Renal Calculi (Kidney Stones)

Definition

Renal calculi, commonly known as kidney stones, are hard deposits made of minerals and salts that form inside the kidneys. They can affect any part of the urinary tract and vary in size and shape.

Aetiology

Renal calculi can form due to various factors, including:

Dehydration: Concentrated urine allows minerals to crystallise and stick together.
Diet: High intake of protein, sodium, and sugar can increase the risk of some types of kidney stones.
Medical conditions: Hyperparathyroidism, gout, and certain urinary tract infections.
Genetics: Family history of kidney stones.
Medications: Certain drugs can increase the risk of stone formation.

Pathophysiology

Kidney stones form when the urine contains more crystal-forming substances such as calcium, oxalate, and uric acid than the fluid in the urine can dilute. At the same time, the urine may lack substances that prevent crystals from sticking together, creating an ideal environment for kidney stones to form.

Risk Factors

Family or personal history of kidney stones.
Dehydration.
Diet high in protein, sodium, and sugar.
Obesity.
Digestive diseases and surgery.
Certain supplements and medications.

Signs and Symptoms

Severe, sharp pain in the side and back, below the ribs.
Pain that radiates to the lower abdomen and groin.
Pain that comes in waves and fluctuates in intensity.
Pain on urination.
Pink, red, or brown urine.
Cloudy or foul-smelling urine.
Nausea and vomiting.
Persistent need to urinate.
Urinating more often than usual.
Fever and chills if an infection is present.

Investigations

Clinical history and physical examination.
Urinalysis: To check for blood, bacteria, and crystals in the urine.
Blood tests: To check for high levels of calcium or uric acid.
Imaging: Non-contrast CT scan is the gold standard; ultrasound can be used in certain cases.
Analysis of passed stones: To determine the type of stone.

Management

Primary Care Management

If the patient is unwell, refer urgently to hospital and then stabilise the patient, ensuring airway, breathing, and circulation (ABCs).
Pain management: NSAIDs or opioids if necessary.
Hydration: Encourage the patient to drink plenty of fluids to help flush out the stone.
Referral to a specialist (urologist) only if symptoms persist and the patient has been assessed in the hospital and told to go to the GP (if they have not already been referred by hospital doctors).
Patient education on diet and lifestyle changes to prevent recurrence.

Specialist Management

Extracorporeal shock wave lithotripsy (ESWL): To break up stones into smaller pieces that can be passed in the urine.
Ureteroscopy: To remove or break up stones using a scope passed into the ureter.
Percutaneous nephrolithotomy: A surgical procedure to remove very large stones directly from the kidney.
Medications: To prevent stone formation in patients with recurrent stones (e.g., thiazide diuretics, allopurinol).
Close monitoring: Regular follow-up to assess for recurrence and manage any complications.

Example Management for Renal Calculi

A patient presenting with severe, sharp pain in the side and back should be evaluated for kidney stones. Initial management includes pain relief with NSAIDs and hydration to help flush out the stone. If the patient is unwell, they should be urgently referred to a hospital. Imaging studies, such as a non-contrast CT scan, should be performed to confirm the diagnosis and determine the size and location of the stone. If the stone is large or causing significant obstruction, the patient may be referred to a urologist for procedures such as ESWL or ureteroscopy. Regular follow-up and patient education on preventing recurrence are essential.

References

NICE. (2024). Renal and Ureteric Stones: Assessment and Management. Retrieved from NICE
NHS. (2023). Kidney Stones. Retrieved from NHS
Scales, C. D., et al. (2012). The Prevalence of Kidney Stones in the United States. European Urology.
Goldfarb, D. S., et al. (2007). Kidney Stones and the Risk of Chronic Kidney Disease. Journal of the American Society of Nephrology.
Taylor, E. N., et al. (2004). Dietary Factors and the Risk of Incident Kidney Stones in Men: New Insights after 14 Years of Follow-Up. Journal of the American Society of Nephrology.