Diseases of the Urinary System

Diseases of the Urinary System are renal insufficiency, cystitis, urolithiasis, acute renal failure, chronic kidney disease (CKD), etc.

The urinary system of animals is comprised of paired kidneys and ureters, one of which communicates to the exterior by means of the urethra.

Kidneys consist of the outer cortex and inner medulla. The nephron is a functional unit of the kidney. There are about four lakh nephrons in each kidney of a dog. Each nephron is made up of a glomerulus (tufts of capillaries), surrounded by Bowman’s capsules, proximal convoluted tubules, descending and ascending loop of henle, and a distal convoluted tubule that joins the common collecting duct.

Kidneys perform several functions, of which excretion of metabolic waste, maintenance of fluid and electrolyte balance, production of erythropoietin and vitamin D3, and selective reabsorption and excretion of certain metabolites are the most important.

Renal insufficiency, also known as kidney insufficiency or renal failure, refers to a condition in which the kidneys are unable to adequately perform their essential functions, such as filtering waste products and excess fluids from the blood, regulating electrolyte balance, and producing hormones that regulate blood pressure and red blood cell production.

Renal insufficiency can occur due to various reasons, including:

• Abnormalities in the rate of renal blood flow.
• The glomerular filtration rate.
• Efficiency of tubular reabsorption.

Principal Manifestations of Urinary Tract Dysfunctions

Principal manifestations of urinary tract dysfunction in animals are:

1. Abnormal constituent in the urine
2. Variation in the daily output of urine
3. Abdominal Pain
4. Palpable abnormalities of kidneys, ureter, bladder & urethra

(1) Abnormal constituent in the urine

A physical, chemical, and microscopic evaluation of a urine sample gives a fair idea about urinary tract disorders. The following list shows the abnormal constituents and tests to detect them:

• Turbidity, pus, and fowl smell in urine: Visual examination
• Protiens: Roberts test
• Blood or haemoglobin: OCCULT blood or benzidine test
• Myoglobin: Benzidine test
• Glucose: Benedict’s test
• Ketone: Rotheras test
• Crystals, cells, and casts: Microscopic examination

(2) Variation in the daily output of urine

• Polyuria: An increase in the volume of urine is called polyuria. It is seen in excessive intake of water, deficiency of ADH, diabetes mellitus, and CRF.
• Oliguria: reduction in the daily output of urine. It is seen in dehydration, shock, and CHF. Urethral obstruction, cystitis, and acute nephritis.
• Anuria: complete absence of urine seen in acute renal failure. Glomerular nephritis and complete obstruction of the urinary tract.
• Pollakiuria is a frequent painful micturition in small quantities commonly seen in cystitis.
• Urinary incontinence: It is constant dribbling urine usually noticed in the loss of tone of the urinary bladder sphincter.
• Dysuria: Difficult and painful urination
• Stranguria: slow and painful urination associated with diseases of the lower urinary tract

(3) Abdominal Pain

Abdominal pain is manifested by constant sit ups, kicking at the belly, constant groaning, overstretching back, and sometimes even rolling on the ground.

(4) Palpable abnormalities of kidneys, ureter, bladder & urethra

Enlargement of these structures on rectal palpation or by ultrasonography or radiography is suggestive of structural involvement of these organs.

End-stage renal failure is characterised by polysystemic signs like uraemic breath, generalised oedematous tendencies, progressive anaemia, and osteodystrophic changes.

Special Examination & Diagnostic Approach for Urinary Tract Dysfunction

• Urinalysis
• Renal function test
• Imaging techniques

Urinalysis

Urinalysis is an essential component of the diagnosis of urinary tract dysfunction by performing urine analysis.

Detection of abnormal constituents of the urine gives an idea about organ involvement, especially gravity of urine, which is also a simple test to detect the capacity of kidneys to retain fluid and excrete solids.

The normal specific gravities in most of the animal species range between 1.028 and 1.032. Increased specific gravity indicates acute renal disease, while decreased specific gravity suggests chronic renal failure.

Renal function test

Renal function tests evaluate the amount of renal blood flow, the rate of glomerular filtration, and effective tubular function. The blood urea and serum creatinine are sensitive indicators of renal function. GFR is measured by the rate of disappearance of sodium sulfanilate given intravenously. Renal blood flow can be evaluated by measuring the clearance of certain dyes, like bromosulfa naphthalene (BSP), which offers IV administration. Elevated levels of GGT in the blood indicate proximal renal tubular damage.

Imaging techniques

Intravenous pyelography using a contrast medium like iohexol shows anatomical structural defects of the urinary tract. Ultrasonography is also being used in canine and equine practice.

Ultrasound guided percutaneous renal biopsy has been tried in dogs and horses; it gives histological defects of renal parenchyma for confirmative diagnosis.

Principles of treatment of Urinary Tract Diseases (UTI/UTD)

Antimicrobial Drugs

Antibiotic sensitivity assays should be done before antibiotic selection. The ideal antimicrobial should have:

• Selective excretion through the kidneys
• Be active in a varied pH of urine
• Low toxicity in the case of administration
• Broad-spectrum activity

In the absence of a sensitivity assay, strepto penicillin, sulpha trimethoprim combination, ampicillin and cloxacillin, new cephalosporins like ceftriaxone, fluoroquinolones like ciproflox and norflox, and recommended doses can be given.

Fluids and Electrolytes

Balanced electrolytes supplemented with calcium and potassium can be used to correct fluid and electrolyte deficits. In the presence of oliguria or anuria, the rate of fluid administration should be monitored to prevent over-dehydration. After correction of the fluid deficit, oliguria can be treated with the help of a diuretic like frusemide at 1-2 mg/kg body weight. In non-responding cases, it can be treated with selective renal vasodilators like dopamine at 5 mg/kg body weight per hour as an infusion.

In Case of Non Regenerative Anaemia

Non-regenerative anaemia is a major problem in CRF cases in dogs, as there is an inherent deficiency of erythropoietin due to damage to the renal parenchyma. Repeated blood transfusions can only be an alternative. Few reports suggest the use of anabolic steroids at 1–5 mg/kg to a maximum of 200 mg to stimulate extra renal erythropoietin synthesis. Vit D3 should also be used in CRF in dogs to counteract osteodystrophic changes.

Dialysis

Peritoneal hemodialysis is considered a palliative but life-saving measure in chronic renal failure (CRF). However, repeated peritoneal dialysis poses a risk of peritonitis, and there is always an inhibitory factor in hemodialysis.