Medically reviewed by Kidney stones are one of the most painful and frequently encountered conditions in urology. They can affect anyone and often come without warning. To understand kidney stones fully from how they form to how they are treated it’s important to first understand the anatomy of the kidneys and how urine is formed and transported.
Structure and Function of the Kidney
The kidneys are two bean shaped organs located on either side of the spine, just below the rib cage. Each kidney filters blood, removes waste products, and produces urine. Urine is collected in the renal pelvis, then flows into a narrow muscular tube called the ureter, which leads to the bladder.
The upper part of the ureter near the kidney is referred to as the pelvic ureter, and this is one of the most common sites where stones become lodged. The ureters are about 25–30 cm in length but only 3–5 mm wide. This small diameter is why even a medium-sized stone can cause painful obstruction and complications.
What are the Causes of Kidney Stones?
Kidney stones form when the balance of substances in urine is disturbed most commonly due to a combination of dehydration, dietary factors, and metabolic or structural issues in the urinary tract.
Inadequate Fluid Intake
When you don’t drink enough water, your urine becomes concentrated. This reduces its ability to dissolve substances like calcium, oxalate, and uric acid leading them to crystallize and form stones. This is especially common in hot climates or among people who sweat excessively without proper hydration.
Diet
Diet is another crucial factor. A high-sodium diet increases calcium levels in the urine, while diets high in oxalate (found in foods like spinach, chocolate, tea, and nuts) can raise oxalate levels. When calcium and oxalate meet in concentrated urine, they form calcium oxalate crystals the most common type of kidney stone. Similarly, excessive consumption of animal protein (red meat, eggs, seafood) can increase uric acid, which contributes to uric acid stones.
Genetics
Genetics and family history also play a role. If kidney stones run in your family, you’re more likely to produce substances that promote stone formation or less likely to excrete inhibitors that prevent stones.
Medical Conditions
Certain medical conditions significantly increase the risk. For instance:
- Hyperparathyroidism raises calcium levels in the blood and urine.
- Gout leads to high uric acid production.
- Inflammatory bowel diseases like Crohn’s or ulcerative colitis (Crohn’s can affect any part of the digestive tract, while ulcerative colitis primarily affects the colon and rectum) can cause chronic dehydration and nutrient imbalances.
- Recurrent urinary tract infections (UTIs) can lead to struvite (a crystalline compound, specifically magnesium ammonium phosphate, often found in urinary tract stones, also known as “infection stones” because they are related to urinary tract infections stones, particularly in women).
- Congenital urinary tract abnormalities, such as Pelvic-Ureteric Junction Obstruction (PUJO) (a condition where the flow of urine is blocked at the junction between the renal pelvis and the ureter), restrict the normal flow of urine. When urine backs up in the kidney due to this blockage, it becomes stagnant providing ideal conditions for crystals to form and grow into stones.
- Certain Supplements including high doses of vitamin D, calcium, antacids, and some diuretics can also increase stone risk. Overuse or unmonitored intake of these substances can lead to elevated levels of stone-forming compounds in the urine.
Symptoms of Kidney Stones
Kidney stones can cause a range of symptoms that vary in intensity based on the stone’s size, location, and movement within the urinary tract. Here are the most common symptoms:
Severe Pain
The hallmark symptom is intense pain, often described as sharp or cramping, typically in the back, side (flank), or lower abdomen. The pain can radiate to the groin and comes in waves as the stone moves.
Painful Urination (Dysuria)
A burning or stinging sensation during urination may occur, especially if the stone reaches the junction between the bladder and ureter.
Frequent Urge to Urinate
A persistent need to urinate, even if only a small amount of urine is passed, can occur, particularly if the stone is near the bladder.
Blood in Urine (Hematuria)
Urine may appear pink, red, or brown due to the presence of blood, which results from irritation caused by the stone.
Cloudy or Foul-Smelling Urine
Urine that appears cloudy or has a strong odor may suggest infection or a reaction to the stone’s presence.
Nausea and Vomiting
The intense pain can trigger nausea or vomiting due to the body’s response to the obstruction in the urinary tract.
Fever and Chills
These may indicate an infection in the kidney or urinary tract and require immediate medical attention.
Difficulty Passing Urine
A stone that causes a blockage can reduce or completely stop urine flow, leading to discomfort and potential complications.
Complications: Hydroureteronephrosis and PUJO
When a stone blocks urine flow, it can result in hydroureteronephrosis a condition in which the ureter and kidney swell due to trapped urine. This can damage kidney tissue if not treated promptly. In some individuals, especially those with structural abnormalities, this blockage may not be due to a stone but to Pelvic-Ureteric Junction Obstruction (PUJO). PUJO occurs at the junction between the renal pelvis and the ureter and can either be congenital or acquired. It impairs normal urine drainage and increases the risk of stone formation.
