Acute Renal Colic from Ureteral Calculus

The new england journal of medicine

clinical practice

Joel M.H. Teichman, M.D.

This Journal feature begins with a case vignette highlighting a common clinical problem. Evidence supporting various strategies is then presented, followed by a review of formal guidelines, when they exist. The article ends with the author’s clinical recommendations.

From the Division of Urology, University A 39-year-old man reports an eight-hour history of colicky pain in the right lower of British Columbia, and the Section of quadrant radiating to the tip of his penis. He had previously had a kidney stone, which Urology, St. Paul’s Hospital — both in Vancouver, B.C., Canada. passed spontaneously. Physical examination shows that he is in distress, is afebrile, and has tenderness of the right costovertebral angle and lower quadrant. Urinalysis N Engl J Med 2004;350:684-93. shows microhematuria. Helical computed tomography (CT) of the abdomen and pel- Copyright © 2004 Massachusetts Medical Society. vis shows a 6-mm calculus of the right distal ureter and mild hydroureteronephrosis. How should this patient be treated?

the clinical problem

Up to 12 percent of the population will have a urinary stone during their lifetime, and recurrence rates approach 50 percent.1 In the United States, white men have the highest incidence of stones, followed in order by white women, black women, and black men.2,3 Fifty-five percent of those with recurrent stones have a family history of urolithiasis,4 and having such a history increases the risk of stones by a factor of three.5 The classic presentation of a renal stone is acute, colicky flank pain radiating to the groin. As the stone descends in the ureter, the pain may localize in the abdominal area overlying the stone and radiate to the gonad. Peritoneal signs are absent. As the stone approaches the ureterovesical junction (Fig. 1), lower-quadrant pain radiating to the tip of the urethra, urinary urgency and frequency, and dysuria are characteristic, mimick- ing the symptoms of bacterial cystitis. Physical examination typically shows a patient who is often writhing in distress, trying to find a comfortable position. Tenderness of the costovertebral angle or lower quadrant may be present. Gross or microscopic hematuria occurs in approximately 90 percent of patients; however, the absence of hematuria does not preclude the presence of stones.6 Owing to the shared splanchnic innervation of the renal capsule and intestines, hydronephrosis and distention of the renal capsule may produce nausea and vomiting. Thus, acute renal colic may mimic acute abdominal or pelvic conditions.

strategies and evidence

diagnosis The best imaging study to confirm the diagnosis of a urinary stone in a patient with acute flank pain is unenhanced, helical CT of the abdomen and pelvis (Fig. 1).7 In a prospective trial of 106 adults with acute flank pain, all patients underwent both unenhanced helical CT and intravenous urography (the previous gold standard),8 and the results of each were interpreted separately and in a blinded fashion by a radiologist. Seventy-five patients received a diagnosis of ureteral stones. The sensitivity of CT was 96 percent, as compared with 87 percent for urography, and the respective specificities were 100 percent and 94 percent (P<0.001 for both comparisons). Positive and negative predictive

