Renal System & Urologic Surgery Flashcards
The kidneys and ureters are located in what space and at what spinal level?
Retroperitoneal space, centered at the L2 vertebral body
Perioperative renal dysfunction can occur as a result of what 3 things?
surgical or medical disease, prolonged reduction in renal oxygen delivery, or nephrotoxin insult. (or all 3)
Renal pain is conveyed by sympathetic fibers back to what spinal cord segments? This sympathetic innervation is supplied by preganglionic fibers from what spinal cord segment?
Pain conveyed back to T10-L1. Innervation supplied from T8-L1
What nerve supplies the parasympathetic innervation to the kidneys?
vagus nerve
Innervation of the ureters is supplied from what spinal cord segments?
S2-S4
Where is the bladder located?
retroperitoneal space
What spinal level is needed for regional anesthesia for bladder surgery?
T10
Sympathetic innervation of the bladder, which conduct pain, touch and temperature sensations, originate from what spinal cord segment?
T11-T12
Bladder stretch sensation is transmitted via what?
Parasympathetic fibers from S2-S4
Does the SNS or PSNS provide most of the motor innervation to the bladder?
Parasympathetic nervous system
SNS and PSNS innervation of the prostate, penile urethra, and penis originate in what spinal cord semments?
SNS = T11-T12 PSNS = S2-S4
What is the pudendal nerve?
it provides pain sensations to the penis via the dorsal nerve of the penis
What level is needed for spinal anesthesia for testicular surgery?
Thoracic level - testicular sensation is conducted to the lower thoracic and upper lumbar segments
What is the microscopic functional unit of the kidney? What two roles does it carry out?
Nephron. carries out excretory and regulatory roles
Within the nephron, what is the capillary network that acts as the basic filtering unit called?
the Glomerulus
What is the name for the initial segment of the renal tubular system which envelopes the glomerulus and acts as the initial receptacle of the filtrate?
Bowman’s Capsule
List the 7 things filtered through the glomerulus.
water, electrolytes, glucose, amino acids, urea, uric acid, and creatinine
Kindeys receive what % of cardiac output and what percent of this volume gets filtered by the glomerulus?
20% of C.O. and 10% of this gets filtered to produce glomerular filtrate
How many L/day of glomerular filtrate is produced, and what % of this filtered fluid gets reabsorbed into circulation?
180L/day and 99% gets reabsorbed into circulation - resulting in 1-2L of urine output per day
GFR (glomerular filtration rate) is a measure of glomerular function expressed as what unit?
mL of filtrate produced per minute
GFR is the product of what 2 things?m Which one exerts the greatest influence on GFR?
- the tendency of the glomerular membrane to allow filtration to occur (membrane permeability and surface area)
- the pressure inside the glomerular capillary forcing fluid through the filter - changes in the pressure exerts the greatest influence on GFR
What are the 2 main determinants of glomerular filtration pressure?
glomerular capillary pressure (most important) and glomerular oncotic pressure (which is directly dependent on plasma oncotic pressure)
glomerular oncotic pressure is a minor influence on filtration rate
Auto-regulation of renal blood flow is effective for MAPs of what range?
50-150 mmHg
What are the two mechanisms for regulating blood flow to the glomerulus? What do they both have in common?
They both involve modulation of afferent arteriolar tone.
- Myogenic Reflex - decrease in arterial pressure cause arteriole dilation
- Tuboglomerular Feedback - dec RBF-> dec GFR -> Inc Cl reabsorption and dec Cl to juxtaglomerular apparatus…causes 2 things- afferent arteriole dilation (inc RBF) and release of renin which -> efferent arteriole constriction (inc glom. pressure)…both lead to inc GFR
Describe how water is reabsorbed at the various points in the nephron and what allows for the ability to produce concentrated urine - allowing for conservation of water and excretion of excess solutes
concentrated urine is accomplished by creating a hyperosmotic medullary interstitium (established within the countercurrrent flow if the limbs of the LoH) and regulating water permeability in the distal tubules and collecting ducts
65% is reabsorbed in the proximal tubule in isoosmotic fashion with Na and Cl
15 % in LoH- Descending limb of the Loop of Henle allows water to follow osmotic gradients - the thin and thick ascending limbs are relatively impermeable to water and play a key role in concentrating urine
Last 20% of water reabsorption occurs in the distal conv. tubules and in the collecting duct - the amount reabsorbed is controlled completely by ADH which is secreted by the posterior pituitary gland
During periods of decreased RBF, which area is especially vulnerable to ischemic injury and why?
the medullary Thick Ascending Limb (mTAL) - it only receives 2% of RBF but is very metabolically active
What is prerenal azotemia and ATN (acute tubular necrosis)?
Prerenal azotemia is the inc BUN associated with renal hypo-perfusion or ischemia that has not caused renal parenchymal damage.
Necrosis of tubular cells releases debris into the tubules, causing flow obstruction, inc tubular pressure and back flow of tubular fluid
Acute Tubular Necrosis is often precipitated by what and is most common what types of patients?
Precipitated by nephrotoxin exposure or reduced cardiac output and in pts w/ preexisting renal vasoconstriction (volume depletion, CHF, sepsis)
What is intrinsic acute renal failure?
“intrinsic” implies not only a primary renal etiology of ARF, but also includes ischemia, toxins, and renal parenchymal diseases
ATN is the most common ischemic lesion
List the 5 exogenous nephrotoxins commonly found in hospitals.
Antibiotics, anesthetic agents (methoxyflurane and enflurane), NSAIDs, Chemotherapeutic-immunosuppressive agents, contrast media
List the 7 endogenous nephrotoxins that are commonly found in the hospital setting.
- Calcium (hypercalcemia) 2. uric acid (hyperuricemia)
- Myoglobin (rhabdomyolysis) 4. Hemoglobin (hemolysis)
- Bilirubin (obstructive jaundiuce) 6. Oxalate crystals
- Paraproteins
What is postrenal azotemia?
an obstructive uropathy that occurs at any point in the collecting system (renal pelvis to distal urethra) …accounts for < 5% of ARF cases
Explain the difference in GFR for pts with ESRD, renal insufficiency, and decreased renal reserve.
ESRD = < 25% normal GFR
Renal Insufficiency = 25-40% normal GFR, elevated BUN and Cr but no symptoms
Decreased renal reserve = 60-75% normal GFR no elev of BUN pr Cr….or ~50% GFR with upper lim of norm BUN and Cr
What is uremic syndrome?
The most extreme for of chronic renal failure. GFR < 10% of norm
causes mult organ system dysfuntions, death without dialysis
unable to reg vol and comp of ECF -> fluid expansion and electrolyte overload, metabol acidosis, anemia, plt dysfun., life threatening hyperkalemia
What group of drugs is most likely to produce prolonged effects in ESRD pts due to their reliance on renal excretion?
Muscle relaxants. Only su, atracurium, cisatracurium, and mivacurium have minimal renal excretion of unchanged parent compound
What is the best test available as the sole indicator of imminent ARF? Why?
The creatinine clearance test. It is a direct reflection of GFR. Collect urine volume for 24hr pd (2 hr correlates)..
Ccr= (urine cr x urine volume)/ plasma cr
What is TUR Syndrome and how do you treat it?
water intoxication from irrigation fluid absorption..causes mult neuro and cardiopulm sxs associated with hyponatremia
120 = confusion, restlessness and poss QRS widening 115 = somnolence, nausea and wide QRS, elevated ST seg 110 = seizures, coma and v-tach or v-fib
Tx - 3% NaCl at rate of < 100mL/hr until Na > 120mEq/L
