Which food would the nurse teach a client with calcium oxalate renal calculi to avoid?

Kidney Stones

American Journal of Nursing: September 1996 - Volume 96 - Issue 9 - p 40

This NCLEX review will discuss renal calculi (kidney stones).

As a nursing student, you must be familiar with renal calculi and how to care for patients who are experiencing a kidney stone.

These type of questions may be found on NCLEX and definitely on nursing lecture exams.

Don’t forget to take the renal calculi quiz.

You will learn the following from this NCLEX review:

• Definition of renal calculi
• Causes of kidney stones
• Types of renal stones
• How it is diagnosed
• Treatment
• Nursing Interventions

NCLEX Lecture Review on Renal Calculi

What are kidney stones? Hard insoluble crystallized minerals and salts that have formed out of the filtrate produced by the nephron.

Remember the nephron is the functional unit of the kidney that filters the blood and reabsorbs/secretes mineral, water, and waste, which is urine. Learn more about the nephron’s structure and function.

Facts about Kidney Stones

Kidney stones can vary in size: they can be very small (like a fine grain of salt) or large (like a walnut….very painful), and are composed of various materials. Hence, there are different types of stones (see the types below).

Most stones tend to form within the kidney, but they can form anywhere throughout the urinary system where there is a concentration of minerals (bladder, ureters).

They can migrate throughout the urinary system where they can further grow or cause blockage of urine.

Most stones can be passed (very painful) if they are less than 5 mm (Diagnosis And Initial Managment Of Kidney Stones 8). If they are larger than this, they can become stuck within the urinary system.

Where can kidneys stones be located?

• Inside the kidney
• Ureters (top, middle, or bottom of ureter before entering bladder)
• Bladder

Remember: For stones to form there has to be a concentration of minerals and salts in the filtrate which will allow for crystallization of the minerals. When a crystal forms it can grow over time and break off and travel through the urinary system. This can lead to the blockage of urine, infection, or other complications.

Types of Kidney Stones

*Calcium Oxalate: most common type of kidney stone, and they tend to form in acidic urine. This type of stone is composed of calcium and oxalate, and forms when there is a high concentration of calcium or oxalate in the filtrate.

What can increase the amount of calcium in the filtrate?

• Hypercalcemia/uria: taking excessive amounts of calcium supplements, eating too much salt (increases the amount of calcium in the urine), renal tubule problems within the nephron, consuming too much animal protein (increases the amount of calcium in the urine)
• Hyperparathyroidism: the parathyroid is responsible for secreting PTH (parathyroid hormone) which causes the bones to release calcium into the blood…overactive parathyroid gland increases calcium levels.

What can increase the amount of oxalate in the filtrate?

• High intake of foods with oxalates (see nursing interventions to see the foods high in oxalate)
• GI disorders like ulcerative colitis and Crohn’s disease due to malabsorption of fats. Normally, calcium and oxalates bind together in the gut, therefore, oxalate is excreted in the stool. However, when a GI disorder like ulcerative colitis is present there is a problem with digesting fats. So, fats bind with calcium…leaving oxalates behind. The leads to the build-up of oxalate in the urine.

Uric Acid: forms when there is too much uric acid in the urine (acidic urine)

What can cause high amounts of uric acid in the urine?

• Eating a diet high in purine or animal protein. These substances are broken down into uric acid and if too much of these products are consumed it can make the urine more acidic. Remember the glomerulus of the nephron is responsible for filtering the blood and removing uric acid.
• Dehydration: urine becomes acidic and the filtrate contains low amounts of water…allowing uric acid to crystallize.
• Gout: patients with Gout have high amount of uric acid in the body
• Metabolic problems like diabetes, especially Type 2 Diabetes

Cystine: forms where there is too much of the amino acid cysteine in the urine. This is rare and tends to run in families.

• Remember amino acids are normally reabsorbed in the Proximal Convoluted Tubule (nearly 100%). However, the nephron fails to do this, so when there is too much cysteine in the urine it crystallizes.

Struvite: this type of stone is also rare and usually forms due to chronic urinary tract infections (UTIs).

• WHY? Certain types of bacteria can cause the urine to become too alkaline and this allows magnesium, ammonium, and phosphate to crystalize, which is the composition of the struvite stone….this stone is also known as staghorn stone and can be fairly large in size.

Calcium phosphate: forms in alkaline urine and can be happen when renal tubule issues are present

*most common type of kidney stone

How does kidney stone formation happen?

Remember the nephron, specifically the glomerulus, filters the blood and all minerals/water/waste are removed from the blood and leak down into Bowman’s Capsule (these substances include nearly everything expect proteins and blood cells).

