Doctor's Notes on Kidney Stones
When crystals form in the urinary tract the begin is very tiny objects smaller than a grain of sand but, over time, they can become quite large (a 5-millimeter stone can block urine flow) as they accumulate layers of crystals within the kidney pelvis and/or ureters. These large crystals are termed kidney stones and produce symptoms when they begin to obstruct the lumen that passes urine and begins at the kidney pelvis and continues down to the bladder with the ureters. Many people have kidney stones but have no realization they do until the kidney stone begins to block urine flow from the kidneys to the bladder. The main symptom of kidney stones is pain that can often be severe. Urine flow can be diminished or stopped by the kidney stone. This causes the urine to be put pressure on the kidney which may swell and cause back and/or flank pain, usually on the right or left side of the body. The pain may radiate to the groin. Waves of pain can occur as the body tries to dislodge the obstructing kidney stones. These waves cause intense pain and are termed renal colic; they may wax and wane but there remains a background level of pain until the stone is passed into the bladder or is destroyed surgically. The patient cannot be comfortable until the obstructing stone is treated or the body is successful in pushing it into the bladder.
Currently, there is no medical agreement as to what causes kidney stones. Theories range from genetics, heredity, dehydration, to diets high in protein, salt, vitamins and calcium. Medications and certain diseases may increase the risk of kidney stone formation but there is no compelling information about a true cause for stone formation.
Kidney Stones Symptoms
When a tubular structure is blocked in the body, waves of pain occur as the body tries to unblock the obstruction. These waves of pain are called colic. This is opposed to non-colicky type pain, like that associated with appendicitis or pancreatitis, in which movement causes increased pain and the patient tries to hold very still.
- Renal colic (renal is the medical term for things related to the kidney) has a classic presentation when a kidney stone is being passed.
- The pain is intense and comes on suddenly. It may wax and wane, but there is usually a significant underlying ache between the acute spasms of pain.
- It is usually located in the flank or the side of the mid back and may radiate to the groin. Males may complain of pain in the testicle or scrotum.
- The patient cannot find a comfortable position and often writhes or paces with pain.
- Sweating, nausea, and vomiting are common.
- Blood may or may not be visible in the urine because the stone has irritated the kidney or ureter. Blood in the urine (hematuria), however, does not always mean a person has a kidney stone. There may be other reasons for the blood, including kidney and bladder infections, trauma, or tumors. Urinalysis with a microscope may detect blood even if it is not appreciated by the naked eye. Sometimes, if the stone causes complete obstruction, no blood may be found in the urine because it cannot get past the stone.
- If an infection is present along with a kidney stone, fever, and chills may occur.
Kidney Stones Causes
There is no consensus as to why kidney stones form.
- Heredity: Some people are more susceptible to forming kidney stones, and heredity may play a role. The majority of kidney stones are made of calcium, and hypercalciuria (high levels of calcium in the urine) is one risk factor. The predisposition to high levels of calcium in the urine may be passed on from generation to generation. Some rare hereditary diseases also predispose some people to form kidney stones. Examples include people with renal tubular acidosis and people with problems metabolizing a variety of chemicals including cystine (an amino acid), oxalate, (a salt of an organic acid), and uric acid (as in gout).
- Geographical location: There may be a geographic predisposition to forming kidney stones, so where a person lives may make it more likely for them to form kidney stones. There are regional "stone belts," with people living in the southern United States having an increased risk of stone formation. The hot climate in this region combined with inadequate fluid intake may cause people to be relatively dehydrated, with their urine becoming more concentrated and allowing chemicals to come in closer contact to form the nidus, or beginning, of a stone.
- Diet: Diet may or may not be an issue. If a person is susceptible to forming stones, then foods high in animal proteins and salt may increase the risk; however, if a person isn't susceptible to forming stones, diet probably will not change that risk.
- Medications: People taking diuretics (or "water pills") and those who consume excess calcium-containing antacids can increase the amount of calcium in their urine and potentially increase their risk of forming stones. Taking excess amounts of vitamins A and D are also associated with higher levels of calcium in the urine. Patients with HIV who take the medication indinavir (Crixivan) may form indinavir stones. Other commonly prescribed medications associated with stone formation include phenytoin (Dilantin) and antibiotics like ceftriaxone (Rocephin) and ciprofloxacin (Cipro).
- Underlying illnesses: Some chronic illnesses are associated with kidney stone formation, including cystic fibrosis, renal tubular acidosis, and inflammatory bowel disease.
Kidney stones are small masses of salts and minerals that form inside the kidneys and may travel down the urinary tract. Kidney stones range in size from just a speck to as large as a ping pong ball. Signs and symptoms of kidney stones include blood in the urine, and pain in the abdomen, groin, or flank. About 5% of people develop a kidney stone in their lifetime.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.