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 login to view 1 more bullet Etiology Pathogenesis substance precipitation affecting the kidney and ureter login to view 1 more bullet Presentation Symptoms colicky flank pain login to view 1 more bullet dysuria urgency and frequency Physical exam low abdominal tenderness costovertebral angle (CVA) tenderness Imaging Renal ultrasound indication login to view 1 more bullet modality login to view 1 more bullet Non-contrast computerized tomography (CT) indication login to view 1 more bullet modality login to view 1 more bullet Studies Labs serum login to view 1 more bullet urine studies login to view 3 more bullets stone composition analysis login to view 2 more bullets 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 login to view 2 more bullets α-blockers or calcium channel blockers login to view 3 more bullets Operative extracorporal shock wave lithotripsy login to view 2 more bullets percutaneous nephrolithotomy login to view 4 more bullets Complications Ureteral obstruction Ureteral stricture Urinary tract infection Renal deterioration Prognosis Small stones are more likely to spontaneously pass