Not every kidney stone needs surgery. Many small stones can pass naturally through the urinary tract, sometimes with pain relief, fluids and medicines that may help stone passage. However, a stone may need active treatment when it is too large to pass, continues to cause significant symptoms, blocks the flow of urine, contributes to infection, or threatens kidney function.
The decision is not based on stone size alone. Doctors consider the stone's location, symptoms, degree of obstruction, kidney function, urinary infection, stone composition and the likelihood that it will pass without intervention.
If treatment is required, there are several modern approaches to Kidney Stone Surgery. Depending on the situation, treatment may involve shock wave lithotripsy, ureteroscopy or percutaneous nephrolithotomy rather than traditional open surgery.
When can a kidney stone be left to pass naturally?
A small stone that is not causing complications may sometimes be managed without surgery. The chances of spontaneous passage depend largely on the stone's size and location within the urinary tract.
When observation is considered appropriate, the patient is usually monitored rather than simply being told to wait indefinitely. The medical team may assess symptoms, imaging findings and kidney function over time. Conservative management may become unsuitable if the stone causes persistent problems or fails to pass as expected.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Six situations when a kidney stone may need active treatment
1. The stone is unlikely to pass on its own
As stones become larger, the likelihood of spontaneous passage decreases. A stone's location also matters. A stone lodged in the ureter may behave differently from a stone sitting inside the kidney.
If imaging shows that a stone has a low likelihood of passing naturally, the urologist may recommend active removal rather than continuing observation. This does not mean that every stone above a particular size automatically requires surgery. Size is one part of the decision, not the only deciding factor.
2. Pain continues despite medication
Kidney stones can cause severe, wave-like pain when they obstruct or irritate the urinary tract. Pain medicines can often control renal colic while a small stone passes, but sometimes the pain remains severe or repeatedly returns despite appropriate treatment.
When pain cannot be adequately controlled, active stone removal or drainage may be considered. Persistent severe pain is therefore more than a question of comfort. It can be a reason to reconsider continued observation.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
3. The stone is blocking urine flow
A stone can become lodged in the ureter and obstruct the normal flow of urine from the kidney to the bladder. Imaging may show swelling of the urinary collecting system, known as hydronephrosis.
A mild or temporary obstruction does not always mean immediate stone removal, but persistent obstruction is an important reason to consider intervention. The situation becomes particularly concerning when obstruction affects both kidneys or occurs in someone with a single functioning kidney. Kidney function may be placed at greater risk in these circumstances.
4. There is an infection behind the blockage
A blocked kidney combined with a urinary infection is a medical emergency. When urine cannot drain properly and infection is present, pressure and bacteria can build up within the urinary system. This can lead to severe infection and sepsis if treatment is delayed.
In this situation, the first priority is usually urgent drainage of the blocked urinary system, rather than immediately trying to remove the stone. A ureteral stent or a nephrostomy tube may be used to restore drainage, while the infection is treated. Definitive stone treatment is generally addressed after the acute infection has been controlled.
5. The stone is affecting kidney function
Persistent obstruction can interfere with the affected kidney's ability to function normally. The concern is greater when there is obstruction on both sides, reduced kidney function, or only one functioning kidney.
In these circumstances, waiting for a stone to pass naturally may carry greater risk than it would for someone with normal kidney function and no obstruction. Doctors may therefore recommend intervention to relieve the obstruction and protect kidney function.
6. The stone is growing or repeatedly causing problems
A kidney stone that is being monitored may eventually require treatment if it grows, begins causing pain or bleeding, produces obstruction, or becomes associated with infection.
Some people also have reasons to consider planned treatment even when symptoms are limited. The decision can take into account factors such as stone location, the risk of future complications, other medical conditions and practical circumstances.
Current guidelines recognize stone growth, obstruction, infection and symptoms such as pain or blood in the urine among the reasons that active treatment may be appropriate.
