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Approach to the Patient Approach to the Patient with Suspected Kidney with Suspected Kidney
StonesStonesBradley Thomas OliverBradley Thomas Oliver
The University of South CarolinaThe University of South Carolina12/14/0512/14/05
OverviewOverview• Renal calculi occur in 5-12% of the American Renal calculi occur in 5-12% of the American
populationpopulation– bilateral in 10-15% of patients. bilateral in 10-15% of patients.
• 80% of patients with urolithiasis form calcium stones 80% of patients with urolithiasis form calcium stones – Most are composed of calcium oxalateMost are composed of calcium oxalate– Less often calcium phosphateLess often calcium phosphate
• The other main types include:The other main types include:– uric acid uric acid – struvite (magnesium ammonium phosphate)struvite (magnesium ammonium phosphate)– cystine stonescystine stones
Overview ContOverview Cont• The same patient may have a mixed stoneThe same patient may have a mixed stone
• Another type limited to HIV patientsAnother type limited to HIV patients– Indinavir-induced stonesIndinavir-induced stones– The drug crystalizes and the stones are composed almost The drug crystalizes and the stones are composed almost
completely of the protease inhibitor. completely of the protease inhibitor. – Happens in 4% to 22% of patients treated with the standard Happens in 4% to 22% of patients treated with the standard
dose of indinavir (800mg three times a day)dose of indinavir (800mg three times a day)
• Stones can cause renal scarring, damage, or even renal Stones can cause renal scarring, damage, or even renal failure if they are bilateral. failure if they are bilateral.
• In 10% of patients, stones recur within 1 year. This In 10% of patients, stones recur within 1 year. This percentage increases to 50% within 10 years. percentage increases to 50% within 10 years.
Calcium StonesCalcium Stones• In general, calcium phosphate stones In general, calcium phosphate stones
are associated with the same risk are associated with the same risk factors as calcium oxalate stonesfactors as calcium oxalate stones
• Excepttions: Calcium phosphate Excepttions: Calcium phosphate stones more typical of Type I RTA stones more typical of Type I RTA and primary hyperparathyroidism and primary hyperparathyroidism
Uric Acid StonesUric Acid Stones• Occur primarily in patients in whom a Occur primarily in patients in whom a
persistently acid urine (pH<5.5) persistently acid urine (pH<5.5) promotes uric acid precipitationpromotes uric acid precipitation
• Example: gout patients that are uric Example: gout patients that are uric acid overproducers (10-20%)acid overproducers (10-20%)
• Also in states of chronic diarrheaAlso in states of chronic diarrhea
Struvite StonesStruvite Stones• Chronic urinary tract infection due to a Chronic urinary tract infection due to a
urease producing organisms such as urease producing organisms such as Proteus or KlebsiellaProteus or Klebsiella
• Often have multiple magnesium ammonium Often have multiple magnesium ammonium phosphate crystals in the urine sedimentphosphate crystals in the urine sediment
• If not adequately treated can develop into a If not adequately treated can develop into a staghorn or branched calculus involving the staghorn or branched calculus involving the entire renal collecting systementire renal collecting system
Cystine StonesCystine Stones• Develop in patients with cystinuria due to Develop in patients with cystinuria due to
the insolubility of cystine in the urinethe insolubility of cystine in the urine
Diagnosis• Initially suspected by the clinical presentationInitially suspected by the clinical presentation
• Should be suspected in all patients with the acute onset of Should be suspected in all patients with the acute onset of atraumatic flank painatraumatic flank pain– Particularly if no abdominal tenderness and with hematuriaParticularly if no abdominal tenderness and with hematuria
• Classically: severe colicky flank pain Classically: severe colicky flank pain – Often with radiation to the groin, testicles, back, and periumbilical Often with radiation to the groin, testicles, back, and periumbilical
region. region.
