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Urinary tract stone disease is likely caused by two basic phenomena.
  1. Most common renal stone is calcium oxalate
  2. Struvite (triple phosphate or stag horn calculi)
    1. Associated with proteolytic organism (Proteous, klebsilla, E.coli, staph areus) infection. Q 
    2. It is associated with alkaline urine Q
  3. Uric acid calculi is radio lucent stone. Q
    1. It is associated with acidic urine Q
    2. It is softest stone Q
  4. Cystin stone is hardest stone.Q
  5. The first is supersaturation of the urine by stone-forming constituents including calcium, oxalate, and uric acid. Crystals or foreign bodies can act as a nidus, upon which ions from the supersaturated urine form a microscopic crystalline structure.
  6. It is likely that the initial crystal agglomerations occur in distal collecting tubules that drain into the renal papilla. As these masses grow, they gradually extrude out into the collecting system through the papilla.
  1. History:
    1. Most common symptoms - Pain
    2. Patients may complain of pain, infection, or hematuria.
    3. It is the passage of stones into the ureter with subsequent acute obstruction, proximal urinary tract dilation and spasm.
  2. Causes:
    1. Elevated urinary levels of calcium, oxalate, and uric acid have been associated with stone formation. Hypercalciuria is the single most common metabolic abnormality found.
    2. Decreased levels of inhibitors (magnesium and especially citrate) in the urine predispose to stone formation. Q
    3.  Low fluid intake, with high concentrations of stone-forming solutes in the urine.
    4. Most common finding on 24 hr urine studies include hyper calciuria, hyperoxaluria, hyper uricosuria.
  3. Lab Studies:
    1. Urinalysis: Approximately 85% of patients with urinary calculi will have hematuria.
    2. Complete blood count, Serum electrolytes, creatinine, calcium, uric acid and phosphorus
Objective indication for metabolic evaluation with 24 hr urine analysis.
  1. Residual calculi after Sx treatment
  2. Initial presentation with multiple calculi
  3. Initial presentation before age 30 yr
  4. Renal failure
  5. Solitary kidney
  6. Family h/o calculi
  7. More than one store in past year
  8. B/L calculi
  1. Imaging Studies:
    1. NCCT scan is the most sensitive and specific is imaging modality of choice.
    2. Plain abdominal radiograph (also known as flat plate or KUB: Calcium-containing stones (~85% of all upper tract calculi) are radio-opaque, but pure uric acid, indinavir, and cystine calculi are relatively radiolucent on plain radiography
    3. Stone easily identified with USG but not visible on try usually uric acid or systemic stone.
    4. Renal sonogram: Its main utility lies in determining any hydronephrosis or ureteral dilation associated with an abnormal density seen on the radiograph.
    5. Intravenous urogram (IVU or intravenous pyelogram (IVP)): The intravenous urogram is also helpful in identifying the specific stone if there are numerous pelvic calcifications and for establishing that the opposite kidney is functional.
    6. It is useful for assessing total stone Burden size, shape & location of calculi.
    7. A lucent stone that is not visible on KUB i.e clearly visible on CT scan may indicate a urine acid calculus.
    8. CT scan with contrast, after non contrast CT is useful in t/t planning & in distinguishing problematic radio opacities

CT Scan has replaced IVU for assessment of urinary tract stone disease, especially for acute renal colic. 

