Kidney Stones: Fluid Intake, Diet by Stone Type, Straining Urine, and Urgent Signs

Who needs this teaching

Clients with a first or recurrent urinary calculus (nephrolithiasis) and the family member who prepares meals. Calcium oxalate stones are the most common type, and stone composition guides the diet. A stone that obstructs the ureter causes renal colic: severe, intermittent flank pain that radiates to the groin.

The priority teaching points

1. Fluid intake. Drink enough fluid to produce at least 2.5 L of urine daily, or the volume the provider sets. This requires about 3 L of fluid daily, mostly water, spread through the day and evening. Urine stays pale yellow. Drink more in hot weather and during exercise. Clients with a prescribed fluid restriction follow the provider's limit.
2. Sodium and animal protein. Limit sodium to 2,300 mg daily or less. High sodium intake increases urinary calcium excretion. Limit nondairy animal protein: meat, poultry, fish, and eggs. Animal protein increases urinary calcium and uric acid and decreases urinary citrate. Eat more fruits and vegetables; they increase urinary citrate, a stone inhibitor.
3. Normal dietary calcium. Keep calcium from food at 1,000 to 1,200 mg daily. Dietary calcium binds oxalate in the intestine. A low-calcium diet increases oxalate absorption and stone formation. Do not take calcium supplements unless prescribed. Take a prescribed supplement with meals.
4. Diet by stone type. Oxalate restriction applies only to calcium oxalate stones with high urinary oxalate. These clients limit spinach, rhubarb, beets, and nuts, and eat a calcium-containing food at the same meal. Ask before vitamin C supplements; the body converts excess vitamin C to oxalate.
5. Straining urine. Strain all urine through the provided strainer or gauze until the stone passes. Save the stone dry in a clean container and bring it to the provider for analysis. Keep follow-up imaging and 24-hour urine collection appointments.
6. Medications. Take the prescribed analgesic for renal colic as directed. An alpha blocker such as tamsulosin relaxes ureteral smooth muscle and helps a distal ureteral stone pass; rise slowly because it causes orthostatic dizziness. Take preventive medications every day: a thiazide diuretic reduces urinary calcium, potassium citrate raises urinary citrate, and allopurinol reduces uric acid.
7. Urgent signs. Fever or chills with flank pain indicates infection behind an obstructing stone (obstructive pyelonephritis). This urologic emergency progresses to sepsis without urgent drainage. Little or no urine output indicates obstruction of both kidneys or of a single functioning kidney. Both require emergency care.

Red flags the client reports

Teach-back questions

• "How much fluid will you drink each day, and how will you know it is enough?"
• "Why will you keep eating dairy foods?"
• "Which salty foods will you cut back on?"
• "Show me how you will strain your urine and save the stone."
• "Which symptoms mean you get emergency care?"

Teaching tips

• Write the fluid goal and the stone type, when known, on the handout.
• Give a strainer and a container for the stone, and demonstrate their use.
• Use a water bottle with volume marks to track daily intake.
• Base oxalate teaching on the stone analysis, not on a general food list.

Read more on NCLEXPace

• Kidney Map: Acute vs. Chronic Failure, Dialysis, and Fluid Balance
• Acute Kidney Injury: The Three Phases and What Changes in Each

Sources

• Pearle MS, et al. Medical Management of Kidney Stones: AUA Guideline. J Urol. 2014;192(2):316-324.
• Assimos D, et al. Surgical Management of Stones: American Urological Association/Endourological Society Guideline, Part I. J Urol. 2016;196(4):1153-1160.