Dogs - Urinary Conditions

 

DISORDERS OF THE URINARY SYSTEM

 

The urinary system consists of the left and right kidney, the ureters which connect the kidneys to the bladder, the bladder itself, and the urethra through which urine is expelled. Some of the disorders affecting this system are listed below.

Leptosporosis: infectious bacterium affecting the liver and kidneys, causes 'flu like' symptoms.

Glomerular disease: glomerulonephritis is an immune based disorder that affects the part of the kidney which filters the blood.

Amyloidosis: deposition of a protein called 'amyloid A' within the kidneys reduces its ability to function properly.

Juvenile renal disease: early onset renal failure can be as a result of an inherited or familial disorder.

Renal tumours: kidneys are a common site for spread of cancer from elsewhere in the body.

Renal cysts: cysts can develop within the kidneys but have to be multiple and affecting both kidneys to cause a problem.

Pyelonephritis: kidney bacterial infection.

Hydronephrosis: obstruction of urine flow results in collection or the urine in the bladder and kidneys, increased pressure can cause damage.

Chemical nephrosis: the ingestion of certain poisonous substances can cause renal failure.

Bacterial cystitis: bacterial infection of the bladder is one the commonest urinary problems seen in general practice.

Urolithiasis: the formation of crystal and stones within the urinary tract can cause obstruction to urine flow.

Bladder tumours: cancer of the bladder.

Leptospirosis

Infection can be with one of two main forms of the disease, the organisms involved being Leptospira canicola, and Leptospira icterohaemorrhagiae these will be dealt with as separate disease syndromes.

Leptospira canicola infection

Mostly dogs under 3 years of age affected, it is transmitted through contact with urine from infected animals, the organism can penetrate through breaks in the skin or mucous membranes. After infection, if immunity is insufficient, it takes approximately 4-7 days for disease to develop. During this time the bacteria multiply in the blood and then invade organs such as the liver and kidney. After this period the immune response starts to eliminate the infection, but it can persist in certain sites within the kidney where it is inaccessible to the immune system. persistence in these sites can last months, or even years, with the bacteria being shed through the urine.

The infection within the kidney causes a swelling and breakdown of the kidney tissue, the immune response creates an influx of white blood cells. The swelling and cell influx cause a rise in kidney pressure which results in a failing of the blood filtration, this leads to a state of uraemia and failure of urine production. The damaged kidney tissue is replaced by fibrous tissue during the healing process. The consequences of this depend on the extent of the damage, small areas of damage will allow complete recovery with only minor scarring on the kidney, in severe cases the blood pressure rises to try and maintain blood filtration, and if this persists it can itself damage the fragile kidney blood vessels leading, over a period of months to years, to terminal renal failure. The initial condition is called 'acute interstitial nephritis', the late kidney failure is the result of 'chronic interstitial nephritis'.

There are 3 stages of clinical disease, initially there is a transient fever, inappetance, and general lethargy lasting 3-5 days. The second stage develops as a result kidney inflammation. Mild cases may pass unnoticed, severe cases become dull, thirsty, anorexic, vomit, and produce either excessive or restricted amounts of urine. There may be some abdominal pain. As uraemia develops mouth ulceration and bad breath (halitosis) can result. The worst cases are fatal within a few days of these developments. The third stage is the development of terminal renal failure at a later stage. Many case will appear to recover after the second stage only to deteriorate later.

Diagnosis can be confirmed by demonstrating Leptospira in the urine. Blood tests for urea, creatinine, and phosphate will indicate kidney damage and tests for antibodies to Leptospira show a rise at 7 to 10 days post infection.

Leptospira icterohaemorrhagiae infection

This is a disease that is relatively uncommon in dogs, and occurs mainly in those exposed to infected rats. The damage that occurs in the initial infection tends to be more severe and is more frequently fatal. The liver is the organ which sustains the most damage in the initial phase which tends to result in jaundice. Spontaneous haemorrhage may be present in several organs and in subcutaneous sites.

