TOC |  Kidney
Kidney Stones  

Kidney Stones / Nephrolithiasis                           kidney stone_calcium  2010     

Incidence: 0.1-0.4% of US population has kidney stones.  Lifetime risk is ~ 12% for men, 6% for women.
Recurrence of Stones:
~14% at 1 year; ~ 35% at 5 years; ~52% at 10 years.
Symptoms & Signs of Kidney Stones:
  • Renal Colic Pain: acute colicky severe flank pain (tenderness) radiated to groin area, typically associated with nausea & vomiting.
  • Hematuria & Dysuria
  • Urinary Obstruction
  • Urinary Infection or Urosepsis:  Infection proximal to obstruction is suggested by fever, urinalysis showing pyuria and bacteriuria, and leukocytosis, and the presence of urosepsis is associated with an increased risk of complications.


Metabolic factors that increase the risk of recurrent stones include:
  • a low urinary volume (less than 2 liters daily),
  • hypercalciuria (more than 250 mg of urinary calcium daily in women, more than 300 mg daily in men, or more than 4 mg per kilogram of body weight daily), and
  • hypocitraturia (less than 320 mg of urinary citrate daily)
  • hyperuricemia  


Evaluation and Diagnostic Tests:

  • Urinalysis for red blood cells, crystals, and pH , urine culture
    - Gross or microscopic hematuria occurs in approximately 90 % of patients; however, the absence of hematuria does not preclude the presence of stones.
  • Abdominal radiograph (KUB x-ray) may detect ~ 80% for stones . It is used to assess whether the stone is radiopaque
  • Abdominal (Renal) ultrasound: sensitivity 60%, specificity 100%
  • Intravenous urography IVP (the previous gold standard)
  • Helical CT abdominal scan: The unenhanced  (Non-contrast) CT of Kidneys, Ureters, & Bladder is the best diagnostic test, sensitivity 96%, specificity 100%
  • Serum electrolytes, calcium, phosphorus, uric acid, creatinine, CBC   
  • 24 hour urine collection for creatinine, calcium & phosphorus, uric acid, citrate, oxalate, magneseium (for Struvite stones), and cysteine if indicated
  • Stone analysis: Patients should be instructed to strain their urine and to submit the stone for composition analysis.


Types of Kidney Stones:
  1. Calcium Stones (as Ca-oxalate Stones):
    account for >75% of all renal stones, usually combined with oxalate to form Calcium oxalate stone (black, grey, or white color).  Calcium phosphate stones are next most common, affected by renal tubular acidosis (Rx: potassium citrate / HCO3-).  They are typically small less than 1 cm.  They are opaque on x-ray.
    Causes: Hyper-PTH, high Ca, Hyperoxaluria
    Rx: Thiazide, citrate, PO4
  2. Uric Acid Stones:
    represent for about ~8% of kidney stones; associated with hyperuricosuria in ~25%.  They are smooth, round, yellow-orange in color, and nearly x-ray transparent unless mixed with struvite or calcium stones.  Types I & II primary hyperoxaluria are rare genetic defects that can casue urate stones.
    Uric acid stones are unique in that they can be managed medically.
    Causes: Hyperuricosuria, low urine pH
    Rx: Allopurinol, oral Cabase
  3. Struvite (magnesium-ammoionium phosphate) and carbonate apatite stones - Stones Associated with Infection .
    Infection stones are made of struvite, tend to fill the entire collecting system (staghorn calculi), and are unlikely to pass into the ureter.
    Causes: Urease producing bacteria as:  Proteus, Haemophilus, Ureaplasma urealyticum, and Klebsiella.  
    Rx: Shock wave, acetohydrxamate
  4. Cystine stones:
    comprise about 1% of all kidney stones.
    Causes: cystinuria
    Rx: Penicillamine, tiopronin


Treatment of Kidney Stones:

Acute Treatment
When urgent intervention is unnecessary, the clinician must decide whether to follow a patient expectantly for spontaneous stone passage or to perform an elective intervention.
The likelihood of spontaneous stone passage decreases as the size of the stone increases.  The majority of stones that are less than 5 mm in diameter are likely to pass spontaneously.

