Nephrolithiasis: what it is, causes and symptoms of kidney stones

Nephrolithiasis is the presence of calculi (stones) in the kidneys. Small stones often cause no symptoms and pass unnoticed in the urine, while large ones cause marked pain and require medical assessment. Below are the definition, mechanism of stone formation, risk factors, symptoms and methods of detection.

What nephrolithiasis is and how it differs from urolithiasis

Nephrolithiasis refers to calculi specifically in the kidneys. Urolithiasis (urolithic disease, ULD) is a broader concept: the formation of calculi in any organs of the urinary system. The terms are sometimes used as synonyms, but nephrolithiasis more precisely indicates stones in the kidneys rather than in other parts of the urinary tract. Nephrolithiasis is the most common cause of calculi appearing in the lower sections; less often stones form in the bladder.

Urolithiasis occurs at any age, more often at 20–50 years. Urolithic disease accounts for 30–40 % of hospital admissions to urology departments; the lifetime risk of developing it reaches 10 %.

How kidney stones form

A stone is a dense formation made of substances in the urine; sizes range from a grain of sand to a pearl.

Three mechanisms of stone formation: sharply acidic urine pH (below 5.5), low diuresis due to insufficient fluid, and hyperuricemia. The most significant is high urine acidity: the solubility of uric acid in such an environment decreases, it crystallizes and forms stones.

• oxalate — from calcium oxalate;
• urate — from uric acid salts, usually in gout;
• cystine — in a genetic disorder of cystine reabsorption in the renal tubules;
• struvite (infectious) — in urinary tract infections.

By size, stones are distinguished as up to 5 mm, from 5 mm to 2 cm, and more than 2 cm; by shape — staghorn and simple.

Causes and risk factors of urolithic disease

ULD is multifactorial: the likelihood of development is influenced by genetic factors, metabolic disorders, anatomical features, lifestyle and diet. Stones form in hyperparathyroidism, gout, diabetes mellitus and other chronic diseases with metabolic disturbance.

Risk factors: insufficient fluid, conditions that increase the concentration of certain chemicals (for example, metabolic syndrome), taking aspirin, antacids, diuretics, antibiotics, impaired urine passage due to the structure of the urinary tract. Recurrence is promoted by a high-protein diet low in fiber, physical inactivity or bed rest, frequent kidney and urinary tract infections, family history, and previous stones.

Symptoms of kidney stones

Small stones cause no symptoms and pass unnoticed in the urine. Large ones cause severe pain: it begins in the side of the abdomen or lower back, radiates to the groin, scrotum or the area around the vaginal opening, and is paroxysmal — periods of marked pain alternate with calm ones.

Other manifestations: elevated temperature, fever, chills or shivering, nausea and vomiting, frequent urination, cloudy urine. Blood in the urine and an unpleasant odor of urine require medical attention.

Obstruction of the ureter by a stone (renal colic) — acute spasmodic pain in the lumbar region, nausea, vomiting, hematuria.

How kidney stones are detected

The diagnosis is often made from the clinical picture: concomitant diseases, medications taken, diet, family history are clarified, and urine and blood tests are performed.

For severe pain the patient is referred to a hospital: adults — computed tomography, pregnant women and children under 16 — ultrasound examination. Ultrasound is the most common method: it assesses dilatation of the calyceal-pelvic system and ureter, the presence of stones, and the condition of the other kidney. A passed stone is collected for analysis of its composition.

Possible complications and when a doctor is needed

A stone may become lodged in the urinary tract, block the outflow of urine and cause marked pain. The most common complication of urolithic disease is inflammation of the kidney; with a long history of urolithiasis, pyelitis and pyelonephritis are possible.

Medical help is needed if stones cause symptoms: severe pain, high temperature or chills, blood in the urine, cloudy or foul-smelling urine, burning during urination.

Kidney stones by themselves are not a reason to call an ambulance; 103 or 112 — for severe pain in the side or lower back that does not go away, and for high temperature with chills.

This material is for reference purposes and does not replace consultation with a doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer