Renal Calculi (Nephrolithiasis)

•    Types of Renal Stones:

o    Calcium oxalate (∼75%): most common; radio-opaque

    Risk factors: hypercalciuria, hyperoxaluria, low citrate, dehydration

o    Uric acid: radiolucent on plain X-ray (visible on CT); acidic urine favours formation

    Seen in gout, high cell turnover (e.g. tumour lysis)

o    Struvite (magnesium ammonium phosphate): staghorn calculi

    Alkaline urine; associated with Proteus, Klebsiella (urease-producing organisms)

o    Cystine: rare, seen in inherited cystinuria; faintly radio-opaque

•    Clinical Features:

o    Renal colic: sudden onset, severe colicky flank pain radiating to groin

o    Haematuria: microscopic or macroscopic

o    Nausea, vomiting

o    Frequency, dysuria if stone is in distal ureter

o    Infection signs: fever, pyuria, sepsis if obstructed infected system

•    Diagnosis:

o    First-line: non-contrast CT KUB (high sensitivity/specificity)

o    Ultrasound: alternative in pregnancy; may detect hydronephrosis

o    Urinalysis: haematuria, crystals, signs of infection

o    Serum calcium, urate, and PTH levels; 24-hour urine in recurrent cases

•    Management:

o    Conservative (most <5 mm pass spontaneously):

    High fluid intake

    NSAIDs (e.g. diclofenac) for pain

    Alpha-blockers (e.g. tamsulosin) to aid passage

o    Referral to urology if:

    Obstruction with infection (urological emergency)

    Persistent pain

    Stone >6 mm or failed conservative management

o    Surgical options:

    ESWL (extracorporeal shockwave lithotripsy)

    Ureteroscopy ± laser

    Percutaneous nephrolithotomy (for large/staghorn calculi)

Nephrocalcinosis

•    Definition: Diffuse calcium deposition in the renal parenchyma, most often in the renal medulla

•    Causes:

o    Hyperparathyroidism (primary or tertiary)

o    Renal tubular acidosis (type 1)

o    Hypervitaminosis D (excess supplementation or granulomatous disease)

o    Medullary sponge kidney

o    Sarcoidosis

o    Hypercalcaemia of malignancy

•    Clinical Features:

o    Often asymptomatic; detected incidentally on imaging

o    May cause nephrolithiasis, CKD over time

•    Diagnosis:

o    Renal ultrasound: echogenic pyramids

o    CT scan: shows medullary calcification more clearly

•    Management:

o    Treat underlying cause (e.g. control PTH, correct acidosis)

o    Hydration, thiazides may reduce urinary calcium excretion