If you’ve been diagnosed with kidney stones (urolithiasis), you may have several options for treatment. These include medical therapy, extracorporeal shock wave lithotripsy (ESWL), percutaneous nephrolithotripsy (PCNL), and ureteroscopy.
A brief anatomy of the urinary tract
The urinary tract includes
- kidneys (two organs that filter waste and extra water from the blood)
- ureters (two tubes bringing urine from each kidney to the bladder)
- bladder (organ that collects urine)
- urethra (a single tube through which urine in the bladder passes out of the body).
The evaluation for kidney stones
If your symptoms suggest kidney stones, imaging is often the first step in an evaluation. For many years the standard of care was a type of abdominal x-ray called an intravenous pyelogram (IVP). In most medical centers, this has been replaced by a type of computed tomography (CT) called unenhanced helical CT scanning. In some cases, such as when a person has impaired renal function or a contrast dye allergy, renal ultrasound may be used as an alternative.
You will also have blood tests, including tests for renal function (creatinine, BUN). Your doctor may suggest other blood tests as well. A urinalysis will be obtained and if infection is suspected, a urine culture will be sent.
Keeping kidney stone pain under control
If you are experiencing the intense discomfort of kidney stones (renal colic), pain control is a top priority. A 2018 analysis of multiple randomized trials looked at different pain relief medicines given to people treated in the emergency department for acute renal colic. It compared nonsteroidal anti-inflammatory drugs (NSAIDs, such as aspirin, ibuprofen, or naproxen) with paracetamol (similar to acetaminophen) or opioids. The study found NSAIDs offered effective pain relief with fewer side effects than paracetamol or opioids. NSAIDs directly inhibit the synthesis of prostaglandins, which decreases activation of pain receptors and reduces renal blood flow and ureteral contractions.
Medical therapy for kidney stones
Most evidence suggests that stones less than 10 mm in diameter have a reasonable chance of passing through the urinary tract spontaneously. You may be offered medical expulsive therapy (MET) using an alpha blocker medication, such as tamsulosin. It’s important to understand that this is an off-label use of the drug. Rarely, tamsulosin causes a condition called intraoperative floppy iris syndrome that can complicate cataract surgery.
Not all experts feel MET is worthwhile, and its use remains controversial. Discuss your options with your doctor or a urologist.
Extracorporeal shock wave lithotripsy
All shock wave lithotripsy machines deliver shock waves through the skin to the stone in the kidney. Most but not all of the energy from the shock wave is delivered to the stone.
Stone size is the greatest predictor of ESWL success. Generally:
- stones less than 10 mm in size can be successfully treated
- for stones 10 to 20 mm in size, additional factors such as stone composition and stone location should be considered
- stones larger than 20 mm are usually not successfully treated with ESWL.
Stones in the lower third of the kidney can also be problematic because, after fragmentation, the stone fragments may not be cleared from the kidney. Due to gravity, these fragments don’t pass out of the kidney as easily as fragments from the middle and upper thirds of the kidney.
Obesity also influences whether ESWL treatment will be successful. The urologist will calculate the skin-to-stone distance (SSD) to help determine whether this treatment is likely to be effective.
The possible complications of ESWL include:
- Injury to kidney tissue, such as bruising (hematoma), can occur in a small number of cases, but usually heals without additional treatment.
- Fragmented stones may accumulate in the ureter and form an obstruction. This is known as a steinstrasse (“street of stones”). A ureteral stent often minimizes any problems associated with steinstrasse. The stent is removed in a few days or weeks.
- A small percentage of patients undergoing ESWL develop hypertension, although the mechanism is not well understood.
- An increased risk of diabetes mellitus following ESWL has also been reported. However, these results were not confirmed by a large population study done at the same institution.
Using ultrasound or fluoroscopic guidance, a surgeon gains access to kidney stones through a small incision in the lower back during percutaneous nephrolithotripsy. A power source, such as ultrasound or laser, breaks the stones into fragments, which are flushed out of the kidney through an external tube or internal stent.
This treatment is usually considered for larger kidney stones (2 cm or more), complex stones, or lower pole renal stones larger than 1 cm. Possible complications may include bleeding, infection, and injury to surrounding organs.
During ureteroscopy, a surgeon places a tube through the urethra and bladder into the ureter, possibly going all the way up into the kidney. Ureteroscopy employs either semirigid or flexible instruments through which the surgeon has an excellent view of everything inside the urethra. The surgeon then uses a power source threaded up through the ureteroscope to fragment the stones under direct visualization. A postoperative stent can be placed for a few days at the discretion of the urologist.
Complications are infrequent, but may include injury to or narrowing of the ureter, as well as sepsis.