RENAL DISEASE (KIDNEY DISEASE)
The kidneys are paired, bean shaped organs located in the abdominal cavity near the spine. Each kidney receives a substantial blood flow with blood coming directly from the aorta and returning back to the heart via the caudal vena cava. The kidneys serve to filter metabolic wastes from the blood, control water and electrolyte balance, regulate the acidity/alkalinity balance of the blood and stimulate the production of red blood cells by the bone marrow.
As the kidneys perform their functions, urine is produced, passed to the urinary bladder through the ureters and excreted at an appropriate time. (Hopefully!) The method of filtration is beyond the scope of this discussion, but suffice it to say that each kidney will contain about a million basic filtration units called nephrons. This equates to a tremendous reserve capacity; no loss of filtration ability will be observed until over two-thirds of these filtration units have been lost.
Like the liver, the kidneys have a great exposure to toxins and infective organisms due to the heavy circulation they receive. Unlike the liver, kidney tissue does not regenerate and damage to these organs becomes progressively worse. As we currently do not have kidney transplants nor dialysis readily available for dogs, any treatment to prevent or slow damage to these organs will help your dog live as long as possible.
Acute renal failure by definition, is a sudden cessation of the filtering ability of the kidneys and a build-up of waste products in the blood. The causes of acute renal failure can include infections by bacteria or viruses, chemicals including antifreeze, poor blood flow to the kidneys, drugs, traumatic injury and obstructions of the urinary tract. Initial symptoms include little or no urinary output, poor appetite, vomiting, depression and dark tarry stools. In some cases dogs will output large quantities of dilute urine when actually the kidneys are not performing their filtration functions at all.
Diagnosis is based on history, physical examination, urine analysis and blood tests. Blood tests consistent with acute renal failure will indicate elevations in waste products in the blood. Tests to measure the filtering functions of the kidneys, X-rays and renal biopsy may also need to be performed to determine the cause and properly direct treatment.
TREATMENT OF ACUTE RENAL FAILURE
Treatment for renal failure should first center around identification of the cause and providing a specific treatment, but most dogs need immediate hospitalization and intravenous fluid therapy to restore fluid and electrolyte balance, flush toxins and wastes from the body and correct acid/base abnormalities. Drugs such as mannitol, furosemide or dopamine are used to try to stimulate urinary output. Antibiotics would be administered if bacterial infections are present or antidotes used if certain toxins have been ingested.
Repeated blood tests, urinalysis and continued fluid and electrolyte therapy will be used to determine if the kidney function is returning to normal. The chances for success in this type of therapy will depend upon how badly the kidneys have been damaged and only in time will your veterinarian be able to determine if your dog will survive and recover.
Chronic renal failure generally connotes a gradual, progressive loss of kidney function and a corresponding increase in waste products in the blood along with severe electrolyte disturbances. Along with the same causes as for acute renal failure, congenital/hereditary renal diseases, glomerular diseases, neoplasia of the kidneys and degeneration of unknown origin (including aging type degeneration) can all lead to chronic renal failure.
Clinical signs will vary with the severity and duration of the disease and often include increased thirst and urination, poor appetite, gradual weight loss, lethargy, vomiting, diarrhea, weakness and pale gums. Diagnosis is based on the history and the presence of the clinical signs, physical examination, urine analysis, blood chemistry and kidney biopsy. On blood tests consistent with chronic renal failure, high levels of many waste products will be noted and red blood cell counts will be decreased. The urine will often be very dilute and appear clear like water.
TREATMENT OF CHRONIC RENAL FAILURE
As with acute renal failure, a search for the cause of the disease is important although in older animals the cause may simply be degeneration secondary to aging. Hospitalization and intravenous fluid therapy to lower serum waste products is essential. Placing dogs on a diet that has lower levels of protein, yet a high quality protein and lower levels of sodium and phosphorus is essential to slow the progression of the disease. Some dogs will need medications like Winstrol to stimulate red blood production, phosphate binders to keep this element out of the blood and drugs to control vomiting. Supplementation with vitamins is also useful in these patients.
Long term success will depend mostly upon the success of the special diet in controlling the elevations in waste products and phosphorus in the blood again. Some dogs will benefit from the periodic administration of fluids to assist in flushing out these waste products before they have a chance to build to toxic levels once more. Periodic blood and urine tests will be employed to evaluate how the dog is responding to therapy.
As an alternative, a form of dialysis called peritoneal dialysis can be employed to clean the blood. In short, this involves placing a permanent catheter in your dog's abdomen and periodically filling the abdominal cavity with fluid and draining it out after the waste products have filtered into the fluid. This technique can be quite effective but requires dedication to perform it on a regular basis; compilations are common.
Pyelonephritis is inflammation of the kidneys, usually caused by a bacterial infection but sometimes secondary to other types of infections. This infection may occur by ascension from a lower urinary tract infection or from the spread of bacteria to the kidneys in the blood stream from other areas of the body. Pyelonephritis may lead to acute or chronic renal failure.
