Urolithiasis: The process of forming stones in the kidney, bladder, and/or urethra (urinary tract). Kidney stones are a common cause of blood in the urine and pain in the abdomen, flank or groin. The development of these stones is related to decreased urine volume or increased excretion of stone-forming components such as calcium, oxalate, urate, cystine, xanthine, and phosphate. The stones form in the urine collecting area (the pelvis) of the kidney and may range in size from tiny stones to staghorn stones which are the size of the renal pelvis itself.

 ETIOLOGY (CAUSEs)

 Stones classified by etiology

§  Non-infection stones

·         Calcium oxalate

·         Calcium phosphate

·         Uric acid

§  Infection stones

·         Magnesium ammonium phosphate

·         Carbonate apatite

·         Ammonium urate

§  Genetic causes

·         Cystine

·         Xanthine

·         2,8-Dihydroxyadenine

§  Drug stones

·                     Ascorbic acid

·                     Calcium 

·                     Laxatives

·                     Vitamin D

 Risk Factors

 This risk of urolithiasis increases as a result of any factor that leads to urinary stasis due to a reduction or obstruction of urinary flow.

Certain risk factors contribute to a higher incidence of stone formation, including:

• Male: Men excrete less citrate and more calcium than women, which is thought to be linked to higher incidence

• Family history: Some families have a tendency to produce excess mucoprotein in the urinary system, which can promote stone formation.

• Medical history: Some health conditions are associated with a raised risk of stone formation, including intestinal disease, recurrent urinary tract infections and cystinuria.

• Diet: Dehydration or reduced fluid intake may increase the risk of stone formation, in addition to increased consumption of sodium, oxalate, fat, protein, sugar, unrefined carbohydrates and vitamin C.

• Environment: Some regions are associated with an increased risk, such as tropical climates, mountainous or desert terrain.

• Medications: Some medication such as ephedrine, guaifenesin, thiazide, indinavir and allopurinol may lead to the development of stones.

Symptoms and Signs

§  Loin pain (radiating to groin)

§  Hematuria (blood in the urine, sometimes clots) 

§  Fever

§  Scalding (burning) micturition (urination)

§  Storage and voiding symptoms (in ureteric, bladder and urethral calculi)

§  Loin tenderness

 Evaluation 

 All patients with newly diagnosed kidney or ureteral stones should undergo a screening evaluation that includes a detailed medical and dietary history.  The purpose of this evaluation is to identify patients at highest risk for stone formation and evaluate for systemic etiologies for kidney stone disease.

Patients identified as high-risk stone formers include those with a family history of stone disease, those with obesity and/or metabolic syndrome, and patients with medical conditions that predispose to stone formation such as gastrointestinal (GI) disease or prior surgical resection resulting in malabsorption, primary hyperparathyroidism, renal tubular acidosis, sarcoidosis, gout, type 2 diabetes mellitus, and urinary tract infection (UTI).

 Stone composition, when known, can also help identify high-risk patients who would benefit from a metabolic evaluation, such as those with cystine or uric acid stones in whom the likelihood of finding a metabolic abnormality requiring medical therapy is high.

Children should generally be evaluated because of concerns about renal damage and long-term sequelae of stone recurrence.

 History

§  Underlying Medical conditions 

§  Medications (calcium, vitamin C, vitamin D, acetazolamide, steroids)

§  Inadequate fluid intake, excessive fluid loss

Multichannel Blood Screen

§  Basic metabolic panel (sodium, potassium, chloride, carbon dioxide, blood urea nitrogen, creatinine)

§  Calcium

§  Intact parathyroid hormone

§  Uric acid

Urine

§  Urinalysis

§  pH >7.5: infection lithiasis

§  pH <5.5: uric acid lithiasis

§  Sediment for crystalluria

§  Urine culture

§  Urea-splitting organisms: suggestive of infection lithiasis

§  Qualitative cystine

Stone analysis (spontaneous expulsion / post procedure)

Stone analysis can provide valuable insight into how and why a patient may have formed a stone.

It can serve as a useful adjunct to serum and urine metabolic evaluation.

 Diagnostic imaging

The most appropriate imaging modality will be determined by the clinical situation, which will differ depending on whether a ureteral or a renal stone is suspected.

• Standard evaluation includes a detailed medical history and physical examination.

• Patients with ureteral stones usually present with flank  pain, vomiting, and sometimes fever, but it may also be asymptomatic.

•  Immediate evaluation is indicated in patients with solitary kidney, fever or when there is a doubt regarding a diagnosis of renal colic.

Ultrasound (US) should be used as the primary diagnostic imaging tool, although pain relief or any other emergency measures should not be delayed by imaging assessments. Ultrasound is safe (no risk of radiation), reproducible and inexpensive. It can identify stones located in the calyces, pelvis, and pyeloureteric and vesico-ureteral junctions (US with filled bladder), as well as in patients with upper urinary tract (UUT) dilatation.

Kidney-ureter-bladder radiography ( X-ray KUB)  is helpful in  localizing the stone ( if radio opaque) and also used for comparison during follow-up.

Non-contrast-enhanced computed tomography ( NCCT) has become the standard for diagnosing acute flank pain. 

NCCT can determine stone diameter, density, its location, anatomic features of urinary system.

When stones are absent, the cause of abdominal pain should be identified.

Non-contrast-enhanced CT can detect uric acid and xanthine stones, which are radiolucent (not visible on X-ray KUB), but not indinavir stones.

