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Renal Calculus, Emergency Medicine

Basics

Description

- Urinary tract obstruction - Intermittent distention of the renal pelvis of proximal ureter produces pain - Kidney stones: - Most common cause of renal colic - Stone composition: - 80%: Calcium stones (calcium oxalate > calcium phosphate) - 5% uric acid - Others: Magnesium ammonium phosphate (struvite), cystine

- 6 " 12% lifetime risk in the general population - Twice as common in men as women - Peak incidence between 40 and 60 yr old - Theories on stone formation: - Urinary supersaturation of solute followed by crystal precipitation - Decrease in the normal urinary proteins inhibiting crystal growth - Urinary stasis from a physical anomaly, catheter placement, neurogenic bladder, or the presence of a foreign body

- Abdominal exam: - Tenderness to palpation, rebound tenderness, or guarding suggests a more serious intra-abdominal process - Palpate the abdominal aorta for tenderness or pulsatile enlargement suggestive of an aneurysm

- Urinalysis - Microscopic hematuria present in >80% - Gross hematuria - Absent urinary blood in 10 " 30% - WBC/bacteria suggests infection - No correlation between the amount of hematuria and the degree of urinary obstruction

- CT: - Helical CT has replaced IV pyelogram (IVP) as test of choice - Detects calculi as small as 1 mm in diameter - Directly visualizes complications, such as hydroureter, hydronephrosis, and ureteral edema - Advantages over IVP: - Performed rapidly - Does not require IV contrast media - Detects other nonurologic causes of symptoms, such as abdominal aortic aneurysms (AAAs)

- Kidney, ureter, and bladder (KUB) radiograph: - Indicated when allergy to IVP dye and when renal scanning and US not available - Distinguishes calcium-bearing stones (radiopaque) from noncalcium stones - Assists in locating radiopaque stones and the exclusion of other pathologies in nonpregnant patients - Difficult to distinguish radiopaque body: - Phlebolith - Bowel contents - Obstruction within the urinary tract on the KUB - Oblique films assist in localizing suspicious calcifications.

- US: - Useful in the detection of larger stones and hydronephrosis - Provides anatomic information only - Helpful in diagnosing obstruction and localizing stones in the proximal and distal portions of the ureter - Ability to detect hydronephrosis: - Sensitivity 85 " 94% - Specificity 100%

- Antiemetics (prochlorperazine, ondansetron, droperidol, hydroxyzine) - α-Blockers (tamsulosin) or calcium-channel blockers (nifedipine) have been shown to decrease time to spontaneous stone passage: - Most efficacious for stones <5 mm in diameter - Tamsulosin and nifedipine equally effective - Prescribe on discharge

- Obstruction in the presence of infection mandates immediate urologic intervention. - Intractable pain with refractory nausea and vomiting - Severe volume depletion - Urinary extravasation - Hypercalcemic crisis - Solitary kidney and complete obstruction - Relative admission indications (discuss with urologist): - High-grade obstruction - Renal insufficiency - Intrinsic renal disease - Stones of size <5 mm usually pass spontaneously; those >8 mm rarely do.

  • Urinary tract obstruction
  • Intermittent distention of the renal pelvis of proximal ureter produces pain
  • Kidney stones:Most common cause of renal colicStone composition:80%: Calcium stones (calcium oxalate > calcium phosphate)5% uric acidOthers: Magnesium ammonium phosphate (struvite), cystineAssociated with infections caused by urea-splitting organisms (e.g., Pseudomonas, Proteus, Klebsiella) along with an alkalotic urine90% of urinary calculi are radiopaque

Etiology

  • 6 " 12% lifetime risk in the general population
  • Twice as common in men as women
  • Peak incidence between 40 and 60 yr old
  • Theories on stone formation:Urinary supersaturation of solute followed by crystal precipitationDecrease in the normal urinary proteins inhibiting crystal growthUrinary stasis from a physical anomaly, catheter placement, neurogenic bladder, or the presence of a foreign body
  • Recurrence rate of 40% at 5 yr and 75% at 20 yr
  • Associated with chronic kidney disease, hypertension, type 2 diabetes mellitus, metabolic syndrome, and an increased risk of coronary artery disease
  • Rare in children
  • When present, often is an indication of a metabolic or genetic disorder
  • 60% present with flank or abdominal pain though up to 30% only present with hematuria
  • Pediatric patients <16 yr comprise ¢ ¼7% of all cases of renal stones.
  • 1:1 sex distribution
  • Causes of stone formation:Metabolic abnormalities (50%)Urologic abnormalities (20%)Infection (15%)Immobilization syndrome (5%)