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clinical practice values were 100 percent and 91 percent, respectively, for CT, as compared with 97 percent and 74 per- A B cent, respectively, for urography. CT scans that were negative for stone disease revealed other abnormalities in 57 percent of patients, including appendici- tis, pelvic inflammatory disease, diverticulitis, abdominal aortic aneurysm, and bladder cancer.7 When CT confirms the presence of a stone, a plain abdominal radiograph should be obtained to assess whether the stone is radiopaque. If CT is un- available, plain abdominal radiography should be performed, since 75 to 90 percent of urinary calculi are radiopaque (Fig. 2). Although ultrasonography C D has high specificity (greater than 90 percent), its sensitivity is much lower than that of CT, typically in the range of 11 to 24 percent. Thus, ultrasonography is not used routinely but is appropriate as the initial imaging test when colic occurs during pregnancy.9 management Urgent Intervention Urgent intervention is indicated in a patient with an obstructed, infected upper urinary tract, impending Figure 1. Plain Abdominal Radiography (Panel A) and Helical CT (Panels B, renal deterioration, intractable pain or vomiting, an- C, and D) in a 68-Year-Old Man with Nausea and Severe, Colicky Pain in the Right Lower Quadrant Radiating to the Tip of the Penis. uria, or high-grade obstruction of a solitary or trans- The plain abdominal radiograph shows a faint area of calcification just below planted kidney. Upper tract obstruction increases the right sacroiliac joint (Panel A). Helical CT demonstrates right hydroneph- renal pelvic pressure, which reduces glomerular fil- rosis (Panel B), right hydroureter (arrow in Panel C), and a 6-mm stone in the tration and renal blood flow.10 Infection proximal distal ureter (Panel D). The patient was treated with ureteroscopy, which to obstruction is suggested by fever, urinalysis show- showed stone impaction. The stone was 90 percent uric acid and 10 percent ing pyuria and bacteriuria, and leukocytosis, and calcium oxalate. the presence of urosepsis is associated with an increased risk of complications. Impaired glomerular filtration inhibits the entry of antibiotics into the er, nonsteroidal antiinflammatory drugs (NSAIDs) collecting system and requires emergency decom- and cyclooxygenase-2 (COX-2) inhibitors also pro- pression by means of either percutaneous nephros- vide effective analgesia by blocking afferent arte- tomy or ureteral stenting (Fig. 2 and 3).11 The most riolar vasodilatation, thereby reducing diuresis, ede- common pathogen is Escherichia coli. Intravenous ma, and ureteral smooth-muscle stimulation.12-15 ampicillin and aminoglycoside provide broad an- NSAIDs are less likely than narcotics to cause nau- tibiotic coverage, although oral fluoroquinolones sea. However, NSAIDs may further diminish renal may be a reasonable alternative; the type of antibi- function in patients with an obstruction, particu- otic should be adjusted once the culture results are larly those with preexisting renal impairment.16,17 known. Infection proximal to an obstructing stone Nonetheless, data indicate that in typical doses ke- differs from a so-called infection stone (formed by torolac — which is commonly used for colic — pos- urease-producing bacteria). Infection stones are es little risk of renal failure and does not increase made of struvite, tend to fill the entire collecting sys- the risk of surgical bleeding (Table 1).18 Although tem (staghorn calculi), and are unlikely to pass into randomized, double-blind trials are lacking, ketor- the ureter. olac and diclofenac appear to be at least as effective as narcotics. When NSAIDs are used for acute renal Pain and Nausea colic, pain relief is achieved most rapidly by intra- The pain associated with ureteral stones has tra- venous administration.12,13,15,19,20 ditionally been managed with narcotics. Howev- Renal colic may also be managed with the anti-

