Surgical Therapy

Urinary stones or calculi are concretions formed by the crystallization of one or more substances normally found in the urine. These calculi can be found anywhere within the urinary tract: the kidneys, ureters or bladder.   Most often these stones are formed within the kidney and travel down the ureter towards the bladder, causing a sudden sharp intense pain along the flank which radiates towards the groin. The pain is often intermittent and escalating in nature, and is associated with nausea and vomiting. This complex of symptoms is commonly referred to as "renal colic". Patients often note difficulty finding a comfortable position and therefore move continuously to try to "shake off" this pain.

EVALUATION

History and Physical Examination

The initial evaluation of a patient suspected of having a kidney stone would consist of a complete history and physical examination. The patient would be asked specifically to describe the symptoms they are having. Their description is usually the first clue to their diagnosis. Past medical history, including prior stones, prior urologic surgeries, hyperparathyroidism, recurrent urinary tract infections, renal tubular acidosis, gastrointestinal diseases, and diarrhea, should be elicited during the history. Use of medications that could contribute to stone formation, including steroids, antacids, water pills, colchicine, and chemotheraputic agents, should be reviewed. On physical exam, the patient will often appear listless, unable to find a comfortable position. The abdomen may be slightly distended and pain is often elicited by gently tapping on the flank region.

LABORATORY TESTS

Intial Laboratory tests include:

1. Urinalysis to assess for the presence of blood in the urine.

2. Blood tests to determine kidney function , blood count, and concentrations of calcium, phosphate and uric acid.

3. Urine culture to assess for the presence of urinary infection.

For patients who are considered high risk stone formers (i.e. genetic predispostion, cysteine or uric acid stones, infection stones, recurrent or bilateral stones, stones in children), a more complete evaluation is mandated. This includes a 24- hour collection of urine to test for oxalate, calcium, magnesium, citrate, and uric acid levels. In addition, further blood tests, including a test to rule out hyperparathyroidism, may be performed. All stones that are spontaneously passed should be collected and analyzed to determine their precise compostion.

RADIOLOGIC EVALUATION

Patients with stones should undergo radiologic evaluation. The essential and basic first evaluation should consist of a CT scan and a KUB ( abdominal plain film).

There are other tests which could be done, but these would be done first. A CT scan without intravenous contrast would show any stone anywhere. It also confirms the calcification seen is a stone in the urinary tract, rather than something else, like a calcification in a blood vessel outside the urinary tract. The KUB is performed to see if the stone seen on CT scan contains calcium. This is important for treatment decisions. Stones that show up on a KUB ( "plain film") and are confirmed to be in the urinary tract by the CT scan can probably be treated with a non -invasive method, which the patient would probably prefer.

"KUB" (Kidney-Ureter-Bladder X-ray or Abdominal Plain Film)

Because the majority of stones ( 90%) are radiopaque, these can be easily identified on X-rays. The number, size, and approximate location of the stone can also be assessed. Because they are radiolucent, uric acid and some cysteine stones may not appear on plain X-rays.

CT Scan (Computed Tomography Scan)

A CT scan can not only identify the stone and show its location, but can also document the presence of obstruction or anatomic abnormalities. Oral contrast may be used to delineate the gastrointestinal tract. Intravenous contrast maybe given to delineate the urinary tract. All stones, including uric acid stones, will appear on a CT scan. A CT scan without contrast is the study commonly done by emergency rooms to diagnose stones quickly. It is also the preferred study when a patient has an allergy to dye or should not take dye because of underlying kidney disease.

IVP (Intravenous Pyelogram)

An intravenous pyelogram is a series of four to six plain abdominal X-rays which are taken after the administration of intravenous contrast material, which is excreted by the kidneys into the urinary tract. This provides anatomic detail of the entire urinary system from the kidneys and ureters, down to the bladder. Urologists use this as a "road map" to identify and pinpoint the precise location of the stone within the urinary tract. This also allows for the identification of urinary obstruction from an impacted stone. Anatomic abnormalities, such as duplicate ureters or a pelvic kidney, can also be identified with this test.

