Lecture 12: Alteration of renal and urinary tract function

alterations of renal and urinary tract function:

• renal and urinary tract function can be altered by a variety of disorders

  • infection of bladder (the most common type)

  • disorders within kidney

  • other systemic disease

urinary tract obstruction:

• a urinary tract obstruction is defined as a blockage of urine flow within the urinary tract

• the obstruction can be caused by a anatomic or functional defect (called obstructive uropathy)

• regardless of cause the consequence is blockage that leads to

  • urinary stasis

  • dilates the urinary system

  • increases the risk for function

• severity of obstructive uropathy is based on

  • location

  • completeness

  • involvement of one or both upper urinary tracts

  • duration

  • cause

• complete blockage causes

  • hydroureter (dilation of the ureter)

  • hydronephrosis (dilation of the renal pelvis and calyces)

  • dilation leads to

    • tubulointerstitial fibrosis is the deposition of excessive amount of extracellular matrix

    • apoptosis

  • tubulointerstitial fibrosis and apoptosis result detectable damage between 7-14 after obstruction

• partial blockage produces less damage

• compensatory hypertrophy is essential to recovery of renal function after an obstruction has occurred

  • obligatory growth- growth of nephrons under influence of human growth hormone

  • compensatory growth- growth of nephrons under influence of unidentified hormone

• postobstructive diuresis- rapid excretion of urine (10 l) in 24 hrs

  • can cause dehydration, electrolyte imbalance

• low bladder wall compliance- create pressure within bladder that reduces or blacks the urine transport

upper urinary tract obstruction:

• kidney stones

  • calculi or urinary stones

    • masses of crystals, protein, or other substances that form within and may obstruct the urinary tract

  • risk factors

    • gender, race, geographic location, seasonal factors, fluid intake, diet, and occupation

  • kidney stones are classifies according to the minerals comprising the stones

kidney stones:

• three factors are required before a stone is formed

  • supersaturation of one or more salts in urine

    • presence of a salt in a higher concentration than the volume able to dissolve the salt

  • precipitation of a salt from liquid to solid state

    • temperature and ph of urine influence the risk of precipitation (alkaline ph increases formation of calcium phosphate stones and acidic ph increase formation of uric acid stone)

  • growth into a stone via crystallization or aggregation

• acute unilateral renal obstruction predispose people to hypertension because

  • the reduced perfusion of the affected kidney activates the renin angiotensin aldosterone system, which causes constriction of peripheral arterioles

• other factors affecting stone formation

  • crystal growth inhibiting substances such as

    • pyrophosphate, potassium citrate, and magnesium

  • particle retention

  • matrix- organic material contained in a urinary calculus

• stones

  • calcium oxalate or calcium phosphate is the most common type of renal stone

    • hypercalciuria is usually atttributable to: hyperthyroidism, intestinal hyperabsorption of dietary calcium, bone demineralization caused by prolonged immobilization

  • struvite stones

    • are more common in women than men

    • they grow large and branch into a staghorn configuration in renal pelvis and calyces

    • they are closely associated with urinary tract infections caused by urease producing bacteria, such as pseudomonas

  • cystinuric stones

  • uric acid stones

• manifestation

  • renal colic

• evaluation

  • clinical symptoms and history

  • imaging and functional studies

  • urinalysis (ex. ph)

  • stone analysis

  • intravenous pyelogram

  • spiral abdominal ct

• treatment

  • stone removal

lower urinary tract obstruction:

• obstruction of lower urinary tract (lut) affects the entire urinary system

• obstruction of lut can be caused by

  • bladder neck dyssynergia- occurs when the smooth muscle of the urethrovesical junction fails to funnel

  • prostate enlargements- causes obstruction of urethra

  • urethral stricture- a scare that narrows urethral lumen

  • severe pelvic organ prolapse- in women causes bladder outlet obstruction

  • neurogenic bladder- disrupts normal bladder filling and emptying

    • spinal cord injury is more likely to cause functional obstruction of the bladder outlet in addition to neurogenic detrusor overactivity

    • caused by lesion of the brain, spinal cord or peripheral nervous system

      • lesion affecting the brain produces neurogenic detrus overactivity without sphincter dyssynergia

        • pons regulate and coordinates the detrusor and urethral sphincter muscles during micturition

      • lesion affecting the spinal cord (c2-s1) produces neurogenic detrus overactivity and sphincter dyssynergia (lack of coordination)

      • low bladder wall compliance

• diagnosis: clinical symptoms (ex. urination more than every two hour during day, awakening urination 3-4 times, perception of incomplete bladder emptying) (bc the obstruction causes the bladder to be unable to empty properly)

• treatment: prolapse would need constructive surgery, bladder neck (consist of circular muscles and adrenergic innervation) need alfa adrenergic blocking medications

tumors:

• renal tumors

  • renal adenomas- usually located near the cortex of the kidney

  • renal cell carcinoma- arises from proximal tubule epithelial cells

• bladder tumors

  • bladder cancer is associated with mutation of the p53 gene

  • papillary tumors

  • nonpapillary tumors

urinary tract infection (uti):

• uti is inflammation of the urinary epithelium following invasion and colonization by some pathogen within the urinary tract

• complicated uti- occurs in an individual with defects of the urinary system

• uncomplicated uti- occurs in an individual without defects of the urinary system