In patients who are NOT susceptible to kidney stones, these substances will travel through the nephron and be reabsorbed or secreted at various points within the renal tubule. Then the excess will be secreted as urine by exiting the collecting tubule/duct to the renal papilla, minor, major calyx, renal pelvis, ureters, bladder, and urethra.

However, in patients with certain predisposing factors, there is an increase in the risk of these minerals coming together to form a crystal. The crystal can grow over time as debris sticks to the crystal and further crystallization happens. The crystal can travel out of the nephron and stay in the renal papilla, ducts, or other parts of the urinary system and grow. In addition, it can break off and travel through the system and get stuck.

Causes of Kidney Stones

Remember the word: “Crystal”

Consuming high amounts of oxalates, purine, animals protein, salt (eating too much salt keeps the body from reabsorbing calcium in the urine), and taking excessive amounts of calcium supplements with Vitamin D (calcium oxalate, uric acids type stones)

Recurrent UTIs (struvite stones)

hYpocitraturia, hYpercalemia/uria, hYperparathyroidism

• Hypocitraturia: Citrate plays a role in stopping the formation of calcium salt crystals (specifically calcium oxalate and calcium phosphate binding). Therefore, citrate binds with calcium and stops it from binding with oxalate or phosphate. Furthermore, it keeps the urine alkaline and prevents it from becoming too acidic….hence preventing uric acid or cystine stones to form since these stones form in acidic urine.

Structural blockage or stasis of the urine (prostate problems, strictures, deformities)

Too much uric acid (gout, dehydration, high diet in purine/animal proteins)

Absorption problems: gut doesn’t absorb fats as with ulcerative colitis or crohn’s diseae…fats bind with calcium and leaves oxalates behind, Acquired (family history)

Low activity: immobile patients tend to have an increased amount of minerals and salts compared to people who are physically active and the urine stays stagnant in the kidney…hence increase risk of kidney stone formation.

Signs and Symptoms of Renal Calculi

Pain: characteristics of the pain depend on the location of the stone and it can change as the stone moves through the urinary system:

• Renal colic: stone in the renal pelvis…dull, deep aching in the flank or costovertebral area (see pic below)

• Ureteral colic: stone residing in the ureter and as it moves it can cause…….intense, sharp, radiating, wavelike pain to the genitalia (scrotum, vaginal area)
  • The patient may feel like they need to void but a small amount is voided.
  • Can have blood in the urine due to stone scraping the ureter (hematuria)

Nausea and vomiting (due to the intense pain)

Signs and symptoms of infection: fever, cloudy, odorous urine

Urinary retention: especially if stone is stuck in neck of bladder…this makes it extremely hard to completely pass all the urine in the bladder…(note the location of the neck of the bladder)

Asymptomatic: until stone moves within the kidneys and to the ureters

Complications  of Renal Stone

• Obstruction: stones blocks the flow of urine. The urine can back up and causes hydrostatic pressure (hence increase water pressure) within the kidney. This will increase pressure in Bowman’s Capsule which will decrease the amount of blood the kidneys can filter.
• Hydronephrosis or Hydroureteronephrosis: due to the back up of urine which causes swelling and dilation in various parts of the kidneys (renal pelvis, minor/major calyx and ureters)…depending on where the stone is located. The end result is the loss of function to the kidney.

• Damage to the nephrons…hence renal failure
• Infection

How is Renal Calculi Diagnosed?

*as the nurse it is important to be familiar with tests the physician may order and your role as the nurse

• KUB (x-ray of the kidneys, ureters, and bladder)
• IVP (intravenous pyelogram): a special dye, which is iodine-based, is given through the patient’s IV. Then x-ray images will be taken to assess the kidneys, bladder, ureters, and urethra.
  • Nurse’s Role:
    • Make sure patient isn’t allergic to iodine or shellfish, pregnant or might be, nursing a baby, impaired renal function or taking metformin/Glucophage.
• Ultrasound or CT scan
• Urine tests:
  • U/A assess for crystals, infection
  • 24 hour urine to measure concentrate of ions (calcium, sodium etc.), waste products in urine (uric acid, creatinine), citrate, pH, kidney function
    • Nurse’s Role
      • Keep specimen cold by keeping it on ice for the whole 24 hours…if not kept cold this can alter the test results.

Nursing Interventions for Renal Calculi

**most patients will pass the stone and the nurse’s job is to keep the patient’s pain controlled, give fluids, strain urine, and monitor for complications.

However, if the stone is large the patient need other treatments (discussed below).

