Urinary system, renal and urinary diseases

• Eliminate waste and toxins from the body – main function
• Produce erythropoietin (EPO) for red blood cell production
• Control blood pressure – renin-angiotensin system
• Help control blood pH and sodium and potassium balance

• Functional unit of the kidney
• Each kidney may contain as many as a million 
• Plasma is filtered at the glomerulus, a specialized capillary tuft surrounded by the proximal end of the renal tubule
• The tubule is divided into functionally and structurally different portions
• In mammals, the proximal and distal portions lie in or near the kidney cortex with an intermediate loop and the final collecting ducts in the medulla

• Contains the primary filtering device of the nephron, the glomerulus
• Blood is transported into the Bowman's capsule from the afferent arteriole which branches off of the interlobular artery
• Within the capsule, the blood is filtered through the glomerulus and then passes out via the efferent arteriole
• Meanwhile, the filtered water and aqueous wastes are passed out of the Bowman's capsule into the proximal convoluted tubule

• The main filter of the nephron - located within the Bowman's capsule
• Resembles a twisted mass of tiny tubes through which the blood passes
• Semipermeable, allowing water and soluble wastes to pass through and be excreted out of the Bowman's capsule as urine
• The filtered blood passes out of the glomerulus into the efferent arteriole to be returned to the renal vein

• 20% of the body’s blood volume must be filtered through the kidneys every minute
• Decreased GFR results in an increase in toxins in the form of ammonia – azotemia
• GFR is screened by testing urea and creatinine

• Blood Urea Nitrogen (BUN) – two ammonia molecules, toxin which produced during normal
• protein metabolism

amino acid which is a metabolite of muscle, produced from normal muscle metabolism

increased blood ammonia which is assessed by measuring BUN and creatinine

• Decreased delivery of blood to the kidney = Prerenal
• Renal Failure = Renal
• Decreased outflow of urine (obstruction) = Postrenal

• NOT primary renal disease
• SECONDARY - reduced renal perfusion 
• Hypoadrenocorticsm -> loss of Na+ -> loss of water -> hypovolemia -> dehydration -> reduced renal perfusion -> AZOTEMIA
• Azotemia with CONCENTRATED urine > 1.030 in dogs and > 1.035 in cats

• Due to a low hypovolemia or hypotension
• Shock,
• cardiac failure,
• dehydration,
• vomiting and/or diarrhea,
• hypoadrenocorticism,
• PU without PD,
• heat stroke,
• blood loss,
• septicemia, etc.

• Must be corrected quickly with fluid support and treating underlying cause otherwise: 
• ->decreased blood flow to kidneys
• -> renal ischemia
• -> loss of nephrons
• -> renal failure

Urine specific gravity is same as blood (Isosthenuric) at 1.008-1.015

• RENAL DISEASE
• acute or chronic
• 65-75% damage to both kidneys
• loss of ability to concentrate urine

• Results from obstruction or rupture of urine outflow tracts
• –Renal pelvis, ureters, bladder, or urethra
• –Urolithiasis, trauma è most common
• -Obstruction can progress to rupture

• Prerenal
• Intrarenal
• Postrenal

• sudden and severe drop in blood pressure (shock)
• interruption of blood flow to the kidneys from severe injury or illness

• direct damage to the kidneys by inflammation,
• toxins,
• drugs,
• infection 
• reduced blood supply

• sudden obstruction of urine flow due to enlarged prostate,
• kidney stones,
• bladder tumor
• injury

• Renal disease
• -> toxins build up = azotemia
• -> pet becomes UREMIC
• -> pet feels sick, toxic, v/d, anorexic, etc.
• -> downward spiral unless toxins are flushed out of system (IV FLUIDS)

multi-systemic toxic syndrome that results from marked loss of kidney function

• Renal disease
• -> less or no EPO produced
• -> non-regenerative (chronic) anemia

• Anorexia
• Vomiting (emesis)
• Seizures
• Ulcers
• Weakness

• Anorexia due to lack of appetite
• One of the most common reasons pet owners seek medical care for their cats when renal failure is the cause

an imbalance of K+ adds significantly to weakness

• Buildup of toxins is the main reason
• Causes further dehydration and loss of K+, further exacerbating the problem in pets with kidney disease

If uremia is severe enough the brain can be affected by the toxins that build up

• Due to waste products are not being eliminated adequately
• Prevalent in the digestive system

