Editing Stones: Diagnosis and Evaluation (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">Patients with newly diagnosed kidney or ureteral stones should undergo a s</span><span style="color:#ff0000">Screening Evaluation</span>''' '''<span style="color:#ff0000">e</span><span style="color:#ff0000">valuation</span>''' '''<span style="color:#ff0000">consisting of</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====
*'''Signs and Symptoms'''
**Flank pain
**Hematuria
**Lower urinary tract symptoms
*'''Risk factors'''
**'''<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>'''
***'''<span style="color:#ff0000">Stone-provoking medications or supplements (9):'''
***#'''<span style="color:#ff0000">Triamterene'''
***#'''<span style="color:#ff0000">Carbonic anhydrase inhibitors such as topiramate, acetazolamide, zonisamide'''
***#'''<span style="color:#ff0000">Probenecid'''
***#'''<span style="color:#ff0000">Some protease inhibitors'''
***#'''<span style="color:#ff0000">Lipase inhibitors'''
***#'''<span style="color:#ff0000">Chemotherapy'''
***#'''<span style="color:#ff0000">Vitamin C'''
***#'''<span style="color:#ff0000">Vitamin D'''
***#'''<span style="color:#ff0000">Calcium'''
====Physical Exam====
*'''General'''
**'''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)
*'''Flank'''
**'''Costovertebral tenderness'''

===Laboratory===
====<span style="color:#ff0000">Urinalysis +/- culture +/- microscopy</span>====
*'''<span style="color:#ff0000">Urinalysis should include pH</span>'''
**'''<span style="color:#ff0000">Normal pH should be between 5.8-6.2[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3126068/ §]</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>'''
*No standard definition exists for complete and partial staghorn stones
**'''Most consider complete staghorn stones to occupy the entire renal collecting system, whereas partial staghorn stones occupy less.'''
===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====
*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

*'''The accuracy of a 24-hour urine collection should be assessed prior to interpretation of results.'''
**'''<span style="color:#ff0000">To assess the adequacy of collection, 24-hour urinary creatinine excretion should be evaluated</span>, taking into account patient gender and body weight, as well as patient recall of the start and end times of his or her collection, should be considered'''
***'''<span style="color:#ff0000">Significant aberrations in total creatinine excretion from estimated volumes (males 20-25mg/kg and females 15-20mg/kg in 24 hours) 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.