Stone Sizes and Chances of Natural Passage
The likelihood that a kidney stone will pass naturally depends heavily on its size. Smaller stones are more likely to pass without intervention, while larger stones often require medical treatment.
- Stones less than 2 mm in size have about an 80% chance of passing naturally without causing significant problems. Stones between 2–4 mm also have an 80% passage rate, although they may cause temporary discomfort.
- For stones between 4–10 mm, the chance of spontaneous passage drops to around 60%, and medical monitoring is often needed. These stones may require medications to aid passage or minimally invasive procedures.
- Once a stone is larger than 10 mm, the chance of passing naturally drops to 20% or less. These stones typically cause severe symptoms and are unlikely to pass through the narrow ureter on their own. At this stage, surgical intervention is often required.
How Are Kidney Stones Treated?
Treatment for kidney stones depends on their size, location, and the severity of symptoms. There are four main methods for kidney stone removal.
Extracorporeal Shock Wave Lithotripsy (ESWL)
Extracorporeal Shock Wave Lithotripsy (ESWL) uses sound waves to break small stones into tiny fragments that can pass through urine. It’s ideal for stones less than 15 mm in size and located in the kidney or upper ureter.
Ureterostomy (URS)
Ureterostomy (URS) involves inserting a thin scope through the urethra to reach the ureter or kidney. A laser is used to break the stone, and the fragments are removed or allowed to pass naturally.
Retrograde Intrarenal Surgery (RIRS)
Retrograde Intrarenal Surgery (RIRS) is a minimally invasive method used for stones up to 20 mm in size. A flexible ureter scope is guided into the kidney through the urinary tract, and a laser is used to pulverize the stone. It has become a preferred option due to its safety and quick recovery.
Percutaneous Nephrolithotomy (PCNL)
Percutaneous Nephrolithotomy (PCNL) is a more invasive procedure for large or complex stones. It involves a small incision in the back to access and remove the stone directly from the kidney.
RIRS in Urology
RIRS (Retrograde Intrarenal Surgery) is an advanced and highly effective treatment for kidney stones located within the kidney. It is especially useful for stones up to 20 mm in size. The procedure is performed under general anesthesia, and since no external cuts are made, the recovery is faster, and postoperative pain is minimal. Most patients are discharged within 24 hours and can return to normal activities within a few days.
DJ Stents and Their Role in Kidney Stone Management
After stone removal procedures or in cases of obstruction, a DJ stent a device in urology to bypass blockages, support healing after surgery, or temporarily relieve obstructions caused by stones or structural issues like PUJO is often placed in the ureter to ensure proper urine flow and reduce swelling.
It is called “Double J” because both ends are curled in a J-shape one end sits in the kidney and the other in the bladder, preventing displacement. DJ stent removal is a short, outpatient procedure typically done a few weeks after placement. Prolonged use of a stent can cause discomfort, infection, or new stone formation, so timely removal is essential.
Recommended Diet for Kidney Stone Patients
1. Stay Hydrated
- Drink at least 2.5 to 3 liters of water daily.
- Aim for clear or very light-colored urine. Include citrus juices like lemon or orange (natural, not sugary drinks), as they contain citrate, which helps prevent stone formation.
- Limit salt to less than 2,300 mg per day (about 1 teaspoon).
- Avoid processed foods, chips, canned soups, fast food, and salty snacks.
3. Moderate Calcium Intake (Don’t Avoid It!)
- Include normal amounts of calcium from food (e.g., milk, yogurt, cheese)—about 1,000 mg/day.
- Avoid calcium supplements, unless advised by your doctor.
4. Limit Oxalate-Rich Foods
- Reduce intake of spinach, rhubarb, beetroot, nuts, chocolate, tea, and soy products.
- If you eat oxalate-rich foods, combine them with calcium-rich foods to bind oxalate in the gut.
5. Limit Animal Protein
- Cut back on red meat, poultry, eggs, and fish.
- Excess protein raises uric acid and reduces urinary citrate.
- Use plant-based protein like lentils or beans moderately.
6. Reduce Sugar and Fructose
- Avoid sugary sodas and juices.
- Limit sweets, desserts, and high-fructose corn syrup products.
7. Include High-Fiber, Whole Foods
Whole grains, vegetables, fruits (especially with citrate), and legumes help regulate digestion and mineral absorption.
Conclusion
Kidney stones are a serious but manageable condition when diagnosed and treated early. Understanding kidney anatomy, recognizing symptoms, and identifying causes are crucial steps in managing the condition effectively.
With advancements in technology like RIRS and supportive measures like DJ stents, even large or complex stones can now be treated safely and with minimal discomfort. Whether it’s a small 7 mm stone or a large 20 mm one, timely intervention can prevent long-term kidney damage and ensure a smooth recovery.