Urology- Introduction Flashcards
What comprises the upper urinary tract?
Kidneys and ureters
What comprises the lower urinary tract?
Bladder and urethra
What is the purpose of the upper urinary tract?
Production and movement of urine
What is the purpose of the lower urinary tract?
Storage and elimination of urine
How much of the CO do the kidneys receive?
20-25%
What is the functional unit of the kidney?
Nephron
What are the functions of the kidneys? (5)
- Excrete waste
- Retrieve filtered particles
- Maintain acid/base balance
- Regulate blood pressure
- Stimulate erythrocyte production
Where is most of the water reabsorbed in the nephron?
Proximal tubule and descending loop of henle
Where is angiotensin 1 converted to angiotensin 2?
Lungs
What gland produces aldosterone?
Adrenal
What cells produce renin?
Juxtaglomerular cells
What does renin stimulate the production of and where?
Angiotensin 1 in the liver
T/F: The kidney is the site of production of active vit D.
True
What is azotemia?
Abnormal increased in concentration of BUN and/or creatinine in the blood
What can pre-renal azotemia be due to?
- Dehydration
- Hypoadrenocorticism
- Cardiac disease
- Shock
- Hypovolemia
What is pre-renal azotemia a result of?
Poor renal perfusion
What can renal azotemia be due to?
- Parenchymal disease
- Infections
- Cysts
- Inflammation
- Neoplasia
- Toxins
What can post-renal azotemia be due to?
Blockage of the ureters, bladder, or urethra
T/F: Azotemia is synonymous with uremia.
False!
Although an azotemic patient may ALSO be uremic
Renal failure is defined by failure to perform what three functions?
Regulatory, excretory, and endocrine
What will renal failure result in?
Retention of nitrogenous solutes and derangement of fluid, electrolytes, and acid-base balance
Loss of what percent of nephrons will result in renal failure?
75%
T/F: An animal cannot survive with only one kidney.
False
Although the animal is then at higher risk for renal failure since it only has 50% of it’s total nephrons.
What is the definition of renal disease?
Presence of morphological or functional lesions in one or both kidneys.
What is uremia?
Collection of clinical signs and biochemical changes associated with the critical loss of functional nephrons.
(Primarily due to accumulation of toxic substances)
T/F: Uremia includes extra-renal manifestations of renal failure.
True
What does the glomerular filtration rate directly related to?
Renal functional mass
What are some accurate techniques to measure GFR? (2)
- Clearance of radioisotopes with renal scintigraphy
- Iohexal/inulin/creatinine clearance tests
What are some indurect methods that indicate GFR?
- Serurm urea levels
- Serum creatinine levels
- Cystatin C
- SDMA
What is the gold standard test for GFR?
Renal scintigraphy
Where is urea synthesized?
Liver
Where is urea excreted?
Kidneys
What does urea do in the kidney?
Helps maintain the concentration gradient in the medulla. (Essential for proper kidney function)
Are all animals going to have the same “normal” levels of urea?
No, normal levels are effected by all the things.
T/F: Urea is a reliable estimate of GFR
False
Why is urea an unreliable estimate of GFR?
Subject to passive re-absorption in the tubules which can be exacerbated by slow rates of flow or tubular damage
What can lead to a falsely high urea level? (3)
GIT bleeds, intravascular hemolysis, high protein diets
What is creatinine synthesized from?
From the breakdown of creatine in muscle
T/F: Creatinine is produced at varying rates depending on muscle activity.
False, produced at a constant rate
T/F: Creatinine levels are dependent on muscle mass.
True, heavier muscled animals will have higher levels or creatinine
Is creatinine influenced by the diet?
Not significantly
Where is creatinine excreted?
Kidneys, unchanged
What will increase serum creatinine levels?
Reduced renal clearance/GFR
What will decrease serum creatinine levels?
Reduced muscle mass (may be significant in old or cachexic patients)
At what percent reduction of GFR will azotemia develop?
75% reduction (aka 25% of normal)
Is the relationship between creatinine excretion and GFR linear?
No, but still better indication than urea
Does creatinine give you an exact reason for the decreased GFR?
No
Will creatinine levels differ dependent on the cause of the azotemia?
No
Will creatinine levels differ dependent on an acute versus a chronic process?