• Control pain (very, very painful)…pain doesn’t go away until it is passed or removed. Patient needs around-the-clock pain medications rather than PRN medications (where the patient has to request it). This will help keep pain medication blood levels constant and hopefully help control the pain. The physician may order NSAIDs to help control the inflammation which can help the stone pass if it is stuck within inflamed areas.
• Maintain oral fluids (3-4 L per day) unless contraindicated:
  • WHY? It is very important in helping the stone pass. Fluid intake increases the pressure which can help move the kidney stone. In addition, it keeps the urine diluted because remember stones are more likely to form in concentrated urine. It also keeps flushing the kidneys to prevent stagnant urine within the urinary system…decreasing the risk of infection.
• Closely monitor I/Os (intake and output)
  •  WHY? The patient will be consuming a lot of fluids and the nurse needs to make sure the kidneys are putting out enough fluid based on the intake. If the fluid output is low, renal function may be impaired, an obstruction may be present or other complications like hydronephrosis,etc.
• Monitor for signs and symptoms of UTI
• Strain urine and ASSESS very closely for stones (VERY IMPORTANT): Then notify the physician who will give you an order to send it to the lab. This is crucial so the physician can determine what type of stone is causing the problem and appropriate treatment can be ordered.
• Keep patient as mobile as possible and try to avoid supine position for long periods of time. Remember immobility is one of the causes of kidney stone formation…if urine stays stagnant it can allow crystallization. Keeping the patient mobile helps the stone pass. If the patient is immobile, turn the patient more frequently.

Prevention Education (can reoccur):

Keep hydrated (prevents concentrated urine) 2L per day

Take medication as prescribed: MD may order the following as preventive measures in preventing kidney stone formation based on the type of stone the patient is susceptible to:

• Allopurinol: decreases uric acid levels (used in gout)…uric acid stones
• “HCTZ” hydrochlorothiazide: decreases the amount of calcium in the urine…calcium type stones

Limiting calcium intake not recommended due to osteoporosis risk, unless patient has metabolic problems or a problem with the nephrons of the kidney. Instead, limiting medication forms of calcium supplements and vitamin D.

Limiting animal proteins (high amount of protein increases the amount of calcium in the urine and increases uric acid levels)

Limit sodium to 2-3 g per day….sodium decreases the reabsorption of calcium which will leave more calcium in the urine (watch hidden sodium foods like canned food, soda drinks, sandwich meats, processed foods)

Avoid foods high in purine: organ meats, beer, pork, red meats, seafood (scallops, anchovies, sardines) (uric acid stones)

Avoid high oxalate foods: spinach, cabbage, rhubarb, tomatoes, beets, nuts, chocolate, wheat bran, strawberries, tea (calcium oxalate stones)

How to stain urine and why it is important and to keep stone so it can be analyzed

Treatments for Renal Stones

Extracoporeal shock wave lithotripsy (ESWL): NONINVASIVE: shockwaves are created to penetrate though the skin and body tissue. Shockwaves will hit the stone and break it down into grains of sand like particles which can be passed out. Several treatments may be required depending on stone size. Stent may be placed to facilitate the passage of the fragments…not for large stones

Nurse’s Role

• Maintain fluid intake to facilitate stone fragment removal
• Keep patient mobile
• Control pain
• May have bleeding in urine
• Strain urine and send stone to lab

Percutaneous Nephrolithotomy: INVASIVE: used when the stone is large or can’t use ESWL. The kidney stone is removed by a urologist and doesn’t have to be passed by the patient as with EWSL.

An incision is made on the back where the kidney is and an nephroscope is used to remove the stone. Sometimes lithotripsy is used to break up the stone.

A nephrostomy tube may be placed to drain urine until healed (this is a catheter placed in the renal pelvis to drain urine)

Nurse’s Role

• Maintain fluid intake of 3-4 liters
• Maintain nephrostomy: it drains kidney and stone fragments, empty the bag regularly, keep site secure so tube doesn’t move, and monitor for infection
• Strain urine and send stones to lab

Ureteroscopy: no incision made…scope is inserted through the urinary system from urethra to the kidneys…can remove the stone or break it up with a laser or lithotripsy…stent may be placed to allow fragments to pass

Nurse’s Role

• Maintain fluid intake to facilitate stone fragment removal
• Keep patient mobile
• Control pain
• May have bleeding in urine
• Strain urine and send stone to lab

More NCLEX Reviews

References

• “Definition & Facts For Kidney Stones | NIDDK”. National Institute of Diabetes and Digestive and Kidney Diseases. Web. 16 May 2017.
• Diagnosis And Initial Management Of Kidney Stones. 63rd ed. American Family Physician, 2001. Web. 15 May 2017.
• Kidney Stones In Adults. 1st ed. National Kidney and Urologic Diseases Information Clearinghouse, 2004. Web. 14 May 2017.
• Reference, Genetics. “Cystinuria”. Genetics Home Reference. Web. 16 May 2017.