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What do kidney stones look like when they come out in urine?

Kidney stones are hard deposits made of minerals and salts that form inside your kidneys. They develop when your urine contains more crystal-forming substances than the fluid in your urine can dilute. When kidney stones move into your ureter — the tube that connects your kidney and bladder — they can cause severe pain.

Kidney stones come in a variety of sizes and shapes. Small kidney stones may go undetected and be passed out painlessly in your urine. However, larger stones can become lodged in the ureters, blocking the flow of urine and causing kidney stone symptoms like severe abdominal and flank pain, nausea and painful urination. Being able to recognize kidney stones in your urine can help you monitor your condition.

What Do Kidney Stones Look Like?

Kidney stones can come in a variety of shapes, colors and textures:


– Round or oval: Smooth, oval-shaped stones are most common.
– Jagged and spiky: Stones with sharp, irregular edges are more likely to get stuck.
– Tiny flecks or sand-like granules: Smaller kidney stones may pass down as flecks or grains.
– Single stone or multiple stones: You may pass one larger stone or many tiny ones grouped together.


– Yellow or gold: Most stones contain calcium and appear yellow or gold.
– Pink or red: Stones with calcium oxalate may be pink or reddish.
– Dark brown or black: Stones containing bilirubin or cystine may be brown or black.
– White or pale: Struvite or uric acid stones look white or pale.


– Smooth and glossy: Calcium oxalate stones are usually smooth.
– Rough and bumpy: Uric acid and struvite stones tend to be rougher.
– Soft and powdery: Cystine stones may feel soft or crumble easily.
– Hard and solid: Very hard stones usually contain calcium.

So in summary, kidney stones can come in many variations of shape, color and texture depending on their mineral composition. Small, smooth and yellowish calcium stones are most common.

What Does it Look Like When Passing a Kidney Stone?

Here are some things to look for when passing a kidney stone in your urine:

Visible Stone or Debris

You may actually see the kidney stone pass out in the toilet after urinating. It may look like a tiny stone pebble or gritty piece of sand. You may also see fine debris or sediment at the bottom of the toilet bowl. This is made up of tiny stone fragments.

Cloudy or Murky Urine

The urine itself may take on a cloudy, murky or milky appearance when stones are present. Small kidney stone particles can create this hazy effect in the urine. Struvite stones may make urine appear foggy.

Pink, Red or Brown Urine

Kidney stones can cause blood in the urine, known as hematuria. This can make urine appear pink, reddish or brownish in color. Stones with high calcium content are most likely to cause bleeding.

Pain While Urinating

Sharp pain while urinating is common when passing kidney stones. This is due to the stone traveling down the narrow ureters and through the urinary tract. The pain may come in waves and affect your lower back, abdomen and groin.

Strong Odor

Urine may have an unusually strong or foul smell when you’re passing kidney stones. This is usually due to a kidney stone infection. See your doctor if your urine has a bad odor.

Small Amounts of Urine

You may only pass small amounts of urine at a time when stones are blocking urine flow. This can lead to straining while urinating. Passing frequent, small amounts of urine is a kidney stone symptom.

Urine Flank Pain

Some people with kidney stones experience discomfort and pain while urinating. The pain may be localized to one side of your back, belly, or groin area. This pain called flank pain may come and go in pulses. It happens when a stone passes through a narrow ureter.

What Types of Kidney Stones Can Form?

There are several major types of kidney stones, which can be identified based on their appearance:

Calcium Stones

Calcium is the most common mineral in kidney stones, making up about 80% of cases. Calcium combines with oxalate or phosphate to form stones.

– Appearance: Smooth, round, small and yellow-colored.

Uric Acid Stones

These stones form when there’s too much acid in the urine.

– Appearance: Round, smooth and transparent; may seem jagged.

Struvite Stones

These are caused by kidney infections and are more common in women.

– Appearance: Large, irregularly shaped and white, brown or pale yellow.

Cystine Stones

Cystine stones result from a genetic disorder that causes cystine amino acids to leak into the urine.

– Appearance: Small, rough-surfaced and pink, yellow or pale brown.

