Urinary system Part 1

Urinary system components

Urinary system components

kidneys, ureters, urinary bladder and urethra

Blood supply For Urinary System

The glomerulus is a tuft of capillaries supplied by an afferent arteriole

Urine formation Parts

Glomerular Filtration

Tubular Reabsorption

Tubular Secretion

Glomerular Filtration

substances move from blood to glomerular capsule

the process by which the kidneys filter waste and excess fluid from the blood into the urine-collecting tubules

Tubular Reabsorption

substances move from renal tubules into blood of peritubular capillaries

a process in the kidneys that moves water and solutes from the filtrate back into the bloodstream

• glucose, water, urea, proteins

• amino, lactic, citric, and uric acids

• phosphate, sulfate, calcium, potassium, and sodium ions

Tubular Secretion

substances move from blood of peritubular capillaries into renal tubules

a process in the kidneys that moves waste products and other substances from the blood into the urine

• drugs and ions

General Diagnostic tests

Urinalysis

Reagent strips (dipsticks)

Microscopic analysis

Urinalysis

physical description of urine (i.e. color, clarity, smell), biochemical, and microscopic analysis

–Normal physical description

• Odorless

• Foul smell from infections

• Sweet smell from diabetes mellitus

• clear to slightly hazy,

• yellow to amber color

–Color varies with concentration of solutes and water

Reagent strips (dipsticks)

pH should be close to neutral

• Vary from acid to basic

• Diet can change pH

–Specific gravity should be between 1.001 (dilute) and 1.030 (concentrated

• Measurement of the dissolved materials in urine

• distilled water=1.000

• indicator of concentrating ability of the kidneys

–All other tests should be negative

Microscopic analysis

inspection for white blood cells, bacteria, red blood cells, or collections of cellular debris, crystals, and cast

• Red blood cells and WBC’s  up to 5/HPF can be normal

• Increased RBC = hematuria

• Increased WBC = pyuria

Crystals in Microscopic Analysis

can be associated with renal calculi

Casts in Microscopic Analysis

are substances secreted in the tubules and retain the shape of the tubule

• Can be benign or associated with kidney disease

Urea

A substance formed by the breakdown of protein in the liver.

• by-product of amino acid catabolism by liver

  • From ammonia

• plasma concentration reflects the amount or protein in diet

• enters renal tubules through glomerular filtration

Uric acid

a waste product that's created when your body breaks down chemicals called purines in food and drinks

• product of nucleic acid metabolism

• enters renal tubules through glomerular filtration

• Increase levels in blood or decreased excretion in urine can lead to gout

BLOOD UREA NITROGEN (BUN)

Elevated BUN does not equal kidney dysfunction

• Can occur in dehydration

  • Results from increase concentration

• High protein diets

• Conditions with increase protein metabolism-trauma,surgery, burns, GI bleeding

creatine phosphate

Contains high energy phosphate bond and is abundant in muscle fibers

most used to resynthesize creatine phosphate

• some is converted to creatinine, which is excreted by kidneys

phosphate

energy-used to synthesize more ATP

Serum Creatinine

a blood test that measures the level of creatinine in your blood, which is a waste product from your muscles. It's a common test that's often used to check how well your kidneys are filtering your blood

Muscle breakdown product that is practically filtered at the glomerulus and is not reabsorbed by the tubules

Increase serum creatinine indicates decreased filtering of creatinine at the glomerulus

Exceptions to rule Of Serum Creatinine

Persons with increased daily muscle breakdown may have abnormally high creatinine

–A frail person will have low amount of serum creatinine daily

Elderly, for example

Azotemia

elevation of BUN and Creatinine

•Related to decreased glomerular filtration rate

Imaging studies

Ultrasound

Intravenous pyelography

Radiographs

Computed tomography scans

MRI

Renal biopsy

a small sample of kidney tissue is removed with a needle.

• The test is sometimes used to evaluate a transplanted kidney.

• It is also used to evaluate an unexplained decrease in kidney function, persistent blood in the urine, or protein in the urine.

Etiology of kidney dysfunction are divided into 3 categories

Prerenal dysfunction

Intrarenal dysfunction

Post renal dysfunction

Prerenal dysfunction

Caused by decreased blood flow and perfusion to kidneys

• Directly related to blood flow and renal perfusion

Prerenal dysfunction Causes

Causes include decrease cardiac output or severe hypovolemia (decrease blood volume-hemorrhage e.g.), shock

• Large blood loss is a common cause of injury caused by ischemia

Intrarenal dysfunction

Develops secondary to actual injuries to the kidney itself

occurs when the kidney itself is damaged by a disease process

Etiology of Intrarenal Dysfunction

Direct damage to nephrons from trauma, toxins, infections or atherosclerosis causing decrease blood supply

Most common cause is nephrotoxic drugs (aminoglycosides, NSAIDS), renal infections (post streptococcal glomerulonephritis), systemic illness

Post renal dysfunction

Related to obstruction of urine outflow from the kidneys

Urine backs up within the ureter and kidneys resulting in a fluid filled kidney (hydronephrosis)

