Define Urinary Calculi. Describe its types, clinical features, investigations and management.

The Concept

Urinary calculi (urolithiasis) are stones that form within the urinary tract — in the kidney, ureter or bladder. They arise when the urine becomes supersaturated with stone-forming salts, which then nucleate and aggregate into a stone, especially where there is dehydration, metabolic abnormality, infection or urinary stasis. Their clinical effects depend on where the stone lodges and whether it obstructs.

Types of Stones

Clinical Features

• Ureteric stone (renal colic) — sudden, severe, colicky loin-to-groin pain in a patient who is characteristically restless and writhing (unlike peritonitis, where they lie still), with nausea, vomiting and haematuria; pain radiates to the groin/testis or labium as the stone descends.
• Renal (kidney) stone — may be asymptomatic, or cause a dull loin ache, haematuria or UTI.
• Bladder stone — suprapubic pain, dysuria, an interrupted stream, and haematuria.
• Complications — obstruction with hydronephrosis, infection (an infected obstructed system, pyonephrosis, is an emergency), and renal impairment.

Investigation

A non-contrast CT of the kidneys, ureters and bladder (CT KUB) is the gold-standard investigation, detecting almost all stones and any obstruction. Urinalysis shows blood; ultrasound and a plain KUB X-ray (for radio-opaque stones) are alternatives; bloods (calcium, urate, U&E) and stone analysis identify the cause.

Management

• Acute renal colic — analgesia (NSAIDs such as diclofenac are first-line), antiemetics and fluids. Most small stones (< 5 mm) pass spontaneously, aided by medical expulsive therapy (tamsulosin).
• Intervention for large, obstructing or non-passing stones — extracorporeal shock-wave lithotripsy (ESWL), ureteroscopy with laser fragmentation, or percutaneous nephrolithotomy (PCNL) for large or staghorn stones.
• An infected, obstructed kidney (pyonephrosis) is a urological emergency requiring urgent decompression (nephrostomy or ureteric stent) plus antibiotics.
• Prevention — good hydration, dietary modification and treating the underlying cause.

Pathophysiology of Renal Colic

The severe, colicky nature of ureteric pain is worth explaining. As a stone lodges and obstructs the ureter, urine builds up behind it, distending the renal pelvis and ureter; the ureter contracts vigorously in waves trying to expel the stone, and it is this peristalsis against an obstruction, plus stretching of the collecting system, that produces the intense, waxing-and-waning pain. The site of pain follows the stone down — loin pain high up, radiating to the groin, then to the testis/labium and tip of the penis as the stone nears the vesico-ureteric junction.

Sites of Impaction & Metabolic Work-up

Stones tend to lodge at the three anatomical narrowings of the ureter — the pelvi-ureteric junction, where the ureter crosses the pelvic brim (iliac vessels), and the vesico-ureteric junction — knowledge that helps interpret imaging. In recurrent stone-formers a metabolic work-up is done (serum calcium, urate, and urinary studies) to detect treatable causes such as hyperparathyroidism, hyperoxaluria or cystinuria, so that recurrence can be prevented rather than merely treating each stone as it arises.

Prevention

Prevention is an important and often-forgotten part of stone management. The single most effective measure is increasing fluid intake to keep the urine dilute; specific measures depend on stone type — reducing dietary oxalate and sodium and maintaining normal calcium for calcium stones, allopurinol and urine alkalinisation for uric acid stones, and treating any underlying infection or metabolic disorder. Advising prevention after a first stone reduces the high recurrence rate.

A Note on Bladder Stones

Although ureteric and renal stones dominate the topic, bladder stones deserve mention: they usually form secondary to stasis and incomplete emptying (bladder outflow obstruction from BPH), a chronic catheter, or infection, rather than descending from the kidney. They cause suprapubic pain, an interrupted stream (the stone intermittently blocking the outlet), dysuria and haematuria, and are treated by fragmentation and removal (cystolitholapaxy) together with correction of the underlying obstruction — linking stone disease back to BPH.

• Calcium oxalate commonest (radio-opaque); struvite → staghorn (Proteus); uric acid radiolucent.
• Non-contrast CT KUB is the gold-standard investigation.
• Renal colic: NSAIDs first-line; stones <5 mm usually pass (± tamsulosin); pyonephrosis → urgent decompression + antibiotics.

Loin-to-groin colic with haematuria is the classic presentation.

• Urinary calculi form from supersaturated urine (dehydration, metabolic, infection, stasis); site of lodging determines the picture.
• Types: calcium oxalate (commonest, radio-opaque), struvite (infection/Proteus → staghorn), uric acid (radiolucent), cystine.
• Renal colic: severe loin-to-groin colicky pain, restless patient, haematuria; complications = hydronephrosis, pyonephrosis, renal impairment.
• Non-contrast CT KUB is the gold-standard investigation.
• NSAIDs + fluids for colic (most small stones pass ± tamsulosin); ESWL/ureteroscopy/PCNL for larger stones; pyonephrosis = emergency decompression.