questions 6

Nephrolithiasis

Topic updated on 08/22/17 8:38pm

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
  • 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
  • Pathogenesis
    • substance precipitation affecting the kidney and ureter
      • e,g., hypercalciuria and low urine volume forms calcium cystals
  • Prognosis
    • small stones are more likely to spontaneously pass
 
Nephrolithiasis Stones
Stone Type
Etiology
Imaging Finding(s)
Stone Shape
Treatment
Calcium
  • Hypercalciuria
    • e.g., idiopathic hypercalcemia
  • Hypocitraturia
    • precipitates calcium oxalate stones
  • Ethylene glycol (antifreeze)
  • Vitamin C abuse
  • Crohn disease
  • Urine alkalinization
    • precipitates calcium phosphate stones
  • Radiography
    • radiopaque
  • Computerized tomography
    • radiopaque
  • Envelope or dumbbell shape
    • calcium oxalate
  • Wedge-shaped prism
    • calcium phosphate
  • Hydrochlorothiazide
  • Citrate
  • Low-sodium diet
Cystine
  • Impaired cystine reabsorption in the proximal convoluted tubule
    • this results in cystinuria
  • Precipitates in acidic urine
  • Diagnosis
    • cyanide-nitroprusside test 
  • Radiography
    • radiolucent
  • Computerized tomography
    • visible at times
  • Hexagonal 
  • Dietary modification
    • low sodium
  • Urine alkalinization
  • Chelating agents
    • in refractory cases
Struvite (magnesium ammonium phosphate)
  • Urease-positive organisms such as
    • Proteus mirabilis
    • Staphylococcus saphrophryticus
    • Klebsiella
  • Urease-positive organisms subesequently alkalinize the urine
    • this causes struvite stones due to precipitation
  • Radiography
    • radiopaque
  • Computerized tomography
    • radiopaque
  • Can result in a staghorn calculi
  • Coffin lid
  • Removal of underlying infection
  • Surgical removal of the stone
Uric acid
  • Hyperuricemia
    • e.g., states of increased cell turnover and gout 
  • Precipitates in acidic urine
  • Radiography
    • radiolucent
  • Computerized tomography
    • minimally visible
  • Rhomboid/rosette
  • Urine alkalinization
  • Allopurinol
  • Adequate hydration prior to chemotherapy treatment 
 
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


  RATE CONTENT
4.0
AVERAGE 4.0 of 5 RATINGS

Qbank (3 Questions)

TAG
(M2.RL.6) A 54-year-old male presents to the emergency department with sudden-onset, excruciating left flank pain radiating to his groin. A CT scan is ordered and shown in Image A. Which of the following best justifies the use of CT in the diagnosis of this patient's condition? Topic Review Topic
FIGURES: A          

1. KUB radiographs have a higher sensitivity but CT scan has a higher specificity and should be used in cases of high positive suspicion
2. Radiolucent stones can be visualized that are missed on KUB radiographs
3. The use of IV contrast can highlight the anatomy of the urinary system
4. CT scans provide additional information for a planned percutaneous nephrostomy placement
5. CT scan should not have been used here for this indication

PREFERRED RESPONSE ▶
TAG
(M2.RL.54) A 45-year-old woman presents to the ED with sharp, severe, colicky right flank pain radiating to the groin that she reports started suddenly several hours ago. She also reports discolored urine when she last voided. Vital signs are within normal limits. On exam, the patient is visibly in pain and shifts positions every few minutes. Costovertebral tenderness is elicited on percussion. Her abdominal radiograph is shown in Figure A. Past medical history is significant for type II diabetes mellitus, fibromyalgia, gout, and depression. What additional information about the patient’s history would likely explain the radiographic findings? Topic Review Topic
FIGURES: A          

1. Recent diagnosis of parathyroid adenoma
2. Frequent Gram-negative bacilli urinary tract infections
3. Recent diagnosis of acute myeloid leukemia
4. Prior history of calcium stones
5. Renal tubular acidosis

PREFERRED RESPONSE ▶
TAG
(M2.RL.88) A 39-year-old male presents with acute-onset, severe right-sided flank pain that radiates to his groin. He has never experienced an episode like this before. CT abdomen and pelvis (Figure A) as well as urine sediment analysis showing envelope-shaped crystals confirm the most-likely diagnosis. Conservative treatment is pursued and the issue resolves spontaneously within a 36-hour waiting period. Which of the following is the next best step in management on discharge of the patient from the hospital? Topic Review Topic
FIGURES: A          

1. Recommend in-depth metabolic evaluation as outpatient
2. Encourage increased hydration
3. Initiate furosemide
4. Recommend 10-day course of prophylactic antibiotics
5. Schedule periodic renal ultrasounds to monitor for recurrence

PREFERRED RESPONSE ▶
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