Diagnosis

Signs and Symptoms

History

  • Sudden onset of severe pain in the costovertebral angle, flank, and/or lateral abdomen
  • Colicky or constant pain:Patient cannot find a comfortable position
  • Hematuria:Gross hematuria in 1/3 of patients
  • Nausea/vomiting
  • Diaphoresis
  • History of prior stone formation

Physical Exam

  • Vital signs:Fever suggests an occult infection.Hypotension with an altered mental status suggests urosepsis
  • Abdominal exam:Tenderness to palpation, rebound tenderness, or guarding suggests a more serious intra-abdominal processPalpate the abdominal aorta for tenderness or pulsatile enlargement suggestive of an aneurysm
  • Genitourinary exam:Examine the genitalia for evidence of hernia, epididymitis, torsion, or testicular masses

Essential Workup

  • UrinalysisMicroscopic hematuria present in >80%Gross hematuriaAbsent urinary blood in 10 " 30%WBC/bacteria suggests infectionNo correlation between the amount of hematuria and the degree of urinary obstruction

Diagnosis Tests & Interpretation

Lab

  • CBC:WBC >15,000 suggests concomitant infection
  • Urine culture
  • Electrolytes, glucose, BUN, creatinine
  • Pregnancy test when suggestive

Imaging

  • CT:Helical CT has replaced IV pyelogram (IVP) as test of choiceDetects calculi as small as 1 mm in diameterDirectly visualizes complications, such as hydroureter, hydronephrosis, and ureteral edemaAdvantages over IVP:Performed rapidlyDoes not require IV contrast mediaDetects other nonurologic causes of symptoms, such as abdominal aortic aneurysms (AAAs)Disadvantages:Does not evaluate flow or renal functionNonenhanced helical CT in the evaluation of renal colic:Sensitivity 95%Specificity 98%Accuracy 97%Indications:1st-time diagnosisPersistent painClinical confusion with pyelonephritis
  • IVP:Establishes diagnosis in 95%Demonstrates the severity of obstructionScout film prior may localize stones that would otherwise be obscured by the dye.Postvoiding filmUseful to identify stones at the ureteral vesicular junction or distal ureter that are obscured by a full bladder
  • Kidney, ureter, and bladder (KUB) radiograph:Indicated when allergy to IVP dye and when renal scanning and US not availableDistinguishes calcium-bearing stones (radiopaque) from noncalcium stonesAssists in locating radiopaque stones and the exclusion of other pathologies in nonpregnant patientsDifficult to distinguish radiopaque body:PhlebolithBowel contentsObstruction within the urinary tract on the KUBOblique films assist in localizing suspicious calcifications.
  • US:Useful in the detection of larger stones and hydronephrosisProvides anatomic information onlyHelpful in diagnosing obstruction and localizing stones in the proximal and distal portions of the ureterAbility to detect hydronephrosis:Sensitivity 85 " 94%Specificity 100%Limitations:May miss stones <5 mm in sizeMay miss an obstruction in the early phase of renal colicTime delay until the onset of pyelocaliectasis even after total obstruction
  • Every effort should be made to minimize ionizing radiation exposure to the fetus
  • US is the imaging modality of choice

Diagnostic Procedures/Surgery

Ureteroscopy, shock-wave lithotripsy, percutaneous nephrolithotomy

Differential Diagnosis

  • Dissecting or rupturing AAA
  • Pyelonephritis
  • Papillary necrosis (sickle cell disease, NSAID analgesic abuse, diabetes, or infection)
  • Renal infarction (vascular dissection or arterial embolus)
  • Ectopic pregnancy
  • Ovarian cyst/torsion
  • Appendicitis
  • Intestinal obstruction
  • Biliary tract disease
  • Musculoskeletal strain
  • Lower lobe pneumonia
  • Malingering or narcotic dependence (diagnosis of exclusion)

Treatment

Pre-Hospital

Parenteral opiates may be required for pain control with long transport times

Initial Stabilization/Therapy

  • Rapid dipstick urine test for blood:Positive test in conjunction with clinical findings sufficient to begin analgesic therapy
  • Provide adequate analgesia when diagnosis suspected on clinical and lab findings

Ed Treatment/Procedures

  • Hydration:Initiate IV crystalloid infusion with 1 L of normal saline infused over 30 " 60 min followed by 200 " 500 mL/hBolus volume compromised patients with 500 mL increments until urine output adequate
  • Analgesics (morphine, ketorolac):Combination of IV NSAIDs and opioids decrease ED stay and provide better pain control than either alone
  • Antiemetics (prochlorperazine, ondansetron, droperidol, hydroxyzine)
  • α-Blockers (tamsulosin) or calcium-channel blockers (nifedipine) have been shown to decrease time to spontaneous stone passage:Most efficacious for stones <5 mm in diameterTamsulosin and nifedipine equally effectivePrescribe on discharge

