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Kidney Stones

Overview

Kidney stones refer to the condition in which stones are formed in your kidneys. Stones are complex substances made up of minerals and salts. A kidney stone is also called renal calculus, and this condition is also referred to as nephrolithiasis or urolithiasis. Since the function of the kidneys is the filtration of the blood and production of urine, sometimes, during the process, large amounts of minerals like calcium, uric acid, oxalates get accumulated in the urine resulting in the formation of stones. These stones start as small but can grow larger and travel down the ureters up to the bladder and urethra. These stones obstruct the flow of urine, and so cause damage to the urinary tract and pain. They are treated with medications that cause the expulsion of the stone. If the stone doesn’t make its way out of the urethra, surgery or lithotripsy may be needed.

 The urinary tract includes a pair of kidneys and ureters (tubes that carry urine from kidneys to the bladder), a urinary bladder, and a urethra (a small box that carries urine from the bladder to outside the body).

Causes

A combination of genetics and environmental factors plays a role in forming stones. Kidney stones run in families. Some people excrete more amounts of calcium in their urine than others. Low urine volumes result in urine supersaturation with stone-forming constituents like calcium, oxalate, uric acid. Crystals can act as a cradle on which more and more ions and minerals are fostered, thus forming a stone. This can result from low fluid intake and a diet rich in foods that contain plenty of minerals and salts. Normal urine contains some substances (citrate) that act as chelating agents of calcium in the urine. It combines with calcium and takes it out with it in the urine. Decreased levels of these agents also lead to stone formation. Some medicines may predispose to stone formation, including diuretics, calcium supplements, etc.

Types: there are different kidney stones, and the treatment depends upon the type of stone you have.

  1. Calcium Stones (75%): they are the most common type of stones. They can be calcium oxalate (most common) or calcium phosphate and are dark brown or black in color.
  2. Struvite (Magnesium Ammonium Phosphate Stones-15%): they are dirty white in color and bigger in size. They are found in people with chronic urinary tract infections with special types of bacteria (gram-negative, urease positive).
  3. Uric Acid Stones (6%): uric acid crystals are insoluble and may result from the degradation of purine-rich food (meat, legumes, fish) or malignancy. They are yellowish or reddish-brown in color.
  4. Cystine (1%): these are rare stones caused by a genetic disorder of cysteine metabolism. They are pink/yellow in color.

Epidemiology

Renal stones are prevalent throughout the world. They are more common in Caucasians and the male gender. The most susceptible age group is between 35-45 years.

Risk Factors

Following risk factors can predispose you to the formation of kidney stones.

  • Fluid intake: low fluid, especially for people living in temperate climates.
  • Lifestyle: obesity, lack of exercise, sedentary lifestyle
  • Diet: consuming food rich in proteins, sugars, sodium, fruit juices
  • Co-morbid diseases: some medical conditions predispose a person to renal calculi like diabetes, hypertension, gout, hyperparathyroidism, hyperoxaluria, renal tubular acidosis, Crohn’s disease, etc. recurrent stones can be checked for these diseases.
  • Family history: a family member with a history of renal calculi also increases your chances of getting one.
  • Medications: use diuretics, calcium and vitamin D supplements, some antibiotics like ciprofloxacin, ceftriaxone, etc.

Signs and Symptoms

Symptoms of a kidney stone depend upon its size and position. Small rocks less than 5 mm can pass through without causing symptoms. Similarly, a stone in the kidney does not cause pain. When a stone passes through the ureters, it causes severe sharp pain at your side and back, starting from the loin, ending at the groin, while coming in waves.

You may also have:

  • Nausea Vomiting
  • Burning Pee
  • Pink, Red, or Brown Urine
  • Urgent Desire to Urinate

Diagnosis

A typical history of pain can direct the diagnosis, although other tests may be performed.

Blood Tests may show the number of minerals and salts in your blood. Also, they can determine your kidney functions or if you have an infection.

Urine tests can tell the urinary infection and the passage of blood and other cells. The collection of 24-hour urine can tell which mineral is in more amount in your urine.

Imaging: these can be used to diagnose a stone. They can show the exact position of the rock and include X-ray KUB, ultrasound, CT scan, MRI.

Stone Lab Test: you may be asked to keep the stone safe that you will pass to be checked in the lab for recurrent rocks and find out the minerals responsible for it.

Differential Diagnosis

Some other diseases may have the same symptoms as the stone, such as  

  • Acute glomerulonephritis
  • Urinary tract infection
  • Pyonephrosis
  • Liver disease
  • Gallstone disease

Treatment

Kidney stones are treated with medications and interventional procedures like lithotripsy, surgery, etc.

Medications

  • Pain Medicines: your doctor may prescribe you paracetamol or pain-relieving other drugs (NSAIDs) for the pain.
  • Stone Expulsive Medicines: some medicines relax the sphincter of the urethra and thus result in the passage of the stone. They include alpha-adrenergic blockers (tamsulosin), calcium channel blockers (nifedipine). You would need to increase fluid intake to flush the stones out
  • Stone Prevention Medicines: these medicines are given to people with recurrent stones of a specific type to prevent further formation. They include thiazide diuretic for calcium stones, allopurinol for uric acid stones, alkaline preparations to keep the urine alkaline, antibiotics to prevent struvite stones.

Surgical Procedures

Extracorporeal Shock Wave Lithotripsy (ESWL): In this procedure, high-intensity ultrasound energy is applied through the body surface by a particular machine to break the stones, which are then made to be expelled using expulsive medical therapy. It can cause pain and bruise at the side of the application.

Ureteroscopy: in this procedure, a flexible tube with the camera is inserted through the urethra up to the ureter; the stones are then broken down into smaller pieces using a laser or taken out directly.

Percutaneous Nephrolithotomy: In this procedure, a small incision is made at your back, and a tube is inserted directly in the ureter, and the stones are retrieved.

Open Surgery: A more extensive incision is made at the abdomen, or the side, the kidney and ureters are reached, and the stones are taken out.

Prognosis

The overall prognosis of kidney stones is good. Small stones may pass by themselves. Medications and other procedures are usually effective for larger stones. In cases of recurrent stones, the doctor may advise more tests to determine the composition and cause of the rock and give you medicines to avoid further stone formation.

Lifestyle Modifications: you can adapt the following habits to avoid the formation of stones,

  • Drink plenty of water. Around 6-8 glasses per day are recommended
  • Do exercise and Try to lose weight
  • Avoid high intake of food rich in proteins (meat, legumes), salts, sugars, and oxalates (spinach, sweet potato, nuts, tea, chocolates)
  • Take fruits and vegetables.

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