Snapshot A 30-year-old man presents to the emergency department with severe, colicky left flank pain of acute onset that radiates to the left groin. He also reports urinary frequency and urgency. Physical examination is significant for left-sided costovertebral angle tenderness. Urine dipstick is heme positive. Urinalysis also shows envelope-shaped crystals. A non-contrast abdominal CT is shown. Introduction Clinical definition calculi (stones) affecting the kidneys; however, these stones can also affect the ureter Nephrolithiasis StonesStone TypeEtiologyImaging Finding(s)Stone ShapeTreatmentCalciumHypercalciuriae.g.,idiopathic hypercalcemiaHypocitraturiaprecipitates calcium oxalate stonesEthylene glycol (antifreeze)Vitamin C abuseCrohn diseaseUrine alkalinizationprecipitates calcium phosphate stonesRadiographyradiopaqueComputerized tomographyradiopaqueEnvelope or dumbbell shapecalcium oxalateWedge-shaped prismcalcium phosphateHydrochlorothiazideCitrateLow-sodium dietCystineImpaired cystine reabsorption in the proximal convoluted tubulethis results in cystinuriaPrecipitates in acidic urineDiagnosiscyanide-nitroprusside testRadiographyradiopaqueComputerized tomographyvisible at timesHexagonalDietary modificationlow sodiumUrine alkalinizationChelating agentsin refractory casesStruvite (magnesium ammonium phosphate)Urease-positive organisms such asProteus mirabilisStaphylococcus saphrophryticusKlebsiellaUrease-positive organisms subesequently alkalinize the urinethis causes struvite stones due to precipitationRadiographyradiopaqueComputerized tomographyradiopaqueCan result in a staghorn calculiCoffin lidRemoval of underlying infectionSurgical removal of the stoneUric acidHyperuricemiae.g., states of increased cell turnover and goutPrecipitates in acidic urineRadiographyradiolucentComputerized tomographyminimally visibleRhomboid/rosetteUrine alkalinizationAllopurinolAdequate hydration prior to chemotherapy treatment Epidemiology Prevalence 12% in men and 7% in women Risk factors hyperparathyroidism hypocitraturia sarcoidosis hyperoxaluria renal tubular acidosis type I nephrocalcinosis cystic fibrosis hyperuricosuria indwelling catheter urinary tract infections malabsorption (e,g., Crohn disease) horseshoe kidney obesity low fluid intake gout medications e.g., allopurinol, indinavir, acetazolamide, and topiramate Etiology Pathogenesis substance precipitation affecting the kidney and ureter e,g., hypercalciuria and low urine volume forms calcium cystals Presentation Symptoms colicky flank pain pain may radiate to the groin or lower abdomen dysuria urgency and frequency Physical exam low abdominal tenderness costovertebral angle (CVA) tenderness Imaging Renal ultrasound indication in patients who are pregnant and children who are suspected to have nephrolithiasis modality abdomen and pelvis to visualize the kidney and bladder Non-contrast computerized tomography (CT) indication preferred imaging for most adults presenting with signs and symptoms concerning for nephrolithiasis modality abdomen and pelvis Studies Labs serum creatinine, uric acid, and ionized calcium should be obtained urine studies urinalysis/dipstick in order to check for red and white blood cells, nitrites, and urine pH urine culture stone composition analysis perform in patients who developed their first stone straining the urine Diagnostic criteria based on clinical presentation and confirmed by imaging Differential Urinary tract infections Acute pyelonephritis Groin hernia Treatment Medical analgesia, bed rest, and intravenous fluids indication considered first-line treatment for uncomplicated urolithiasis < 10 mm α-blockers or calcium channel blockers indication can be considered to facilitate the passage of ureteral stones appears to relax the ureter Operative extracorporal shock wave lithotripsy indication preferred for renal stones < 2 cm percutaneous nephrolithotomy indication preferred for renal stones > 2cm note flexible ureterorenoscopy can be an option if percutaneous nephrolithotomy cannot be done Complications Ureteral obstruction Ureteral stricture Urinary tract infection Renal deterioration Prognosis Small stones are more likely to spontaneously pass