eMedicine Specialties > Emergency Medicine > Genitourinary

Renal Calculi: Follow-up

Author: Sandy Craig, MD, Adjunct Associate Professor, Department of Emergency Medicine, University of North Carolina at Chapel Hill, Carolinas Medical Center
Contributor Information and Disclosures

Updated: Oct 29, 2009

Follow-up

Further Inpatient Care

• Admission rate for patients with acute renal colic is approximately 20%. Three absolute indications for admission are (1) infected hydronephrosis, (2) unrelenting pain or vomiting despite analgesics and antiemetics, and (3) dehydration.
  • Infected hydronephrosis is defined as UTI proximal to an obstructing stone. Infected hydronephrosis mandates admission for antibiotics and prompt drainage.
    • Midstream urine culture and sensitivity was a poor predictor of infected hydronephrosis in one series, being positive in only 30% of cases.²⁷
    • The clinical presentation of infected hydronephrosis is variable. Pyuria (>5 WBC/hpf) is almost always present but not diagnostic of proximal infection. In one small series of 23 patients with infected hydronephrosis, the temperature was higher than 38°C in 15 patients, the peripheral WBC count was more than 10 X 10⁹/L in 13 patients, and the creatinine level was greater than 1.3 mg/dL in 12 patients.²⁸
    • Renal ultrasonography or helical CT may distinguish pyonephrosis from simple hydronephrosis by demonstrating a fluid-fluid level in the renal pelvis (urine on top of purulent debris). In 2 small studies, the ultrasonographic sensitivity for pyonephrosis was found to be 62-67%. CT sensitivity for pyonephrosis has not been reliably determined.^29,30 The emergency physician must maintain a high index of suspicion.³¹ Antibiotics should cover E coli and Staphylococcus, Enterobacter, Proteus, and Klebsiella species.
    • In another small study of 38 patients with hydronephrosis, 16 had infected hydronephrosis and 22 had sterile hydronephrosis. Ultrasonography alone detected 6 of 16 cases of pyonephrosis, a sensitivity of 38%. Using a cutoff value of 3 mg/dL for C-reactive protein and 100 mm/h for erythrocyte sedimentation rate, the diagnostic accuracy of detecting infected hydronephrosis and pyonephrosis increased to 97%.³²
  • Patients with complete obstruction, perinephric urine extravasation, a solitary kidney, renal transplant, renal failure, or pregnancy, and those with a poor social support system, also should be considered for admission, especially if rapid urologic follow-up is not reliably available.
  • A stone less than 4 mm in diameter has an 80% chance of spontaneous passage; this falls to 20% for stones larger than 8 mm in diameter. The urologist may choose to admit a patient with a ureteral stone larger than 6 mm because of low likelihood of spontaneous passage.
• About 15-20% of patients require invasive intervention due to stone size, continued obstruction, infection, or intractable pain. Several techniques are available to the urologist when the stone fails to pass spontaneously.³³
  • Extracorporeal shock wave lithotripsy (ESWL) utilizes an underwater energy wave focused on the stone to shatter it into passable fragments. Approximately 70% of stones can be treated with ESWL alone. This technique is especially suitable for stones that are smaller than 2 cm and lodged in the upper or middle calyx. Anesthesia or sedation is required. ESWL is contraindicated in pregnancy, untreatable bleeding disorders, patients weighing more than 300 lb, tightly impacted or cystine stones, or in cases of ureteral obstruction distal to the stone.
  • Ureteroscopy is especially suitable for removal of stones that are 1-2 cm, lodged in the lower calyx or below, cystine stones, and high attenuation ("hard") stones. Stones smaller than 5 mm in diameter generally are retrieved using a stone basket, whereas tightly impacted stones or those larger than 5 mm are manipulated proximally for ESWL or are fragmented using an endoscopic direct-contact fragmentation device.
  • Percutaneous nephrolithotomy involves entering the renal pelvis percutaneously using the Seldinger technique after ultrasonography or fluoroscopic localization. Renal calyces, pelvis, and proximal ureter can be examined and stones extracted with or without prior fragmentation. This technique is especially useful for stones larger than 2 cm in diameter. A percutaneous nephrostomy can be used as an emergency procedure to relieve obstruction in a high-risk patient in whom other treatments are not feasible.³⁴
  • Open nephrostomy rarely is used since the development of ESWL and endoscopic and percutaneous techniques. Open nephrostomy now constitutes only 1-2% of all interventions. Disadvantages include longer hospitalization, longer convalescence, and increased requirements for blood transfusion.

