Renal anatomy and diagnostic tests

renal
system
organs of
the urinary system

1. kidneys
2. ureters
3. urinary bladder
4. urethra
5. internal urethral sphincter
6. external urethral sphincter
urinary system functions of the kidney
? elimination of metabolic wastes
? blood pressure regulation
? red blood cell production
? vitamin d synthesis
? prostaglandins synthesis
? electrolyte & fluid balances
? acid-base balances
? gluconeogenesis

internal anatomy of the kidney
a frontal sections of a kidney reveals 3 regions:
1. renal cortex
2. renal medulla
3. renal pelvis


kidney physiology
urine formation and the simultaneous adjustment of blood composition involves
three major processes:
1. glomerular filtration
2. tubular reabsorption
3. secretion

kidney physiology
filtration is the movement of substances from the glomerulus into the lumen of bowman’s capsule. this forms filtrate.
reabsorption is the movement of substances, solutes and water, across the walls of nephron into the capillaries associated with the nephron.
secretion is the movement of substances from the capillaries, associated with the nephron, across the walls of nephron into the filtrate with the nephron.
glomerular filtration
gfr is held relatively constant by three important mechanisms that regulate renal blood flow.

1. renal autoregulation
2. neural controls
3. hormonal controls
tubular reabsorption
? the proximal convoluted tubules are the most active in tubular reabsorption.
? all glucose, lactate, and amino acids are reabsorbed in this area.
? about 65% of sodium, 70% of water, are also reabsorbed 90% of bicarbonate ions, 50% of chloride ions, and 55% of potassium are reabsorbed in the proximal convoluted tubules.

tubular secretion
this process is important for:
1. disposing of substances which were not filtered & not reabsorbed.
2. removal of excess k+ .
3. controlling blood ph.
4. most secretion occurs within the pct. substances such as:
? neurotransmitters, bile pigment, uric acid, penicillin, atropine, morphine, h+ ions, and ammonia are secreted.
5. the dct receives mainly k and hydrogen ions from the blood.


kidney physiology
? one of the most important hormones in the control of urine concentration and volume is antidiuretic hormone, adh.

? amount filtered = amount reabsorbed + amount excreted


antiduretic hormone
the results of adh:
1. a decrease in osmolality

2. a increase in blood volume

3. a decrease in urine output
a ntiduretic hormone
antiduretic hormone
pathology
? hypersecretion can produce siadh.
? hyposecretion can produce diabetes insipidus.
aldosterone
other hormones
? estrogen is a female sex hormone produced by the ovaries.
? cortisol is a hormone produced by the cortex of the adrenal gland. it helps in the conversion of lipids and proteins to form glucose (gluconeogensis).
? calcitonin is a hormone produced by the thyroid gland in response to high levels of ca2+ ions in the blood.
? parathyroid hormone: reabsorption of ca2+ ions from the dct.



thyroid hormone ,parathyroid hormone,acid-base balance
blood ph dropings to 7.3
how does the body compensate?
breath faster to get rid of carbon dioxide eliminates acid

blood ph increases to 7.45
how does the body compensate?
breath slower to retain more carbon dioxide
? retains more acid
acid-base imbalance
? respiratory acidosis: any condition that impairs breathing can cause respiratory acidosis. this can result in an increase in the amount of carbon dioxide in the blood and a reduction in the ph.
? respiratory alkalosis: any condition that leads to hyperventilation can cause respiratory alkalosis. this can result in an decrease in the amount of carbon dioxide in the blood and a increase in the ph.


acid-base imbalance
? metabolic acidosis: is caused by excess acids in the blood. this can be the result of
? renal disease (acute & chronic renal failure),
? diabetes mellitus, or
? a decrease in the number of bicarbonate ions in the blood.
? metabolic alkalosis: is caused by a reduction in the amount of acid in the blood. this can be the result of
? vomiting, diarrhea
? diuretics, or
? excessive bicarbonate ions in the blood.


