Passing a Kidney Stone: When to Wait, What to Eat, and When to Call a Doctor

If you are reading this, you or someone you care about is likely in a world of pain. Kidney stones are often described by patients as the closest thing to childbirth a man can experience, and for women, it’s frequently cited as even worse. The sudden onset of sharp, cramping pain in the lower back or side—known medically as renal colic—can be terrifying.

This guide provides a comprehensive, medically grounded roadmap for navigating the days ahead. We will cover the timeline of passing a stone, dietary adjustments to speed up the process, and the critical red flags that mean you need emergency care.

Disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional for diagnosis and treatment.

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The Timeline: What to Expect When You’re Expecting (a Stone)

A kidney stone is a hard deposit of minerals and salts that forms inside your kidneys. Passing one is essentially a waiting game, but understanding the “stages” can help reduce anxiety.

Stage 1: The Silent Phase (Formation)

You likely won’t know you have a stone during this phase. It sits inside the kidney, often adhering to the interior lining. Unless it blocks a specific calyx (chamber) or moves, it is usually painless.

Stage 2: The Acute Phase (The Attack)

This is when the stone detaches and enters the ureter (the narrow tube connecting the kidney to the bladder). This tube is only 3–4mm wide. If the stone is larger than that, it causes a blockage.

• Symptoms: Sudden, severe flank pain that comes in waves. The pain fluctuates because the ureter uses peristalsis (rhythmic contractions) to try to push the stone out. You may feel nausea or vomit due to the shared nerve pathways between the kidneys and the gut.
• Duration: This phase can last from a few hours to several days.

Stage 3: The Bladder Phase (Relief & Pressure)

Once the stone drops into the bladder, the intense flank pain usually subsides almost instantly. However, you aren’t done yet.

• Symptoms: You might feel immense pressure in your bladder or a constant need to urinate. For men, pain may radiate to the tip of the penis.+1
• Duration: The stone may sit in the bladder for days before finally exiting through the urethra.

Stage 4: Exit

The final exit through the urethra is often surprisingly less painful than the journey through the ureter. You might hear a “clink” in the toilet bowl.

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Strategic Nutrition: What to Eat (and What to Avoid)

While you are actively passing a stone, your diet serves two purposes: keeping your urine volume high to “flush” the system and managing your body’s chemistry to prevent the stone from growing larger.

1. Hydration: The Golden Rule

Water is your most potent medicine. You need to generate enough hydraulic pressure behind the stone to push it forward.

• Goal: Aim for 2.5 to 3 liters of water per day.
• Citrus: Add fresh lemon or lime juice to your water. Citrate, a compound found in these fruits, helps break down calcium-based stones and prevents new ones from forming.+1

2. The “Calcium Paradox”

A common myth is that you should avoid calcium if you have calcium stones. This is incorrect.

• The Science: If you cut dietary calcium, oxalates (a compound in food) have nothing to bind to in your digestive tract. They then get absorbed into your bloodstream, end up in your kidneys, and form more stones.
• The Fix: Eat calcium-rich foods (yogurt, cheese, milk) during meals. This traps oxalates in the stomach before they reach the kidneys.

3. Foods to Avoid (The “Danger Zone”)

While passing a stone, you want to minimize inflammation and kidney workload.

Category	Foods to Limit/Avoid	Why?
High Oxalates	Spinach, rhubarb, beets, almonds, peanuts, chocolate.	These are the “building blocks” of the most common stones (calcium oxalate).
Sodium (Salt)	Processed foods, canned soups, fast food, deli meats.	Sodium causes the kidneys to excrete more calcium into the urine, fueling stone growth.
Animal Protein	Red meat, poultry, eggs, seafood.	High protein intake increases uric acid and lowers urinary citrate (the “stone fighter”).

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Medical Management: Can You Speed It Up?

“Medical Expulsive Therapy” (MET) is a fancy term for using drugs to help pass a stone.

• Alpha-Blockers (e.g., Tamsulosin/Flomax): These medications relax the smooth muscle of the ureter. Studies suggest they can increase the passage rate of stones (especially those 5mm–10mm) and reduce the time it takes to pass them by several days.
• Pain Management: Over-the-counter NSAIDs (like ibuprofen) are often more effective than narcotics for renal colic because they reduce inflammation in the ureter directly. However, always check with a doctor, especially if you have kidney function issues.

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Red Flags: When to Stop Waiting and Call 911

Most stones (especially those under 5mm) will pass on their own within 4–6 weeks. However, “waiting it out” is not always safe. You must seek immediate medical attention if you experience:

1. Fever and Chills: This is the single most dangerous sign. A blocked kidney combined with a fever suggests an infection behind the blockage (pyelonephritis or sepsis). This is a life-threatening medical emergency requiring immediate drainage and antibiotics.
2. Intractable Pain: If pain medication (oral) is not touching the pain, or if you are vomiting so much you cannot keep pills or water down, you need IV fluids and pain management in the ER.
3. Anuria (No Urine): If you stop passing urine entirely, it may mean both kidneys are blocked (or your solitary functioning kidney is blocked). This leads to rapid kidney failure.
4. Visible Clots: While pink or reddish urine is normal with stones, passing thick, ketchup-like blood or clots warrants a check-up to rule out other issues.

Conclusion: Patience is Key

Passing a kidney stone is a test of endurance. By staying aggressively hydrated, managing your pain, and knowing the signs of infection, you can navigate this painful episode safely.

If the stone has not passed within 4–6 weeks, your urologist may intervene with shockwave lithotripsy (breaking the stone with sound waves) or ureteroscopy (removing it with a basket). You have options, and you will get through this.

Frequently Asked Questions

How long does it take to pass a kidney stone?

Stones smaller than 4–5 mm usually pass within one to four weeks. Stones larger than 6 mm are less likely to pass on their own and often need treatment such as ureteroscopy or laser surgery.

What should I eat and drink while passing a kidney stone?

Drink 2.5–3 litres of fluid a day, add lemon or citrus juice, keep salt low, avoid excess meat and do not cut down on dietary calcium. Limit very high-oxalate foods such as spinach and nuts if your stone is calcium oxalate.

When should I go to the hospital for a kidney stone?

Go immediately if you have fever or chills with stone pain, pain not controlled by medicines, persistent vomiting, very little urine, or a single functioning kidney. These can signal infection or a blocked kidney that needs urgent drainage.

Related guides: kidney stones treatment · surgical removal of kidney stones · laser surgery for kidney stones