Nephrolithiasis

Nephrolithiasis Epidemiology More common in men More common in people aged less than 65 80% are made out of calcium 35% calcium oxalate 10% calcium phosphate 35% mixed oxalate and phosphate Risk factors Idiopathic Most common Dehydration Most important modifiable risk factor Previous stones or family history Metabolic conditions E.g. cystinuria, primary hyperparathyroidism, gout Medications Diuretics Antiretrovirals Antacids Obesity Bowel disease E.g. inflammatory bowel disease Types Calcium oxalate Most common Calcium phosphate Struvite stone Usually large soft stones Most common cause of staghorn calculi Stone fills renal pelvis Locations Renal calyx Renal pelvis Ureters Pelviureteric junction Pelvic brim VUJ Most common site Bladder Ureter vesicular junctions Clinical features Pain Most common Ureteric/renal colic Occurs from the increased peristalsis from around the site of obstruction Sudden onset Severe Radiates from flank to pelvis Loin groin Nausea and vomit Distal stones Increased urinary frequency or need to micturate Despite empty bladder Haematuria In 90% of cases Non-visible If stone becomes infected Rigors Fevers Lethargy Examination usually remarkable But may have some tenderness on the affected flank Features of dehydration From reduced intake or losses through vomit Investigations Urine dipstick Microscopic haematuria Urine microscopy cultures and sensitive Check for infections If negative does not exclude infected obstructed system Bloods FBC: routine and features of anaemia from bleeding and leucocytosis CRP: inflammatory markers Calcium and urate levels U&E and Cr: renal function Lactate: if raised -> sign of worsening sepsis Imaging Non-contrast CT of KUB High sensitivity and specificity Ultrasounds Hydronephrosis Can detect renal stones but not ureteric stones Not very accurate for stones Excluding other causes such as pregnancy AXR KUB Rarely used for initial assessment Not all stones are radio-opaque Radio-opaque Calcium oxalate Calcium phosphate Struvite Radiolucent Uric acid Cystine Management Conservative: Fluids If stone less than 5mm -> waiting trial can be used Analgesia Most will pass spontaneously Anti-emetics Patients should be reviewed as outpatients in about 4 weeks Medical management: Medical expulsive therapy and analgesia NSAIDs -> main Alpha adrenoreceptor blocker Use of expulsive therapy is controversial For small distal ureteric stones Limited use Evidence of infection IV antibiotics Surgical management: For patients who have one of the following: Stone more than 10 mm ? Persisting pain despite good adequate analgesia AKI Infected-obstructed kidney Urgent Bilateral obstructed kidney/obstructed kidney in a patient who has functioning kidney Emergency Stent placement Placed at the ureter Allows for urine passage Under GA Retrograde insertion Allows for ureter to remain open -> relieves obstruction Approaching from distal to proximal via cystoscopy Nephrostomy No GA Percutaneous insertion of a tube straight into the kidney Urine drainage Protects the kidney by preventing damage and infection from backup (hydronephrosis) Complications such as bleeding At a later date need treatment of their stone: Ureteroscopy and laser fragmentation or extracorporeal shock wake lithotripsy extracorporeal shock wave lithotripsy performed while the patient is awake -> shockwaves focused into an area of the stone -> breaks the stone and allows for passage if these procedures not available -> place ureteric stent -> patient comes back on elective basis Emergency when bilateral tones or obstructing stone in patients with a single kidney rapid life-threatening deterioration Criteria for admission Post-obstructive kidney injury Uncontrolled pain from simple analgesics Evidence of an infected stone Large stones -> more than 5 mm. Complications Infection Post-renal AKI Ureter obstruction -> hydronephrosis Obstruction is the most common complication Recurrent stones -> renal scarring and loss of kidney function