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antly for spontaneous stone passage or to perform an elective intervention. The likelihood of spontaneous stone passage decreases as the size of the stone increases (Table 2).24,26,27 The majority of stones that are less than 5 mm in diameter are likely to pass spontaneously.27,28 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.25 A ureteral stone that has not passed within one to two months is unlikely to pass spontaneously with continued observation.25,28 Furthermore, ureteral stones that are still symptomatic after four weeks have a complication rate of 20 percent (including renal deterioration, sepsis, and ureteral stricture).26 Thus, observation for up to four weeks is generally reasonable if follow-up can be ensured. Patients should be instructed to strain their urine and to submit the stone for composition analysis. Repeated imaging (plain abdominal radiography for radiopaque stones and CT for radiolucent stones) Figure 2. Abdominal Scout Film Showing a Stent and is warranted to confirm stone passage. If follow-up Ureteral Calculus in a 52-Year-Old Man Who Presented with Left-Flank Pain Radiating to the Lower Quadrant cannot be ensured or if follow-up imaging reveals and Associated with Vomiting. no movement after a month, intervention is gener- The stent was placed to decompress the upper tract, and ally warranted. the pain and vomiting resolved. The patient was treated unsuccessfully with shock-wave lithotripsy, followed by Uric Acid Stones successful ureteroscopy. The composition of the stone is rarely known at presentation, but uric acid stones may be suspected on the basis of a history of uric acid stones or of gout diuretic desmopressin,14,17,21 although data on (which is present in approximately 20 percent of pa- this approach are limited. If NSAIDs, COX-2 inhib- tients with uric acid stones).29 The typical patient itors, or desmopressin is used, overhydration should has normal amounts of uric acid in an acidic urine; be avoided, since the objective of treatment is to re- this condition increases the likelihood of uric acid duce ureteral spasms. crystallization.30 Pure uric acid calculi are radiolu- Alternative approaches to pain relief have been cent on plain imaging but visible on ultrasonogra- less well studied. One randomized, prospective tri- phy or CT. Other radiolucent stones that should be al demonstrated that the pain from renal colic may considered in appropriate clinical settings include be reduced by wrapping the patient’s abdomen in a matrix stones (which are made of organic material resistive heating blanket set to 42°C.22 Acupuncture and are occasionally seen in patients with urease- may also reduce pain, but it has not been compared producing bacteria) and indinavir stones. directly with commonly used medications.23 Uric acid stones are unique in that they can be Because the pain is due to renal capsular disten- managed medically.31 At a urinary pH below 5.5, tion, intractable pain is controlled by decompress- uric acid is poorly soluble; solubility increases at a ing the obstruction. In rare instances, patients may pH above 6.5.32 Alkalinizing the urine with potas- have intractable vomiting. These patients also re- sium citrate (or sodium citrate or sodium bicarbon- quire decompression and intravenous hydration. ate) dissolves pure uric acid stones.33,34 A standard therapy is 20 mmol of potassium citrate orally two Spontaneous Passage of the Stone to three times daily, with reassessment to verify ad- When urgent intervention is unnecessary, the clini- equate urinary alkalinization (to pH 6.5 to 7). cian must decide whether to follow a patient expect- The time to dissolution varies with the size of

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clinical practice Follow-up or ureteroscopy patient’s preferences upper tract anatomy and Follow intervention pathway Follow and size of stone; determine Assess composition, location, Consider metabolic evaluation Consider Perform shock-wave lithotripsy Assess likelihood of signs identified No stone or secondary spontaneous stone passage Radiopaque stone identified Stone present Consider nonurologic causes Consider Follow intervention pathway Follow

Observation Obtain follow-up radiograph of kidneys and upper bladder Follow-up Stone passed Consider metabolic evaluation Consider Follow nonurgent pathway Follow Obtain helical CT of abdomen and pelvis Stone still present for radiopaque stone Follow nonurgent pathway Follow Administer oral dissolution therapy Obtain follow-up CT Uric acid stone possible Radiolucent stone identified intervention required Determine whether urgent bladder to assess radiopacity Ureteral stone identified; obtain radiograph of kidneys and upper Follow-up Stone dissolved Metabolic evaluation Follow nonurgent pathway Follow Management of Acute Renal Colic Related to a Ureteral Stone. Management of Acute Renal Colic of the following present: solitary kidney Perform nephrostomy or insert stent if any Obstructed, infected upper urinary tract Impending renal deterioration Intractable pain, nausea, or vomiting Anuria or high-grade obstruction of Figure 3.

