Renal colic 

Incidence of 131 cases per 100,000 population

Site of pain is notoriously inaccurate at predicting location of stone

Calculus size, location, and patient discomfort predict the likelihood of spontaneous stone passage.

Approximately 90% of stones less than 5 mm pass within four weeks. Up to 95% of stones larger than 8 mm can become impacted, requiring intervention to pass

History and Physical

• Patients experiencing renal colic may present in very severe pain. Classically, these patients are unable to find a comfortable position and are often writhing or constantly pacing around the examination table
• sudden onset of flank pain –> radiating laterally to the abdomen and/or to the groin
• dull constant level of pain + colicky episodes of increased pain.
  • dull constant pain
    • is often due to stretching of the renal capsule due to obstruction
  • colicky pain
    • caused by peristalsis of the ureteral smooth muscle
• associated nausea or vomiting, and some may report gross hematuria.
• As the stone migrates distally and approaches the bladder, the patient may experience
  • dysuria
  • urinary frequency
  • urgency
  • difficulty in urination.

Differential Diagnosis

• Angiomyolipomas
• Aortic aneurysms
• Biliary colic
• Iliac aneurysms
• Endometriosis
• Ovarian torsion
• Peritonitis
• Pyelonephritis
• Renal cancer
• Renovascular compromise
• Wunderlich syndrome (rare condition with spontaneous renal subcapsular and/or retroperitoneal bleeding and hematoma formation)

Workup

Test	Purpose & interpretation
Urinalysis ± MCS	• Microscopic / macroscopic haematuria is found in ≈ 85 % of stone‑related colic. • Presence of blood supports the diagnosis but is not diagnostic; absence does not exclude a calculus. • MCS screens for concurrent UTI, which may mandate urgent urological review.
• U&E / creatinine – renal function and baseline for contrast studies. • Serum uric acid – hyperuricaemia suggests urate stones or metabolic syndrome. • Serum calcium – if elevated, measure intact PTH to rule out primary hyperparathyroidism.	Detects metabolic contributors and guides long‑term prevention.
Send any passed or extracted calculus for laboratory composition analysis.	Identifies stone type (calcium oxalate, urate, cystine, struvite, etc.) and directs tailored metabolic evaluation.
24‑h urine for volume calcium oxalate citrate urate sodium creatinine; ± serum phosphate bicarbonate magnesium	Extended metabolic screen (recurrent, bilateral, <30 y, single kidney) Comprehensive risk stratification and secondary prevention planning.

Imaging

Low‑dose non‑contrast CT KUB is the definitive first‑line investigation for most adults with suspected renal colic. Ultrasound is reserved for radiation‑sensitive groups, and plain KUB films complement CT for ongoing surveillance of radio‑opaque stones. Intravenous contrast studies or MRI have limited, specialist‑driven roles.

Gold‑standard test

Modality	Key metrics	Clinical advantages	Caveats
Low‑dose, non‑contrast CT KUB	Sensitivity ≈ 93 % (100 % for stones > 3 mm); specificity ≈ 97 % RACGP	• Detects size, site & density of the calculus • Quantifies obstruction (hydroureter/‑phrosis, peri‑ureteric oedema) • Rapidly rules in/out dangerous mimics (AAA, appendicitis, ovarian torsion, malignancy) • Modern low‑dose protocols ≈ 2‑5 mSv (ultra‑low‑dose ≈ 0.8 mSv) SpringerLink	• Ionising radiation – minimise repeat scans; use shielding/protocol optimisation

Practice tip: In adults without pregnancy or radiation‑sensitive circumstances, request “low‑dose non‑contrast CT KUB (prone if distal stone suspected)”.

