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Oliguria and Anuria in Dogs

Oliguria is the medical term for a condition in which an abnormally small amount of urine is produced by the body, with urine production at a rate of less than 0.25 milliliters per kilogram per hour. Anuria is the medical term for a condition in which essentially no urine is produced by the body, with urine production at a rate of less than 0.08 milliliters per kilogram per hour.

Physiologic oliguria occurs when a dog's kidneys limit the loss of renal water in order to preserve body fluid and electrolyte balance. Pathologic oliguria results from severe impairment of kidney tissues, which can occur as the result of a number of factors. Anuria may result from kidney disease, or obstruction of urinary flow.

Symptoms and Types

Generally, a key symptom of oliguria or anuria is a decreased amount of urine being produced and excreted. Additional symptoms vary depending on the type of oliguria or anuria present. Signs of physiologic oliguria include dehydration, pale mucous membrane, a weak pulse, a rapid or irregular pulse, and a history of fluid loss (through excessive vomiting or diarrhea, for example). Signs of pathologic oliguria typically include a history of progressive kidney disease with symptoms such as poor appetite and weight loss. Symptoms of anuria may be observed during a physical examination, with revealing signs such as fluid infiltration into the tissues surrounding the urinary tract, and pain in the abdomen on palpation.

Causes

Various conditions can be responsible for different types of oliguria and anuria. Physiologic oliguria may be occasioned by renal hypoperfusion, which is caused by low blood volume or pressure, or hypertonicity, an increased pressure of fluids in the body. Pathologic oliguria is usually due to acute kidney failure or chronic kidney disease. Anuria may result from a complete obstruction in the urinary tract, a rupture in the urinary excretory pathway, or from severe kidney failure.

A number of risk factors may increase the odds of developing oliguria or anuria, including dehydration, low blood pressure, kidney disease, liver disease, trauma - such as from a car accident, sugar diabetes, and multiple organ failure.

Diagnosis

Key diagnostic procedures include an urethrocystoscopy, which uses an insertable diagnostic tool to view the interior of the urinary tract and bladder wall, and which may provide evidence for obstruction or rupture of the urinary tract. Additional tests may include urine analysis, an electrocardiograph (ECG), abdominal radiographs, and ultrasounds to rule out or confirm urinary obstruction.