Presents with fever, lethargy, anorexia, and occasionally sudden death. Later weight loss, vomiting and dehydration. Jaundice and haemorrhage can be seen on the mucous membranes, the abdomen is painful. Acute kidney failure can occur causing uraemia and oliguria.

Blood tests will show a mild anaemia and raised levels of liver enzymes, antibody tests can be used to confirm infection.

Treatment and control are the the same for both conditions. The treatment of choice for leptospirosis is a combination of penicillin and streptomycin or oxytetracycline, continuing the course for around 10 days. Fluids to reverse dehydration and diuretics to induce urine production. In chronic renal failure low protein diets to reduce urea levels, unrestricted access to water and vitamin B supplementation are useful. In cases of liver disease anabolic steroids may be used during recovery.

Vaccination confers effective immunity when 2 doses are given with a 2-4 week interval.

These are organisms capable of causing disease in man, spread mainly by urine contamination. Clinically healthy animals can shed these organisms in their urine. Leptospira icterohaemorrhagiae is responsible for Weil's disease in man. Good hygiene is essential to minimize the health risk.

Glomerular Disease

Glomerulonephritis is a problem related to the immune system. When antibodies react to foreign material in the body they do so by binding to the unusual proteins (antigens) forming a large complex of antibodies and antigens. These become trapped in the small capillary blood vessels in the glomerular basement membrane and compromise its ability to filter blood. Numerous infectious diseases can stimulate this response, as can some tumours and certain types of inflammatory disease. The result is the basement membrane becomes too permeable and blood proteins leak through into the kidney tubules. There is also a reduction in the ability to reabsorb water, causing excessive urine production.

The first sign of the kidney failure is usually excessive urine production (polyuria), matched by increased thirst (polydipsia), an increased level of urinary protein (proteinuria), and a degree of weight loss. As the kidney fails to filter urea its blood levels start to rise, causing a clinical state known as uraemia. In the dog it is responsible for vomiting, diarrhoea, anaemia, and sometimes oral ulceration. Excessive protein loss through the kidney leads to a depletion of blood proteins which causes oedema of the limbs and fluid build up in the abdomen or thorax. Oedema of the intestine can result in diarrhoea. Dogs in end stage renal failure will become significantly dehydrated.

Diagnosis of renal failure is often made on the basis of the clinical signs, the measurement of urine protein, and the measurement of blood urea, creatinine and inorganic phosphate levels. The specific diagnosis can only be made by renal biopsy.

If the animal is oedematous then diuretics should be used to reduce and control the fluid build up, frusemide is probably best for this purpose, it can be stopped once the fluid build up has disappeared. If uraemia is part of the problem then it is essential to reduce dietary protein intake (urea is a metabolite of protein). If vomiting is excessive then intravenous fluids should be given to correct dehydration and electrolyte deficiencies, antiemetic drugs such as metoclopramide can be given to help control vomiting.

Most cases are well advanced by the time clinical signs appear and it is not possible to achieve a cure. The condition will progress and the long term prognosis is poor. Non-uraemic nephropathies can survive several months, occasionally over one year.

Amyloidosis

This disease involves the deposition of Amyloid A protein within the tissues. This can be stimulated by concurrent inflammatory disease or tumours, but many cases have no obvious inciting cause. The first organ to become seriously affected is the kidney so the observed clinical signs are usually those of chronic renal failure, other affected organs include the liver, spleen and the intestinal tract. The deposition in the kidney results in protein leakage into the urine, as the problem progresses the destruction of the kidney nephrons leads to chronic renal failure and uraemia.

Weight loss as a result of the protein loss may be the first indication of illness, as the uraemia develops then lethargy, anorexia and vomiting occur, increased thirst and urination are common.

In order to diagnose this condition the measurement of urine protein should be positive on repeated occasions, blood tests will reveal a raised blood urea level and low blood protein levels. Confirmation of the diagnosis is best achieved by renal biopsy.