• PU/PD
• Dilute urine with little color or odor/litter box wetter
• Nocturia
• Vomiting & Dehydration
• Anorexia & Weight loss
• Muscle weakness & Lethargy
• Small and irregular kidneys upon abdominal palpation or imaging
• Large or nodular kidneys if a cyst or cancer present
• Constipation or diarrhea
• Hypertension
• Acute blindness/dilated pupils
• Cervical ventroflexion in cats
• Oral ulers, ptyalism, halitosis
• Gastic ulcers
• Pale gums/anemia
• Elevated BUN
• Elevated Creatinine
• Albuminuria/Proteinuria
• Dysuria – anuria, oliguria

• Stage 1 - diminished reserve - GFR decreased by 50% - no clinical abnormalities
• Stage 2 - chronic renal
• insufficiency GFR 20 – 50 % of normal – azotemia, anemia, polyuria
• Stage 3 - chronic renal
• failure GFR – 20 – 25 % of normal – dehydration, all of the above, hypocalcemia, azotemia, GI, neurologic, and cardiovascular signs
• Stage 4 - end-stage renal disease < 5% of renal function- all signs of renal failure

• diminished reserve
• GFR decreased by 50%
• no clinical abnormalities

• chronic renal insufficiency GFR 20 – 50 % of normal
• azotemia,
• anemia,
• polyuria

• chronic renal failure GFR – 20 – 25 % of normal
• dehydration
• all of the above
• hypocalcemia
• azotemia
• GI
• neurologic
• cardiovascular signs

• end-stage renal disease < 5% of renal function-
• all signs of renal failure

• BUN = blood urea nitrogen
• Creatinine
• Phosphorous
• Potassium
• Albumin

• Elevated phosphorous could mineralize in tissues
• Calcium is sometimes decreased
• High anion gap -> metabolic acidosis

• •CBC – anemia
• •Blood chemistry – azotemia, phosphorous, albumin
• •Urinalysis – urine specific gravity, sediment, culture and sensitivity
• •Electrolytes – potassium
• •Blood gases – metabolic acidosis
• •Radiographs - survey
• –Contrast studies - excretory urogram, cystography, urethrogram
• •Abdominal ultrasound – uroliths, tumors, structural abnormalities

• Acute primary renal disease
• Infection of the upper urinary tract – kidneys and ureters

• asymptomatic,
• PU/PD,
• abdominal or lumbar pain,
• signs or lower urinary tract infection,
• fever,
• small or enlarged kidneys

• Usually from an ascending bacterial infection of aerobic bacteria,
• E. coli,
• Staphylococcus,
• Proteus,
• Streptococcus,
• Pseudomonas 

• •Infection of the urinary bladder – aerobic bacteria
• •More common in female dogs than males
• •Uncommon in young cats, common in cats greater than 10 years of age

• asymptomatic,
• pollakiuria (frequent voiding of small amounts),
• dysuria (painful of difficult),
• periuria (urinating in inappropriate places),
• break in house training,
• hematuria,
• cloudy or foul
• smelling urine

• •Urinalysis via cystocentesis – hematuria, proteinuria, pyuria
• •Urine culture necessary for definitive diagnosis

appropriate antibiotics

• •Also called FLUTD, feline idiopathic cystitis (FIC), old name feline urological
• syndrome (FUS)
• •Young to middle aged cats

• dysuria,
• hematuria,
• pollakiuria,
• periuria,
• outflow obstruction,
• thickened bladder wall

Stress

Urinalysis – hematuria and proteinuria without significant pyuria (WBC’s) or bacteriuria, crystalluria

• -Often self-limiting in 4-7 days – reoccurs unpredictably
• -Change diet to all canned diet which helps to increase urine volume and promote
• flushing of the bladder
• -analgesics, anxiolytic drugs, prazosin

• •Most common tumor of the urinary bladder
• •Usually in the trigone - eventually
• occludes the urethra
• •Middle-aged to aged female small breed dogs

• same as iFLUTD
• dysuria,
• hematuria, 
• pollakiuria, 
• periuria, 
• outflow obstruction, 
• thickened bladder wall

Contrast radiographic studies and ultrasound

• -piroxicam (NSAID with antitumor activity), chemotherapy
• -Progressive – long term survival poor

Can occur anywhere in the urinary tract

• Struvite
• Calcium phosphate
• Calcium oxalate
• Urate
• Cystine

• Uroliths
• magnesium ammonium phosphate

• Uroliths
• genetic predisposition
• Dalmations
• English bulldogs
• Yorkshire terriers

• depends on composition of uroliths
• correct urine pH
• antibiotics
• surgery
• change diet

• –Due to lack of estrogen
• –Urethral Sphincter Mechanism Incompetence
• –20% of early spayed female dogs will develop

• –Lower urinary tract infection 
• –Excessive consumption of water -> •Psychogenic polydipsia
• –Spinal cord disease
• –Canine cognitive dysfunction
• –Ectopic ureter (young dogs)