No
Will creatinine levels differ dependent on reversible or irreversible failure?
No
T/F: Severity of clinical signs of azotemia are directly proportional to the magnitude of the increase.
False, there is massive individual variation
Is the severity of the azotemia a good prognostic indicator?
No, just gives you an indication that there IS a problem
What is cystatin C?
Small polypeptide protease inhibitor produced by all nucleated cells
Why is cystatin C a good indicator for GFR?
Freely filtered by the glomeruli and does not undergo tubular secretion
T/F: Cystatin C is completely reabsorbed by the proximal tubular cells and catabolized into amino acids
True
What is SDMA?
Symmetic dimethlarginine- methlyated form of arginine which is produced by all cells and released into the blood during protein degradation
What is the advantage of SDMA over creatinine as an indication of GFR?
Increases earlier than creatinine and can be detected at 40% decline in GFR
Is SDMA impacted by extra-renal factors or lean body mass?
No, kidney function specific
What is an important test for determining kidney function?
Urinalysis
What is the best method for urine collection for analysis?
Cystocentesis
What is a disadvantage of cystocentesis?
May give a false positive for blood
What kind of animal is urinary catheterization most used it?
Male dogs
What are the only useful tests on dipsticks?
Protein, pH, blood, glucose, ketone
Dipsticks are designed for humans, not animals
What are the two ways in which we can measure urine concentration?
Gold standard: osmolality
Used in practice: specific gravity
How are refractometers calibrated?
Distilled water set to 1.000
What solute can result in a falsely increased specific gravity?
Glucose
What range of SG is hyposthenuria?
1.000 - 1.007 or
What range of SG is is isosthenuria?
1.008 - 1.012 or ~300mOm
What range of SG is hypersthenuria?
> 1.012 or >300mOm
What range of SG is minimally concentrated urine?
1.013 - 1.030
What range of SG is is inadequately concentrated urine?
What range of SG is adequately concentrated urine?
Dogs >1.030
Cats >1.035
What do we look for in sediment exams?
Bacteria, cells, casts, crystals
What are some causes of hyposthenuria?
- Psychogenic polydipsia
- Diabetes insipidus
- Hyperadronocorticism
What does a partial water deprivation test differentiate between?
Psychogenic polydipisa and diabetes insipidus
What would a failure to concentrate durin a partial water deprivation test indicate?
Nephrogenic DI or medullary washout
What is the fractional excretion of electrolytes used to assess?
Renal tubular dysfunction
What is the most common fractional excretion used?
Na- fractional excretion
What are the electrolytes compared to in a fractional excretion value?
Creatinine
What percentage Na-fractional excretion would indicate prerenal disease?
What precentage Na-fractional excretion would indicate renal disease?
> 1%
Which breed of dog is predisposed to calcium dihydrate crystals?
Bischons
Which breed of dog is predisposed to cystiene crystals?
Bulldogs
Which breed of dog is predisposed to ammonium biurate crystals?
Dalmatians
Which animal is predisposed to struvite crystals?
Cats
What toxin will result in calcium monohydrate crystals?
Ethylene glycol
What is the urine protein creatinine ratio used to correlate?
Protein excretion during a 24hr period
What are the urine protein creatinine ratio values for a cat?
> 0.4 = proteinuric
0.2-0.4 = borderline, recheck in 2mo
What are the urine protein creatinine ratio values for a dog?
> 0.5 = proteinuric
0.2-0.5 = borderline, recheck in 2mo
Should urine protein creatinine ratio be interpreted by itself?
No, only after sedimentation and culture
Are bladder tumor anitgen tests super useful?
No, very poor specificity/sensitivity which gets worse with concurrent urinary tract disease
What are the most common types of bacteria found in the urinary tract?
Gram negative aerobic bacteria
E. coli most common
What is a common source of bacteria in urine?
Environmental contamination- false positive
T/F: Presence of bacteria in any quantity is enough to diagnose a UTI.
False- must be a certain number of CFU’s per mL
What are the storage time limits for a urine sample to culture?
Fresh- within 30 min
Refrigerated- up to 6 hours
Chemical preservatives and regrigeration- up to 72 hours
What part of the kidney should be biopsied with ultrasound or endoscope?
