Stones - GU Flashcards
1
Q
Stone Composition
A
- Supersaturation of urine by stone forming constituents
- Calcium compound deposits/forms in renal papilla, gradually erode through papillary urothelium, eventually breaking free
Types of Stones:
- Calcium Oxalate
- Calcium Chloride
- Less common: Uric acid, cystine, ammonium acid urate, xanthine
2
Q
Pathophysiology of Obstruction
A
Decreased ureteral flow initially results in:
- Increased ureteral peristalsis and dilatation of ureter proximally
- Increased renal blood flow
- By 24 hours, both of these have decreased
- Increased renal interstitial edema with increased lymphatic absorption
- Increased blood flow to contralateral kidney
3
Q
Stone Formation
A
- Dehydrated state
- Higher concentration of stone forming solutes (Calcium, oxalate, urate, etc.)
4
Q
Calcium Stone
A
- Any condition that may result in hypercalciuria
- Increased intake (dietary)
- Increased absorption or resorption (hyperparathyroidism)
- Renal calcium and phosphate leak
- Hyperoxaluria, hyperuricosuria, hypocitraturia, hypomagnesuria
5
Q
Struvite (Magnesium Ammonium Phosphate) Stone
A
- Associated w/ gram negative bacterial infection (Pseudomonas, Proteus and Klebsiella but not E. coli)
- These bacteria split urea and form ammonium which combine w/ magnesium and phosphate
- May form a “stag horn” calculus
- Need to remove calculus for UTI to resolve
6
Q
Other Stones (far less common)
A
- Urate (associated w/ gout, high purine intake and some malignancies)
- Cystine (metabolic renal issue resulting inability to reabsorb cystine)
- Drugs: HIV, triamterine, sulfa drugs, guaifenesin, magnesium silicate containing antacids
7
Q
Epidemiology
A
- Men (12%) > Women (7%) lifetime risk
- Risk doubles if + family history
- Upper tract stones more common in developed world
- Peak incidence 35-45 years of age
- Rare in children
- Race: More common in Asians and whites than all other ethnicities
- Geography: more common in dry/hot areas
Locations: UVJ, pelvic brim, UPJ
8
Q
Prognosis
A
- Majority of stones will pass (80-85%)
- Hospital admission rate approximately 20% (refractory pain, dehydration, infection, unable to pass stone)
- Many patients will experience recurrence, up to 70% by ten years from initial presentation
9
Q
Tx - stones
A
- Anti-inflammatory (ketorolac parenterally)
- Opioid (morphine, hydromorphone parenterally)
- Antiemetics
- Hydration (IV Normal Saline:) Not necessary always in well hydrated patient, May contribute to increased hydrostatic pressure
Meds:
- Ketorolac parenterally (antiprostaglandin and has ureteral relaxation effects) - NSAID
- Ketorolac intranasal (outpatient, for up to 5 days)
- Ibuprofen (orally)
- Pain meds/Narcotics
- Desmopressin (DDAVP): Desmopressin (DDAVP)
- Anitemetics: Metoclopramide (CNS dopamine receptor blocker) has been well studied. Also provides pain relief. Ondansetron, Prochlorperazine
10
Q
History
A
- VERY Uncomfortable appearing, marked distress, writhing about on the exam bed
- Very painful
- Came on all of a sudden
- Pain in back can radiate and shoot to abdomen
- nausea and vomiting
- Continuous pain: nothing really makes it better
- nothing makes it better, cant get comfortable
- no guarding of abdomen
11
Q
Diagnostic Tests
A
- Urinalysis: so simple, but don’t rely solely upon this (may be absent in 5-15% of patients)
- Screen for infection
- May indicate type of stone if crystals are seen
CT
- Standard test for acute presentation of renal/ureteral colic
- Allows accurate diagnosis of stone, degree of obstruction and other incidental findings (inflammation, tumor, AAA, etc.)
- Rapid assessment (most CT scanners take 5 minutes maximum now)
- Negatives: radiation exposure, $$
Intravenous Pyelogram (IVP)
- No longer first line imaging test
- Longer accession time
- Need for IV contrast resulting in allergy and contrast nephropathy
- Was sufficient for evaluating degree of obstruction, and location of stone in many cases
Ultrasonography
- Limited use in diagnosing smaller stones (<5mm), especially in ureters
- Detect significant urinary obstruction
- Hyperechoic stones (of more significant size) can be seen in kidney and UPJ at times
- Doppler ultrasonography could be used to detect ureteral obstruction (this is not commonly used)
12
Q
Retrograde Pyelogram
A
- Performed when a precise diagnosis cannot be made by other means
- When exact anatomy of the ureter must be clarified (prior to ureteroscopy)
- Prior to surgery due to uncontrollable pain, infection, large stone (typically > 8 mm) or possible anatomic problems (ureteral strictures)
- Not used commonly
13
Q
Medical Expulsive Therapy
A
- NSAID
- Opioid analgesic (narcotic/acetaminophen combination)
- Alpha-adrenergic blocker (Tamsulosin (flomax) 0.4 mg by mouth daily)
- Treat no longer than 10-14 days (stone should have passed in this amount of time)
14
Q
Diet
A
- HYDRATION!
- Calcium, oxalate, uric acid and citrate assessed
- 24 hr urine collection (can assess for output as well)
Western diet as we know it not conducive to stone prevention
- High Protein
- High Dairy
- High Oxalate
15
Q
Surgical Treatment
A
- ESWL (extracoporeal shockwave lithotripsy): Intense shockwaves focused on the stone(s)
- Best for stones less than 2 cm
- Upper to mid calyx preferred
- Varying degrees of analgesia