• Gross or microscopic hematuria occurs in the majority of Gross or microscopic hematuria occurs in the majority of patients with symptomatic nephrolithiasispatients with symptomatic nephrolithiasis– Other than actually passing a stone or gravel, single most Other than actually passing a stone or gravel, single most
discriminating predictor of a stone in patients with AUFPdiscriminating predictor of a stone in patients with AUFP
Symptoms Cont.Symptoms Cont.• Hematuria, however, is not detected Hematuria, however, is not detected
in approximately 10 to 30% of in approximately 10 to 30% of patients with documented stonespatients with documented stones
• Other symptoms: nausea, vomiting, Other symptoms: nausea, vomiting, dysuria, and urgencydysuria, and urgency
PassagePassage• Stones smaller than 4 mm pass spontaneously Stones smaller than 4 mm pass spontaneously
in approximately 80% of patients. in approximately 80% of patients.
• Stones that are 4-6 mm pass in approximately Stones that are 4-6 mm pass in approximately 50% of patients50% of patients
• Stones larger than 8 mm pass in only Stones larger than 8 mm pass in only approximately 20% of patients. approximately 20% of patients.
Differential DiagnosisDifferential Diagnosis• 1). Bleeding within the kidney1). Bleeding within the kidney
• 2). Ectopic Pregnancy2). Ectopic Pregnancy
• 3). Aortic Aneruysm3). Aortic Aneruysm
• 4). Acute Intestinal Obstruction4). Acute Intestinal Obstruction
• 5). Malingering5). Malingering
Abdominal Plain FilmAbdominal Plain Film• Will identify radiopaque stones Will identify radiopaque stones
– Struvite stonesStruvite stones– Calcium stonesCalcium stones– Cystine stonesCystine stones
• Will miss radiolucent uric acid stonesWill miss radiolucent uric acid stones
• May not detect small stones or stones overlying May not detect small stones or stones overlying bony structuresbony structures
• Will not detect obstructionWill not detect obstruction
Abdominal Plain Film Cont.Abdominal Plain Film Cont.• Reasonable initial test in patients Reasonable initial test in patients
with history of radiopaque calculi and with history of radiopaque calculi and acute pain that is similar to previous acute pain that is similar to previous episodesepisodes
• May, however, also miss stones in May, however, also miss stones in the ureterthe ureter
Intravenous PyelogramIntravenous Pyelogram• Higher sensitivity and specificity than a Higher sensitivity and specificity than a
abdominal film alone abdominal film alone
• Provides information about the degree of Provides information about the degree of obstructionobstruction
• Can produce contrast reactionsCan produce contrast reactions
• Therefore, has been replaced by non-contract –Therefore, has been replaced by non-contract –enhanced helical CT as the test of choiceenhanced helical CT as the test of choice
• IVP showing right kidney completely obstructed IVP showing right kidney completely obstructed by a 7 mm radiopaque calcium oxalate stone in by a 7 mm radiopaque calcium oxalate stone in the proximal ureter the proximal ureter
• The right kidney appears dense due to The right kidney appears dense due to accumulated radiocontrast that cannot be accumulated radiocontrast that cannot be excreted. excreted.
• The left kidney shows a normal excretory phase The left kidney shows a normal excretory phase of the study with contrast in the renal pelvis and of the study with contrast in the renal pelvis and ureter. ureter.
Non-contrast Helical CT Non-contrast Helical CT ScanScan
• Gold StandardGold Standard
• Can detect both the stone and urinary tract Can detect both the stone and urinary tract obstructionobstruction
• Can also define an alternate significant Can also define an alternate significant diagnosisdiagnosis– In one report of patients with their first episode of In one report of patients with their first episode of
a suspected kidney stone, 33% had an alternate a suspected kidney stone, 33% had an alternate diagnosis, not suspected on clinical grounds (50% diagnosis, not suspected on clinical grounds (50% of these had significant disease)of these had significant disease)
Non-contrast Helical CT Non-contrast Helical CT compared to IVPcompared to IVP
• Higher sensitivity and specificityHigher sensitivity and specificity– regardless of its size, location, and chemical compositionregardless of its size, location, and chemical composition
• FasterFaster– 26 versus 69 minutes26 versus 69 minutes
• Only slightly more expensiveOnly slightly more expensive– $600 versus $400$600 versus $400
** Chen, MY, Zagoria, RJ. Can noncontrast helical computed tomography replace ** Chen, MY, Zagoria, RJ. Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic?. J intravenous urography for evaluation of patients with acute urinary tract colic?. J Emerg Med 1999; 17:299.Emerg Med 1999; 17:299.