No effective treatment is available, if there is any underlying inflammatory or neoplastic disease causing the problem then it should be treated. Supportive treatment for chronic renal failure should be instituted (low protein diet and antiemetics to control vomiting), and if oedema develops then diuretics can be used to control it.

The outlook is very poor, survival time depends on the rate of deposition of amyloid. In those cases that progress slowly a survival time of up to one year is possible.

Juvenile Renal Disease

This refers to the onset of renal failure in young dogs in the absence of an infectious cause. If it occurs in related animals it may be referred to as 'familial' in which case the condition is either known or thought to be inherited, in certain breeds (Samoyed, Cocker Spaniel, Shih Tzu) the inheritance mode has been confirmed. The condition may be congenital (present at birth), or develop later in life.

Examples of congenital problems include renal agensis (absence of one kidney), aplasia (failure to develop ), and hypoplasia (incomplete development). If these problems only involve one kidney then there may be no clinicial signs. If both kidneys are involved then early onset renal failure is likely. Renal cysts arise due to abnormal development and are also thought to be familial.

Most of these conditions will lead to the onset of chronic renal failure. The age at presentation can vary from a few months old to middle age, few cases will present older than 5-6 years. In those animals affected soon after birth the presenting signs will be poor growth, dullness, inappetance, and increased thirst. Anaemia and fibrous osteodystrophy may develop beyond 4 months of age. In older animals the presentation is typical of chronic renal failure with protein loss in the urine, thirst, vomiting, diarrhoea, and occasionally the development of nervous signs such as twitching or convulsions.

Before any changes are registered in blood urea or creatinine levels the kidneys will have lost 65-70% of renal function.

Treatment is as for chronic renal failure, with supportive therapy and low protein diets. Growing pups may struggle to gain weight on low protein food, and a compromise is to use meat free diets. Survival depends entirely on the rate of disease progression, it may be as little as a few weeks or extend beyond 18 months.

Renal Tumours

Tumours arising in the kidney are relatively rare, the most common is the renal carcinoma which usually only affects one kidney, it is most common in 7-8 year old males. The second most frequently found tumour is the nephroblastoma, both tumours will spread elsewhere, usually to the lungs.

Because around 70% of kidney function can be lost before the onset of renal failure the presentation can be one of general dullness and weight loss rather than renal failure, or related to the organs into which the tumour spreads. This complicates the diagnosis, the kidney involvement can be demonstrated with ultrasound scans or contrast radiography. Urine may contain blood or even some tumour cells.

If only one kidney is affected and X-rays of the lungs do not show spread of the tumour then surgical removal is a viable treatment option. If surgery is not feasible then with certain types of tumour chemotherapy may induce remission for a few months.

The kidney is a very common site for spread from tumours elsewhere in the body, the original tumour usually produces ill health before the onset of kidney failure.

Renal Cysts

Small, individual, isolated cysts in the kidneys will rarely cause problems. Disease develops when multiple cysts (polycystic) obliterate the functional kidney tissue. They will present with the usual signs of renal failure, thirst, excessive urination, vomiting, anorexia, weight loss and possibly oedema. Diagnosis can be confirmed by blood tests to show increased levels of urea and creatinine, and by visualisation of the cystic structures on X-ray or ultrasound scans. Treatment is with low protein diets and symptomatic drug therapy, the prognosis is poor.

Pyelonephritis

This is a bacterial infection of the kidney tissues, most cases affect both kidneys and many originate from infection further down the urinary tract. E.coli is the most commonly isolated organism. Initially there is swelling of the kidney tissue and collection of pus within the parenchyma, as the organ starts to heal it contracts and fibroses leading to scar formation within the kidney.

In the initial acute phase of the infection the dog develops fever, inappetance, lethargy, and abdominal pain associated with the kidneys. Blood is likely to be mixed with the urine, in the later stage, if severe enough, chronic renal failure may develop with the onset of uraemia.

Blood tests will show abnormal proportions of white blood cells, as well as raised urea and creatinine levels. Urine analysis will reveal blood, pus, protein and bacteria.