Further Outpatient Care

• Patients who do not meet admission criteria may be discharged from the ED in anticipation that the stone will pass spontaneously at home.
  • Arrange for follow-up with a urologist in 2-3 days. Patients should be told to return immediately for fever, uncontrolled pain, or vomiting.
  • Patients should be discharged with a urine strainer and encouraged to submit any recovered calculi to a urologist for chemical analysis.
  • Follow-up for patients with first-time incidence of stones should consist of stone analysis and abbreviated metabolic evaluation to rule out hyperparathyroidism, renal tubular acidosis, and chronic infection with urea-splitting bacteria.
  • Patients with recurrent ureterolithiasis should undergo a more thorough metabolic evaluation. Patients with recurrent stones who undergo thorough metabolic evaluation and specific therapy enjoy a remission rate in excess of 80% and can decrease the rate of stone formation by 90%. A stone chemical analysis together with serum and appropriate 24-hour urine metabolic tests can identify the etiology in more than 95% of patients. A typical 24-hour urine determination should include urinary volume, pH, specific gravity, calcium, citrate, magnesium, oxalate, phosphate, and uric acid. Most common findings are hypercalciuria, hyperuricosuria, hyperoxaluria, hypocitraturia, and low urinary volume. Therefore, the emergency physician should encourage urologic follow-up.

Inpatient & Outpatient Medications

• Discharge on an oral analgesic and an antiemetic if needed. No studies exist that demonstrate superiority of one oral analgesic over another. Typical choices include agents such as hydrocodone, oxycodone, meperidine, or oral anti-inflammatory agents.
• Medical therapies to aid in passage of a stone have been studied. Multiple randomized controlled prospective studies show that outpatient treatment with sustained-release nifedipine 30 mg/d plus prednisolone 25 mg/d or tamsulosin 0.4 mg/d decreases the time to spontaneous passage of the stone; increases the overall spontaneous expulsion rate; and decreases the need for analgesics, hospitalization, and endoscopic intervention.^21,22,23

Deterrence/Prevention

• Patients with recurrent nephrolithiasis traditionally have been instructed to drink 8 glasses of fluid daily to maintain adequate hydration and decrease chance of urinary supersaturation with stone-forming salts.
• Prospective studies suggest that daily consumption of coffee, tea, beer, or wine decreases risk of stone formation, while daily consumption of apple or grapefruit juice increases risk of stone formation.³⁵

Complications

• Infected hydronephrosis is the most deadly complication because the presence of infection adjacent to the highly vascular renal parenchyma places the patient at risk for rapidly progressive sepsis and death.
• Calyceal rupture with perinephric urine extravasation due to high intracaliceal pressures occasionally is seen and usually is treated conservatively.
• Complete ureteral obstruction may occur in patients with tightly impacted stones. This is best diagnosed via IVP and is not discernible on noncontrast CT scan. Patients with 2 healthy kidneys can tolerate several days of complete unilateral ureteral obstruction without long-term effects on the obstructed kidney. If a patient with complete obstruction is well hydrated and pain and vomiting are well controlled, the patient can be discharged from the ED with urologic follow-up within 1-2 days.

Prognosis

• Approximately 80% of ureteral stones pass spontaneously without hospitalization or invasive intervention.
• Approximately 20% of patients require hospitalization due to dehydration, continued pain or vomiting, or inability to pass the stone spontaneously.
• Recurrence rates after an initial episode of ureterolithiasis are 14%, 35%, and 52% at 1, 5, and 10 years, respectively. Risk of recurrence can be reduced drastically by specific medical therapy based on analysis of the stone and serum and urine metabolic profiles.

Patient Education

• For excellent patient education resources, visit eMedicine's Kidneys and Urinary System Center. Also, see eMedicine's patient education articles Blood in the Urine and Kidney Stones.

Miscellaneous

Medicolegal Pitfalls

• Failure to diagnose or delay in diagnosing symptomatic AAA: Pain of a leaking abdominal aortic aneurysm often is misdiagnosed initially as renal colic.
• In one series of 134 patients with symptomatic AAA presenting to the ED, the following statistics were reported:³⁶
  • Eighteen percent had an initial misdiagnosis of nephrolithiasis.
  • All were older than 60 years of age and none had a prior history of renal calculi.
  • Eighty percent had a pulsatile mass noted by at least one examiner.
  • Forty-three percent had microhematuria on urinalysis.
  • Delay of diagnosis of AAA in the ED was associated with higher mortality and morbidity rates than in the group who received the correct diagnosis promptly.
• Failure to diagnose UTI proximal to a ureteral stone and to seek urgent urologic intervention in these patients

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