Renal Colic

Renal colic is severe, intermittent, loin-to-groin pain caused by acute obstruction of the urinary tract, nearly always from a calculus.

• Lifetime stone prevalence is 10 to 12 percent in men and 5 to 7 percent in women; peak age 30 to 60 years; recurrence is 50 percent in 10 years.
• Pain results from raised pelvic pressure, hyperperistalsis and prostaglandin-mediated dilatation of the collecting system.
• Other causes: blood clot, sloughed papilla, pyelo-ureteric junction obstruction, tumour, fungal ball, pus.

Sudden severe, colicky flank pain (patient restless, unable to find a comfortable position) radiating to the groin, testis or labia, with nausea, vomiting, sweating, haematuria and urinary frequency (low ureteric stones).

• Fever with rigors points to infection above an obstruction.
• Differential diagnosis: acute pyelonephritis, appendicitis, diverticulitis, ruptured abdominal aortic aneurysm, ectopic pregnancy, ovarian torsion, testicular torsion, biliary colic, bowel obstruction, musculoskeletal pain, herpes zoster, pancreatitis, renal infarction.
• Complications: obstructive uropathy, infected hydronephrosis (pyonephrosis) and urosepsis, acute kidney injury (solitary kidney, bilateral stones), perinephric abscess, forniceal rupture, stricture and recurrent stones.

Urinalysis (blood in about 85 percent, pyuria, nitrites), urine culture, pregnancy test, full blood count, creatinine, electrolytes, calcium, uric acid, C-reactive protein.

• Low dose non-contrast CT of kidneys, ureters and bladder is the most accurate (sensitivity above 95 percent); ultrasound (hydronephrosis, stones in the kidney) is used first in pregnancy, children and young adults; plain radiography detects radio-opaque stones and monitors progress.
• Contrast CT or intravenous urography seldom needed.
• Stone analysis and metabolic evaluation after recovery.

Supportive: oral fluids to maintain urine output (no forced diuresis); heat to the flank; antiemetics (ondansetron 4 mg IV or oral, metoclopramide 10 mg).

Pharmacological

• Initial analgesia: diclofenac 75 mg IM or 50 mg orally, or 100 mg rectally (repeat after 12 hours; maximum 150 mg daily); ketorolac 30 mg IV or 10 mg orally; paracetamol 1 g IV or orally every 6 hours.
• Opioids if inadequate: morphine 2.5 to 5 mg IV every 10 to 15 minutes titrated to pain, or pethidine 50 mg IM.
• Avoid NSAIDs in renal impairment, pregnancy (third trimester), gastrointestinal bleeding, and with dehydration.
• Medical expulsive therapy for distal ureteric stones of 5 to 10 mm: tamsulosin 0.4 mg once daily at night (or silodosin 8 mg daily) for up to 4 weeks; nifedipine extended release 30 mg daily is an alternative.
• Antibiotics for infection: ceftriaxone 1 to 2 g IV daily or gentamicin 5 mg/kg daily, tailored to culture.

Procedures

• Urgent decompression (ureteric stent or percutaneous nephrostomy) for obstruction with infection, solitary kidney, bilateral obstruction, acute kidney injury or intractable pain.
• Definitive treatment: extracorporeal shock wave lithotripsy for stones below 20 mm, ureteroscopy with holmium laser lithotripsy for ureteric stones and renal stones, percutaneous nephrolithotomy for stones above 20 mm.

Special groups: pregnancy (ultrasound, paracetamol, conservative care, stent or nephrostomy if infection), children (ibuprofen 5 to 10 mg/kg), elderly (cautious analgesia).

Red flags: fever above 38 C, hypotension, anuria, solitary kidney, pain not controlled after two doses, diagnostic uncertainty in patients older than 60 years (aortic aneurysm).

Follow-up: strain urine and send the stone for analysis; repeat imaging at 2 to 4 weeks for retained stones; metabolic evaluation after the second stone; fluids 2.5 to 3 L daily.