Urolithiasis

• Crystals bound by muco-protein (Matrix)
• Normally present in urine in solution
• Physiological substances keep the crystals in solution - stone inhibitors!

STONE FORMING FACTORS

• Uric acid
• Calcium phosphate
• Triple phosphate
• Cystine crystal
• Oxalate & Infection

STONE ANTI-FORMING FACTORS

• Magnesium
• Citrate
• Pyrophosphate
• Nephrocalcin
• Tamm-Horsfall glycoprotein

• Increase in the quantity and concentration of the crystal forming constituents in the urine and/or serum.
• Decrease in inhibitors of crystallization and crystal growth
• Risk factors - Family history, Dehydration, alkaline urine!
• Nucleus Formation
• Stasis/Obstruction

R-I-N-D-I-S

FACTORS FOR STONE FORMATION:

• Increased crystalloid concentration
• Relative - reduced urine volume
• Absolute - excessive excretion of the crystals
• Urinary reaction acts by altering the solubility of the crystals
• Absence of stone-inhibitors

Citrate - 50%, magnesium - 20%, pyrophosphates, macromolecules e.g., Glycosaminoglycan, Tamm Horsfall protein, Nephrocalcin, RNA

PROCESS OF STONE FORMATION

• Phase of Nucleation - precipitation of crystal in a state of super saturated solution
• Phase of Growth and Aggregation - the embryo nuclei enlarge in size
• Phase of Trapping - large crystal aggregate is now entrapped in some part of renal anatomy
• Phase of 'Stone' Formation - entrapped crystals now grow forming stone

• Calcium Stones - 90% (oxalate, phosphate)
• Oxalate Stones
• Phosphate Stones
• Uric Acid Stones

COUP

CALCIUM STONES:

Crystals of oxalate:

• Monohydrate (whewellite - bi-concave dumb-bells)
• Dihydrate (Weddelite - bi-pyramid dodecahedron)

Crystals of phosphate:

• Calcium phosphate may be Brushite, Whitlockite, hydroxy-apatite or octa-calcium phosphate

• Normal serum calcium: 9-11 mg% (50% bound to protein)
• Absorptive hypercalciuria
• Normal urinary excretion of calcium: 150 mg/day

Factors: age, sex, climate, diet. >300 mg/day = hypercalciuria

(>4 mg/kg-1/day)

Hypercalciuria: >300 mg/day, may be associated with:

• Hypercalcaemia: (hyperparathyroidism - absorptive/resorptive)
• Normo-calcaemia: present in 95% of cases
• Absorptive hypercalciuria
• Renal hypercalciuria - primary renal tubular leakage of calcium that is dependent on Vit D and parathormone
• Idiopathic hypercalciuria
• Hyperparathyroidism hypercalciuria
• Secondary hypercalcaemia
• Renal Tubular Acidosis
• Medullary sponge Kidney

OXALATE STONES

• Commonest renal stone
• Calcium-oxalate precipitation is inhibited by: mucoproteins, urea, magnesium, pyrophosphate, etc.
• Natural sources: rhubarb, spinach, pepper, tea, cocoa, etc.
• Daily intake: 100-900 mg (10% absorbed)
• Excreted via urine: 10-50 mg/day

PHOSPHATE STONES

• Phosphates are an integral part of the blood-bone urolithiasis circuit
• Normal plasma level: 3-5 mg%, 13% bound, 90% filtered in the glomerulus, 20% excreted in urine
• Pyrophosphate prevents crystallization
• Calcium phosphate supersaturation causes Brushite stone

Causes:

• Hyperparathyroidism
• Hypovitaminosis D
• Alkaline urine - Triple phosphate stone
• Prolonged immobilization

Types:

• Calcium phosphates - Octacalcium phosphate, Brushite, Whitlockite & Hydroxy-apatite
• Magnesium phosphate - Newberyite
• Triple phosphate - Struvite

