Urinary Tract Stones (Calculi)

Urinary Tract Stones (Calculi)

Urinary Tract Stones (Calculi)

Epidemiology of stones : Incidence❏10% of population❏male:female ratio 3:1❏50% chance of recurrence by 5 years Etiology and Pathogenesis Multifactorial process: Temperature, PH, Diet, Genetic…❏factors promoting stone formation• stasis (hydronephrosis, congenital abnormality)• medullary sponge kidney• infection (struvite stones)• hypercalciuria• increased oxalate• increased uric acid❏loss of inhibitory factors • Mg (forms soluble complex with oxalate)• citrate (forms soluble complex with calcium)• pyrophosphate• glycoprotein

Supersaturation: The formation of stones needs supersaturated urine.Ksp (solubility product) a critical state at which the substance is easily soluble above this meatasatble: a capability of initiating crystal growth (Nucleation), & the epitaxy aggregation of crystals each on the other as (Ca+, Oxalate over urate).Kfp (formation products) unstable solutions in which a spontaneous homogenous nucleation occur. Matrix: non crystalline mucoprotein + proteus infection Exogenous substances: Indinavir – antiviral Triamterene } rudiolucent stones

Stones of the upper urinary tract

Clinical Presentation❏urinary obstruction ––> distension ––> pain• flank pain from renal capsular distension (non-colicky)• severe waxing and waning pain radiating from flank to groin dueto stretching of collecting system or ureter (ureteral colic)• never comfortable, always moving❏nausea, vomiting❏hematuria, usually microscopic, occasionally gross (90%)❏symptoms of trigonal irritation (frequency, urgency), diaphoresis, tachycardia, tachypnea❏+/– fever, chills, rigors secondary to pyelonephritis

Differential Diagnosis of Renal Colic❏other causes of acute ureteral obstruction• UPJ obstruction• sloughed papillae• clot colic from gross hematuria❏radiculitis (L1 nerve root irritation)• herpes zoster• nerve root compression❏pyelonephritis (fever, chills, pyuria)❏acute abdominal crisis (biliary, bowel)❏leaking abdominal aortic aneurysm

Location of Stones❏calyx• may cause flank discomfort, recurrent infection or persistent hematuria• may remain asymptomatic for years and not require treatment❏pelvis• tend to cause UPJ obstruction❏renal pelvis and one or more calyces• staghorn calculi• often associated with infection • infection will not resolve until stone cleared• may obstruct renal drainage❏ureter• < 5 mm diameter will pass spontaneously in 75% of patients❏the three narrowest passage points for upper tract stones include: UPJ, pelvic brim, UVJ

Investigations❏screening labs• CBC ––> elevated WBC in presence of fever suggests infection• Electrolytes, Cr, BUN ––> to assess renal function❏urinalysis• routine and microscopic (WBCs, RBCs, crystals)• culture and sensitivity❏KUB x-ray • 90% of stones are radiopaque❏spiral CT• no contrast, good to distinguish radiolucent stone from soft tissue filling defect❏abdominal ultrasound • may demonstrate stone (difficult in ureter)• may demonstrate hydronephrosis

❏IVP • establishes diagnosis• demonstrates • anatomy of urine collecting system• degree of obstruction• extravasation if present• renal tubular ectasia (medullary sponge kidney)• uric acid stones ––> filling defect❏strain all urine ––> stone analysis❏later (metabolic studies for recurrent stone formers)• serum lytes, calcium, phosphate and uric acid• PTH if hypercalcemic• creatinine and urea• 24 hour urine x 2 for creatinine, Ca2+, PO4, uric acid, magnesium, oxalate and citrate


Acute Management❏medical• analgesic (tramadol, pethidine, morphine) +/– antiemetic• NSAIDs help lower intra-ureteral pressure• +/– antibiotics for UTI• IV fluids if vomiting❏indications for admission to hospital• severe persistent pain uncontrolled by oral analgesics• fever ––> infection• high grade obstruction • single kidney with ureteral obstruction• bilateral ureteral stones• persistent vomiting❏surgical• ureteric stent• high grade obstruction• single kidney❏radiological• percutaneous nephrostomy (alternative to stent)

Elective Management❏medical• conservative if stone < 5mm and no complications• alkalinization of uric acid and cystine stones may be attempted (potassium citrate)• patient must receive one month of therapy before being considered to have failed❏surgical• kidney• extracorporeal shock wave lithotripsy (ESWL) if stone < 2.5 cm• + stent if 1.5-2.5 cm• percutaneous nephrolithotomy• stone > 2.5 cm• staghorn• UPJ obstruction• calyceal diverticulum• cystine stones (poorly fragmented with ESWL)• open nephrolithotomy• extensively branched staghorn

• ureter• ESWL is primary modality of treatment• ureteroscopy• failed ESWL• ureteric stricture• reasonable alternative for distal 1/3 of ureter• open ureterolithotomy• rarely necessary (failed ESWL and ureteroscopy)

BLADDER STONES❏etiology• stasis (bladder outflow obstruction)• foreign body• Infection • dietary❏description• large• often multiple❏signs and symptoms• frequency and urgency• pain at end of urination• pyuria• hematuria• obstructive symptoms❏stone types• often Ca2+ oxalate/phosphate• uric acid