1.  Pain Control Rx

2.  Stone Removal to relieve urinary obstruction

  • IV or oral hydration to enhance spontaneous stone passage
  • Extracorporeal  Shock Wave Lithotripsy (ESWL)
      Shock-wave lithotripsy is generally used for proximal ureteral calculi that are 1 cm or smaller.
      Stones made of calcium oxalate dihydrate or struvite fragment more effectively than stones made of calcium oxalate monohydrate, calcium phosphate (brushite), or cystine.  
      However, the composition of a stone is rarely known before lithotripsy is performed.
  • Ureteroscopy with use of the holmium:yttrium–aluminum–garnet (YAG) laser is effective for stones of all compositions and sizes.
    Proximal ureteral stones that exceed 1 cm are treated more successfully by ureteroscopy than shock-wave lithotripsy.
  • Cystoscopic Basketing or Fragmentation  with ureteral stent placement  
  • Surgery: percutaneous or open nephrolithostomy, open ureterolithotomy

3.  Infection Rx with antibiotics as indicated


Give iv fluids to patients with acute nephrolithiasis only to treat volume depletion.

  • Give iv saline solution to patients with acute nephrolithiasis only if extracellular fluid volume depletion is present and the patient is unable to take fluid by mouth.
  • Do not recommend routine attempts to force diuresis with iv saline therapy if renal colic is present in hopes of facilitating stone passage.


  • Intravenous fluid administration is a standard therapy for obstructing stones, but no trial has been conducted to show that it is effective in promoting stone passage.
  • It is also possible that giving saline could exacerbate renal colic if stone passage is not facilitated.

Consider elective urologic treatment of any asymptomatic intracalyceal stones after passage of or urologic intervention for a symptomatic stone.

  • After passage of or urologic intervention for a symptomatic stone, consider performing elective urologic intervention for other asymptomatic intracalyceal stones noted at the time of the acute episode.
  • Do not remove asymptomatic intracalyceal stones 4 mm (e.g., by ESWL) but continue to observe for expected spontaneous passage.
  • Consider patient preference when managing larger stones.
  • Consider removal of asymptomatic intracalyceal stones by ESWL if the patient has been unable to tolerate the pain of ureteral obstruction, if occupational issues are important (e.g., airline pilots), or if patient lives in a remote region.

Drug Therapy of Renal Calculi

  • Use NSAIDs as Ketorolac, opiates, or both to provide effective analgesia for renal colic.
  • Use tamsulosin to facilitate stone passage; use steroids and nifedipine as a second choice
  • Use drug therapy to lower urinary calcium excretion in patients with hypercalciuria for secondary prevention of stones.
    Use thiazides, such as chlorthalidone or hydrochlorothiazide, to treat patients with hypercalciuria.
  • Use citrate supplementation for secondary prevention of calcium stones in selected patients, and consider magnesium supplementation in patients with bowel disease.
    Use potassium citrate supplementation to increase urinary citrate excretion in patients with low urinary citrate excretion or in “unselected” calcium stone formers who have not done 24-hour urine collections.
    Reserve magnesium supplementation for patients with kidney stones and chronic bowel disease predisposing them to hypomagnesemia.
  • Use allopurinol to prevent calcium oxalate stone formation in patients with hyperuricosuria.
  • Prevent uric acid stone recurrences with urinary alkalinization.
    Use potassium citrate to increase urine pH and dissolve uric acid.
  • Treat and prevent recurrence of struvite stones with combinations of urologic intervention and medication.
    Refer patients with large struvite stones for percutaneous nephrostolithotomy.
    After surgery and clearance of infected stone material use suppressive antibiotics, keeping in mind that:
    - Long-term therapy (3 to 6 months) after surgery should be with culture-specific antibiotics at doses lower than the usual therapeutic doses
    - Appropriate drugs include trimethoprim/sulfamethoxazole, quinolones, cephalosporins, and tetracycline
    - Occasionally nonspecific suppressive therapy with nitrofurantoin is useful postoperatively
  • Use drug therapy as part of an aggressive prevention strategy in managing patients with cystinuria.