Treatment involves antibiotics which ideally should be chosen on the basis of sensitivity testing on the bacteria involved. At least a 10 day course is recommended after which the urine should be rechecked for bacteria and the antibiotics continued if necessary until clear. Diuretics such as frusemide can be used to increase urine production.

Hydronephrosis

This develops secondary to complete or partial obstruction of urinary flow, the resulting back pressure on the kidney causes a dilatation of the renal pelvis and destruction of the functional kidney tissue. The obstructions can be congenital deformations of the urinary tract, or they can develop secondary to imflammation, tumours or calculi (kidney/bladder stones). Unless the obstruction is removed or relieved then tissue damage becomes irreversible. If only one kidney is affected then renal failure will not develop as long as the other kidney is functioning properly, if both kidneys are involved then uraemia and acute renal failure will develop.

The back pressure causes kidney swelling, if this is a gradual process affecting one kidney then it can become transformed into a large fluid filled sac, if it is an sudden process then the condition becomes painful due to the stretching of the renal capsule. Any part of the urinary tract which contains static collections of fluid is prone to developing an infection (pyonephrosis). Enlarged kidneys may be palpable, if not then X-rays or ultrasounds scans will reveal the problem.

The clinical signs will involve pain in the affected kidney, some blood may be passed in the urine. If the obstruction is at the level of the bladder or urethra then the animal will be unable to pass urine. Uraemia will develop, secondary infection is common which can lead to fever and lethargy. Blood tests will show increased urea and creatinine levels if both kidneys are affected.

The only available treatment is to relieve the obstruction, usually surgically. Antibiotics are necessary to control secondary infection. Once changes have developed in the kidney tissues then the change is irreversible. If one kidney has been severely affected and the opposite kidney is normal then removal of the affected kidney may be advisable. If renal failure has started to develop then conservative management and symptomatic treatment should be instituted.

The prognosis is good if only one kidney is affected and the cause is non-neoplastic. Bilateral involvement has a guarded prognosis.

Chemical nephrosis

This condition develops as a result of ingestion of toxic materials, these can include metals (lead, mercury, arsenic), organic compounds such as antifreeze (ethylene glycol), certain types of drugs and chemotheraputic agents.

Initial signs of ingestion may be those of acute renal failure, or instead may reflect the effect of the substance on another body system, for example vomiting and diarrhoea induced by gastrointestinal damage. Acute renal failure will present with a lethargic, inappetant animal that is also vomiting. The abdomen will be painful and the kidneys may be swollen. The increased pressure within the kidney will initially stop urine production, if this subsides the urine production may become excessive for a period while the tissues recover.

Blood tests will have a raised urea, creatinine and phosphate, urine tests will show a large amount of debris from the damaged kidneys, with certain toxins crystal formation occurs and these are visible under a microscope and are an aid to diagnosis.

Treatment should start as soon after the ingestion of the toxin as possible, and not wait for clinical signs to develop. In many cases owners are not aware that their pet has ingested toxic material until illness develops. The animal should be induced to vomit (sodium bicarbonate or similar drug), and if necessary a gastric lavage performed to empty and flush out the stomach. With certain toxins specific treatments or antidotes may be required, for example antifreeze poisoning in cats can be treated with eythl alcohol and calcium infusion. Intravenous fluids are useful if urine production is functioning, diuretics may also help to stimulate diuresis.

The prognosis depends on the extent of the damage but is often poor, chronic renal failure is likely to develop even if the animal survives the acute episode.

Cystitis

Cystitis can be caused by allergies, trauma, calculi, bladder tumours, or even secondary to drug treatment (cyclophosphamide) or diabetes, but by far the major cause is bacterial infection. The infection ascends from the tip of the urethra and the best defence against this is 'washing out' the urethra by passing urine, hence those problems which interfere with flow and create static pooling of urine predispose to urinary tract infection. The most common organisms include E.coli, Pseudomonas, Streptococcus, and Staphlococci.

The clinical signs include blood in the urine, some degree of incontinence, increased frequency of urination, and pain may be elicited by bladder palpation. Often there is no fever and the dog is bright and alert. There may be some pain on urination.