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Table 1. Drugs Commonly Used to Treat Colic.*

Class and Name of Drug Adult Dose Adverse Effects Contraindications NSAIDs Ketorolac 30–60 mg IV or IM loading Common: dyspepsia, nausea, abdominal Absolute: hypersensitivity, active peptic dose, then 15 mg IV or IM pain, diarrhea, headache, dizziness, ulcer disease, cerebrovascular every 6 hr; oral continua- elevated aminotransferase levels, hemorrhage, breast-feeding, 3rd tion dose: 10 mg orally drowsiness, tinnitus, pain at trimester of pregnancy every 4–6 hr (maximum, injection site Relative: advanced age, hypertension, 40 mg/day), not to Rare but serious: anaphylaxis, gastro- congestive heart failure, nasal polyps, exceed 5 days† intestinal bleeding, acute renal volume depletion failure, bronchospasm, interstitial nephritis, Stevens– Johnson syndrome, agranulocytosis Diclofenac 50 mg orally 2 or 3 times/day Thrombocytopenia; others similar to Similar to those for ketorolac those of ketorolac Cyclooxygenase-2 inhibitors Rofecoxib 50 mg/day Common: diarrhea, hypertension, nausea, Absolute: hypersensitivity, NSAID- epigastric discomfort, peripheral induced asthma, hepatic failure, renal edema, dyspepsia, fatigue, dizziness failure, 3rd trimester of pregnancy, Rare but serious: gastrointestinal bleed- peptic ulcer disease, gastrointestinal ing, esophagitis, hypersensitivity, bleeding bronchospasm, hypertension, Relative: renal failure, liver failure, congestive heart failure, potentially hypertension, ischemic coronary ar- increased risk of myocardial infarction, tery disease, dehydration, congestive hepatotoxicity, blood dyscrasias, renal heart failure, fluid retention, advanced failure age Narcotics Meperidine 1 mg/kg of body weight IM Common: dizziness, lightheadedness, Absolute: hypersensitivity, use of mono- every 3–4 hr sedation, nausea, vomiting, dyspho- amine oxidase inhibitors within 14 days ria, dry mouth, urinary retention, Relative: advanced age, respiratory hypotension, agitation, disorienta- depression, seizure disorder, liver tion, constipation, flushing failure, renal failure, hypothyroidism Rare but serious: respiratory depression, respiratory arrest, seizure, cardiac arrest, arrhythmia, shock Morphine sulfate 0.1 mg/kg IM or IV every 4 hr Biliary spasm, paralytic ileus, toxic Absolute: hypersensitivity, paralytic ileus megacolon, increased intracranial Relative: chronic obstructive pulmonary pressure, miosis, bradycardia; others disease, biliary disease, acute similar to those of meperidine alcoholism Narcotic combinations Acetaminophen 300 mg of acetaminophen Common: lightheadedness, sedation, Absolute: hypersensitivity with codeine with 30 mg of codeine, dizziness, constipation, nausea, Relative: glucose-6-phosphate 2 tablets orally every 4–6 hr vomiting, hypotension, rash, biliary dehydrogenase deficiency spasm, urinary retention, miosis Rare but serious: pancytopenia, thrombocytopenia, liver damage, respiratory depression, hemolytic anemia, neutropenia Antidiuretics Desmopressin 40 µg/spray (if single dose Common: headache, rhinitis, nausea, Absolute: type IIB von Willebrand’s ineffective after 30 min, dizziness, epistaxis disease, hypersensitivity consider NSAIDs or Rare but serious: hyponatremia, water Relative: coronary artery disease, narcotics) intoxication, seizure, anaphylaxis, hypertension, hyponatremia, young thrombosis age, advanced age, risk of thrombosis

* NSAIDs denotes nonsteroidal antiinflammatory drugs, IV intravenous, and IM intramuscularly. † The dose is adjusted for patients older than 65 years and for those weighing less than 50 kg.

