Urinary tract stones

Most urinary tract stones occur in the upper urinary tract. Their composition varies widely depending upon metabolic alterations, geography and presence of infection. Their size varies from gravel to staghorn calculi. Some are the result of inborn errors of metabolism - gout, cystinuria, primary hyperoxaluria. Most are radio-opaque.

• small stones arising in the kidney are more likely to pass into the ureter where they may cause severe colicky pain; large stones may be asymptomatic because of their immobility
• superimposed infection may result from mucosal trauma and/or obstruction.

Usual presentation of renal/ureteric stones is as an acute episode with severe pain (1)

• although some stones are picked up incidentally during imaging or may present as a history of infection
• the initial diagnosis is made by taking a clinical history and examination and carrying out imaging; initial management is with painkillers and treatment of any infection
  
  
• ongoing treatment of renal and ureteric stones depends on the site of the stone and size of the stone (less than 10 mm, 10 to 20 mm, greater than 20 mm; staghorn stones)
  
  
• options for treatment range from observation with pain relief to surgical intervention
  • open surgery is performed very infrequently; most surgical stone management is minimally invasive and the interventions include shockwave lithotripsy (SWL), ureteroscopy (URS) and percutaneous stone removal (surgery)
    
    
  • as well as the site and size of the stone, treatment also depends on local facilities and expertise. Most centres have access to SWL, but many use a mobile machine on a sessional basis rather than a fixed site machine, which has easier access during the working week. The use of a mobile machine may affect options for emergency treatment, but may also add to waiting times for non-emergency treatment
    
    
  • URS for renal and ureteric stones is increasing (there has been a 49% increase from 12,062 treatments in 2009/10, to 18,066 in 2014/15), there is a trend towards day-case/ambulatory care, with this increasing by 10% to 31,000 cases a year between 2010 and 2015
• total number of bed-days used for renal stone disease has fallen by 15% since 2009/10

Because the incidence of renal and ureteric stones and the rate of intervention are increasing (2) - there is a need to reduce recurrences through patient education and lifestyle changes. Assessing dietary factors and changing lifestyle have been shown to reduce the number of episodes in people with renal stone disease

• number of upper urinary tract stone hospital episodes increased by 63% to 83,050 in the 10-year period 2000/2001 to 2009/2010 (2)
• incidence of kidney stone disease (urolithiasis) has a lifetime risk of 10–15%, and a recurrence rate of 50% within 10 years (3)

Patients with known urinary stones also require urgent referral if their pain is uncontrolled with oral analgesia, or if they have signs of sepsis (3)
For patients whose symptoms have settled, less urgent imaging can be requested, as long as there are no other clinical concerns. Renal function should also be checked (3)

References:

1. NICE (December 2018).Renal and ureteric stones: assessment and management (NG118)
2. Turney BW et al. Trends in urological stone disease.BJU Int. 2012 Apr;109(7):1082-7
3. Wilcox CR et al. Kidney stone disease: an update on its management in primary care. BJGP 2020; 70: 205–206.