15th July 2024

Nephrolithiasis

Background

Renal stones can present to both medical and surgical teams. When the medical team finds itself looking after those with renal stones, this is often due to the patient initially presenting with sepsis or stones being found further down the line in a patient with acute kidney injury (AKI). Therefore, it is important to have some familiarity with the management of renal stones.

Clinical presentation

Pain and AKI are the commonly seen clinical presentations. Haematuria can be microscopic or macroscopic, whilst patients may also give a history of recurrent urine infections. Progressive chronic kidney disease (CKD) may also be a possible presentation in those with recurrent obstruction, infection and renal interstitial damage.

Patents may also have lifestyle factors which put them at risk of renal stones, such as fluid restriction to avoid bathroom breaks in the case of taxi drivers. Or they may have systemic disorders predisposing, such as gouty tophi.

Diagnosis & Treatment

Diagnosis is based on simple investigations such as urinalysis (microscopic haematuria, proteinuria, leucocytes and nitrites may all be present). Urine pH can vary depending on the type of stone present. Urine microscopy and culture can demonstrate crystals or concomitant infection.

In addition to routine bloods, it is important to check calcium levels, phosphate and serum urate.

CT-kidney-ureters-bladder (CT-KUB) is the single best test. It is a non-contrast scan; therefore, it is rapidly performed and avoids contrast administration. A KUB x-ray will only identify radio-opaque stones, such as calcium-containing or struvite stones, but not uric acid or cystine stones. Ultrasound can identify obstruction well and is sensitive for stones in the renal pelvis. However, it can miss ureteric stones.

Infection and obstruction are indications for urgent intervention. Non-steroidal anti-inflammatory drugs (NSAIDs) are often effective for the pain, however given the often co-existing renal dysfunction morphine can be used instead.

Treatment very much depends on the size of the stone and the extent of obstruction, as well as the co-existent infections. Those with stones smaller than 10mm may be able to expel them without any surgical intervention. However, this becomes less likely as the stone enlarges and is not an option if the patient is unwell.

Shockwave lithotripsy, percutaneous nephrolithotomy and ureteroscopy are all surgical options, although interventional radiology may also have a role to play.

Thereafter, patients are advised to drink plenty of water, avoid carbonated drinks and reduce salt intake. Thiazides and potassium citrate may also play a role in preventing recurrence.

References

• Steddon S, Ashman N, Chesser A, Cunningham J. Oxford Handbook of Nephrology and Hypertension (2ⁿᵈ ed.). Oxford (UK): Oxford University Press; 2014
• National Institute for Health Care Excellence. Renal and ureteric stones: assessment and management. London: NICE; 2019. (NICE Guideline No. 118). Available from: www.nice.org.uk/guidance/ng118