Studydroid is shutting down on January 1st, 2019

by mtoom

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Regarding nephrolithiasis:
  • What is prevalence of nephrolithiasis?
  • What proportion of people develop a stone by age 70?
  • More common in males or females?
  • When in life is peak incidence?
  • Prevalence is 2-3%
  • 1 in 8 develop a stone by age 70
  • More common in males
  • Peak incidence: 20s to 40s
Name 6 potential causes of Nephrolithiasis
  • Supersaturation theory
  • Nucleation theory
  • Lack of Stone Inhibitors
  • Crystal aggregation
  • Stasis of urine
  • Changes in urinary pH
What is supersaturation theory?
  • Central event in stone formation
  • When urine becomes saturated with ions, forming a salt
  • Crystal precipitation occurs due concentration surpassing solubility maximum
What is nucleation theory?
Stone formation is initiated by:
  • the presence of a crystal
  • cellular debris in urine saturated with crystal forming minerals

This initial crystal or debris clump is the "nucleus" of stone formation
What is the "Lack of stone inhibitors" theory?
  • Urine has natural substances to inhibit stone formation
    -RNA peptides
  • Certain individuals who form stones lack inhibitors in urine 
What is the crystal aggregation theory?
Microcrystals adhere together to become macrocrystals
How does statis of urine contribute to formation of crystals?
  • Crystals have an increased opportunity to adhere in urine that is static (rather than flowing)
  • Congenital anatomical abnormalities of kidney predispose to urine stasis
How do alterations in urinary pH contribute to solubility of dissolved minerals in urine?
  • Changes in acidity affect the solubility of dissolved minerals in urine
  • e.g. uric acid stones form in acidic urine
  • e.g. struvite stones form in abnormally alkaline urine
Describe 3 common locations of obstruction in ureter?
  • Ureteropelvic junction (ureter and kidney pelvis)
  • Pevic brim (ureter and vessels)
  • Uretovesicular junction (ureter and bladder)
What are symptoms of acute renal colic (6)?
  • Flank pain +/- radiation to groin/labia/testis
  • Gross hematuria
  • Nausea +/- vomiting
  • Diaphoresis or chills
  • Voiding difficulties
  • Anuria (lack of urine production)
What are signs of acute renal colic (6)?
  • Pallor
  • Costovertebral tenderness on palpation
  • Writhing
  • Hypertension
  • Possible fever
  • Suprapubic distension (suspect urinary retention)
  • Abdominal distension
What are the 5 elements of initial management for renal colic?
  • Treat pain
    -Narcotic analgesics
    -Antispasmodic agents
  • Hydrate patient by IV
  • Treat nausea with antiemetics
  • Start broad-spectrum antibiotics if infection is suspected
  • Promote passage of stone
    -use alpha-blockers to facilitate smooth muscle relaxation
Describe 3 laboratory investigations that are useful in Acute Renal Colic
  • Urinalysis
    -evaluate hematuria, pyruia, crystals 
  • Urine culture
    -if infection suspected 
  • Serum creatinine
    -assess renal function 
What are 4 potential radiological options for Acute Renal Colic?
  • Computerized Tomography (CT)
  • KUB (X-ray)
  • Intravenous pyelogram
  • Renal ultrasound
What is the gold standard for evaluation of the abdomen and pelvis?
  • Gold standard for evaluating nephrolithiasis
  • Cross-sectional transverse images of the body at 3mm intervals
Name 4 advantages and 3 disadvantages of CT of abdomen/pelvis
  • Quick
  • No IV or oral contrast needed
  • Can detect stones as small as 2mm
  • Allows examination of adjacent organs
  • More radiation than X-ray
  • More expensive than X-ray
  • Should be avoided in pregnancy
What is a KUB? 2 advantages, 3 disadvantages?
KUB = X-ray of kidneys, ureters, bladder (in supine position)

  • 90% of stones can be seen on KUB
  • Quick, minimal radiation exposure
  • Uric acid stones not visible
  • Tiny stones may be obscured by stool, bony structures
  • Calcified lymph nodes and pelvic phleboliths can be confused with stones (calcification within a vein)
Describe an intravenous pyelogram (IVP)?
  • IV contrast injection of radiopaque dye, followed by serial X-rays
  • Utility replaced by CT scans
  • Still used in rural centers
What are advantages (3) and disadvantages (4) of IV pyelogram?
  • Distinguish between urological and non-urological calcifications
  • Can define anatomical level of obstruction
  • Can define severity of obstruction
  • More time-consuming than CT
  • Less sensitive for small calculi
  • Dye is problematic (hard on kidneys, allergies are problem)
  • Laxative preparation required 
What are advantages (2) and disadvantages (2) or renal ultrasound?
  • No radiation exposure
  • Can detect renal stones and hydronephrosis
  • Poor anatomical detail
  • Unable to diagnose size or location or ureteral stones
What imaging study should be chosen for renal colic?
  • Acute renal colic?
  • In rural setting?
  • In pregnant patient? 
  • Acute renal colic: CT-KUB
  • Acute renal colic and CT unavailable: IVP
  • Pregnant patient: Ultrasound

