CM2 4-Nephrolithiasis

renal calculi composition

• 75% calcium (oxalate, phosphate)

• 10% struvite

  • “Staghorn” calcli

  • Infection with urea spitting organisms

  • Alkaline urine

• 10% uric acid

• <5 cystine and others

urea splitting organisms

Proteus, Klebsiella, Pseudomonas, Staph, H. pylori, mycoplasma, ureaplasma

RF for stone formation: metabolic conditions

• Primary hyperparathyroidism and hypoparathyroidism=

• Gout

• Obesity

• DM

• crohn’s/UC*

• Recurrent UTI

• Hypercalciuria=

  • * increases urinary oxalate excretion -> stone formation

  • = tendencies to form calcium stones

RF for stone formation: anatomic

• Medullary sponge kidney=

• Gastric bypass*=

• Short bowel syndrome*=

RF for stone formation: dietary

• Diets low in calcium, fluids, potassium, phytate

• Diets high in vit C, oxalate, protein, sodium, sucrose

urea splitting organisms are able to do what?

synthesize “urease” which creates ammonia, which helps form struvite

stone formation requires what?

super-saturation of solute in water

stone formation is inhibited by

1. inc urine flow

2. citrate, pyrophosphate

stone formation inc risk

1. urine stasis

2. foreign body

RF for uric acid stones

 persistent urine pH <5.5, hyperuricemia, and increased uric acid excretion

RF for struvite stones

only form in pts with chronic upper UTI d/t urease-producing (urea splitting) organisms in alkaline pH

RF for cystine stones

autosomal recessive disorder, assoc. With cystinuria

what happens when a stone blocs part of the kidney?

1. transient, prostaglandin-dependent INC in renal blood flow

2. inc intra-ureteral pressure + hyperperistalsis → PAIN

3. RBF dec, GFR falls

4. compensatory inc GFR in contralateral kidney (BUN/CR do not rise acutely)

5. permanent renal injury if prolonged (>4 weeks)

evaluating kidney stones

• hx and pe: previous stone, +FH, DM, HTN, gout, low fluid intake, marathon runners, flank or groin pain

• lab: hematuria!

imaging for kidney stone

• non-contrast helical CT almost 100% specific

• U/S if pregnant

• KUB (kidney, ureters, bladder) for pts w/ hx previous radio-opaque stones

IVP for imaging kidney stones

• highly sensitive and specific

• shows anatomy AND function

• delayed nephogram (a finding you can see on IVP)

KUB imaging usage (pros)

1. diagnosis

2. follow known stone

3. adjunct to CT

(r/o phlebolith = radiolucent center)

KUB cons

only visualizes radio-opaque stones

cons of U/S

misses small stones <5 mm, mid-ureter stones, over-reads hydronephrosis

pros of U/S

pregnancy, children, can be done at bedside, no contrast/radiation

pros for CT scan

highly sensitive/specific, fast, no contrast

cons for CT scan

higher radiation

struvite stones can go into the ureter, T/F?

usually no, they don’t stay small long enough

Major determinant of likelihood of spontaneous passage?

stone size (<4 mm)

Most common place where stones lodge

#1 UV junction

#2 is UPJ (pelvis)

#3 crossing of iliac vessels

what type of ureteral stones less likely to pass spontaneously?

proximal

Tx for kidney stones

• #1 choice: NSAIDs - Ketorolac (Toradol)

• Opioids

• Alpha blockers (tamsulosin)

• Dihydropyridine CCBs

• Antiemetics

• Force fluids

alpha blockers (tamsulosin) MOA

relax distal ureteral smooth msucle

dihydropyridine CCBs MOA

relaxes ureteral smooth muscle

when do you consult urology for kidney stones?

1. anuria

2. unyielding pain or N/V

3. obstruction accompanied by infection

4. complete obstruction beyond 2 weeks

5. evidence of new or preexisting impaired renal function

6. pregnancy

7. >7 mm, staghorn calculus

8. solitary or transplanted kidney

9. complicated medical history

failure to pass an obstructing stone after 4 weeks greatly increases risk of what?

irreversible damage to kidney

surgical management options for kidney stones

1. stenting (double J)

2. percutaneous nephrostomy tube

3. ureteroscopy

4. lithotripsy

5. surgery

follow up for kidney stones

• send stone for lab analysis

• evaluate for underlying cause of stone disease (including primary hyperparathyroidism, hyperuricosuria, hyperphosphatemia, hypocitraturia, etc)

preventing calcium stones

thiazide diuretics (reduces urinary calcium excretion)

preventing oxalate stones

low oxalate diet (avoid spinach/nuts)

calcium supps can bind to oxalates

prevention of uric acid stones

decrease uricosuria with reduce purine diet, allopurinol

allopurinal

needed for oxidation of hypoxanthine to xanthine and then xanthine → uric acid

stones in ____ are less likely to pass

kidney

renal stones tx

nephroscopic lithotripsy + ECSWL