Kidney Stones

Kidney stones (also known as nephrolithiasis) form when common urine substances build up, crystallize and harden into stone-like deposits.

The most common stones are composed of calcium oxalate, calcium phosphate, uric acid, or struvite. Kidney stones are very common in the United States. The most common stone symptom is flank pain caused by a blockage in the flow of urine to the bladder. About 1 in 10 people experience kidney stones, and about 50% of people have another stone episode within 10 years of the initial event. Management of your kidney stones will be personalized based on size and the location of stones. Although certain types of kidney stones may be treated with medications, the vast majority require a procedure for removal. Not all kidney stones require immediate treatment however, and some may be observed if asymptomatic and located in the kidney.

Causes and Risk Factors

Stone disease is a chronic medical condition affected by multiple risk factors that include:

Increasing age
Male gender
Family history of kidney stones
Obesity
Hot weather
Poor fluid intake
Diet rich with animal proteins
Chronic urinary tract infections
Anatomic abnormalities of the urinary system
Genetic conditions that affect mineral metabolism in the urine
Diabetes
Certain surgeries such as gastric bypass
Certain digestive disorders such as Crohn’s Disease

When to Speak with a Urologist about Kidney Stones

You should talk to a Urologist about kidney stones if you or your primary care doctor suspect you have stones based on symptoms such as flank pain or blood in the urine or based on imaging results. If you have severe pain with fevers, chills, or persistent vomiting, you should seek care immediately at an Emergency Room for possible inpatient evaluation by a Urologist.

What to Expect when Seeking Treatment

In addition to a history and physical examination, the initial assessment typically includes urine testing to rule out infection and blood work to assess renal function and mineral levels. Imaging with non-contrast CT scan of the abdomen and pelvis should be obtained in order to delineate the number and location of the stones as well as to determine the anatomy and inform the most appropriate surgical approach. Sometimes imaging can be with renal and bladder ultrasound and abdominal x-ray. Any stone fragments that have passed spontaneously can be sent for mineral testing to understand the specific type of stone present. Additional metabolic testing may include completion of a 24-hour urine study to precisely determine and identify mineral abnormalities in the urine.

Treatment Options

Appropriate management is personalized based on patient preference and anatomy as well as stone number and location.

Surveillance is an acceptable option for management of asymptomatic non-obstructing renal stones. The risk of a symptomatic stone episode or requiring an intervention is about 10% per year with cumulative risk of 25-50% after 5 years of observation. Surveillance wound include annual imaging to monitor for stone growth.

Initial management for patients with stones in the ureter that are less than 10mm involves observation with medical expulsive therapy if pain is controlled and there are no signs of infection or high-grade obstruction. Spontaneous passage is possible and happens more frequently for smaller stones that are more distal (2-4mm, 95% chance; 4-6mm, 50% chance).

Medical expulsive therapy sometimes includes an oral medication called tamsulosin in an off-label indication to relax the ureter that has been shown to increase spontaneous passage to around 80% from around 60% for larger distal stones. The urine should be strained at home during this time to monitor for spontaneous stone passage. Medical expulsive therapy should not be continued for more than 4-6 weeks before progressing to definitive management to prevent possible permanent kidney dysfunction and progression should occur sooner if pain worsens, kidney function decreases or signs of infection are present.

In the event of the presence of simultaneous infection and obstruction, drainage must be obtained emergently without attempt to remove the stone. Stone removal must be delayed until after the infection is treated.

Ureteral stones requiring treatment may be managed with outpatient procedures including either ureteroscopy (URS) or shockwave lithotripsy (ESWL). URS involves passing small cameras into the ureter through the urethra and bladder to treat stones by fragmentation with lasers and by removal with basketing. ESWL is non-invasive and fragments stones with shockwaves through the flank. It then relies on spontaneous passage of the fragments to clear the stone. ESWL is reserved for patients with stones that are visible on x-ray imaging and that are in the upper portion of the ureter or kidney.

ESWL has less morbidity and fewer complications but URS offers a higher likelihood of being stone free in a single procedure (90% for URS vs 73% for ESWL). A temporary ureteral stent may be placed as part of URS. Occasionally a stent must be placed to dilate the ureter for about 2 weeks if the ureter is too narrow to pass the instruments at URS, or a stent may be left in place for 3-7 days after URS to facilitate healing. A stent may cause some discomfort, which can be treated with various medications (tamsulosin, oxybutynin, Pyridium, NSAIDs). Stents are rarely needed with ESWL.

URS risks include bleeding, infection, injury to the bladder or ureter, ureteral perforation, or ureteral stricture. ESWL risks include bleeding, infection, and about a 5% chance of sufficient stone debris in the ureter to cause blockage postoperatively requiring a temporary stent.

Patient preference helps guide treatment approach with patients preferring to maximize chances of being stone free choosing URS and those preferring to minimize risk and discomfort choosing ESWL.

Renal stones may be managed with URS, ESWL or percutaneous nephrolithotomy (PCNL). PCNL is typically reserved for larger stones and involves passing an instrument directly through a small (1 cm) incision in the flank to address the stone. PCNL does require brief hospitalization.
PCNL does involve a higher risk of complications which include need for blood transfusion (7%), postoperative fever (20%), sepsis (3%), injury to surrounding organs (2%).

For renal stones with greater than 2 cm total stone burden, PCNL is first-line management. In this setting the stone-free rate is higher with PCNL than URS (94% vs 75%) and requires fewer procedures.

After surgical treatment for kidney stones, follow up imaging with ultrasound is required to ensure there are no residual signs of obstruction. Further treatments focus on reducing the risk of kidney stone recurrence. Depending on the clinical situation, various medications, such as chlorthalidone, potassium citrate or allopurinol, may be recommended.

Dietary and Lifestyle Modifications

Certain dietary and lifestyle modifications can also greatly reduce the risk of stone recurrence:

Increasing fluid intake in order to produce over 2.5 liters of urine daily, which can decrease recurrence by around 50%.
Avoidance of dark colas and teas and instead consume clear sodas or citrus drinks with lemonade and lemon juice being particularly beneficial in order to increase urinary citrate and urine pH.
Limiting salt (sodium) intake to less than 2,200 mg daily.
Maintaining moderate calcium intake around 1,000 to 1,200 mg daily. If calcium supplements have been recommended for bone health, take the supplement with meals as opposed to at bedtime and consider using calcium citrate supplements.
Diet high in fruits and vegetables and relatively low in animal proteins.
Limiting foods high in oxalate which includes: spinach, rhubarb, rice bran, almonds, beets. The key is moderation and not strict avoidance.
Avoidance of high-dose vitamin C supplements with maximum daily dose under 2 gm.
Taking a vitamin B6 supplement 100 mg daily.