6 - Acute Stone Management | Smiths General Urology, Seventeenth Edition (LANGE Clinical Medicine)

Authors: Macfarlane, Michael T.

Title: Urology, 4th Edition

> Table of Contents > Part One - Chief Presentations > Chapter 6 - Acute Stone Management

Chapter 6

Acute Stone Management

Presentation

The patient with stone typically presents with unilateral renal colic and hematuria. Renal colic refers to an intermittent flank pain arising in the kidney or ureter and may radiate to the ipsilateral groin or testis. Patients generally toss about and cannot find a comfortable position. Guarding with nausea and vomiting is occasionally noted. Low-grade fever and mild elevation of the white blood cell count may be present. Evidence of serious infection (e.g., high-grade fever, white count, and pyuria) demands immediate intervention, especially in diabetics.

Diagnosis

Urinalysis will almost always show red blood cells, and 90% of stones can be demonstrated on a kidney, ureter, and bladder (KUB) film of the abdomen. If a stone is seen on KUB, then the intravenous urogram (IVU) need not be obtained immediately. A thorough bowel preparation and a high-quality nonemergent study will yield more information. A stone protocol (non-contrast) computed tomography (CT) scan has become the standard initial workup of patients with suspected stone. However, if high-grade obstruction requiring acute intervention is suspected, then an emergency IVU should be obtained.

Workup

Laboratory Tests

A urinalysis should always be obtained. Hematuria will be present in most cases. Pyuria would suggest an associated infection that will need immediate attention. A urine culture should be ordered if the urinalysis indicates pyuria or significant bacteriuria. A serum creatinine level should be obtained to evaluate renal function. A complete blood count may be indicated to screen for evidence of serious infection.

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Imaging Studies

A noncontrast CT scan of the abdomen and pelvis using a stone protocol has replaced the standard IVU in the initial workup for acute stone in most emergency room settings. Its advantages are speed, no need for intravenous contrast or monitoring, and the ability to identify even small radiolucent uric acid stones. A negative CT is strong evidence against the presence of a stone. However, CT can be a poor indicator of the degree of obstruction and hydronephrosis. An IVU may still be useful if the severity of obstruction is in question.

Management

Immediate care of the patient with acute stone is based on the following considerations:

Size and location of the stone and likelihood of its passing spontaneously
Any complicating medical problems (e.g., diabetes or solitary kidney)
Complications related to the stone (e.g., high-grade obstruction or infection)

Indications for Hospitalization

High-grade obstruction, especially when associated with stones greater than 10 mm, will require early intervention (i.e., ureteral stents or percutaneous nephrostomy).
High fever (>101 F) suggests pyelonephritis is present, and appropriate antibiotics should be started immediately.
Patients with uncontrollable pain requiring parenteral analgesics should be hospitalized.
Patients with severe nausea with dehydration requiring intravenous fluids should be hospitalized.
Patients with a single functioning kidney at risk of acute renal failure require hospitalization.

Diabetics

The diabetic patient with acute stone disease has an increased risk of developing complications (e.g., infection and contrast-mediated nephrotoxicity). This is especially true for insulin-dependent diabetics out of control. Hospitalization is often indicated. Caution is

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indicated when intravenous contrast is given to diabetics on metformin (Glucophage). Metformin should be discontinued for 48 hours after intravenous iodinated contrast is used. Nonionic, iso-osmolar contrast should be used whenever possible.

Pregnancy

Pregnant woman who present with renal colic and microscopic hematuria should undergo renal ultrasound. If hydronephrosis is present, presumption of a ureteral calculus can be made. If renal colic fails to resolve with hydration and analgesics or in the setting of severe obstruction or sepsis, then retrograde placement of a silicone double-J ureteral stent under local anesthesia is a reasonable course.

Extracorporeal Shock Wave Lithotripsy Treatment

Patients who have had recent extracorporeal shock wave lithotripsy (ESWL) may present with renal colic owing to passing stone fragments (Steinstrasse). Stent placement may be necessary.

Inpatient

Patients admitted for acute stone management should receive vigorous fluid resuscitation, especially the diabetic with infection. Antibiotics should be given as indicated. High-grade obstruction should be relieved with placement of a retrograde ureteral stent or percutaneous nephrostomy. Urine should be strained for stones.

Outpatient Management

For the otherwise healthy individual with an acute stone less than 5 mm in diameter, outpatient management is appropriate. Patients should be instructed to drink plenty of fluids, strain the urine to catch the stone, and save the stone for analysis. They should be given an adequate supply of oral analgesics. Follow-up should include a weekly or biweekly KUB to monitor progress of the stone passage. Patients with stones between 5 and 10 mm are less likely to pass the stone spontaneously and should be considered for early elective intervention in the absence of other complicating factors (e.g., infection, high-grade obstruction, or solitary kidney). Stones that are larger than 10 mm will rarely pass.

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Papillary Necrosis

Papillary necrosis is the result of toxic or ischemic injury to the papillary tip with subsequent necrosis. It is most commonly associated with analgesic abuse, pyelonephritis in diabetics, sickle cell disease, and systemic vasculitis in middle-aged women. Rarely will patients present with renal colic and hematuria (similar to an obstructing stone) secondary to acute sloughing of necrotic papillae with ureteral obstruction. Most patients will present with insidious onset of renal failure. An intravenous pyelogram (IVP) will show calyceal irregularities or ring shadows around sloughed papilla within the calyx. Fragments of the papillae may be found in the urinary sediment. The sloughed papillae can cause obstruction or serve as a nidus for persistent infection. Management consists of treating infection, relieving obstruction, and removing causative agents (analgesics).