Kidney Stones
Nephrolithiasis, Renal Calculi, Urinary Calculi, Urolithiasis, 

Clinical features, Diagnosis, Management, Prognosis,

Urinary calculi (urolithiasis, nephrolithiasis) consist of aggregates of crystals and small amount of proteins and glycoproteins Type of stones in the order of how frequent they are:

• calcium oxalate (the most frequent)
• mixed calcium oxalate and calcium phosphate
• calcium phosphate
• magnesium ammonium phosphate
• cystine
• uric acid

Different type of stone occur in different parts of the world and dietary factors probably play a part in determining the varying patterns. In developing countries bladder stones are common particularly in children whereas in industrialised developed countries the incidence of childhood bladder stone is low and renal stones in adults more common.

Conditions associated with stone formation:

• Obstruction of the urinary tract at any level (calcium phosphate stones)
• Infection of the urinary tract (magnesium ammonium phosphate stones also known as infection calculi - bacteria may produce enzyme urease that splits urea into ammonia to make urine less acidic and thus better environment for survival and multiplication)
• Climate or occupation giving rise to excessive sweating (high concentration of salts in reduced volume of urine resulting in precipitation)
• Hypercalciuria that may be idiopathic or found in hyperparathyroidism, Vitamin D intoxication due to excessive vitamin D intake (calcium phosphate or calcium oxalate stones)
• Hyperoxaluria may be primary (inherited) or caused by excess ingestion of oxalate-containing foods such rhubarb, spinach, cocoa, nuts, tea (calcium oxalate stones)
• Rare inherited metabolic disorders such as cystinuria, which is a defect of reabsorption of amino acid cystine in the kidneys
• Hyperuricosuria may be caused by excess intake of purine (in liver, meat, fish and poultry) or associated with gout and certain type of leukaemia or severe psoriasis, where there is overproduction of uric acid (uric acid stones)

Urine normally contains glycosaminoglycans, pyrophosphate and citrate which, by forming complexes, may keep otherwise insoluble salts in solution. Artificially made solution with chemical composition of urine but without these anti-precipitating agents is very unstable and prone to crystalisation. It appears that in certain circumstances these protective mechanisms fail, which may result in stone formation.

Today, in prosperous countries most stones occur in healthy young men in whom investigations reveal no clear cause for stone formation. Multiple aetiological factors are probably present in such cases, and an alteration in the relative proportions of crystalloids and glycosaminoglycans in the urine may be of particular importance. On the other hand women tend to suffer more that men from magnesium ammonium phosphate stones because UTIs are more common in women.

Urinary calculi vary greatly in size. There may be particles like sand anywhere in the urinary tract or large round stones in the pelvic or bladder. Staghorn calculi fill the whole renal pelvis and branch into the calyces forming casts of the kidney outflow section; they are usually associated with chronic pyelonephritis. Deposits of calcium may be present throughout the renal parenchyma, giving rise to nephrocalcinosis.

Clinical features:  < BACK TO TOP >

       Symptoms vary according to the size, shape and position of the stone(s), and the nature of the underlying condition.

       Stones may be asymptomatic, discovered incidentally during radiological or ultrasound examination.

       Most commonly they cause pain or recurrent urinary infection.

       The pain is intermittent and dull in the loin or back, increased by movements as the stone bumps into the mucosa, and there may be some blood in the urine due to mucosal damage.

       Calculi in the bladder may cause suprapubic pain and haematuria.

       When a stone moves from the pelvis and becomes impacted in the ureter an attack of renal colic develops, when the pain is excruciating and radiates round the flank to the genital region and inner thigh.

       The pain is caused by vigorous contractions of the ureteric muscle trying to push down the impacted stone, whose surface is often rough, sometimes with sharp edges or spikes.

       The intensity of pain steadily increases to reach a maximum in a few minutes, and the patient is restless and generally tries to obtain relief by changing position and by pacing the room.

       There is pallor, sweating, nausea and often vomiting.

       Frequency, dysuria and haematuria may occur (sometimes fresh red blood is voided).

       The intense pain usually subsides within 2 hours, or on treatment only to recur again later in similar fashion, until the stone is passed into the bladder or returned into the pelvis.

Diagnosis:  < BACK TO TOP >

       The diagnosis of renal colic is usually suspected from the history and by finding abundant red blood cells in the urine.

       Any patient suspected of having stones should have an X-ray of the urinary tract; most urinary stones can be visualised on X-ray, except cystine and pure uric acid stones.

       Ultrasound may detect all stones, including those not visible on plain X-ray, but very small stones (sand) may be missed.

       If there is doubt about the cause of pain an IVU may help (stones are seen as filling defects), as well as CT.

       Chemical analysis of the excreted calculus provides information as to what investigation to pursue; urine collected for 24 hours may be checked for calcium, urate, cystine or oxalate.

Management  < BACK TO TOP >

       The immediate treatment of loin pain or renal colic is bed-rest, application of warmth to the site of pain, and administration of strong analgesics [Pethidine, Fortral, Tramal] and antispasmodic drugs [Pro-Banthine, Buscopan, Mebentyl] usually intramuscularly.

       If possible the patient should drink 2 L/day of fluid, which increases urine flow and may help to flush the stone out.

       Small stones, less than 5 mm in diameter, are usually passed naturally in a day or two.

       Lithotripsy is a method of applying shock (hydraulic) waves to the body surface precisely focused on the stone through a water-filled cushion on a special table, when the fragmentation of relatively small stones (< 2 cm in diameter) can be achieved. Full name of this procedure is extracorporeal shock wave lithotripsy (ESWL). This procedure is generally well tolerated and may cause only minor pain, haematuria or bruising in the lumbar area.

       In retrograde intrarenal surgery (RIRS) a this fibreoptic endoscope is placed through the urethra into the bladder and into the ureter and kidney pellvis. The stone is seen through this optical instrument and can be manipulated, crushed by ultrasound probe, evaporated by laser probe, grabbed by small forceps, pushed back into the kidney (for subsequent ESWL). This is done under general anaesthesia, but there is no hospitalisation or skin incision.

       Larger stones can be removed by open surgery or endoscopically via percutaneous nephrostomy and nephrolithotomy (fragmentation of the stone with an instrument).

       Antibiotic cover should be given for stone removal to prevent secondary infection.

Prognosis  < BACK TO TOP >

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(source : Dr Zoran Pletikosa)