Ureteral Stone

A ureteral stone is a calculus lodged in the ureter after migrating from the kidney, producing obstruction and renal colic. Lifetime risk is 10 to 15 percent in men and 5 to 10 percent in women. Incidence peaks at 20 to 50 years, and the recurrence rate is about 50 percent at 5 to 10 years.

Stones form in the kidney. When they enter the ureter they stop at the three physiological narrowings:

• The ureteropelvic junction.
• The pelvic brim, where the ureter crosses the iliac vessels.
• The ureterovesical junction (the narrowest part, 1 to 5 mm in diameter).

Stone composition:

• About 80 percent are calcium oxalate or calcium phosphate.
• 10 percent are uric acid.
• 5 to 10 percent are struvite.
• 1 to 2 percent are cystine.

Spontaneous passage depends on size:

• For stones of 4 mm or less, about 80 to 90 percent pass spontaneously.
• For 5 to 7 mm, about 50 to 60 percent.
• For above 8 mm, 20 to 30 percent or less.

Stones in the distal ureter pass more often than proximal ones. Passage typically takes up to 4 to 6 weeks.

• Renal colic: sudden onset severe unilateral flank pain radiating to the groin, testis or labium, colicky in character, and the patient is restless and cannot find a comfortable position; peaks at 20 to 60 minutes.
• Nausea and vomiting, haematuria (microscopic in 85 percent), urgency, frequency and dysuria, and strangury (with stones at the ureterovesical junction).
• Fever, rigors and sepsis in infected obstruction (an emergency).
• Costovertebral angle tenderness; abdomen is usually soft.
• Anuria or oliguria with obstructed solitary kidney or bilateral stones.
• Differential: appendicitis, ectopic pregnancy, ovarian torsion, aortic aneurysm leak or dissection, pyelonephritis, musculoskeletal pain, biliary colic.

• Non-contrast low dose CT of the kidneys, ureters and bladder is the gold standard (sensitivity and specificity of 95 to 98 percent).
• CT gives stone size, location, density in Hounsfield units (above 1,000 hard, resistant to shock wave lithotripsy), skin-to-stone distance, hydronephrosis and alternative diagnoses.
• Ultrasound as first line in pregnancy and children: hydronephrosis, stone at the pelvic or ureterovesical junction, and absent ureteric jets (sensitivity about 45 percent for ureteral stones). Combine with plain X-ray of the kidneys, ureters and bladder (shows radiopaque stones, about 60 to 70 percent).
• Urinalysis (haematuria, pH, crystals, nitrites, leucocytes), urine culture, full blood count, C-reactive protein, creatinine, electrolytes, calcium, uric acid, and pregnancy test.
• Metabolic evaluation after a first stone in higher risk patients, and for recurrent stones: serum calcium, phosphate, uric acid, and parathyroid hormone if the calcium is high.
• Also 24-hour urine collection (volume, calcium, oxalate, citrate, uric acid, sodium, pH, creatinine, cystine), and stone analysis (infrared spectroscopy or X-ray diffraction).

Acute pain control and decision between expectant, medical expulsive and interventional treatment.

• Analgesia: ketorolac 30 mg intravenous or intramuscular (or diclofenac 75 mg intramuscular, or 50 mg orally three times a day, or ibuprofen 400 to 800 mg three times a day) as first line. Non-steroidal drugs are more effective than opioids (avoid in renal impairment, pregnancy, and peptic ulcer disease).
• Other analgesia: paracetamol 1 g intravenously every 6 hours; opioids (morphine 5 to 10 mg intravenous or tramadol) as rescue; antiemetics (ondansetron 4 mg). Intravenous fluids are given for dehydration, with no benefit for forced diuresis.
• Medical expulsive therapy for stones of 5 to 10 mm in the distal ureter, in a patient with controlled pain and no infection: tamsulosin 0.4 mg daily (or silodosin 8 mg daily) for up to 4 weeks. This increases the stone passage rate (by about 25 percent for distal stones above 5 mm).
• Nifedipine 30 mg daily is an alternative; stones below 5 mm usually pass without medical expulsive therapy. Review at 1 to 2 weeks with imaging and at 4 weeks.
• Urgent decompression (emergency): infected obstructed system (fever, leucocytosis, positive urine culture), obstructed solitary kidney, bilateral obstruction, acute renal failure, or intractable pain. Place a ureteric stent (double-J) or percutaneous nephrostomy.
• Give broad spectrum intravenous antibiotics (ceftriaxone 1 to 2 g daily, or piperacillin tazobactam 4.5 g every 8 hours, or gentamicin 5 mg/kg daily). Delay definitive stone treatment until the infection is cleared.
• Definitive treatment indications: stones above 10 mm, stones that fail to pass after 4 to 6 weeks of observation, persistent pain, obstruction with infection or renal impairment, and special occupations (pilots) or comorbidities.
  • Ureteroscopy (semirigid for distal and mid-ureter stones, flexible for proximal) with holmium:YAG laser lithotripsy (0.6 to 1.0 J at 6 to 10 Hz, or dusting with high frequency settings) and basket extraction. The stone free rate is 90 percent or more for distal stones, 80 to 90 percent for proximal.
  • A postoperative stent for 1 to 2 weeks if there was trauma, residual fragments, or a complicated procedure (tamsulosin or oral antimuscarinics such as solifenacin 5 mg may relieve stent symptoms).
  • Extracorporeal shock wave lithotripsy: effective for stones below 10 mm in the proximal ureter, with 70 to 80 percent success. It is less successful for distal and hard stones above 1,000 Hounsfield units. It is contraindicated in pregnancy, uncorrected coagulopathy, untreated infection, and distal obstruction.
  • Percutaneous antegrade ureteroscopy or laparoscopic ureterolithotomy for large impacted proximal stones, or after failure of other methods.
• Pregnancy: ultrasound and magnetic resonance imaging, analgesia with paracetamol and opioids, hydration; stent or nephrostomy for failed conservative treatment, ureteroscopy in the second trimester.
• Prevention of recurrence: fluid intake of at least 2.5 to 3 L daily to maintain a urine volume above 2 to 2.5 L; normal calcium intake (1,000 to 1,200 mg per day), restriction of sodium (below 2.3 g daily) and animal protein, and weight loss.
• Thiazide (hydrochlorothiazide 25 to 50 mg daily or chlorthalidone 25 mg) for hypercalciuria.
• Potassium citrate (30 to 60 mEq per day in divided doses) for hypocitraturia, calcium stones and uric acid stones.
• Allopurinol 100 to 300 mg daily for hyperuricosuria with calcium oxalate stones.