Stone Type Appearance Color
Calcium oxalate Smooth, round, small Yellow, gold
Calcium phosphate Small, granular Yellow, brown
Uric acid Smooth, round Transparent, pale yellow
Struvite Large, bumpy, irregular White, brown, pale yellow
Cystine Rough, bumpy, small Pink, yellow, pale brown

This table summarizes the most common types of kidney stones and their general appearance. The composition and structure of the stone affects its color, shape, texture and size when passed.

How Can You Tell the Difference Between Stones and Other Particles?

It can sometimes be difficult to determine if particles in your urine are kidney stone fragments or something else. Here are a few ways to tell:

Look at the shape and texture

Kidney stones often have smooth, rounded, pebble-like shapes. They are hard and gritty in texture. Other particles like sediment or debris tend to be soft and powdery.

Note the color

Stones are often yellowish, pink or brown, depending on their mineral content. Other urinary particles may be white, black or other colors. Blood in the urine can also cause red or brown urine.

Consider the timing

Kidney stone symptoms like pain often accompany the passing of stones. If particles appear suddenly along with pain, this points to kidney stones.

Watch for recurrence

Isolated particles may be debris or contamination. Recurrent particles likely indicate kidney stones or crystallization.

Monitor other symptoms

Cloudy urine, blood, foul smell or pain while urinating are signs of stones versus other debris. Stones may also cause nausea, vomiting and fever.

Talk to your doctor

Your physician can analyze your urine’s chemical makeup and examine any passed particles. They can determine if stones are present and recommend treatment.

How Can You Tell if You’re Passing a Small Stone?

It’s not always easy to know if you’re passing a very small kidney stone. Here are some signs:

– You may feel a fleeting pinch, twinge or ‘tickle’ while urinating.

– There may be a single occasion of blood-tinged urine.

– Your urine could appear slightly cloudy once then clear up.

– Irritation may cause a mild burning sensation during urination.

– There may be a day or two of increased urgency to urinate.

– Mild, intermittent pain or discomfort may be felt in the back or abdomen.

– Nausea, vomiting and fever are less likely with a small stone.

– Larger stones usually cause moderate to severe pain, lasting days to weeks.

So mild, temporary symptoms may indicate a tiny kidney stone has been passed. Larger stones can still cause extreme pain but may pass unnoticed if they break into tiny pieces. When in doubt, save any particles for analysis.

Can Kidney Stones Recur Once Passed?

Unfortunately, people who have experienced kidney stones are very likely to develop new stones. Recurrence rates are estimated at about 50% over 5-10 years. Some factors that can cause stones to redevelop include:

– Underlying metabolic or genetic conditions like hyperparathyroidism, cystinuria or gout.

– Dietary habits: Eating too much salt, sugar, animal protein and oxalate-rich foods.

– Dehydration: Low fluid intake allows minerals to crystallize.

– Obesity: Increased body weight is linked to higher kidney stone risk.

– Prior stone history: Having stones once makes you more prone to recurrence.

– Medications: Certain diuretics, calcium antacids and others can alter urine composition.

To prevent recurrence, your physician may recommend medication, dietary changes and increased hydration based on the type of stone. Regular urine testing and straining to catch new stones for analysis is also advised.

When to See a Doctor

Make sure to consult your healthcare provider if:

– Severe pain, nausea and vomiting occur with urination
– Stones larger than 5 mm are detected
– Stones don’t pass within a month
– Signs of infection accompany stone passage
– You’re unable to drink fluids or keep food down
– Bloody, cloudy or foul-smelling urine persists
– Stones keep recurring frequently

Medications, surgical removal or shock wave therapy may be required for larger, complicated or recurring kidney stones. Getting an accurate diagnosis and following your doctor’s treatment plan is crucial.

The Takeaway

Being aware of the signs and symptoms of passing kidney stones in urine is important for monitoring your condition. Kidney stones can vary in shape, color, texture and size depending on their mineral makeup. While small stones may pass unnoticed, larger ones usually cause severe pain, blood in the urine and urinary symptoms. Stones have a high likelihood of recurring once formed. Seeing a physician for proper diagnosis and follow-up care is essential to prevent painful complications.