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clinical practice the stone and the extent of urinary alkalinization. converge and induce fragmentation. Machines have A 2-cm uric acid stone bathed in urine with a con- different shock-wave intensities (peak pressures) stant pH of 7 takes approximately nine days to dis- and focal volumes, and different machines result in solve.32 Imaging can be repeated at one month to different fragment sizes and re-treatment rates.41-43 determine whether dissolution has occurred. Unless The desired outcome is the elimination of all stones a stone is pure uric acid, however, oral dissolution (as assessed by repeated imaging). The presence therapy is not possible. If oral dissolution therapy of residual fragments increases the risk of further fails, treatment should proceed as for a radiopaque symptomatic episodes or re-treatment.44 Stones stone. made of calcium oxalate dihydrate or struvite fragment more effectively than stones made of calcium areas of uncertainty oxalate monohydrate, calcium phosphate (brush- ite), or cystine. However, the composition of a stone timing of elective intervention is rarely known before lithotripsy is performed. Re- Although intervention is generally recommended cent data show that shock-wave lithotripsy is poor after one month of observation, the optimal dura- at fragmenting stones whose attenuation value on tion of observation is uncertain. In dogs with com- helical CT exceeds 1000 Hounsfield units, although plete unilateral ureteral obstruction, irreversible re- further study is needed before the use of this mea- nal deterioration begins at two weeks10; fortunately, sure can be recommended in practice.45 ureteral stones rarely produce complete obstruc- Proximal ureteral stones that exceed 1 cm are tion. Before the advent of helical CT (when intra- treated more successfully by ureteroscopy than venous urography was used to identify ureteral shock-wave lithotripsy.42,46 In a retrospective analy- stones), observation for months was common in the sis of ureteral stones treated by either ureteroscopy absence of high-grade obstruction. One retrospec- or shock-wave lithotripsy (with the use of a Dornier tive study evaluated 21 patients with ureteral stones DoLi machine), the stone-free rates for stones of that had been impacted for 2 to 48 months (a series 1 cm or greater were 93 percent and 50 percent, re- of “worst-case” obstructions).35 After stone remov- spectively.46 For stones less than 1 cm, the stone- al, ureteral strictures developed in five patients (24 free rates did not differ significantly between the two percent) after at least five months of impaction, but groups (100 percent and 80 percent, respectively). four of these patients had a history of iatrogenic For distal ureteral calculi, the preferred treat- ureteral perforation from failed intervention. In the ment is controversial. In a randomized, prospective other 16 patients, intravenous urography or nucle- trial of patients with distal ureteral stones (mean ar-medicine studies were normal after stone remov- size, 7 mm), shock-wave lithotripsy (with the use of al. A longer duration of obstruction, a history of re- an unmodified Dornier model HM3 machine) and current stone disease, and prior iatrogenic injury ureteroscopy resulted in similar stone-free rates.47 from manipulation are associated with an increased The percentage of patients who said they would risk of renal impairment after stone passage.36-38 repeat the procedure was slightly though not sig- Whether nuclear renography is necessary to evaluate a patient for renal deterioration, and if so, how frequently it should be performed and what magnitude of change in function warrants inter- Table 2. Likelihood of Passage of Ureteral Stones.* 39 vention are matters of controversy. Although CT Mean No. of Days is the best imaging test to use to diagnose a stone, Required to Pass Likelihood of Eventual it does not discriminate between severe and mild Size of Stone Stone Need for Intervention obstructions.40 % ≤2 mm 8 3 type of intervention 3 mm 12 14 The ureter is divided anatomically into the proximal 4–6 mm 22 50 and distal portions (proximal and distal, respectively, to the iliac vessels). Shock-wave lithotripsy is >6 mm† — 99 generally used for proximal ureteral calculi that are * Data were obtained from Hubner et al.24 and Miller and Kane.25 1 cm or smaller. The patient is positioned so that † A stone of this size is unlikely to be passed spontaneously. the stone lies at the focal point, where shock waves