Does stone size determine whether surgery is needed?
Stone size is important, but there is no single measurement that means “surgery is always required.” A small ureteral stone may still need intervention if it causes persistent obstruction or uncontrolled pain. Conversely, some stones found incidentally inside the kidney may be monitored when they are not growing and are not causing complications.
For larger kidney stones, active treatment becomes more likely. Current European guidance recommends percutaneous nephrolithotomy (PCNL) as the first-line treatment for renal stones larger than 2 cm, while other approaches may be considered when PCNL is unsuitable.
The location of the stone also matters. For example, larger stones in the lower part of the kidney may be less suitable for shock wave treatment because fragments may have more difficulty leaving the kidney.
Does every kidney stone require “surgery”?
No. The word surgery can make kidney stone treatment sound more invasive than it often is. Modern stone treatment commonly uses minimally invasive techniques that reach or break the stone without a large surgical incision.
Shock wave lithotripsy (SWL)
SWL uses focused shock waves from outside the body to break a stone into smaller fragments that can then pass through the urinary tract. It may be appropriate for selected stones, but its effectiveness depends on factors such as stone size, location, composition and the patient's anatomy. Some patients may need more than one treatment session.
Ureteroscopy
During ureteroscopy, a thin scope is passed through the urinary tract to reach the stone. The stone can be removed or broken into smaller pieces, often using laser energy. Ureteroscopy can be used for many ureteral and kidney stones and is often considered when a higher likelihood of becoming stone-free with a single procedure is important. It is minimally invasive, although it still carries risks and may involve temporary stent placement.
Percutaneous nephrolithotomy (PCNL)
PCNL is generally used for larger or more complex kidney stones. A small opening is made through the back to allow instruments to reach the kidney and remove or fragment the stone. It is particularly important for large renal stone burdens, with current guidance recommending it as the primary treatment for stones larger than 2 cm in appropriate patients.
What if the stone is causing an emergency?
One of the most important distinctions is between planned stone treatment and urgent drainage. If a stone blocks the urinary tract and the patient also has signs of infection, the immediate priority is not simply to remove the stone. The blocked system needs to be drained and the infection treated.
Urgent medical attention is particularly important if a person with a known or suspected kidney stone develops:
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
- Fever or chills
- Severe or worsening pain
- Repeated vomiting
- Difficulty passing urine
- Feeling faint, confused or extremely unwell
- Known obstruction together with symptoms of infection
How does a urologist decide whether you need surgery?
The decision usually combines the patient's symptoms with imaging and other clinical information. The assessment may consider:
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
- Stone size: Larger stones are generally less likely to pass naturally.
- Stone location: A stone in the ureter may have different treatment considerations from one inside the kidney.
- Obstruction: Persistent blockage can make active treatment more important.
- Infection: An infected obstructed kidney requires urgent management.
- Pain: Persistent pain despite appropriate medication can support intervention.
- Kidney function: Reduced function, bilateral obstruction or a solitary functioning kidney can change the urgency.
- Stone composition and density: These can influence which treatment is most likely to work.
- Overall health and anatomy: Other medical conditions and anatomical factors can affect procedure selection.
The Bottom Line
A kidney stone does not automatically need surgery simply because it has been diagnosed. Many smaller stones can pass naturally, particularly when they are not causing complications and the patient can be safely monitored.
Active treatment becomes more likely when a stone is unlikely to pass, causes persistent pain despite medication, produces ongoing obstruction, contributes to infection, threatens kidney function, grows over time or repeatedly causes symptoms.
The most important exception is an obstructed kidney with infection. This is an emergency and usually requires urgent drainage and treatment of the infection before definitive stone removal.
When a procedure is needed, the choice is individualized. Shock wave lithotripsy, ureteroscopy and percutaneous nephrolithotomy are the main modern approaches, and the best option depends on the stone's size, location and characteristics as well as the patient's health and anatomy.