Avoid NSAIDs in pregnancy, particularly in 3rd trimester

Medication

  • Hydromorphone (Dilaudid): 1 " 4 mg (peds: 0.015 mg/kg/dose) IM/IV/SC q4 " 6h PRN. Reduce dose in opiate-naive patients.
  • Hydroxyzine hydrochloride (Vistaril): 25 " 50 mg (peds: 0.5 " 1 mg/kg/dose) IM (not IV) q4 " 6h
  • Ketorolac (Toradol): 30 " 60 mg IM or 30 mg (peds: 0.5 mg/kg/dose up to 1 mg/kg/24 " 48 h) IV (alone or with opiates); reduce dose to 30 mg IM or 15 mg IV if >65 yr or <50 kg.
  • Morphine sulfate: 2 " 10 mg (peds: 0.1 " 0.2 mg/kg/dose q2 " 4h) IM/IV/SC q2 " 6h PRN; may redose more frequently if needed
  • Nifedipine 30 mg PO daily.
  • Ondansetron (Zofran): 4 mg (peds: 0.1 mg/kg 1) IM/IV, not to exceed 8 mg/dose IV.
  • Prochlorperazine (Compazine): 5 " 10 mg IM/IV q4 " 6h; 25 mg suppository PR
  • Promethazine (Phenergan): 12.5 " 25 mg (peds: 0.25 " 1 mg/kg not to exceed 25 mg) IM/IV/PR q4 " 6h
  • Tamsulosin (Flomax) 0.4 mg PO daily for 4 wk

Follow-Up

Disposition

Admission Criteria

  • Obstruction in the presence of infection mandates immediate urologic intervention.
  • Intractable pain with refractory nausea and vomiting
  • Severe volume depletion
  • Urinary extravasation
  • Hypercalcemic crisis
  • Solitary kidney and complete obstruction
  • Relative admission indications (discuss with urologist):High-grade obstructionRenal insufficiencyIntrinsic renal diseaseStones of size <5 mm usually pass spontaneously; those >8 mm rarely do.

Discharge Criteria

  • Normal vital signs
  • No evidence of concomitant urinary tract infection
  • Adequate analgesia
  • Able to tolerate PO fluids to maintain hydration status
  • Reliable patient with an adequate home situation
  • Appropriate outpatient follow-up arranged
  • Normal renal function
  • Provide a urine strainer to collect the stone for possible future stone analysis
  • Arrange urologic follow-up

Issues for Referral

Imaging if pain persists and diagnosis not established in ED

Followup Recommendations

All patients should have urology follow-up, especially:

  • 1st episode of renal stone
  • Large stone >5 mm
  • Patients who fail to pass a stone after 4 wk of conservative therapy

Pearls and Pitfalls

  • Do not miss a vascular catastrophe mimicking as renal colic
  • Aggressive pain management and hydration promote passage of stones
  • The absence of hematuria does not exclude the diagnosis of acute renal colic

Additional Reading

  • Hollingsworth JM, Rogers MA, Kaufman SR, et al. Medical therapy to facilitate stone passage: A meta-analysis. Lancet. 2006;368:1171 " 1179.
  • Marx JA, Hockberger RS, Walls RM, eds. Rosens Emergency Medicine: Concepts and Clinical Practice. 7th ed. St. Louis, MO: Mosby; 2009.
  • Schissel BL, Johnson BK. Renal stones: Evolving epidemiology and management. Pediatr Emerg Care. 2011;27(7):676 " 681.
  • Teichman JM. Clinical practice. Acute renal colic from ureteral calculus. N Engl J Med. 2004;350:684 " 693.
  • Worcester EM, Coe FL. Clinical practice. Calcium kidney stones. N Engl J Med. 2010;363(10):954 " 963.

Codes

ICD9

  • 592.0 Calculus of kidney
  • 592.1 Calculus of ureter
  • 788.0 Renal colic

ICD10

  • N20.0 Calculus of kidney
  • N20.2 Calculus of kidney with calculus of ureter
  • N23 Unspecified renal colic

SNOMED

  • 95570007 Kidney stone (disorder)
  • 266556005 Calculus of kidney and ureter
  • 7093002 Renal colic (finding)
  • 427649000 Calcium renal calculus
  • 274401005 Uric acid renal calculus (disorder)