Investigation GUE US Plain XR of pelvis Cystoram CT scan

Treatment
Lithotrities: Cystolitholapaxy: Mechanical crushing device Electrolaydraulic Lithotripsy US lithotripsy Pneumatic lithotripsy Cystolithotomy Remove outflow obstruction (TURP or dilatation of stricture)

STONE TYPES

Calcium Stones❏account for 80% of all stones❏Ca2+ oxalate most common, followed by Ca2+ phosphate❏description• grey or brown due to hemosiderin from bleeding• radiopaque

Etiology❏hypercalciuria (60-70% of patients)• 95% of these patients have normal serum calcium levels• 5-10% of people without stones have hypercalciuria❏ Types of hypercalciuric Ca2+ stones: absorptive causes (majority of patients)• increased vitamin D sensitivity ––> idiopathic • sarcoidosis ––> ↑production of 1,25(OH)2vit D• abnormal vitamin D metabolism ––> ↑1,25 (OH)2vit D• excess vitamin D intake• increased Ca2+ intake (milk alkali syndrome)• renal phosphate leak ––> ↓PO4––> ↑1,25(OH)2 vitamin D ––> absorptive hypercalcemia• treatment• cellulose phosphate (decrease intestinal absorption of Ca2+) or orthophosphates (inhibit vitamin D synthesis)


resorptive causes (i.e. ↑Ca2+ from bones)• hyperparathyroidism• neoplasms (multiple myeloma, metastases)• Cushing’s disease• hyperthyroidism• immobilization• steroids

renal leak of calcium• distal renal tubular acidosis (RTA I) ––> 6.0 pH + ↓citrate ––> ↑CaPO4stones• treat with HCO3 to ↑citrate• medullary sponge kidney (tubular ectasia) • anatomic defect in collecting ducts; • 5-20% of Ca2+ stone formers

❏idiopathic (25-40% of patients)• normocalcemic• normocalciuric• may have ↓citrate; ↓Mg; ↑oxalate; ↑urine acidity; dehydration• treatment• hydrochlorothiazide (HCTZ) 25 mg PO daily ––> ↓Ca2+ in urine• increase water intake

❏hyperuricosuria (25% of patients with Ca2+ stones)• uric acid acts as nidus for Ca2+ stone formation• treatment• add allopurinol if uric acid excretion > 5 mmol/day❏hypocitraturia (12% of patients)• associated with type I RTA or chronic thiazide use• treatment• potassium citrate

❏hypercalcemia (5% of patients)• primary hyperparathyroidism • malignancy } 90% of cases• sarcoidosis• increased vitamin D• hyperthyroidism• milk-alkali syndrome❏hyperoxaluria (< 5% of patients)• inflammatory bowel disease (IBD)• short bowel syndrome• dietary increase (caffeine, potatoes, rhubarb, chocolate, vitamin C)• primary increase in endogenous production• treatment• calcium or cholestyramineincrease water intake, avoid oxalate-containing foods• oral

Struvite Stones ❏etiology and pathogenesis• account for 10% of all stones• contribute to formation of staghorn calculi• consist of triple phosphate (calcium, magnesium, ammonium)• due to infection with urea splitting organisms NH2CONH2+ H2O ––> 2NH3+ CO2• NH4 alkalinizes urine, thus decreasing solubility❏common organisms•Proteus•Klebsiella•Pseudomonas•Provididencia•S. aureus• not E. coli❏treatment• complete stone clearance (ESWL/percutaneous nephrolithotomy) • acidify urine, dissolve microscopic fragments• antibiotics for 6 weeks• follow up urine cultures

Uric Acid Stones ❏account for 10% of all stones❏description and diagnosis• orange coloured gravel, needle shaped crystals• radiolucent on x-ray• filling defect on IVP• radiopaque on CT scan• visualized with ultrasound

❏etiology• hyperuricosuria (urine pH < 5.5)• secondary to increased uric acid production, or drugs (ASA and probenecid)• hyperuricemia • gout• myeloproliferative disease • cytotoxic drugs• defect in tubular NH3synthesis (ammonia trap for H+)• dehydration, IBD, colostomy and ileostomy❏treatment• increase fluid intake• NaHCO3• allopurinol• avoid high protein/purine diet

Cystine Stones ❏autosomal recessive defect in renal tubular transport❏seen in children❏aggressive stone disease❏description• yellow, hard• radiopaque (ground glass)• staghorn or multiple• decreased reabsorption of “COLA”• cystine• ornithine• lysine }soluble in urine• arginine ❏diagnosis• amino acid chromatography of urine ––> see COLA in urine

❏treatment• greatly increase water intake ––> 3-4 L urine/day• HCO3• decrease dietary protein ––> methionine• penicillamine chelators ––> 2 g daily, soluble complex formed; use cautiously• a-mercaptopropionylglycine (MPG) ––> similar action to penicillamine, less toxic• captopril (binds cystine)• irrigating solutions: N-acetylcystine (binds cystine), Tromethamine-E