The advantage of non-contrast imaging must be balanced against loss of information on renal function as well as higher radiation dose.

 EVALUATION IN PREGNANT PATIENTS

In pregnant women radiation exposure may cause (teratogenesis or carcinogenesis, mutagenesis) effects.

 ·         Ultrasound (when necessary, using changes in renal resistive index and transvaginal/transabdominal US with a full bladder) has become the primary radiological diagnostic tool when evaluating pregnant patients suspected of renal colic. However, normal physiological changes in pregnancy can mimic ureteral obstruction

 ·         Magnetic resonance imaging can be used, as a second-line procedure  to define the level of urinary tract obstruction, and to visualise stones as a filling defect. The use of gadolinium contrast is not recommended in pregnancy to avoid toxic effects to the embryo.

  Preventive measures

All stone formers, independent of their individual risk, should follow the preventive measures 

The main focus is normalisation of dietary habits and lifestyle risks. Stone formers at high risk need specific prophylaxis for recurrence, which is usually pharmacological treatment based on stone analysis.

General preventive measures

• Fluid intake (drinking advice)

• Fluid amount: 2.5-3.0 L/day

• Balanced diet rich in vegetables and fibre

• Normal calcium content: 1-1.2 g/day

• Salt restricted diet:  up to 4-5 g/day

• Reduce animal protein content: 0.8-1.0 g/kg/day

Eat fewer oxalate-rich foods

Some kidney stones are made of oxalate, a natural compound found in foods that binds with calcium in the urine to form kidney stones. Limiting oxalate-rich foods may help prevent the stones from forming.

Foods high in oxalates are :

• Spinach

• Chocolate

• Sweet potatoes

• Coffee

• Beets

• Peanuts

• Rhubarb

• Soy products

• Wheat bran

 Lifestyle advice to normalise general risk factors

• BMI: Retain a normal BMI level

•  Adequate physical activity

• Balancing of excessive fluid loss

 TREATMENT

Disease Management

A) Renal colic

Pain relief

Non-steroidal anti-inflammatory drugs (NSAIDs)  and paracetamol are effective in patients with acute stone colic and have better analgesic efficacy than opioids (Also increased incidence of vomiting) .

It should be taken into consideration that the use of diclofenac and ibuprofen increase major coronary events.  Diclofenac is contraindicated in patients with congestive heart failure (New York Heart Association class II-IV), ischaemic heart disease and peripheral arterial and cerebrovascular disease. Patients with significant risk factors for cardiovascular events should be treated with diclofenac only after careful consideration.

 B) Ureteral stones

ANALGESICS

For patients with ureteral stones that are expected to pass spontaneously (distal ureteric stone, < 8mm, no structural abnormality), NSAID tablets or suppositories (e.g., diclofenac sodium, 100-150 mg/ day, 3-10 days) may help reduce inflammation and the risk of recurrent pain.

Although diclofenac can affect renal function in patients with already reduced function, it has no functional effect in patients with normal renal function.

Medical expulsive therapy ( MET)

• Medical expulsive therapy should only be used in informed patients if active stone removal is not indicated.

• Treatment should be discontinued if complications develop (infection, refractory pain, deterioration of renal function).

• Several drug classes are used for MET

Patients receiving α-blockers, calcium-channel inhibitors (nifedipine) and phosphodiesterase type 5 inhibitors (PDEI-5) (tadalafil) are more likely to pass stones with fewer colic episodes than those not receiving such therapy.

The greatest benefit is among those with (distal) ureteral stones.

NON MEDICAL MANAGEMENT

1)  Extracorporeal Shock Wave Lithotripsy (ESWL)

For stones between 1 cm and 2 cm that are not located in the lower pole, ESWL had traditionally been recommended as first-line therapy. However, the success of ESWL depends on other factor also,  i.e. stone composition, stone attenuation, patient’s habitus, and renal anatomy.

Contraindications to Shock Wave Lithotripsy (SWL)

·         Pregnancy

·         Uncorrected coagulopathy or bleeding diathesis

·         Untreated urinary tract infection

·         Arterial aneurysm near stone (renal or abdominal aortic aneurysms)

·         Obstruction of urinary tract distal to stone

·         Inability to target stone (skeletal malformation)

Factors Negatively Affecting Shock Wave Lithotripsy Success

• Stone composition (cystine, brushite, calcium oxalate monohydrate,matrix)

• Stone attenuation ≥1000 HU

• Skin-to-stone distance >10 cm (morbid obesity)

• Renal anatomic anomalies (horseshoe kidney, calyceal diverticulum)

• Unfavorable lower pole anatomy (narrow infundibulopelvic angle, narrow infundibulum, long lower pole calyx)

• Relative or complete patient immobility

2) Ureteroscopy (URS)

·         Rigid/ flexible URS can be used for the ureter, pelvis and renal stone

 ·         Ureteric stones achieve higher stone clearance with URS.

·         Stones which are impacted or large in size, are retrieved by fragmenting into smaller particles with the help of energy sources (pneumatic/laser)

·         Flexible URS for stones in renal pelvis and kidney usually of size up to 2 cm, where PCNL is contraindicated (bleeding disorders, difficulty in positioning)

3) Percutaneous nephrolithotomy ( PCNL) 

Percutaneous nephrolithotomy remains the standard procedure for large renal calculi. ( > 2 cm)