be provided by intravenous feeding (known as “parenteral nutrition”) in vomiting pets
  • Tube feeding may be provided for pets that are not eating (anorexia) and are not vomiting—caloric and protein requirements may be supplied by using kidney diets that have been liquefied in a kitchen-type blender, special liquid diets, or formulated diets

Surgery

  • Surgical incision into the bladder (known as “cystotomy”) to flush (known as “lavage”) and remove inflamed tissue (known as “debridement”) the lining of the bladder mucosa is not recommended
  • Surgical opening of the urethra (known as “perineal urethrostomy”) to minimize recurrent blockage of the urethra (urethral obstruction) should be considered only when the obstructive disease is localized to the area of the urethra within the penis (known as the “penile urethra”) by contrast x-rays (radiographs) of the urethra

Medications

  • Medications presented in this section are intended to provide general information about possible treatment. The treatment for a particular condition may evolve as medical advances are made; therefore, the medications should not be considered as all inclusive

Inadequate Urine Production

  • Ensure the pet has normal blood volume
  • Administer medications to remove excess fluid from the body (diuretics), such as mannitol or furosemide (alternative or subsequent to mannitol)
  • If diuretic treatments fail to induce increased production of urine within 4–6 hours, consider dialysis (procedure to remove waste products from the body)

Acid-Base Disorders

  • Bicarbonate

Vomiting

  • No food or water (nothing by mouth) until vomiting subsides
  • Reduce stomach-acid production—famotidine or ranitidine or omeprazole
  • Medication to protect the lining of the stomach (known as a “mucosal protectant”)—sucralfate
  • Medications to control nausea and/or vomiting (known as “antiemetics”)—metoclopramide, ondansetron, or dolasetron

Peritoneal Dialysis or Hemodialysis

  • ”Peritoneal dialysis” is a type of dialysis in which fluids are put into the abdomen and the lining of the abdomen (known as the “peritoneum”) acts as a filter to remove waste products from the blood—after a certain amount of time, the fluids and waste products are removed from the abdomen; “hemodialysis” is a procedure to remove waste products from the blood
  • Dialysis can stabilize the pet until kidney function is restored or until corrective surgery is performed; without dialysis, most pets that produce only small amounts of urine (oliguria) die before kidney repair can occur

Follow-Up Care

Patient Monitoring

  • Fluid, electrolyte, and acid–base balances; body weight; blood pressure; urine output; and clinical status—monitor daily

Preventions and Avoidance

  • Anticipate the potential for sudden (acute) kidney injury in aged pets or those with generalized (systemic) disease, generalized bacterial infection (sepsis), trauma, receiving kidney toxic drugs, multiple organ failure, or those undergoing prolonged anesthesia
  • Maintenance of hydration, mild saline volume expansion, and administration of mannitol may be preventive
  • Monitor urine production and increased levels of urea and other nitrogenous waster products (azotemia) in high-risk pets

Possible Complications

  • Seizures; coma; irregular heartbeats (known as “cardiac arrhythmias”); increased blood pressure (hypertension); congestive heart failure; fluid buildup in the lungs (known as “pulmonary edema”); inflammation of the lungs due to the presence of urea and other nitrogenous waste products (known as “uremic pneumonitis”); aspiration pneumonia; bleeding in the gastrointestinal tract; shock due to low blood volume; generalized bacterial infection (sepsis); stopping of the heart and breathing (known as “cardiopulmonary arrest”); and death

Expected Course and Prognosis

  • Prognosis depends on cause, extent of damage, coexistent diseases, and multiple organ involvement
  • Infectious and obstructive causes have a better prognosis for recovery than toxic causes

Key Points

  • Poor prognosis for complete recovery
  • Potential for complications of treatment (such as fluid overload, generalized bacterial infection [sepsis], and multiple organ failure)
  • Prolonged hospitalization and treatment is expensive
  • Alternatives to conventional medical management are available; they include peritoneal dialysis or hemodialysis (procedures to remove waste products from the blood) and kidney transplantation
  • Leptospirosis has zoonotic potential; “zoonoses” are diseases that can be passed from animals to people