Editing Stones: Evaluation and Medical Management (section)

== Diagnosis and Evaluation of Metabolic Stone Disease ==

=== UrologySchool.com Summary ===

==== AUA'''<span style="color:#ff0000">[https://pubmed.ncbi.nlm.nih.gov/24857648/ ★]</span>''' ====

* '''<span style="color:#ff0000">Screening Evaluation</span>'''
**'''<span style="color:#ff0000">History and Physical Exam</span>'''
**'''<span style="color:#ff0000">Laboratory (5)</span>'''
**#'''<span style="color:#ff0000">Urinalysis +/- culture</span>'''
**#'''<span style="color:#ff0000">Serum electrolytes (Na, K, Cl, HCO3)</span>'''
**#'''<span style="color:#ff0000">Serum calcium</span>'''
**#'''<span style="color:#ff0000">Serum creatinine</span>'''
**#'''<span style="color:#ff0000">Serum uric acid</span>'''
**'''<span style="color:#ff0000">Imaging</span>'''
***'''<span style="color:#ff0000">Obtain or review available imaging studies to quantify stone burden.</span>''' 
* '''<span style="color:#ff0000">Extended evaluation</span>'''
** '''<span style="color:#ff0000">One or two 24-hour urine collections</span>'''
***'''<span style="color:#ff0000">Indications (7):</span>'''
***#'''<span style="color:#ff0000">Recurrent stone formers</span>'''
***#'''<span style="color:#ff0000">Family history of stone disease</span>'''
***#'''<span style="color:#ff0000">Solitary kidney</span>'''
***#'''<span style="color:#ff0000">Malabsorptive intestinal disease or resection</span>'''
***#'''<span style="color:#ff0000">Obesity</span>'''
***#'''<span style="color:#ff0000">Recurrent UTIs</span>'''
***#'''<span style="color:#ff0000">Medical conditions predisposing to stones (e.g., RTA Type 1, primary hyperparathyroidism, gout, diabetes mellitus type)</span>'''

=== Goals of Evaluation ===
*'''Identify potential associated metabolic disorders such as (5)'''
*#'''Distal renal tubular acidosis (RTA)'''
*#'''Primary hyperparathyroidism'''
*#'''Enteric hyperoxaluria'''
*#'''Cystinuria'''
*#'''Gouty diathesis'''
*'''Reduce risk of stone recurrence'''
**First-time stone formers have been estimated to have a 50% risk for recurrence within the subsequent 10 years
** Patients at higher risk for repeat episodes (6):
**# Family history of stones
**# Intestinal disease (particularly when causing chronic diarrheal states)
**# Pathologic skeletal fractures
**# Osteoporosis
**# UTI
**# Gout
=== History and Physical Exam ===

==== History ====
* '''Screen for factors that predispose to calculi'''
** '''<span style="color:#ff0000">Conditions associated with stone disease (8):</span>'''
**#'''<span style="color:#ff0000">Obesity</span>'''
**#'''<span style="color:#ff0000">Hyperthyroidism</span>'''
**#'''<span style="color:#ff0000">Gout</span>'''
**#'''<span style="color:#ff0000">Renal tubular acidosis (RTA) type 1</span>'''
**#'''<span style="color:#ff0000">Diabetes mellitus type 2</span>'''
**#'''<span style="color:#ff0000">Bone disease</span>'''
**#'''<span style="color:#ff0000">Primary hyperparathyroidism</span>'''
**#'''<span style="color:#ff0000">Malabsorptive gastrointestinal states</span>''' due to bowel resection, bariatric surgery or bowel or pancreatic disease
**##'''Chronic diarrhea that could be caused by inflammatory bowel disease (Crohn disease, ulcerative colitis) or irritable bowel syndrome'''
**## Gout may predispose the patient to hyperuricosuria or gouty diathesis with either uric acid calculi or calcium oxalate stone formers
**## '''Surgical history should be obtained focusing particularly on bariatric surgery and surgeries of the intestinal tract.''' 
**###'''Roux-en-Y-gastric bypass surgery may significantly increase the overall risk for stone formation'''
**###'''In contrast to gastric bypass surgery, restrictive bariatric surgeries such as gastric sleeve or gastric band do not seem to increase the risk for kidney stones'''
**'''<span style="color:#ff0000">Dietary history</span>'''
***'''Should include average daily intake of fluids (amount and specific beverages), protein (types and amounts), calcium, sodium, high oxalate-containing foods, fruits and vegetables and over-the-counter supplements.'''
**** '''Nutritional factors associated with stone disease, depending on stone type and risk factors, include'''
*****Calcium intake below or significantly above the recommended dietary allowance (RDA)
*****Low fluid intake
*****High sodium intake
*****Limited intake of fruits and vegetables
*****High intake of animal-derived purines
**'''<span style="color:#ff0000">Medications</span>'''
***'''Stone-provoking medications or supplements (9):'''
***#'''Probenecid'''
***#'''Some protease inhibitors''' 
***#'''Lipase inhibitors'''
***#'''Triamterene'''
***#'''Chemotherapy'''
***#'''Vitamin C''' 
***# '''Vitamin D'''
***#'''Calcium'''
***#'''Carbonic anhydrase inhibitors such as topiramate, acetazolamide, zonisamide'''