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nificantly greater for shock-wave lithotripsy (100 discharged, and the stone absorbs the laser’s ener- percent) than ureteroscopy (87 percent). Another gy, producing photothermal lithotripsy.53 In a se- study found that patients prefer shock-wave litho- ries of 504 patients treated with the use of this ap- tripsy.48 proach, stones were eliminated in 98 percent of There has been concern that shock-wave litho- those with distal ureteral calculi, 100 percent of tripsy might adversely affect ovarian function, al- those with middle ureteral calculi, and 97 percent though the limited available data have shown no of those with proximal ureteral calculi.54 Ureteros- obvious detrimental effect.49,50 Either this approach copy is less expensive than shock-wave lithotripsy,55 or ureteroscopy may be used in women of child- but it is more time consuming and technically more bearing age if not pregnant. Regardless of the demanding. In experienced hands, ureteroscopy is mode of treatment used, the composition of all associated with a low risk of ureteral injury. stones should be determined. Ureteroscopy with use of the holmium:yttrium– metabolic evaluation and prophylaxis aluminum–garnet (YAG) laser is effective for stones Renal deterioration is more likely from recurrent of all compositions and sizes.51,52 This technique than solitary episodes of ureteric stones.35,37 A pa- involves passing the ureteroscope retrogradely tient with a recurrence of stones warrants a meta- through the urethra, bladder, and ureter to the stone bolic evaluation, although there is controversy re- under video guidance. The laser is delivered through garding which tests are routinely indicated; the yield a small-diameter fiber passed through the uretero- of testing and its effect on outcomes are uncertain. scope. The fiber tip touches the stone, the laser is It is also controversial whether testing is indicated

Table 3. Metabolic Tests for Ureteral Stones.

Test Ideal Candidate Comments Stone-composition analysis All patients 24-Hr urine collection for volume, Patients with recurrent stones, those Sulfate measurement optional†; elevat- pH, calcium, oxalate, uric acid, with a family history of stones, ed urinary sulfate values suggest high phosphate, sodium, citrate, young patients, patients who intake of animal proteins, indicating creatinine, sulfate* request stone risk reduction possible need for dietary counseling to reduce intake of animal protein 24-Hr urine collection for volume, Patients with cystine stones Quantitative measurement of cystine pH, creatinine, quantitative guides titration of medications to re- measurement of cystine* duce urinary cystine (e.g., tiopronin and penicillamine) Measurement of serum calcium, Patients with recurrent stones, those High normal serum calcium and elevat- potassium, bicarbonate, with a family history of stones, ed serum calcium warrant parathy- creatinine, blood urea young patients,‡ patients who roid hormone and 1,25-dihydroxy- nitrogen, chloride, uric acid request stone risk reduction vitamin D assays Measurement of serum intact Patients with hypercalcemia (or serum Elevated serum calcium and parathyroid parathyroid hormone, calcium at high end of normal hormone suggestive of primary hy- 1,25-dihydroxyvitamin D range) perparathyroidism; elevated serum calcium and vitamin D with sup- pressed parathyroid hormone suggestive of sarcoidosis Urine culture and sensitivity Patients with signs or symptoms of infection; those with alkaline urine; those with struvite stones

* The 24-hour urine collection is generally obtained while the patient follows a random diet. A three-week delay is recommended after stone passage owing to concern that acute inflammation or bleeding may affect the results, although data on this risk are limited. Two 24-hour urine collections are often recommended, though this approach is controversial. If two are obtained, the second specimen should probably be collected while the patient follows a calcium-restricted diet59,60 (to identify whether hypercalciuria is dependent on dietary intake). † Measurement of sulfate aids in the identification of a high intake of animal proteins, which may also be inferred from the dietary history. ‡ The risk of recurrence is assumed to be high for patients with a first stone before the age of 20 years and possibly for those with a first stone before the age of 30 years.

