Renal stones, also known as kidney stones or nephrolithiasis, are a common and often painful condition. Understanding their formation, types, symptoms, diagnosis, and management is crucial for PLAB 1 preparation. This module will cover the core knowledge required.

Renal stones are solid masses made of minerals and salts that form inside your kidneys. They can develop when your urine contains more crystal-forming substances—such as calcium, oxalate, and uric acid—than the fluid in your urine can dilute. At the same time, your urine may lack substances that prevent crystals from sticking together, creating an ideal environment for kidney stones to form.

The classic symptom of a renal stone is renal colic: sudden, severe pain that typically begins in the flank (side and back) below the ribs and radiates forward and down toward the groin. The pain is often described as sharp or cramping and can come in waves.

Other symptoms may include:

• Hematuria: Blood in the urine (may be visible or microscopic).
• Nausea and vomiting: Due to the severity of pain.
• Urinary urgency and frequency: Especially if the stone is near the bladder.
• Dysuria: Painful urination.
• Fever and chills: If an infection develops (pyelonephritis).

Diagnosis involves a combination of clinical assessment, laboratory tests, and imaging.

Laboratory tests include:

• Urinalysis: To check for hematuria, infection (leukocytes, nitrites), and crystal presence.
• Urine culture: If infection is suspected.
• Serum creatinine and electrolytes: To assess kidney function and electrolyte balance.
• Serum calcium, phosphate, uric acid, and parathyroid hormone (PTH): To investigate the underlying cause of stone formation, especially for recurrent stones.

Management strategies depend on the stone's size, location, type, and the presence of symptoms or complications.

For small stones (<5 mm) that are likely to pass spontaneously:

• Hydration: Encouraging fluid intake (2-3 liters per day) to increase urine output and help flush the stone.
• Pain relief: Analgesics such as NSAIDs (e.g., ibuprofen, diclofenac) or opioids are used for renal colic. Alpha-blockers (e.g., tamsulosin) may help relax the ureter to facilitate stone passage.

For larger stones, persistent pain, infection, or significant obstruction:

• Extracorporeal Shock Wave Lithotripsy (ESWL): Uses shock waves to break stones into smaller fragments that can be passed.
• Ureteroscopy with Laser Lithotripsy: A flexible or rigid scope is passed into the ureter to visualize and break up stones with a laser.
• Percutaneous Nephrolithotomy (PCNL): A surgical procedure for very large or complex stones where a scope is inserted directly into the kidney through a small incision in the back.

Preventing future stone formation is key, especially for those with recurrent stones. This often involves dietary modifications and, in some cases, medical therapy based on stone analysis and metabolic workup.