  Adjunct or follow‑up imaging

Modality	Appropriate use	Limitations
Plain KUB X‑ray	• Taken with the index CT if stone is radio‑opaque; provides a baseline for serial monitoring with <0.7 mSv per film RACGP	• ~50 % of calculi visible (mainly calcium‑based); uric‑acid & cystine stones radiolucent • No information on obstruction or renal parenchyma; bowel gas & bony pelvis often obscure ureteric segments
Ultrasound (USS)	• First‑line in pregnancy, children, or adults < 50 y when radiation avoidance is paramount • Excellent for hydronephrosis grading & renal stones	• Operator‑/body‑habitus‑dependent • Sensitivity for ureteric stones only 45‑60 %, especially poor for mid‑ureter & stones < 5 mm RACGP
Intravenous pyelogram / CT urogram	• Rare in acute diagnosis; reserved for complex anatomy, haematuria work‑up or surgical planning	• Higher contrast dose ± radiation; not required routinely
MRI	• Niche role (e.g. equivocal USS in pregnancy)	• Limited stone conspicuity; no routine role in urolithiasis

possible protocol

1. Adult, non‑pregnant – order low‑dose CT KUB.
2. If stone is CT‑visible on plain radiograph window, add KUB X‑ray before patient leaves; use it for radiation‑sparring follow‑up.
3. Pregnancy or paediatric pain – start with USS. Escalate to CT only after obstetric/urology consultation if diagnosis remains uncertain.
4. Repeat presentations / monitoring – use plain KUB or USS (if hydronephrosis was present) unless complications dictate re‑CT.

Treatment

• Conservative
  • Majority of stones that migrate to the ureter will pass spontaneously = <5mm should pass
  • Up to 70% of stones less than or equal to 6mm in transverse diameter will pass spontaneously
  • Increases to 90% with addition of Tamsulosin 400mcg /day (nonPBS)
    • alpha blockade medications (tamsulosin or nifedipine) is theorized to facilitate stone passage by decreasing intra-ureteral pressure and dilating the distal ureter.
  • Paracetamol/NSAID
    • celecoxib 200mg daily
    • indomethacin 50mg TDS
  • Strain urine – avoid imaging if passed, stone analysis
  • No evidence for increasing oral fluids, only has role in prevention
  • Silent (asymptomatic) obstruction should be considered, need repeat imaging after 6 weeks to ensure that the stone has passed

• Indications for hospital admission
  • significant renal stone in a solitary kidney
  • severe kidney injury
  • infected renal stone
  • intractable pain or nausea
  • urinary extravasation
  • hypercalcemic crisis

• Urology review if
  • Infected/sepsis
  • Obstructed/infected
  • Drop in GFR
  • Uncontollable pain
  • Complete obstruction
  • Single kidney
  • With significant CKD
  • >6mm unlikely to pass

Interventional

• Absolute
  • Infection (pyonephrosis)
    • fever or history of fever, infection in an obstructed system can result in life threatening Gram negative sepsis. Antibiotics alone cannot readily treat, drainage of the upper tract required by retrograde stenting and percutaneous nephrostomy
  • Renal failure deteriorating
    • renal function mainly an issue for patients with a solitary kidney, early intervention offered for this group
• Relative
  • Ongoing or recurrent pain-  patients may choose to have surgery after a trial of conservative management
  • stone larger than 6mm unlikely to pass or take longer to pass may benefit from early intervention
  • occupational / social some – occupations require complete removal of stones (eg. airline pilots) before they can return to work, planned overseas holidays particularly to remote locations

• Definitive treatment of stones in the kidney
  • Currently most patients that require intervention for ureteric stones will have ureteroscopic laser lithotripsy
  • Intervention for a stone is recommended by 4 weeks with no changes even if the patient is asymptomatic.
  • This is due to the likelihood of scarring and other complications

Stone Prevention

• Type of stone
  • Recurrence rates are high following first stone 50% within 5 yrs
  • At first presentation urinalysis, serum calcium uric acid and electrolytes
  • Stone analysis if available
  • Stone type can also be inferred from the radiological findings
  • Stone recovery pee into white ice cream container and recover stone, improves compliance over straining all urine
• Prevention
  • increasing fluid intake, especially water to maintain dilute urine output
  • avoiding added salt
  • maintaining a well balanced diet
  • patients with calcium oxalate stones should be advised to keep a low oxalate diet (the majority of published evidence now favors dietary salt and oxalate reduction rather than calcium)
  • Common oxalate rich foods include tea, chocolate, spinach, beetroot, rhubarb, peanuts, cola and vitamin C (most supplementary vitamin C is converted to oxalate)