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
Melamine_nephrolithiasis2009.pdf
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.
 |
| 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
REF: ACP PIER 2009
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.
Rationale:
-
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.
Evidence:
-
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.
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TOC |
Kidney