Kidney and Ureteric Stones

Overview

Urinary stones (urolithiasis) are solid mineral deposits that form within the kidney or urinary tract. They are a common condition, affecting approximately one in ten people at some point in their lives, and have a marked tendency to recur. The most frequent type is calcium oxalate, accounting for around 80% of stones. Other types include calcium phosphate, uric acid, struvite (infection stones), and the rarer cystine stones.

Stones may remain in the kidney without causing symptoms, or they may migrate into the ureter — the tube connecting the kidney to the bladder — causing obstruction and the characteristic severe pain of ureteric colic.

Symptoms

Ureteric colic is the hallmark presentation of a stone that has passed from the kidney into the ureter. It is typically described as:

• Severe, sudden-onset loin pain radiating to the groin, scrotum, or labia
• Colicky in nature — pain that builds, peaks, and subsides, then recurs
• Associated nausea and vomiting
• Haematuria (blood in the urine, visible or microscopic)
• Frequency and dysuria if the stone is in the lower ureter near the bladder

Stones that remain in the kidney may cause a dull ache in the flank or may be entirely asymptomatic, discovered incidentally on imaging performed for another reason.

Red flag symptoms requiring urgent attention include fever (suggesting infection behind an obstructed kidney — a urological emergency), anuria (no urine output), or pain in a patient with a single functioning kidney.

Diagnosis

• CT-KUB (computed tomography of the kidneys, ureters, and bladder) — a non-contrast CT scan; this is the investigation of choice as it detects virtually all stone types and provides information about stone size, location, and whether the kidney is obstructed. It exposes the patient to ionising radiation, so alternatives may be preferred in young people and pregnant women.
• Urine dipstick — often shows blood; in the presence of fever, midstream urine culture is essential
• Blood tests — kidney function (creatinine), full blood count, and inflammatory markers; calcium levels help screen for metabolic causes
• Plain X-ray (KUB) — can identify calcium-containing stones; useful for monitoring known stones but misses many
• Ultrasound — avoids radiation, useful in pregnancy, but less sensitive for ureteric stones than CT

After a first stone episode, a metabolic workup including 24-hour urine collection may be arranged to identify treatable risk factors.

Treatment

Conservative management Small stones (approximately less than 6 mm) in a patient without infection or severe pain can be managed conservatively with high fluid intake, analgesia, and an alpha-blocker medication (such as tamsulosin) to facilitate spontaneous passage. Most will pass within four weeks.

Ureteroscopy and laser lithotripsy (URS) A thin flexible or rigid telescope is passed via the urethra and bladder into the ureter or kidney. Laser energy (holmium or thulium) is used to fragment the stone into small pieces. Fragments can be retrieved with a basket or allowed to pass spontaneously. A temporary ureteric stent is usually placed at the end of the procedure and removed after one to two weeks. This is the primary treatment for ureteric stones and small-to-medium kidney stones.

ESWL (Extracorporeal Shock Wave Lithotripsy) Sound waves focused from outside the body break the stone into fragments. Effective for suitable kidney stones up to approximately 2 cm; requires no incision. Several sessions may be needed.

PCNL (Percutaneous Nephrolithotomy) For large or complex kidney stones (typically over 2 cm), a small tract is made through the skin directly into the kidney under imaging guidance. Stones are fragmented and removed through this tract. This is a more involved procedure requiring a general anaesthetic and a short hospital stay.

Prevention Adequate hydration is the cornerstone of stone prevention. Dietary adjustments (limiting high-oxalate foods, maintaining moderate calcium intake, reducing salt and protein excess) and, in selected cases, medication (potassium citrate, thiazide diuretics, allopurinol) can significantly reduce the risk of recurrence.