• persistent uti- ongoing infection despite at least 3 days of treatment

• clinical manifestations of a urinary tract infection (of a patient who is 85 yrs old) would be: confusion and poorly localized abdominal discomfort

• uti is commonly caused by bacteria, but fungi and protista could also cause uti

• most common bacterial pathogens

  • escherichia coli (the most common causes of uncomplicated urinary tract infections)

  • staphylococcus saprophyticus

  • enterobacter spp

• virulence of uropathogens- is a potential pathogens ability to evade the host defense mechanisms and cause infection

  • host defense mechanisms- ex. high urea in the urine is bacteriostatic

• cystitis

  • cystits is an inflammation of the bladder

  • manifestations

    • frequency, dysuria, urgency, and lower abdominal and/or suprapubic pain

  • treatment

    • antimicrobial therapy, increased fluid intake, avoidance of bladder irritants, and urinary analgesics

• pyelonephritis

  • chilical manifestation: flank pain

  • pyelonephritis is usually caused by antibody coated bacteria

  • acute pyelonephritis

    • acute infection of the ureter, renal pelvis, and/or renal parenchyma

  • chronic pyelonephritis

    • persistent or recurring episodes of acute pyelonephritis

    • risk of chronic pyelonephritis increases in individuals with renal infections and some type of obstructive pathologic condition

glomerular disorgers:

• the glomerulopathies are disorders that directly affect the glomerulus

• low serum complement is found in glomerular disorders

• membranous glomerular lesion is characterized by thickening of the glomerular wall with immune deposition of immunoglobulin g (igg) and c3

• glomerular disease demonstrates a sudden or insidious onset of hypertension, edema, and an elevated blood urea nitrogen (bua)

• decreased glomerular filtration rate

  • elevated plasma creatinine, urea, and reduced creatinine clearance

• glomerular damage causes a decreased glomerular membrane surface area, glomerular capillary blood flow, and blood hydrostatic pressure

• increased glomerular capillary permeability and loss of negative ionic charge barrier result in passage of plasma proteins into the urine

• resulting hypoalbuminemia encourages plasma fluid to move into the interstitial spaces

  • edema

• glomerulonephritis

  • inflammation of the glomerulus

    • immunologic abnormalities (most common)

    • drugs or toxins

    • vascular disorders

    • systemic diseases

    • viral causes

glomerulonephritis:

• mechanisms of injury

  • deposition of circulating soluble antigen antibody complexes, often with complement fragments

  • in glomerulonephritis, the glomerular cell walls damages by lysis from complement

  • formation of antibodies against the glomerular basement membrane

  • strepococcal release of neuroamidase

    

• a patient has hematuria with red blood cell casts and proteinuria exceeding 3 to 5 g/day with albumin as the major protein (no clue what this is doing here or what its trying to say)

nephrotic syndrome:

• excretion of 3.5 g or more of protein in the urine per day

• the protein excretion is due to glomerular injury

• nephrotic syndrome is characterized by

  • hypoalbuminemia, edema, hyperlipidemia, and lipiduria

• proteinuria causes edema- loss of plasma albumin decreases the plasma oncotic pressure, which normally holds water in the capillaries

renal dysfunction:

• decreased renal function is caused by:

  • renal insufficiency- decline in renal function (loss of about 25%)

  • renal failure- significant loss of renal function

  • end stage renal failure- when less than 10% of renal function remains

  • uremia- renal failure and elevated blood urea and creatinine levels

  • azotemia- increase serum level caused by renal insufficiency or renal failure

acute renal failure (arf):

• prerenal acute renal failure is the most common cause of arf and is caused by impaired renal blood flow

  • gfr declines due to the decrease in filtration pressure

• intrarenal acute renal failure

  • acute tubular necrosis (atn) is the most common cause of intrarenal renal failure

  • characteristics of acute tubular necrosis (atn) is urine sodium >30 mEq/L

• postrenal acute renal failure

  • occurs with urinary tract obstructions that affect the kidneys bilaterally

• manifestation

  • initiation phase- the phase of reduced perfusion or toxicity that leads to renal injury

  • maintenance phase- the period of established renal injury

  • recovery phase- the renal injury is being repaired

• glucose and insulin used to hyperkalemia associated with acute renal failure

  • when insulin transports glucose into the cell, it also carries potassium with it

• anemia of renal failure can be successfully treated with erythropoietin

chronic renal failure:

• chronic renal failure is the irreversible loss of renal function that affects nearly all organ systems

• progression

  • reduced renal reserve

  • renal insufficiency

  • renal failure

  • end stage renal disease

• chronic renal failure affects

  • creatinine and urea clearance

    • creatinine is constantly released from muscle tissue and excreted primarily by glomerular filtration

  • sodium and water balance

  • phosphate and calcium balance- metabolism of calcium and phosphate is mediated by parathyroid hormone (pth) and vitamin d

  • potassium balance- potassium excretion is related to distal tubular secretion mediated by aldosterone

  • acid base balance

  • skeletal and bone alteration

    • when the glomerular filtration (gfr) declines to 25% of normal

      • parathyroid hormone (pth) is no longer effective in maintaining serum phosphate levels

      • there is impaired synthesis of 1,25-vitamin d3, which reduces intestinal absorption of calcium, and effectiveness of calcium and phosphate resorption from bone by parathyroid hormone

  • cardiopulmonary system

  • neural function

  • endocrine and reproduction

  • hematologic alterations