rbc production

? erythropoietin is a hormone that controls rbc (erythrocyte) production in bone marrow.
? secreted in response to decreased amount of oxygen delivered to kidneys.
? anemia or hypoxia

vitamin d & prostaglandin synthesis
? vitamin d from food sources must be converted into its active form by the kidneys.
? active vitamin d is needed for absorption of calcium by the renal tubules and the intestines
? promoting bone and teeth metabolism
? prostaglandins
? primarily locally-acting, vasodilating substances
? counter the effects of raas and the sns on the kidneys
? vasodilatation ?? renal blood flow.
? promoting na+ excretion.
? n.b.: ? prostaglandin in renal failure ?? blood pressure.
renal assessment and diagnostic procedures
renal failure
is a severe impairment or a total lack of renal function which leads to disturbances in all body systems.
? classification according to onset:
? acute: developing within hours to days with little time to adjust to the biochemical changes, but is potentially reversible. (sudden, rapid onset, reversible)
? chronic: insidious & progressive development over a period of several years allows for some adjustment to biochemical changes, but is irreversible and always necessitates some form of dialysis or transplantation for long-term survival. (gradual, progressive, irreversible)
general symptoms
weakness ,fatigue.dyspnea
peripheral edema, nocturia,nausea
metallic taste in mouth,loss of appetite
rapid weight gains,pruritus,dry, scaly skin

health history
the nurse elicits information regarding:
? past medical and familial medical history
? recent changes:
? urinary patterns
? general: nausea & vomiting, fatigue, lethargy or changes in mentation
? personal habits: sleep or work
? recent weight gains or losses need to be explored
? medications (current & recent)
? over-the-counter and prescribed medications (nsaids e.g., ibuprofen) antibiotics e.g., aminoglycosides)
? recent events:
? trauma (presence of pain), infection, illicit drug use or expose to nephrotoxic substances
physical assessment
inspection:
? bleeding
? flank or posterior thorax
? grey-turner sign for renal trauma & purplish discoloration
? volume depletion / overload {box- 19-1}
? neck and hand veins (> 5 seconds in dep. suggests hypovolaemia in elevation suggests hypervolaemia )
? skin turgor, oral mucosa , edema
? lower extremities, orbital or sacral area
auscultation:
? volume
? heart sounds (s3 & s4)
? blood pressure
? orthostatic hypotension
? lungs: dyspnea / added breath sounds (shallow gasping breathing with periods of apnea may reflect acidosis)
percussion:
? a dull painless thud is normal,
? pain may indicate infection or trauma

abdomen

? ascites
additional assessment parameters
? mentation
? i&o and daily weights (arf less than 30 ml/hour or 400 ml/day)
? hemodynamic monitoring {table 19 - 1}
? cvp (nl: 2-6 mmhg) /
? paop (nl: 5-12 mmhg)
? ci
? map
laboratory assessment
serum studies
? bun (9-20mg/dl)
? creatinine (0.7-1.5 mg/dl)
nb: the ratio of bun to creat. = 10:1
? hgb (hemoglobin) & hct (hematocrit)
? albumin
? electrolytes
? k+, na+, ca+, magnesium & phosphate


urine studies:
? urine analysis (ua)
? color, appearance, ph, specific gravity, glucose, protein, wbc, rbc and casts.
? culture & sensitivity (c&s)
? bacteria
? urinary collection:
? 24 hour urine
? i.e. creatinine or electrolytes
? spot / random urine
? first a.m. void preferred
combination studies:
? creatinine clearance (110-120 ml/min)
? 24 hour urine and a serum sample
? equivalent to gfr best overall indicator of renal function
diagnostic studies
renal radiological examinations:
? kidney-ureter-bladder (kub)
? an x-ray which identifies the position, size and shape of the kidneys and the urinary tract
? assist in identifying renal masses
? i.e. renal calculi, tumors or cysts
? intravenous pyelogram (ivp)
? a series of x-rays following injection of radiopaque-contrast dye.
? allows visualization of the internal renal tissue.
? check allergies watch contrast !!
? if there is evidence of renal impairment, it is contraindicated.
other (non-invasive) renal studies:
? renal ultrasound
? size and shape of kidneys and urinary tract may reveal fluid accumulation, obstructions from masses (solid or fluid )
? renal computed tomography (ct)
? i.v. radiopaque-contrast dye can be done without
? cross-sectional view of the kidneys and urinary tract
? can assess renal perfusion and identify masses (fluid or solid), tissue necrosis or hemorrhage
? renal magnetic resonance imaging (mri)
? high-energy radiofrequency waves provide three-dimensional views clearer images
? can assess: trauma, lesions, malformations of vessels or tubules and necrosis
more-invasive renal studies:
? renal angiography
? interventional radiology procedure
? visualize renal blood flow
? can also, detect stenosis, clots, cysts or necrosis
? renal biopsy
? gold standard to diagnosis specific renal disease last resort in critically-ill client
? percutaneous: u/s guided / fluoroscopy
? open
? cautiously bleeding tendency