Cortex
Blind sampling of the medulla risks hitting a interlobar artery
Can full thickness/wedge biopsies be obtained from a kidney?
Yes, requires general anesthesia and abdominal surgery
What is hematuria?
Presence of blood or red blood cells in the urine
What is gross hematuria?
Sufficient blood present to be apparent to the naked eye
What is occult hematuria
Blood present in insufficient quantities to be visible to the naked eye
What is pseudohematuria?
Red to brownish urine without intact red blood cells
What can pseudohematuria be due to the presence of?
Hemoglobin, myoglobin, or chemicals
What is a systemic cause of hematuria?
Hemostatic disorders
What are renal causes of hematuria
Neoplasia, calculi, trauma, infarction, cysts, glomerulonephritis, infection
What are lower urinary tract causes of hematuria?
Bacterial infection, calculi, trauma, neoplasia, polyps, cyclophosphamide therapy, feline idiopathic cystitis
What are genital tract causes of hematuria?
Prostatic disease, oestrus, infection, neoplasia, trauma
Can hematuria lead to hemoglobinuria?
Yes, if the red cells lyse
Are animals with hematuria usually dysuric?
No, not unless there is concurrent lower urinary tract disease/obstrution
What are the clinical manifestations of kidney disease?
- PU/PD
- Anorexia/GI issues/ wt. loss
- Pale MM
- Lethargy
- Blindness
- Distended abdomen
Why will renal disease/failure patients have pale MM?
Anemia due to decreased EPO production
Why will renal disease/failure patients be blind?
Hypertension due to increased angiotensin 2
What is pollakiuria?
Frequent, small volumes of urine
What is dysuria?
Trying to urinate with little no to production
NOT straining
What is stranguria?
Straining to urinate
May be painful
What are some clinical findings of an animal with LUTD?
- Dehydration
- Enlarged bladder (may be profound)
- Difficult/impossible urinary catheterization
- Localized SQ fluid around perineum or ventral abdomen (post-renal)
- Free peritoneal fluid
- Urine retention/incontinence
- Straining or abnormal posture
What is a normal urine output?
1-2 mL/kg/hr
Should specific gravity be measured prior to any fluid therapy?
Yes- fluid therapy can falsely decrease SG
What are some things that can be used to differentiate between acute and chronic renal failure?
- Weight loss
- PU/PD history
- PCV
- USG
- Size of parathyroid glands
- Carbamylated Hb
Is renal neoplasia common in small animals?
No
What are the primary renal neoplasms?
Adenocarcinoma
Lymphoma
Sarcoma
Nephroblastoma
Is the kidney a possible site of metastasis?
Yes
Are renal carcinomas more common in dogs or cats?
Dogs
Do renal carcinomas typically cause clinical signs in early stages?
No
What are some features of renal carcinomas?
- Hematuria and wt loss
- Typically unilateral causing renomegaly
- Rarely causes azotemia
- Can cause polycythemia and hypertrophic osteopathy
What percentage of animals will have metastasis from renal carcinomas at time of diagnosis?
50%
How do you treat renal carcinomas?
Nephrectomy (make sure other kidney is okay first!)
What is the prognosis for renal carcinomas?
Most dogs survive about 16mo without treatment
Are renal lymphomas more common in dogs or cats?
Cats
What are some features of renal lymphomas?
- Usually bilateral and enlarging
- Weight loss, inappetance
- PU/PD
- Commonly azotemic
- Often systemic
- Tendency to spread to CNS
- Fair association with FeLV
How do you treat renal lymphomas
- Multi-agent chemotherapy
What is the prognosis for renal lymphoma?
About 60% go into remission
Most cats survive 91 days with treatment
What are some non-neoplastic causes of renomegaly?
- Renal inflammation
- Amyloidosis
- Hydronephrosis
- PKD
- PSS
Which breed is predisposed to PKD?
Persian cats- mutation in PKD-1 gene
Is PKD generally symptomatic?
Depends on severity of cyst infiltration
Why is renal pain difficult to assess?
Typically referred or interpreted as spinal pain
What are some causes of renal pain?
- Pyelonephritis
- Renal Calculi
- Acute nephrosis
- Early hydronephrosis
- Renal trauma
- Abscess
- Neoplasia (rare)