ULTRASOUND (SONOGRAM)

Songoraphy is often used for patients in whom intraveous contast is contraindicated due to allergy or renal impairment. Songrams can see the kidney and bladder, but can't see the ureters well. The finding of a dilated kidney on sonography may suggest the presence of obstruction lower downstream within the ureter. Ultrasonography does not use radiation, so its often used to evaluate urinary problems during pregnancy.

NATURAL PROGRESSION

The natural course of kidney stones without treatment must be balanced against the relatively limited risks of treatment that are now possible with non-surgical techniques. Kidney stones that are more than 1 cm. in size (about 1/2 an inch) within the kidney will rarely pass through the urinary system without complications. Therefore, treatment is recommended for kidney stones larger than 1 cm.

The kidney stone that has passed into the ureter, the tube that connects the kidney to the bladder, is the stone most likely to create symptoms. The ureter is a narrow tube that propels urine along toward the bladder with rhythmic contractions. When a stone gets into the ureter, it may stop at the edge of the pelvis or just outside of the bladder, two natural areas of narrowing within the ureter. If the stone blocks urine flow, pressure builds up in the ureter and subsequently the kidney, causing the classic rhythmic spasms of pain associated with kidney stones. Pain medication is required for these cases. Any infection behind a stone must be aggressively managed.

What happens to the stone if it's not removed? The chance of a ureteral stone passing is proportional to the width of the stone. For stones less than 3 mm in width, the chance of spontaneous stone passage is very high. Stones more than 8 mm.in width are only about 20% likely to pass spontaneously over one year. Unfortunately, stones may produce significant pain and symptoms during passage, and emergent interventional treatment may be required, so earlier treatment, before the patient has symptoms, is suggested for stones felt likely to cause future problems.

For anyone who has suffered the pain of a kidney stone, the thought of passing a second stone is not appealing. Unfortunately, 60% of patients who have a kidney stone will have another -emphasizing the importance of evaluating the possible causes of stone formation and looking for ways to prevent them.

CONSERVATIVE THERAPY

Hydration

Hydration has remained the mainstay of any treatment program aimed at preventing kidney stones. Stones form by the crystallization of one or more substances which exist in high concentrations in the urine. Increased fluid intake will decrease the chance of stone formation by maintaining a high urinary output and by decreasing the likelihood that these substances will crystallize by diluting them. There are no strict recommendations with regards to the number of glasses of fluid to drink, however, the goal should be to achieve a urine output of greater than two liters per day. Stones that are less than 5 millimeters in size have a high chance (90%) of passing through the urinary tract spontaneously with hydration therapy alone. Larger stones (>6 millimeters) have a much lower chance of passing on their own, and often need surgical intervention.

Diet

Dietary modifications can reduce the chance of stone formation for certain stone types. Therefore, each patient should seek the advice of their urologist before changing their diet. In general, a diet low in animal protein, sodium, and oxalate can reduce the chance of calcium oxalate stone formation. Foods rich in oxalate include: chocolate, tea, spinach, asparagus, and nuts. A diet rich in fiber is also advised. Patients should not restrict dairy products, but should avoid overindulgence- i.e. no more than 3 glasses of milk a day.

Medications

Allopurinal can decrease the formation of uric acid and therefore is often used in patients with uric acid stones. Thiazide diuretics (e.g. hydrochlorothiazide) can decrease calcium concentrations in the urine by promoting its reabsorption by the kidney. Thiazides are useful in some patients with calcium oxalate stones. Citrate is an important inhibitor of stone formation. Administered as potassium citrate, it causes alkalinization of urine (elevates urinary pH) and thus is given to patients with uric acid stones and cystine stones which crystallize at a low urinary pH environment. Uric acid stones can often be completely dissolved if adequate alkalinization of urine can be maintained (urinary pH >7). Citrate can also inhibit the crystallization of calcium in the urine. Oral antibiotic therapy is used in patients with infection stones.

SURGICAL THERAPY

Surgical intervention may be warranted for stones that are resistant to conservative therapy, large stones, obstructing stones, or for patients with anatomic abnormalities of their urinary tract that may prevent the passage of even small stones.   Several types of surgical therapies will be described here.