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clinical practice after a patient has a single stone. The same types of intake.63 A nonrandomized study of patients with metabolic abnormalities are found among patients absorptive hypercalciuria showed that restriction who have had a single stone and patients with re- of both dietary calcium and oxalate, combined with current stones, suggesting that early evaluation may treatment with a thiazide (2 to 4 mg of trichlorme- be useful. An evaluation may be appropriate in pa- thiazide daily, 50 mg of hydrochlorothiazide daily, or tients with risk factors for a recurrence (such as a 1.25 to 2.5 mg of indapamide daily) and potassium family history of stones or a young age).56 Because citrate (35 mmol daily) reduces urinary supersatu- the rate of compliance with long-term prophylaxis ration and stone recurrence.64 The relative benefits against stone formation, which entails any combi- of dietary management, pharmacologic manage- nation of changes in fluid intake and diet and the ment, or the two in combination are uncertain. If use of medications, is only 36 to 70 percent, a pa- other metabolic abnormalities are identified (for tient’s potential compliance and motivation should example, hyperoxaluria, distal renal tubular acido- be assessed before the metabolic evaluation.57,58 sis, primary hyperparathyroidism, hyperuricosuria, Common metabolic tests are summarized in hypernitraturia, or sarcoidosis), appropriate thera- Table 3. The goal of these tests is to identify derange- py is warranted.65 ments that are amenable to intervention. Metabol- ic factors that increase the risk of recurrent stones guidelines include a low urinary volume (less than 2 liters daily), hypercalciuria (more than 250 mg of urinary cal- The American Urological Association published cium daily in women, more than 300 mg daily in management guidelines for ureteral calculi in men, or more than 4 mg per kilogram of body 1997 (they are available at http://www.auanet. weight daily), and hypocitraturia (less than 320 mg org/timssnet/products/guidelines/main_reports/ of urinary citrate daily). These threshold values must UreStnMain8_16.pdf ).28 These guidelines recom- be viewed cautiously, since solute concentration is mend that patients whose stones have a low proba- a continuous variable. Even patients with apparent- bility of spontaneous passage (on the basis of their ly normal values might be at risk for a recurrence of size and location) should be offered intervention. stones if urinary output and solute concentration Shock-wave lithotripsy is considered first-line ther- fluctuate. apy for those with proximal ureteral stones of less A low urinary volume increases urinary super- than 1 cm. For proximal ureteral stones of 1 cm or saturation, so patients should be instructed to in- larger, shock-wave lithotripsy, ureteroscopy, and crease their fluid intake to achieve a urinary output percutaneous nephrolithotomy are all acceptable of more than 2 liters per day. Because patients gen- treatments. Either shock-wave lithotripsy or ure- erally do not measure their urinary output, a simple teroscopy is recommended for distal ureteral cal- instruction is for patients to drink enough fluids to culi.28 These guidelines were written before the maintain a clear-colored urine rather than a yellow successful experience with ureteroscopy became urine. As they increase their fluid intake, patients widespread.55 should avoid increasing their sodium intake (for example, by drinking soft drinks), because this pro- conclusions motes natriuresis and hypercalciuria. Lemonade and recommendations is a good beverage choice, since it reduces calcium oxalate supersaturation and increases urinary cit- Patients with ureteral calculi typically present with rate.61 No study has compared lemonade with wa- renal colic and hematuria. The unenhanced CT is ter, however, and the effects of drinking lemonade the best diagnostic test. Pain control is important as a sole intervention against stone recurrence have initially; I generally use ketorolac, although stud- not been reported. ies directly comparing ketorolac with other medi- Dietary calcium restriction alone is no longer cations are lacking. Urgent intervention is indicated recommended to reduce the risk of recurrence of for a patient with an obstructed, infected upper uri- calcium stones.62 A randomized, prospective trial nary tract, impending renal deterioration, intrac- showed a lower rate of recurrences among patients table pain or vomiting, anuria, or high-grade ob- who restricted their intake of animal protein and struction in a solitary or transplanted kidney (Fig. 3). salt than among those who restricted their calcium In the absence of these factors, patients should be

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followed closely for stone passage, with CT repeat- should undergo metabolic evaluation, which I ed after three to four weeks. would recommend be performed three weeks af- The patient described in the vignette has a 6-mm ter stone removal. To reduce the risk of stone re- distal ureteral stone that is unlikely to pass spon- currence, the patient should be encouraged to drink taneously. He should be offered shock-wave litho- enough fluid to produce at least 2 liters of urine tripsy or ureteroscopy. He had a prior stone and per day.

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