==== Physical Exam ====

* '''Body mass index'''
** '''Increased BMI, larger waist size, and weight gain are correlated with an increased risk for stone episodes'''
*** '''The association of obesity and uric acid stone formation is primarily due to change in urinary pH'''
*** '''The association of obesity with calcium oxalate stone formation is primarily due to increased excretion of promoters of stone formation''' (oxalate, uric acid, sodium, and phosphorus)

=== Laboratory ===

==== <span style="color:#ff0000">Urinalysis +/- culture +/- microscopy</span> ====
* '''<span style="color:#ff0000">Urinalysis should include pH</span>'''
** '''<span style="color:#ff0000">pH > 7.0 is suggestive of infection lithiasis or RTA</span>'''
** '''<span style="color:#ff0000">pH < 5.5 suggests uric acid lithiasis secondary to gouty diathesis</span>'''
* '''Urine culture'''
** '''Should be obtained in patients with a urinalysis suggestive of UTI.'''
**'''Presence of urea-splitting organisms, such as Proteus species, raises the possibility of struvite stones'''
**Many infected calculi will harbor bacteria even after treatment with broad-spectrum antibiotics
** Half of infected calculi grow bacterial cultures that are different from the preoperative urine specimen
*'''Urine microscopy'''
**'''Identify crystals pathognomonic of stone type.'''

==== <span style="color:#ff0000">Serum chemistries</span> ====

*'''<span style="color:#ff0000">Includes</span>''' 
*#'''<span style="color:#ff0000">Electrolytes (Na, K, Cl, HCO3)</span>'''
*#'''<span style="color:#ff0000">Calcium</span>'''
*#'''<span style="color:#ff0000">Uric acid</span>'''
*#'''<span style="color:#ff0000">Creatinine</span>'''
* May suggest underlying medical conditions associated with stone disease (e.g., primary hyperparathyroidism, gout, RTA type 1 or other metabolic derangements)
* '''Assessment of underlying renal function is necessary'''

==== <span style="color:#ff0000">Parathyroid hormone (PTH)</span> ====
*'''<span style="color:#ff0000">Indicated as part of the screening evaluation if primary hyperparathyroidism is suspected</span>'''
**'''<span style="color:#ff0000">Primary hyperparathyroidism should be suspected when (3):</span>'''
**#Mid-range PTH despite '''<span style="color:#ff0000">high or high normal serum calcium</span>'''
**#'''<span style="color:#ff0000">Increased urinary calcium</span>'''
**#'''<span style="color:#ff0000">Predominantly calcium phosphate stone composition</span>'''
*'''Measurement of vitamin D levels may be helpful as''' '''low vitamin D levels may mask primary hyperparathyroidism, or contribute to secondary hyperparathyroidism.'''
*A high or high normal intact PTH in these settings should prompt further endocrine evaluation, imaging or referral for consideration of parathyroidectomy.

