Renal failure in dogs
Renal failure or acute kidney injury (AKI) is a common consequence of a variety of diseases and conditions in dogs. Causes of renal failure in dogs can be divided into primary, secondary and hereditary conditions. Primary or congenital conditions affecting the kidneys that cause renal failure include nephrotic syndrome and glomerulopathies. Secondary causes of renal failure include acute nephropathies (e.g., toxic nephropathies, ischemic nephropathies, and infectious diseases) and chronic nephropathies (e.g., nephrosclerosis, tubulointerstitial nephritis, and nephropathies resulting from urogenital malformations). Inherited nephropathies and polycystic kidney disease (PKD) are frequently associated with secondary renal failure.
Signs and symptoms
A number of clinical signs may occur in dogs with renal failure. The most common clinical sign is uremic poisoning. Uremic poisoning manifests in dogs with renal failure as lethargy, vomiting, and decreased food consumption. Other clinical signs include fever, dyspnea, hyperhidrosis, and muscle weakness.
In dogs with non-traumatic AKI, clinical signs such as vomiting, lethargy, fever and dyspnea are most likely caused by volume depletion, uremia and/or sepsis, with a few studies showing that the most common clinical sign associated with AKI is lethargy. In humans, AKI is associated with an increased incidence of hospitalization, and increased length of hospital stay and mortality. Dogs with renal failure that have received dialysis treatment have longer duration of hospitalization than those that have not received dialysis treatment.
Clinical signs also occur as a result of chronic or acute kidney injury. The clinical signs of chronic renal failure include weight loss, lethargy, vomiting, anorexia, diarrhea, and polyuria. Clinical signs of acute renal failure include lethargy, vomiting, abdominal pain, diarrhea, and a marked increase in the serum BUN:creatinine ratio, which is used as a measure of renal function. Acute and chronic kidney injury are both associated with a loss of appetite and may be a sign of dehydration.
Hematologic changes include increased numbers of immature and mature neutrophils and monocytes, thrombocytopenia, and increased levels of serum lactate dehydrogenase, creatine kinase and alkaline phosphatase. Thrombocytopenia is seen as a result of renal sequestration of platelets, which have an increased tendency to accumulate in the lungs.
Renal failure can be classified into five categories based on the underlying cause of disease and includes primary, secondary, hereditary, traumatic and toxic causes.
Primary renal diseases
Primary renal diseases affecting the kidneys include nephrosis, glomerulopathies and nephropathies resulting from urogenital malformations. A wide variety of primary renal diseases have been documented in dogs.
Nephrotic syndrome is a primary renal disease that presents as proteinuria, hypercholesterolemia, hyperfibrinogenemia, anemia and azotemia. Causes of nephrotic syndrome in dogs include a congenital or genetic origin, and include congenital dysalbuminemic nephropathy (e.g., the Labrador Retriever), familial nephropathies (e.g., the Golden Retriever), and nephrotic syndrome in certain breeds (e.g., the Boxer). Congenital or genetic nephropathies are most commonly associated with a reduction in glomerular filtration rate. Congenital or genetic causes of nephrotic syndrome include nephronophthisis, polycystic kidney disease (PKD) and some congenital nephrotic syndromes. Nephronophthisis is characterized by the presence of multiple renal cysts and is often associated with a decreased lifespan in affected dogs.
Glomerulopathies are a group of primary renal diseases that affect glomerular function. Glomerular diseases that result in AKI include focal segmental glomerulosclerosis (FSGS), membranous glomerulopathy (MGN), endocapillary proliferative glomerulonephritis (PGN) and membranoproliferative glomerulonephritis (MPGN). Glomerular diseases in dogs include nephrotic syndrome-like glomerulopathies, fibrillary and amyloid glomerulopathies and others. Glomerulopathies can be classified as primary, secondary and hereditary.
Primary glomerular diseases include nephrotic syndrome-like glomerulopathies, fibrillary and amyloid glomerulopathies and others. Nephrotic syndrome-like glomerulopathies are characterized by increased albuminuria, edema, hypoalbuminemia and hypercholesterolemia. Amyloid glomerulopathies are characterized by deposition of amyloid protein in the glomerular basement membranes. Nephrotic syndrome-like glomerulopathies are the most common glomerular diseases in dogs and are characterized by increased albuminuria, proteinuria, hypoalbuminemia, edema and hypercholesterolemia. Other glomerular diseases include amyloidosis, proliferative glomerulonephritis, glomerulosclerosis and glomerulomegaly.
Nephropathies resulting from urogenital malformations include disorders that result in renal agenesis, renal dysplasia and nephroblastoma. The nephroblastoma is most commonly diagnosed in the bladder and less commonly in the penis. Nephroblastomas are typically found in dogs with Golden Retrievers, Labradors, Boxers, Beagles and other large breeds of dogs. In humans, Wilms' tumors are the most common nephroblastoma, and in dogs, nephroblastomas are most commonly associated with Golden Retrievers, Lab