• Urine is toxic to cells

• Urine stagnation predisposes to secondary infection

Etiology of Post renal dysfunction

obstructive uropathy - Examples: uroliths, prostatic enlargment

Glomerulonephritis

inflammation and damage to the filtering part of the kidneys (glomeruli)

Can be acute or chronic

Etiology Of Glomerulonephritis

infections, immune mediated diseases, inherited

Leading cause of chronic kidney disease

Decrease urine output (oliguria) from blocked glomeruli by inflammation

Less urine formation leads to less waste product being excreted (accumulate in blood)-increase BUN and Creatinine

Protein (albumin) and red cells leak through damaged glomerular membrane

Low GFR leads to hypervolemia and increase in blood pressure

• Low albumin in blood (hypoalbuminemia) leads to diminished oncotic pressure

Inflammatory changes impair kidney’s ability to excrete waste and excess fluid

Injury to the glomerulus causes cellular changes that impair filtration of blood

Nephrotic syndrome

refers to a group of abnormalities characterized by a severe loss of protein in the urine

Combination of clinical finding that occur when the glomerulus is damaged , which allows proteins to be lost in the urine

– Proteinuria, hypoalbuminemia, massive generalizededema

Etiology of Nephrotic syndrome

Glomerulonephritis-chronic and progressive

– Diabetes (causing glomerular changes)

– Most common type

– Systemic lupus erythematosus, SLE-affect connective tissue; autoimmune disease

– Associated with NSAID use

Lower Urinary tract infection UTI

Very common; maybe acute or chronic

• Most infections are caused by gram-negative bacteria

– E. coli most common

• Organisms contaminate perianal and genital areas and ascend urethra

Lower urinary tract infections

Bladder and urethra

– Cystitis: affects only the bladder

Conditions protective against infection Lower Urinary Tract infections

Free urine flow

–Large urine volume

–Complete bladder emptying

–Acid urine: most bacteria grow poorly in an acidic environment

–Immunoglobulin A secreted by WBC’s in urinary tract prevents adherence of bacteria to bladder wall

•Some women are non-secretors of IgA

Predisposing factors Of UTI

Any condition that impairs free drainage of urine

–Stagnation of urine favors bacterial growth

–Injury to mucosa by kidney stone disrupts protective epithelium allowing bacteria to invade deeper tissue

–Introduction of catheter or instruments into bladder may carry bacteria

Cystitis

Affects only the bladder

inflammation of the bladder, usually caused by a bladder infection.

Population of Cystitis

More common in women than men; shorter female urethra, and, in young sexually active women, sexual intercourse promotes transfer of bacteria from urethra to bladder

Common in older men, because enlarged prostate interferes with complete bladder emptying—benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH)

a noncancerous condition that causes the prostate gland to enlarge

common in men 50 years or older

•Idiopathic

•Prostate enlargement leads to urethral obstruction, which obstructs urine outflow

•Predisposes to UTI, bladder calculi,hydronephrosis

Clinical manifestations

congestion inflammation of bladder mucosa

–Burning pain on urination-

•Dysuria= painful or difficulty urinating

–Desire to urinate frequently

–Urine contains many bacteria and leukocytes

–Elderly have high risk and may present with confusion

–Responds well to antibiotics

–May spread upward into renal pelvis and kidneysC

Diagnostic test: Of UTI

Urinalysis: + leukocyte esterase and + blood and alkaline pH (typically)

• WBC/hpf >100/hpf

• RBC/hpf 2-5/hpf

• Casts None

• Other Many leukocytes

• Culture and sensitivity for definitive identification of organism and antibiotic

Pyelonephritis

Suppurative inflammation of the kidney and renal pelvis, caused by Escherichia coli found in the colon; streptococci, and staphylococci are examples

–Acute or chronic

Pyelonephritis Location and population

Involvement of upper urinary tract from

• Ascending infection from the bladder (ascending pyelonephritis)

  • Most common; higher incidence in young women

  • Older men with prostatitis

  • Obstructive uropathy  predisposes to infection

  • E. coli is most common

• Carried to the kidneys from the bloodstream (hematogenous pyelonephritis)

  • Less common

  • Staphyloccocus aureaus is most common

Define pyelo

pelvis

Clinical manifestations For Pyelonephritis

Localized pain and tenderness over affected kidney

•Back pain that spreads over the abdomen

–-fever, chills

–Nausea and vomiting

–+/- gross hematuria

–Responds well to antibiotics

–Cystitis and pyelonephritis are frequently associated

•Signs will include those of lower UTI

Chronic pyelonephritis may have more subtle signs/symptoms

–Some cases become chronic and lead to kidney failure

•Kidneys will become shrunken and contain Increase scar tissue

•Renal functions declines

Histological lesions

kidney is infiltrated with leukocytes and bacteria

–Many tubules filled with leukocytes

urinalysis:  hematuria , bacteria, wbc’s (pyuria)

       wbc casts

Culture and sensitivity for definitive diagnosis

Imaging studies