 

Extracorporeal Shock Wave Lithotripsy (ESWL)

General - ESWL is a noninvasive method of breaking kidney stones using high energy shock waves. The shock waves are generated outside of the body by a lithotripter machine and travel through the body and are focused directly onto the stone by X-ray guidance. The stone is fragmented into smaller pieces, which can then pass spontaneously.

Indications - ESWL can be used for any type of stone, however, in gerneral, ESWL works best for softer calcium and magnesium stones, and is less successful with hard stones, like calcium oxalate monohydrate or cystine stones. ESWL is commonly used for stones located in the kidney and for stones less than 1 to 2 centimeters. It can be used to treat ureteral stones, depending on their location. Multiple ESWL treatments may be required for larger or multiple stones. 

Procedure- ESWL can be performed with either intravenous sedation or general anesthesia. Because ESWL is a noninvasive procedure, an incision is not required. During ESWL, the patient typically lies flat on the lithotripter table. A small flexible plastic internal tube (called a ureteral stent) is sometimes passed into the ureter from the bladder using a cystoscope, to promote passage of stone fragments and to prevent obstruction from the stones. Most times this is not necessary. An ESWL procedure typically takes 45 minutes to perform. 

Contraindications - Contraindications to ESWL include bleeding tendencies, pregnancy, uncontrolled hypertension, active urinary tract infection, morbid obesity, and certain anatomic abnormalities of the urinary tract.

Postoperative - Performed asan outpatient procedure, overnight stay in the hospital is not required. A small amount of bleeding in the urine is expected after this procedure. Postoperative pain is usually described as a "bruise"-like sensation in the flank. Patients usually return to routine activities/ work in 48 hours.

URETEROPYELOSCOPY AND LASER LITHOTRIPSY

General / Indications - When stones get caught in the ureter during passage to the bladder, and urinary obstruction due to impaction of the stone occurs. This is often seen with stones larger than 5 mm in size. If these stone fragments do not pass spontaneously after conservative therapy (i.e. hydration and pain medication), then ureteropyeloscopy and laser lithotripsy may be required. (ESWL can also often be used to treat these stones -depending on their location.)

Procedure - Ureteropyeloscopy is usually done under general anesthesia. Ureteropyeloscopy is performed by introducing a small telescope (called a ureteroscope) through the urethra, into the bladder, and up the ureter. With direct visualization of the stone within the ureter, a laser fiber can be used to fragment the stone into smaller pieces. A ureteral stent is often required with this procedure. Ureteropyeloscopy with laser lithotripsy can require anywhere between 1-3 hours depending on the size and location of the stone within the urinary tract.

Contraindications - Contraindications to ureteropyeloscopy include bleeding tendencies, active urinary infections, or patients deemed unsuitable for general anesthesia.

Postoperative - A small amount of bleeding in the urine is expected after this procedure. Postoperative complaints include urge to urinate from irritation of the bladder and urethra from passage of the ureteroscope. This is short-lived and resolves quickly over a day or so. Overnight stay in the hospital is typically not required.

PERCUTANEOUS NEPHROSTOLITHOTOMY (PCNL)

General/indications - For kidney stones larger than 2 centimeters in size or for hard stones, a more invasive but extremely effective therapy called percutaneous nephrostolithotomy is generally recommended.

Procedure - PCNL must be performed under general anesthesia. This procedure involves direct fragmentation of the kidney stone through a small puncture made in the flank through which a telescope (called a nephroscope) is passed directly into the kidney. Ultrasonic, electrohydraulic, or laser fragmentation of the stone can then be performed throught the nephroscope under direct vision. A plastic tube (called a nephrostomy tube) is temporarily left in the kidney, exiting the flank, in order to optimize drainage of the urine from the kidney following PCNL. It is later removed in the office.

Contraindications - Contraindications to PCNL include bleeding tendencies and active urinary infection.

Postoperative - PCNL often requires a one to two night stay in the hospital. Mild to moderate bleeding in the urine is common after PCNL. Patients often have a mild to moderate amount of pain at the site of the nephrostomy tube which is easily managed with oral pain medications.

Open Surgical Techniques

General/Indications - With the advent of ESWL and PCNL techniques, open surgical procedures on the kidney have been made virtually obsolete.