Pain Control:
IM Ketorolac 60 mg
provides effective pain relief with less sedation than opiates and, therefore, is preferred for patients who are discharged from the ER before a stone has passed.

In a randomized controlled trial of 130 patients with renal colic and moderate pain, patients received either morphine, 5 mg and then 5 mg at 20 minutes; ketorolac, 15 mg and then 15 mg at 20 minutes; or a combination of both. The combination of morphine and ketorolac was superior to either drug along for pain relief and required less "rescue analgesia" (48).

Comments: Among opiates, meperidine causes more nausea and vomiting in some patients and is contraindicated in the presence of renal insufficiency.

For ureteral dilatation and relaxation:
Treat patients with distal ureteral stones less than 10 to 15 mm in diameter with tamsulosin (Flomax 0.4 mg), with steroids or nifedipine  XL 30 mg/day as a second choice.

Rationale: Steroids may reduce ureteral edema to facilitate stone passage, whereas nifedipine, a calcium-channel blocker, presumably causes ureteral dilatation and relaxation.

Tamsulosin, an a1-adrenergic antagonist, may also act as a spasmolytic, increasing distal ureteral stone expulsion, but has only been examined in one pilot study.


  • In a randomized, double-blind, controlled trial of 86 patients with a unilateral ureteral radiopaque stone 15 mm, patients were randomly treated for a maximum of 45 days with methylprednisolone, 16 mg, plus nifedipine, 40 mg/d, or with methylprednisolone, 16 mg, plus placebo daily. In the group with nifedipine, 34 patients had stone passage without surgical manipulation, and in 5 patients the process failed (success rate 87%) compared to 24 and 13, respectively, in the group that did not receive nifedipine (success rate 65%). In the first group the mean interval for stone passage in the successful cases was 11.2 days, compared to 16.4 days in the second group (49).
  • In a randomized, controlled trial of 96 patients with 1 cm or smaller radiopaque stones located in the distal ureter, patients either randomly received oral treatment with deflazacort (a prednisolone derivative), 30 mg/d (maximum 10 days), plus slow-release nifedipine, 30 mg/d (maximum 4 weeks), or underwent a wait-and-watch approach. Both groups of patients were allowed to use diclofenac on demand. Stones were expelled in 38 (79%) of 48 patients in the steroid-nifedipine group and in 17 (35%) of 48 patients in the control group. The average expulsion time was 7 days (range, 2 to 10 days) for the first group and 20 days (range, 10 to 28 days) for the second group, and the first group used less NSAID (50).
  • In a third study, 35 patients were randomly assigned to a control arm and received ketorolac and oxycodone-acetaminophen combination tablets and prochlorperazine suppositories. Thirty-five patients were randomly assigned to the treatment arm and received ketorolac and plain acetaminophen plus nifedipine XL, prednisone, and trimethoprim/sulfamethoxazole combination tablets. The treatment arm had higher (86% vs. 56%) stone passage rates and fewer lost workdays (mean 1.76 vs. 4.9), emergency room visits (1 vs. 4), and surgical interventions (2 vs. 15) (51).
  • In a pilot study in patients with small stones (mean size, 6.7 ± 2.1 mm; range, 3.8 to 13 mm) in the distal ureter, near the bladder, a significantly greater number of stones passed and passed more quickly in patients treated with tamsulosin, the a1-adrenergic antagonist often used for treatment of benign prostatic hypertrophy. The drug was compared with floroglucine-trimetossibenzene, a spasmolytic. Each group was made up of 30 patients, and both groups also received an oral steroid (deflazacort), an antibiotic (cotrimoxazole), and the NSAID diclofenac as needed. The stone expulsion rate was 70% for the control group (mean expulsion time, 111.1 hours) as compared with 100% for the group treated with tamsulosin (mean expulsion time, 65.7 hours). Tamsulosin is a very well tolerated drug with mild side effects like dizziness and rhinitis and causes very little of the postural hypotension seen with other a1-adrenergic antagonists (52).