Clinical signs include fever, depression, vomiting, abdominal pain, increased thirst and increased urination. Low-grade cases can become chronic and symptoms may be ongoing. Diagnosis is based on the history and clinical signs, urinalysis that will often show signs of a heavy infection, blood tests where white blood counts may be quite elevated, X-rays and cultures of the urine. Biopsy of the kidneys may be needed for a final diagnosis.
TREATMENT OF PYELONEPHRITIS
Cultures are very important to determine which antibiotic will be most effective. Long term (4+ weeks) use of penicillin, cephalexin, sulfa drugs, or other antibiotics will be required. If dehydration or electrolyte disturbances are present, a few days in the animal hospital with fluid and electrolyte therapy will help restore your dog to normal.
The glomerulus is a tuft or bundle of capillaries and nerves at the beginning of each nephron (individual filtration unit). In short, this is where filtration and regulation begins in the kidneys. Diseases of the glomerulus include glomerulonephritis and amyloidosis, both immune-mediated diseases that can lead to damage and cause dysfunction of the glomerulus.
Glomerulonephritis occurs when the body produces antibodies that attack the glomerulus or when complexes (large clumps) of antibodies get deposited (lodged) in and damage the glomerulus. This alters the functional ability of the nephron leading to loss of protein in the urine, a decrease in protein in the blood, an increase in blood cholesterol and fluid collecting in areas of the body (edema). Progressive kidney damage usually occurs leading to renal failure.
Clinical signs include loss of weight, swelling of the limbs, fluid collection in the abdomen, legs and possibly the lungs. If renal failure occurs clinical signs specific to that problem will also occur and most dogs will die. Diagnosis is based on these signs, blood and urine tests and a biopsy of the kidney.
Amyloid is a protein-sugar mixture that has a long, fibrous appearance, often produced secondary to other bodily infections. This amyloid is deposited in the glomerulus just as the immune complexes are in glomerulonephritis. This alters the functional ability of the nephron leading to loss of protein in the urine, a decrease of protein in the blood, an increase in blood cholesterol and fluid collecting in areas of the body (edema). Progressive kidney damage usually occurs leading to renal failure.
Clinical signs include loss of weight, swelling of the limbs, fluid collection in the abdomen, legs and possibly the lungs. If renal failure occurs, those clinical signs also occur and most dogs will die. Diagnosis is based on these signs, blood and urine tests and a biopsy of the kidney.
TREATMENT OF GLOMERULONEPHRITIS AND AMYLOIDOSIS
There is no known cure for these conditions. Certain strong immunosuppressive drugs and cortisone are used but the success rate is not high. Management of renal failure, control of the protein in the diet, the use of diuretics to help remove fluid from the extremities and abdomen and identification and control of any other diseases present will be supportive for these dogs.
Stones in the kidneys are called renoliths. The stones are usually composed of various minerals and an organic base. Infections, metabolic changes, trauma and unknown factors may all contribute to the origination of the stones. Certain dogs seem more prone to developing stones so there may be a hereditary relationship to the disease. If the stones become large enough, blockage of the urinary tract can occur leading to renal failure. ((Stones))
Symptoms include blood in the urine, abdominal pain, vomiting, discomfort, and if obstruction occurs, the clinical signs of renal failure will be present as well. Diagnosis is based on history, physical examination, blood and urine testing, X-rays and ultrasound.
TREATMENT OF RENOLITHIASIS
Treatment for kidney stones may not be needed if there are no clinical signs present. Sometimes a special diet or medications can be used to dissolve the stones. Antibiotics are used if infection is present with surgical removal used in cases where medical therapy is ineffective or an obstruction occurs.
Hydronephrosis occurs when the flow of urine from the kidneys is blocked, often due to renoliths, uroliths, tumors, parasites and complications of surgery in the area. These conditions produce a mechanical obstruction to urine outflow from the kidneys. Urine will then backup in the kidney(s) and the kidney will fill with fluid, dilate and functional tissue will become compressed. Fortunately, the condition is quite rare.
Clinical signs may be absent if only one kidney is involved, as the other kidney will carry the filtration load. Otherwise, frequent urination or increased amounts of urine being passed, blood in the urine, straining to urinate and signs of chronic renal failure are seen. Diagnosis is based on clinical signs, physical examination, blood counts, serum chemistries, urinalysis, X-rays including dye studies, ultrasound and kidney biopsy.
TREATMENT OF HYDRONEPHOSIS
If at all possible, surgical removal of the cause of the obstruction will result in a complete cure in early cases. Removal of stones or kidney worms can be performed. In extreme cases the kidneys may need to be surgically removed. IV fluids, electrolytes and related supportive care is needed in cases of chronic renal failure.