In order to confirm the diagnosis testing of urine should reveal a high protein content and bacteria. X-rays may show a thickened bladder wall but can also reveal any other conditions (bladder stones or tumours in the bladder wall).

Treatment is with antibiotics, if the condition is recurrent then the bacteria should be tested for sensitivity to the drug. The antibiotic course should be maintained for up to 14 days. Suitable antibiotics include ampicillin, clavulanate potentiated amoxycillin, cephalexin, and tetracycline. Most antibiotics are effective at an acidic urine pH (ideally pH 5.5) so urinary acidifiers such as ammonium chloride or vitamin C may be of use. If the infection has spread to cause a prostate or kidney infection then longer courses of antibiotics may be needed.

Urolithiasis

This condition arises due to the deposit of minerals as stones or gravel (uroliths) in the urinary tract. The presence of these uroliths may go unnoticed, but those responsible for clinical signs should be removed. The minerals can be phosphate (struvite), cystine, urate, oxalate, or carbonate. The rate of formation depends on the conditions within the urinary tract and the concentration of mineral secreted in the urine. Alkaline urine speeds the formation of phosphate uroliths, acid urine predisposes to cystine uroliths. Most bitches suffer from phosphate, males tend to form cystine, oxalate, and urate uroliths. Certain animals, or breeds, have intrinsic defects in the kidneys which result in over excretion of minerals in the urine, for example urate stone formation in Dalmatians. In other breeds urate stones are usually a result of a concurrent liver disorder.

Uroliths may be present in the bladder without causing clinical signs, they can be responsible for irritation of the bladder wall, or even acute obstruction of urine flow. Bitches usually present as a case of cystitis, urinating frequently and often containing blood. Males often present with complete or partial urinary obstruction. This will lead to bladder distension with the back pressure on the kidneys causing uraemia and vomiting. X-rays or catheterisation will reveal the position of the blockage. Contrast agents placed in the bladder will reveal those types of urolith which do not show on plain X-rays.

Treatment with modification of the diet to dissolve the uroliths can be used in animals not in urgent need of surgical removal. Prescription diets are available which can change the urine pH and contain reduced levels of protein, calcium, magnesium and phosphorus. Antibiotics to control urinary infection should be administered. In cases of urinary obstruction immediate relief from pressure by catheterisation, surgical removal of uroliths, or draining the bladder with a needle and syringe must be carried out before acute renal failure develops.

In males suffering from recurrent urinary obstruction an operation known as a permanent urethrostomy can be carried out to divert the urine away from the narrowest portion of the urethra which is most likely to block. The urethra will open instead in the perineal or pre-scrotal region.

Prevention is through adjusting the acidity of the urine to prevent urolith formation, prompt treatment of any urinary infections, and increasing fluid intake and urine output to reduce the mineral concentrations in the urine. The use of prescription diets can help to achieve this.

Bladder Tumours

The major bladder tumour in the dog is called a transitional cell carcinoma, benign fibromas and papillomas are also reasonably common . It can present with incontinence, straining to pass urine, blood in urine, and excessive thirst and urination. It is common to have a secondary bacterial cystitis in conjunction with bladder tumours. Occasionally some other clinical signs will develop due to the effects of the tumour on the other body systems. Tumours will mainly affect older dogs. Diagnosis can be helped by urine analysis which may contain protein, blood, bacteria, and even cancerous cells. Confirmation of diagnosis can be achieved with X-rays, often by using a radiographic contrast medium to highlight the bladder wall, or by ultrasound scanning of the bladder. Distinct masses may be apparent or just a change in thickness or irregularity of the bladder wall.

Treatment of choice is surgical removal, but the feasibility of this depends on the site of the tumour and the extent of the bladder involvement. It is highly successful with benign tumours, with malignant tumours regrowth often occurs after a few months. Chemotherapy has not been particularly successful but treatment of transitional cell carcinomas with piroxicam has shown some success in extending survival times by a few months.