==== Stone composition, if available ====
*'''When a stone is available, a stone analysis should be obtained at least once.'''
*Can direct metabolic investigation or potentially obviate the need for a complete metabolic evaluation
*'''<span style="color:#ff0000">Calcium phosphate stone composition associated with:</span>'''
*#'''<span style="color:#ff0000">RTA Type 1</span>'''
*#'''<span style="color:#ff0000">Primary hyperparathyroidism</span>'''
*#'''<span style="color:#ff0000">Medullary sponge kidney</span>'''
*#'''<span style="color:#ff0000">Use of carbonic anhydrase inhibitors</span>'''

=== Imaging ===

* '''Obtain or review available imaging studies to quantify stone burden.''' '''<span style="color:#ff0000">[https://pubmed.ncbi.nlm.nih.gov/24857648/ ★]</span>'''

=== Metabolic/Extended Diagnostic Evaluation ===
* '''<span style="color:#ff0000">Consists of one or two 24-hour urine collections obtained on a random diet[https://pubmed.ncbi.nlm.nih.gov/24857648/ ★]</span>'''

==== Indications ====
*'''<span style="color:#ff0000">AUA (7):[https://pubmed.ncbi.nlm.nih.gov/24857648/ ★]</span>'''
*#'''<span style="color:#ff0000">Recurrent stone formers</span>'''
*#'''<span style="color:#ff0000">Family history of stone disease</span>'''
*#'''<span style="color:#ff0000">Solitary kidney</span>'''
*#'''<span style="color:#ff0000">Malabsorptive intestinal disease or resection</span>'''
*#'''<span style="color:#ff0000">Obesity</span>'''
*#'''<span style="color:#ff0000">Recurrent UTIs</span>'''
*#'''<span style="color:#ff0000">Medical conditions predisposing to stones (e.g., RTA Type 1, primary hyperparathyroidism, gout, diabetes mellitus type)</span>'''
*Included in other lists
*# Pathological skeletal fractures
*# Osteoporosis
*# Infirm health (unable to tolerate repeat stone episodes)
*# Anatomic abnormalities
*# Stones composed of cystine, uric acid, and struvite
*# Children should generally be evaluated because of concerns about renal damage and long-term sequelae of stone recurrence

==== 24-hour urine collections</span> ====

*Can be used to inform and monitor treatment protocols
*'''<span style="color:#ff0000">Analyzed at minimum for (9): [https://pubmed.ncbi.nlm.nih.gov/24857648/ ★]</span>'''
*#'''<span style="color:#ff0000">Volume</span>'''
*#'''<span style="color:#ff0000">pH</span>'''
*#'''<span style="color:#ff0000">Creatinine</span>'''
*#'''<span style="color:#ff0000">Sodium</span>'''
*#'''<span style="color:#ff0000">Potassium</span>'''
*#'''<span style="color:#ff0000">Calcium</span>'''
*#'''<span style="color:#ff0000">Oxalate</span>'''
*#'''<span style="color:#ff0000">Uric acid</span>'''
*#'''<span style="color:#ff0000">Citrate</span>'''
*#'''In stone formers with known cystine stones or a family history of cystinuria or for those in whom cystinuria is suspected, urinary cystine should additionally be measured.'''
*#Sulfate can be added to assess the volume of protein loading from animal meat

* '''<span style="color:#ff0000">Assess adequacy of 24-hour urine collection, prior to interpretation of results'''
**'''<span style="color:#ff0000">To assess the adequacy of collection, 24-hour urinary creatinine excretion should be considered</span>, taking into account patient gender and body weight (males 20-25mg/kg and females 15-20mg/kg in 24 hours),''' as well as patient recall of the start and end times of his or her collection
***'''Significant aberrations in total creatinine excretion from estimated volumes imply incomplete collection, overcollection, greater than expected muscle mass, or less than expected muscle mass'''
**** For abnormally collected 24 hour urine collections, can divide metabolite excretion by creatinine excretion to compare collections
*'''Markers of protein intake, such as urine urea nitrogen or urinary sulfate, are reflective of animal protein intake and can be used to assess dietary adherence'''.
*Urinary potassium measured at baseline can be compared to urinary potassium obtained during follow-up to gauge compliance with medication regimens.
*'''Primary hyperoxaluria should be suspected when urinary oxalate excretion > 75 mg/day in adults without bowel dysfunction. These patients should be considered for referral for genetic testing and/or specialized urine testing'''
*Fast and calcium load testing should not be performed routinely to distinguish among types of hypercalciuria
*If a patient with calcium urolithiasis uses calcium supplements, 24-hour urine samples should be collected on and off the supplement.
**If urinary supersaturation of the calcium salt in question increases during the period of supplement use, the supplement should be discontinued.