NumbersNumbers• Standard CT cuts are generally 8mm, Standard CT cuts are generally 8mm,
but 3 to 5mm cuts are optimal for the but 3 to 5mm cuts are optimal for the detection of stonesdetection of stones
• Specificity is nearly 100%Specificity is nearly 100%
• Negative study should prompt Negative study should prompt consideration of a differential diagnosisconsideration of a differential diagnosis
An ExceptionAn Exception• Nephrolithiasis secondary to HIV protease Nephrolithiasis secondary to HIV protease
inhibitors, primarily indinavirinhibitors, primarily indinavir
• These stones are not radiopaque and signs These stones are not radiopaque and signs of obstruction may be minimal or absentof obstruction may be minimal or absent
• Contrast-enhanced CT may be needed for Contrast-enhanced CT may be needed for diagnosisdiagnosis
Possible PitfallPossible Pitfall• In patients who do not have evidence In patients who do not have evidence
of urinary tract obstruction, the of urinary tract obstruction, the occasional inability to distinguish occasional inability to distinguish ureteral stones from phleboliths ureteral stones from phleboliths overlying the course of the ureteroverlying the course of the ureter
• Phleboliths are focal calcified venous thrombiPhleboliths are focal calcified venous thrombi
• Frequently seen along the normal anatomical course of Frequently seen along the normal anatomical course of the lower ureter. the lower ureter.
• They are usually the result of injury to the vein wall They are usually the result of injury to the vein wall commonly from venous hypertension and are composed commonly from venous hypertension and are composed of concentric calcified strata around a central kernel. of concentric calcified strata around a central kernel.
• Typically, phleboliths are rounded with a central lucency Typically, phleboliths are rounded with a central lucency and are seen in the true pelvis often below the distal and are seen in the true pelvis often below the distal ureter.ureter.
• Circumferential periureteral edema, or the soft tissue "rim" sign, Circumferential periureteral edema, or the soft tissue "rim" sign, described as a rim of soft tissue attenuation seen around the described as a rim of soft tissue attenuation seen around the circumference of an intraureteral calculus on non-contract CTcircumference of an intraureteral calculus on non-contract CT
• Theoretically, phleboliths will not show a "rim" sign. Theoretically, phleboliths will not show a "rim" sign.
• Since larger stones result in stretching of the ureteral wall, the Since larger stones result in stretching of the ureteral wall, the "rim" sign tends to be more commonly associated with the "rim" sign tends to be more commonly associated with the presence of smaller stones.presence of smaller stones.
• The "comet" sign refers to the adjacent eccentric, The "comet" sign refers to the adjacent eccentric, tapering soft-tissue mass corresponding to the non-tapering soft-tissue mass corresponding to the non-calcified portion of pelvic vein contiguous to a phlebolith. calcified portion of pelvic vein contiguous to a phlebolith.
UltrasonographyUltrasonography• Procedure of choice for patients who Procedure of choice for patients who
should avoid radiation, i.e. those pregnantshould avoid radiation, i.e. those pregnant
• Very sensitive for the diagnosis of Very sensitive for the diagnosis of obstruction and can detect radiolucent obstruction and can detect radiolucent stones missed on KUBstones missed on KUB
• May miss small stones and ureteral stonesMay miss small stones and ureteral stones
ReferencesReferences• eMedicine. 2005eMedicine. 2005• UpToDate. 2005UpToDate. 2005• Urolithiasisby Urolithiasisby David S Goldfarb, MDDavid S Goldfarb, MD and and
Fredric L Coe, MDFredric L Coe, MD, , Best Practice of Best Practice of MedicineMedicine. October 2003. . October 2003.