URIC ACID STONE

• 5-7% of stones
• Purine metabolism in humans results in uric acid (cf: highly soluble Allantoin in animals)
• Normal plasma uric acid level: 2-5 mg%
• 100% ultrafiltrate: nearly all reabsorbed in the proximal tubule
• Daily urinary excretion: 600 mg
• Dietary purine content has a direct relationship with urinary excretion

Causes of uric acid stones

• Gout: 20% in gout patients!
• Secondary hyperuricaemia: tumors, TLS
• Hyperacid uric
• Ileostomy
• Dietary purine: yeast, meat

CYSTINE STONE

Cystine is an amine of sulphur-containing amino acid

Cystinuria: normal excretion is 30-50 mg/24h but in cystinuria, it increases to 300-1000 mg

• It is a genetic renal tubular defect, of tubular reabsorption of cystine, based in chromosome 2
• Excessive secretion of arginine, ornithine, lysine, and cystine - poor solubility, especially in acidic urine

RINDIS!

• Risk Factors: Family history, Dehydration, Urine pH
• Increase in the quantity and concentration of the crystal forming constituents in the urine and/or serum
• Nucleus Formation: inspissated pus, clump of bacteria, blood clot, a scar, FB
• Decrease in inhibitors of crystallization and crystal growth: citrate, pyrophosphate
• Infection: urea splitting organisms
• Stasis

• Silent stone
• Fixed pain
• Colicky pain
• Gastro-intestinal symptoms
• Infective symptoms
• Retention of urine
• Haematuria
• Irritative bladder symptoms
• Calculous anuria
• Uraemic features

• Urinalysis
• Uro-bacteriology
• Urinary biochemistry
• Calcium: 300 mg
• Cystine: >250 mg/gm of creatinine
• Oxalate: >44 mg/day
• Uric acid: >600 mg/day
• Ammonium chloride test
• Plain X-ray
• USS
• Intravenous Urography
• CT Scan
• NCCT
• CT Urography or CECT
• Blood Biochemistry
• Plasma calcium
• Inorganic phosphate
• Uric acid
• BUE/Cr, ALP
• Endoscopy
• Stone Analysis

MEDICAL TREATMENT

• Expectant Treatment:
• Bed Rest
• Antispasmodic
• Liberal oral fluid
• Diagnostic Investigation
• Observation
• Medical Expulsion Treatment:
• Tamsulosin/Nifedipine
• Prophylactic Medical Treatment:
• Hydrotherapy
• Diet
• Control UTI
• Oral Potassium Citrate

SURGICAL TREATMENT

• Indications
• Stones too large for spontaneous passage, usually greater than 7 mm.
• Stones associated with symptomatic infection
• Stones causing impaired renal function
• Stones causing persistent pain or worsening of symptom
• Patient with only one kidney

Close procedure:

• Lithotripsy (Extracorporeal Shockwave lithotripsy (ESWL)
• Noninvasive
• Percutaneous Nephrolithotomy

Open Procedure

• Ureterolithotomy
• Pyelolithotomy
• Nephrolithotomy
• Partial or total nephrectomy

• Avoid protein intake: usually protein is restricted to 60g/day to decrease urinary excretion of calcium and uric acid.
• A sodium intake of 3 to 4 g/day is recommended. Table salt and high-sodium foods should be reduced because sodium competes with calcium for reabsorption in the kidneys.
• Low-calcium diets are not generally recommended, except for true absorptive hypercalciuria. Evidence shows that limiting calcium, especially in women, can lead to osteoporosis and does not prevent renal stones.
• Avoid intake of oxalate-containing foods (e.g. spinach, strawberries, tea, peanuts, wheat bran).
• During the day, drink fluids (ideally water) every 1 to 2 hours.
• Drink two glasses of water at bedtime and an additional glass at each night time awakening to prevent urine from becoming too concentrated during the night.
• Avoid activities leading to sudden increases in environmental temperatures that may cause excessive sweating and dehydration.
• Contact your primary health care provider at the first sign of a urinary tract infection.