Urolithiasis

Urolithiasis is the presence of stones in the urinary tract - in the renal pelvis (nephro-), ureter (uretero-), bladder (cysto-) or urethra (urethrolithiasis) or stone-forming substances in the renal parenchyma (nephrocalcinosis), in our country is the most common calcium oxalate.

Pathogenesis

Crystallization and aggregation

The causes include:

• supersaturation of urine with stone-forming substances (Ca2 +, urates, oxalate), supported by reduced diuresis,
• urinary incontinence (obstructive uropathy),
• changes in urine pH (incl. urea-degrading bacteria - Proteus, Pseudomonas, Klebsiella - struvite lithia),
• lack of inhibitors of crystallization and aggregation (citrates, pyrophosphates, Mg2 +, glycoproteins),
• some drugs (sulfonamides, antacids).

Cystolithiasis occurs in chronic residual subvesical obstruction or neurogenic bladder.

Concretions are divided into:

• Contrast X-ray - Ca-oxalate, Ca-phosphate, struvite (MgNH4PO3), cystine,
• Non-contrasting X-ray - urate, xanthine.

Clinical symptoms

Urolithiasis can occur asymptomatically (immobile stones).

Manifesting urolithiasis can be divided according to location into:

• nephrolithiasis - dull kidney pain (palpation, positive tapottement), ev. how many when blocking the drain,
• ureterolithiasis - renal colic with vegetative accompaniment, spread according to location (back, inner thigh),
• cystolithiasis - pain behind the buckle, polakisuria, urgency.

It is often manifested by hematuria and other complications - inflammation (pyelonephritis, cystitis).

Complications

Complications include obstruction - renal colic, hydronephrosis, infection to urosepsis, bleeding and renal insufficiency in bilateral disability.

Diagnostics

• Urine: sediment, chemically (incl. Cystine), pH, density, culture (negative with complete blockade).
• Biochemistry: Ca2 +, phosphates, uricaemia, Astrup (exclusion of RTA - renal acidosis).
• Examination of concretion:
  • chemical,
  • mineralography - polarizing microscope, X-ray distraction,
  • imaging methods:
    • Ultrasound - identification of stones and dilatation of the urinary tract, so-called acoustic shadows can be seen
    • X-ray (native nephrogram, excretory urography), cystolithiasis cystography, cystoscopy,
    • spiral CT,
    • static renal function study (DMSA).

• Hypercalcaemia, hypercalciuria, hyperphosphaturia - suspected hyperparathyroidism.
• Urolithiasis with hypokalemia - suspected RTA - renal acidosis.
• Hypercalciuria - absorption type (↑ resorption of Ca2 + from the intestine) and renal (↓ reverse resorption in the tubules).
• Hyperoxaluria - a disorder of intestinal fat resorption (chronic pancreatitis, obstructive jaundice).
• Hyperuricosuria - myeloproliferative diseases, disorders of purine metabolism, chemotherapy.
• Hypercystinuria - a congenital disorder of renal cystine transport.
• Hypocitration - chronic diarrhea, administration of thiazide diuretics.

Metabolic examination in urolithiasis

• Serum: urea, creatinine, uric acid, Na +, K +, Ca2 +, Mg2 +, Cl−, phosphorus, glycemia, total protein, liver tests, cholesterol (LDL, HDL), triglycerides.
• Urine in 24 hours: volume, urine pH. Wastes in 24 hours: phosphorus, uric acid, creatinine, Na +, K +, Ca2 +, Mg2 +, Cl−, oxalates, citrates, sulphates.
• Calculations: creatinine clearance, uric acid clearance, Ca2 + / creatinine ratios, Ca2 + / Mg2 +.
• Proteinuria.
• Calcium-free diet followed by oral administration of 1000 mg eferv. calcium tablets

Differential diagnostics

• Pain - sudden abdominal event, biliary colic, gynecological disease.
• Hematuria - tumor, urinary tract infection, coagulopathy (warfarinization).
• Defect in the filling of the hollow system - urothelial tumor.

Treatment

• Acute renal colic:
  • analgesics, antispasmodics, non-steroidal anti-inflammatory drugs (indomethacin National Office for Drug Control: indomethacin),
  • sufficient hydration,
  • supravesical urine derivation with signs of urinary tract infection or urosepsis.

• Chronic urolithiasis:

1. endoscopic methods,
2. instrumentation - nephrostomy, ureteral probing with extraction or crushing of the stone, cystoscopy with extraction or crushing of the stone - extracorporeal shock wave lithotripsy,
3. open surgery (in about 1%) - lithotomy (pyelo-, uretero-, cysto-), nephrotomy, nephrectomy,
4. conservative treatment - symptomatic treatment of colic, metaphylaxis (prevention of recurrences).

• Concretion extraction - forceps, Zeiss loop, Dormia basket.
• Concret crushing - mechanically, ultrasound, electrohydraulic, laser, grinding.
  • Indication:

1. X-ray contrast up to 2 cm made of soft material (weddellite), good anatomical conditions and outflow,
2. stone over 2 cm, hard (whewellite, struvite, Ca-oxalate, urate), unfavorable anatomy and outflow (stenoses),
3. Non-contrast X-ray (cannot be targeted by lithotripter), in the lower 2/3 of the ureter,
4. minor asymptomatic nephrolithiasis, ureterolithiasis up to 4 mm - conservative treatment.

• Urine pH change:
  • urate stones - alkalization of urine (sodium citrate, potassium citrate),
  • struvite stones - acidification of urine.

• Metaphylaxis:

1. non-specific - drinking and diet regime (↑ fluid intake, ↓ Ca2 + and salt intake, meat,…),
2. specific - according to the composition of stones - most often citrates, in hyperuricaemia and urate lithiasis allopurinol.

Links

References

1. KNIGHT, J, D G ASSIMOS a L EASTER, et al. Metabolism of fructose to oxalate and glycolate. Horm Metab Res [online]. 2010, vol. 42, no. 12, s. 868-73, dostupné také z <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3139422/?tool=pubmed>. ISSN 0018-5043 (print), 1439-4286. 
2. BARTONÍČKOVÁ, K. Urolitiáza. Postgraduální medicína [online]. 2006, roč. -, vol. 2, s. -, dostupné také z <https://zdravi.euro.cz/clanek/postgradualni-medicina/urolitiaza-172263>.