For following progress of stones: Serial KUBs
When can a trial of spontaneous stone passage be attempted (3)?
  • 1. Patient is relatively pain free
  • 2. Patient has good contralateral kidney function
  • 3. Stones are sufficiently small
    (e.g. 90% of stones smaller than 4mm will pass spontaneously)
What are indications for acute intervention (3)?
  • High fever
  • Unremitting pain or nausea
  • Renal failure
    -obstruction of solitary kidney
    -bilateral ureteral obstruction
    -impairing function of contralateral kidney
  • What is ESWL?
  • For what stone size is it an option?
ESWL = Extracorporeal shockwave lithotripsy = Emits shock waves focused onto stone to fragment the stone (non-invasive)
  • Option when size of stone is 1.5 cm or less 
  • Describe retrograde ureteroscopy and lithotripsy
  • For what stone size is it an option?
Retrograde ureteroscopy and lithotripsy
  • Long, narrow fiber-optic scope passed backward from urethra, into bladder, and into the ureter or kidney
  • Energy source such as a laser is passed through the scope and can fragment the stone
  • A stone basket is used to extract the stones
  • Silicon stent used so ureter can heal
  • Option for stones under 2cm
  • What is antegrade percutaneous nephrolithotomy?
  • For what stone size is it an option? 
  • Rigid scope is placed directly from the back into kidney via a narrow tract
  • Patients are in prone position
  • Stone is fragmented and removed

  • Used primarily for large stones >2cm 
What is open nephrolithotomy or ureterolithotomy?
Open surgery to remove stones

Rarely used now, because less invasive techniques are very good
  • What is nephrectomy?
  • When is it used? 
  • Removal of an entire kidney
  • For poorly functioning or non-functioning kidneys associated with large stones 
  • When there are kidney stones in pregnancy, how is it managed?
  • What test/procedure are contraindicated
  • Attempt to allow stones to pass spontaneously
  • Renal ultrasound is the 1st test
  • If non-diagnostic, limited IVP can be performed (CTs are contraindicated)

ESWL is contraindicated
CT-KUB is contraindicated 
Describe 7 reasons that Calcium stones form
  • Increased intestinal reabsorption of calcium
  • Decreased renal absorption of calcium
  • Increased bone resportion (elevated PTH)
  • Elevated urinary oxalate levels
  • Elecated uric acid levels
  • Decreased urinary citrate levels
  • Distal renal tubular acidosis
Describe the pathogenesis of struvite stones
  • Some bacteria have urease, which splits urea into ammonia, which increases the pH, making things more basic
  • Change in pH reduces solubility of Mg2+, ammonium and phosphate leading to crystal precipitation

Proteus, Klebsiella, Pseudomonas are the most common organisms
Describe a typical struvite stone
Staghorn (i.e. multi-branched)
  • Neurogenic bladder, foreign bodies are associated with higher risk of struvite stones
Describe 5 risk factors for uric acid stones
  • Low urine pH (chronic diarrhea)
  • Dehydration
  • Uricosuric drugs (salicylates, thiazide)
  • High protein diet
  • Elevated serum uric acid levels (gout, chemo, leukemia)

Uric acid is a product of purine metabolism and is excreted in urine
For Cystine stones, what is the etiology?
  • Inherited defects in renal tubular reabsorption of 4 amino acids
  • Form in acidic urine
  • May form staghorn calculi
What stones form in acidic urine?
  • Uric acid stones
  • Cystine stones
Describe 6 tests useful in investigating stones
  • Stone analysis
  • Urine culture
  • Urinalysis
  • Serum (Ca2+, uric acid, phosphate, electrolytes)
  • 24 hour urine (volume, Ca2+, oxalate, phosphate, uric acid, citrate, cystine)
  • Serum PTH if serum calcium is elevated
Describe 5 dietary changes to avoid stones
  • High fluid intake (at least 3 litres/day)
  • Decreased consumption of animal protein (decrease uric acid and calcium)
  • Decreased sodium excretion (decreases urinary calcium excretion)
  • Increase citrate intake (useful as stone inhibitor, acts as urinary alkalizer, lemons and oranges)
  • Reduce foods high in oxalate (tea, coffee, chocolate, beer, peanuts, spinach; and avoid mega-dose of Vitamin C)
In calcium stones, what if patient has elevated serum Calcium? (1)
Work up for hyperparathyroidism
In calcium stones, what is a commonly prescribed electrolyte for preventing stones?
Potassium Citrate
In calcium stones, what if you have Normal serum and urine Calcium, what do you prescribe to prevent stones? (1)
Potassium citrate
In calcium stones, if you have normal serum Calcium and elevated urine Calcium, what do you prescribe to prevent stones? (2)
  • Hydrochlorothiazide
  • Potassium citrate
In calcium stones, if the patient has elevated urinary uric acid levels, what do you prescribe to prevent stones? (2)
  • Potassium citrate
  • Allopurinol
In calcium stones, if you have distal renal tubular acidosis, what do you prescribe to prevent stones? (1)
Potassium citrate
What does allopurinol do?
Reduces production of uric acid
For uric acid stones, with hyperuricemia and hyperuricosuria, what do you prescribe to prevent stones? (2)
  • Potassium citrate or Sodium bicarbonate
  • Allupurinol
For uric acid stones, If only hyperuricosuria, what do you prescribe?
  • Potassium citrate or Sodium bicarbonate
  • Allopurinol (only if urine uric acid levels are very high)

Urine pH should be 6.5 to 7
What effect can urinary alkalization have on uric acid stones?
Can cause them to dissolve
What effect do antibiotics have on struvite stones?
Can retard growth but ultimately stones usually need to be removed surgically
For cystine stones, how do you manage? (2)
Alkalinization of urine (raise pH to above 7.0)

Add p-penicillamine or alpha-MPG complex with cystine to form solube compounds
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