  1. Treatment:  Medical Care: 
    Stone size less 6cm can pass spontaneously (Not required any intervention for stone size less than 6 cm).
    1. Emergency Management - General Guidelines: consideration needs to be made of the presence or     absence of obstruction or infection.
      1. Obstruction in the absence of infection can be managed initially with analgesics and other medical measures towards facilitation of passage of the stone.
      2. Infection in the absence of obstruction can be managed initially with antimicrobial therapy.
      3. Morphine sulfate is the narcotic analgesic drug of choice
      4. Medical Expulsion therapy for stone disease includes calcium channels blockers nifedipine and alpha-blocker terazosin / tamsulosine with analgesic.
      5. Limit of medical expulsion therapy to a 10-14 days course only as most stone pass during this time.
    2. Calcium-containing urinary calculi
      1. Urinary calculi composed predominantly of calcium currently cannot be dissolved with medical therapy.
    3. Uric acid and cystine calculi
      Uric acid and cystine calculi, however, can be dissolved with medical therapy. Patients with uric acid stones who do not require urgent surgical intervention for reasons of pain, obstruction, or infection can often have their stones dissolved with alkalinization of the urine.
    4. Surgical Care:
      1. The indications for surgical treatment include pain, infection, and obstruction.
      2. General contraindications to definitive stone manipulation include the following:
        1. Active untreated urinary tract infection
        2. Uncorrected bleeding diathesis
        3. Pregnancy is a relative, but not absolute, contraindication,
      3. Specific contraindications may apply to a given treatment modality. e.g. ESWL should not be performed if there is ureteral obstruction distal to the calculus or in pregnancy.
      4. There are virtually no contraindications to emergency surgical relief of an obstructed and infected collecting system secondary to stone disease, by either ureteral stent placement (a small tube placed endoscopically into the entire length of the ureter from the kidney to the bladder) or percutaneous nephrostomy.
      5. In general, stones that are 4 mm in diameter or smaller will probably pass by themselves, while stones that are > 7 mm are unlikely to pass spontaneously.
    5. Extracorporeal shock wave lithotripsy (ESWL)
      1. The shockhead delivers shock waves developed from an electrohydraulic, electromagnetic or piezoelectric source. The shock waves are focused onto the calculus, and the release of energy as the shock wave encounters the stone produces fragmentation.
      2. Extracorporeal shock wave lithotripsy is limited somewhat by the size and location of the calculus, in that stones greater than 2.5 cm in size or those located in the lower calyx of the kidney are less successfully treated, in addition, results may not be optimal and obese patient especially if the skin to stone distance exceeds 10 cm.
      3. Absolute contraindications are- PREGNANCY, Bleeding Diathesis, Distal Obstruction and infection.
Relative contraindications include the following:
  1. Renal ectopy or malformations (eg, horseshoe kidneys and pelvic kidneys)
  2. Complex intrarenal drainage (eg, infundibular stenosis)
  3. Poorly controlled hypertension (due to increased bleeding risk)
  4. Gastrointestinal disorders: In rare cases, these may be exacerbated after ESWL treatment.
  5. Renal insufficiency: Stone-free rates in patients with renal insufficiency (57%) (serum creatinine level of 2–2.9 mg/dL) were significantly lower than in patients with better renal function (66%) (serum creatinine level <2 mg/dL).
    1. Preexisting pulmonary and cardiac problems are not contraindications, provided they are appropriately addressed both preoperatively and intraoperatively.
    2. In patients with a history of cardiac arrhythmias, the shockwave can be linked to electrocardiography (ECG), thus firing only on the R wave in the cardiac cycle (ie, gated lithotripsy). 
  1. ​Ureteroscopy
    1. Ureteroscopic retrival (URS) is regarded as option of choice for lower uretric tract stone.
    2. Ureteroscopic manipulation of the stone is the next most commonly applied modality. A small endoscope, which may be rigid, semi-rigid, or flexible, is passed into the bladder and up the ureter to directly visualize the stone.
  2. Percutaneous nephrostolithotomy
    1. Percutaneous approaches to the kidney allow fragmentation and removal of very large calculi from the kidney and ureter. A needle and then a wire, over which is passed a hollow sheath, is inserted directly in the kidney through the skin of the flank. 
    2. Because of its increased morbidity, compared to ESWL and ureteroscopy, percutaneous procedures are generally reserved for large renal stones.
    3. In some cases, a combination of ESWL and percutaneous techniques is necessary to completely remove all stone material from a kidney. Called sandwich therapy, this technique is reserved for staghorn stone cases.
    4. Most common complication of PCNL is Bleeding.
    5. If PCNL is done through 11th rib approach then most common complication is Hydrothorax. Q
  3. Open surgery: In selected instances, "complex" stones (extremely large or hard stones) may not respond
    1. well to shock wave lithotripsy or percutaneous stone removal techniques.
  4. Complications:
    Serious complications of urinary tract stone disease include the following:
    1. Abscess formation
    2. Serious infection of the kidney such that renal function is diminished
    3. Urinary fistula formation
    4. Ureteral scarring and stenosis
    5. Ureteral perforation
    6. Extravasation
    7. Urosepsis
    8. Renal loss due to longstanding obstruction
Extra Edge:
Uric Acid Stones Management
  • Cornerstone of treatment: Low purine diet, hydration and alkalization of urine
  • Allopurinol (Inhibits conversion of hypoxanthine and xanthine to uric acid)
  • Acetazolamide (may be added if urine pH is <6.5)
Struvite stones Management
  • Complete stone removal +Treatment of a metabolic abnormality + Correction of any anatomic abnormalities contributing to stasis
  • PCNL + ESWL (best treatment option)
  • Antibiotics to prevent stone recurrences or growth after operative procedure
  • Acetohydroxamic acid (irreversible inhibitor of urease) decreases likelihood of precipitation
  • Low calcium, low phosphorus diet.
  • Upto 50% of patient have stone recurrences or UTI over 10 years follow up
Cystine Stones Management
  • Stone removal
  • To lower cystine concentration in urine (Low methionine diet and alkalization
  • Cystine complexing agents: D-Penicillamine and Alpha-mercaptopropionylglycine (MPG)
Randall's plaques are soft tissue calcifications found in the deep renal medulla skirting the surface of the epithelium of the papilla, where they act as nucleating elements for renal calculi or stones. 

Calcium Oxalate Crystals
  • Calcium oxalate crystals in the urine are the most common constituent of human kidney stones, and calcium oxalate crystal formation is also one of the toxic effects of ethylene glycol poisoning,
  • Excessive oxalate may occur secondary to the accidental or deliberate ingestion of ethylene glycol (partial oxidation to oxalate.
This may result in diffuse and massive deposition of calcium oxalate crystals and may occasionally lead to renal failure.
Dietl's Crisis
Intermittent hydronephrosis (Dietl's crisis): A swelling in the loin is associated with acute renal pain. Some hours later the pain is relieved and the swelling disappears when a large volume of urine is passed.
Contraindications of ESWL
Absolute Relative
• Bleeding disorder
        • UTI                                            
        • Unrelieved distal obstruction
        • Cardiac pacemaker
        • Severe orthopaedic deformity
        • Uncontrolled hypertension
        • Weight >300 pounds
        • Severe renal failure
        • Aneurysm
Renal calculi associated with Proteus infection? (AIPG 2011)
A. Uric acid                      
B. Struvite stones                                 
C. Calcium oxalate                                
D. Xanthine
Ans. B. Struvite stones

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