REF: Rosen's Emergency Medicine: Concepts and Clinical Practice, 6th ed. 2006

The most important factor that relates to passage of a calculus though the genitourinary tract is its size.
The critical size for spontaneous passage is 5 mm. Approximately 90% of stones that are smaller than 5 mm and located in the lower part of the ureter pass spontaneously within 4 weeks.
This number decreases to 15% for stones between 5 and 8 mm. In contrast, 95% of stones larger than 8 mm become impacted along the genitourinary tract, and lithotripsy or surgical removal is generally required. Intervention can be performed in most cases in an outpatient setting.

Ureteral stones originate in the kidney, with gravity and peristalsis contributing to their passage along the ureter. Renal calculi seldom cause complete obstruction. There are five sites along the ureter where calculi are likely to become impacted. First, a stone may lodge in the calyx of the kidney or pass into the renal pelvis and become lodged at the ureteropelvic junction. The relatively large renal pelvis (1 cm) narrows abruptly at its distal portion, where it equals the diameter of its adjoining ureter (2 to 3 mm). The third region is near the pelvic brim where the ureter arches over the iliac vessels posteriorly into the true pelvis. The most constricted area along the ureter, and a common location for impaction, is at the ureterovesicular junction. This location is the site where the ureter enters the muscular coat of the bladder (intramural ureter). At the time of diagnosis, up to 75% of stones are located in the distal third of the ureter. Finally, calculi may become lodged in the vesical orifice.

Prevention or Chronic Treatment

  • For hypercalciuria (Calcium renal stone):
    Potassium citrate +/- thiazide diuretics; low salt/animal protein diet.
  • For gouty diathesis (Uric renal stone):
    Potassium citrate: Alkalinizing the urine with potassium citrate (or sodium citrate or sodium bicarbonate) dissolves pure uric acid stones.  A standard therapy is 20 mmol of potassium citrate orally two to three times daily, with reassessment to verify adequate urinary alkalinization (to pH 6.5 to 7).
    Unless a stone is pure uric acid, however, oral dissolution therapy is not possible. If oral dissolution therapy fails, treatment should proceed as for a radiopaque stone.
  • For Dietary Hyperoxaluria:
    Restrict dietary oxalate; avoid severe calcium restriction
  • For Enteric Hyperosaluria:
    Potassium citrate, calcium or magnesium citrate
  • For Hypocitraturic Calcium:
    Potassium citrate
  • For Infectious Struvite Stones:
    Antibiotic & Acetohydroxamic acid
  • For Mild Cystinuira:
    Chelating agent, Potassium citrate, high fluid intake
  • For Moderate to Severe Cystinuria (>500 mg/day)
    Potassium citrate & Tiopronin

Two thirds of the ureteral stones that pass spontaneously pass within four weeks after the onset of symptoms. The mean time to stone passage also increases as the size of the stone increases.  A ureteral stone that has not passed within one to two months is unlikely to pass spontaneously with continued observation.  Furthermore, ureteral stones that are still symptomatic after four weeks have a complication rate of 20 % (including renal deterioration, sepsis, and ureteral stricture).  Thus, observation for up to four weeks is generally reasonable if follow-up can be ensured.


ACP Online PIER:  (see the .pdf  format file )

Acute Renal Colic from Ureteral Calculus  
Joel M.H. Teichman, M.D.  NEJM Feb. 12, 2004; Volume 350:684-693