All about Stones in the Kidney and the Urinary Tract

Formation of calculi (stones) in the urinary tract is one of the oldest diseases known to man kind. They can be formed at any site in the urinary tract: the kidney (where urine is produced), the ureters (which act as a conduit of urine), the urinary bladder (where urine is stored until passed out – micturition) and urethra (through which urine is passed out) and can also descend once formed. They are seen to occur three times more commonly in men compared to women and the occurrence is commoner among whites with a sedentary life style living in temperate climates with less humidity. Urinary calculi commonly affect individuals in their 30s to 50s and are seen to occur recurrently in those who have had stones before giving rise to the statement, “Once a stone former is always a stone former”.

The commonest forms of calculi seen include:

1. Calcium oxalate – 70% of stones

2. Uric acid – 10%

3. Phosphate – including calcium phosphate and triple phosphate stones (calcium, magnesium and ammonium phosphate)

4. Cysteine and Xanthine

Four mechanisms have been attributed for the formation of stones or calculi in the urinary tract.

1. Supersaturation – over abundance of a solute in urine (e.g. – uric acid, cysteine)

2. Matrix (nidus) – non-crystalline proteins or foreign bodies acting as a base for the formation of stones (e.g. – suture materials after urinary tract surgeries, stone formation after certain infections in the urinary tract)

3. Lack of inhibitors – in normal individuals there are chemical compounds in urine which prevent formation of stones. Lack of these or over dilution of these result in stone formation.

4. Exogenous substances – certain drugs can induce stone formation (e.g. – Indinavir which is a drug given for patients infected with HIV)

With the above mechanisms operating, several diseases and abnormalities in the urinary tract place the individuals at a higher risk of developing urinary calculi. Hyperparathyroidism, renal tubular acidosis, hyperoxaluria and cyctinuria are almost always associated with stone formation. In addition, common conditions such as Crohn’s disease, intestinal resection, diarrhoea going on for a long period, sarcoidosis, hyperthyroidism (excessive function of thyroid gland) increase the risk of stone formation. Any structural abnormality in the urinary tract may also lead to formation of stones as a complication. Infections in the urinary tract are a common cause of stone formation, hence the saying “a stone in urinary tract is a tomb stone of infection”.

Pain is the commonest complaint of patients having calculi in the urinary tract. The pain may vary in character depending on the site where the stone is. The stones in kidneys usually produce a dull ache in the loin (space between the rib cage and the iliac bones in the back). The classic pain of a stone, which is known as a ureteric colic, occurs when the stone is in the upper ureter and is said to be of constricting in nature lasting for 20 – 30 minutes in high intensity before decreasing to a lower intensity in a cyclical manner. It is said to start in the loin and radiate down around the waist, obliquely across the abdomen, just above the hip to the base of the penis or scrotum or labia. This can become extremely severe and in such instances may be accompanied by nausea, vomiting and profuse sweating. The pain may be aggravated (increased) by alcohol, high intake of water or treatment with diuretics (e.g. – frusemide – lasix) and is not relieved by any native treatment.  Calculi in the mid ureter may produce a pain over the lower abdomen and those in the lower ureter may give rise to pain during passage of urine (micturition) and increased frequency of passage of urine. Stones in the bladder are known to produce a jolting type of pain radiating to the tip of the penis or the labia usually towards the end of micturition. Once a stone gets stuck in the urethra – through which the urine is passed out – which is almost always seen only in men, a severe cutting like pain is said to occur in the penis.

Stones in the urinary tract may also lead to infections in the urinary tract ranging from simple lower urinary tract infections to severe infections in the upper urinary tract, which may present as high grade fever accompanied by chills and rigors and can be life threatening if not attended and treated promptly with high doses of antibiotics. In addition, the stones can give rise to features such as passage of blood along with urine, pain during passage of urine, increased frequency of passage of urine and urge to pass urine in the absence of passage of urine. A calculus may occasionally be seen to pass out while passing urine. When lasting for a long period, urinary calculi can cause obstruction to the flow of urine and may result in chronic renal failure. Occasionally, a stone may last for a long period without producing any symptoms until it is discovered accidentally while investigating for some other disease.

Investigations carried out when the presence of a stone is suspected include a special radiograph (X-ray film) of the lower abdomen to visualize the kidney, ureters and the bladder (known as X-ray KUB) and ultrasound scan of the kidney and the urinary tract. In case if the above investigations fail to locate a stone and still the patient remains symptomatic, an IVU (intravenous urogram) may be performed where a dye is injected to a vein in the hand and the filtration of the dye, into the urinary tract by the kidneys, is imaged with a series of X-ray films. The most sensitive modality of investigation to detect stones in the urinary tract is CT scan of the area, though this has the risk of exposure to a high dose of radiation.

Once diagnosed and located, management of the condition depends on;

1. Size of the stone

2. Location of the stone

3. Type of the stone

4. Degree of obstruction to the flow of urine

5. Presence or absence of infection

6. Shape of the stone

7. Condition of the patient

The available modalities of treatment are described in detail in a separate hub with their advantages and draw backs along with measures to be taken to prevent the formation of calculi in the urinary tract. Urinary calculi can be disabling due the severe pain and the high rate of infection associated with the disease. As the disease commonly affects the working class of the society, this exerts an immense burden on the economy of the family as well as the country. Therefore, prevention and prompt treatment once diagnosed are important in order to assure a better quality of life to the patients as well as the society.